This is the 4.9.306 stable release

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2022-03-11 11:10:37 +01:00 · 2022-03-11 11:10:37 +01:00 · bf0024db2f
commit bf0024db2f
parent ad8bfa47c3 0f4e5f2852
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--- a/Documentation/hw-vuln/index.rst
+++ b/Documentation/hw-vuln/index.rst
@ -9,6 +9,7 @@ are configurable at compile, boot or run time.
 .. toctree::
   :maxdepth: 1

+   spectre
   l1tf
   mds
   tsx_async_abort
--- a/Documentation/hw-vuln/spectre.rst
+++ b/Documentation/hw-vuln/spectre.rst
@ -0,0 +1,785 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Spectre Side Channels
+=====================
+
+Spectre is a class of side channel attacks that exploit branch prediction
+and speculative execution on modern CPUs to read memory, possibly
+bypassing access controls. Speculative execution side channel exploits
+do not modify memory but attempt to infer privileged data in the memory.
+
+This document covers Spectre variant 1 and Spectre variant 2.
+
+Affected processors
+-------------------
+
+Speculative execution side channel methods affect a wide range of modern
+high performance processors, since most modern high speed processors
+use branch prediction and speculative execution.
+
+The following CPUs are vulnerable:
+
+    - Intel Core, Atom, Pentium, and Xeon processors
+
+    - AMD Phenom, EPYC, and Zen processors
+
+    - IBM POWER and zSeries processors
+
+    - Higher end ARM processors
+
+    - Apple CPUs
+
+    - Higher end MIPS CPUs
+
+    - Likely most other high performance CPUs. Contact your CPU vendor for details.
+
+Whether a processor is affected or not can be read out from the Spectre
+vulnerability files in sysfs. See :ref:`spectre_sys_info`.
+
+Related CVEs
+------------
+
+The following CVE entries describe Spectre variants:
+
+   =============   =======================  ==========================
+   CVE-2017-5753   Bounds check bypass      Spectre variant 1
+   CVE-2017-5715   Branch target injection  Spectre variant 2
+   CVE-2019-1125   Spectre v1 swapgs        Spectre variant 1 (swapgs)
+   =============   =======================  ==========================
+
+Problem
+-------
+
+CPUs use speculative operations to improve performance. That may leave
+traces of memory accesses or computations in the processor's caches,
+buffers, and branch predictors. Malicious software may be able to
+influence the speculative execution paths, and then use the side effects
+of the speculative execution in the CPUs' caches and buffers to infer
+privileged data touched during the speculative execution.
+
+Spectre variant 1 attacks take advantage of speculative execution of
+conditional branches, while Spectre variant 2 attacks use speculative
+execution of indirect branches to leak privileged memory.
+See :ref:`[1] <spec_ref1>` :ref:`[5] <spec_ref5>` :ref:`[6] <spec_ref6>`
+:ref:`[7] <spec_ref7>` :ref:`[10] <spec_ref10>` :ref:`[11] <spec_ref11>`.
+
+Spectre variant 1 (Bounds Check Bypass)
+---------------------------------------
+
+The bounds check bypass attack :ref:`[2] <spec_ref2>` takes advantage
+of speculative execution that bypasses conditional branch instructions
+used for memory access bounds check (e.g. checking if the index of an
+array results in memory access within a valid range). This results in
+memory accesses to invalid memory (with out-of-bound index) that are
+done speculatively before validation checks resolve. Such speculative
+memory accesses can leave side effects, creating side channels which
+leak information to the attacker.
+
+There are some extensions of Spectre variant 1 attacks for reading data
+over the network, see :ref:`[12] <spec_ref12>`. However such attacks
+are difficult, low bandwidth, fragile, and are considered low risk.
+
+Note that, despite "Bounds Check Bypass" name, Spectre variant 1 is not
+only about user-controlled array bounds checks.  It can affect any
+conditional checks.  The kernel entry code interrupt, exception, and NMI
+handlers all have conditional swapgs checks.  Those may be problematic
+in the context of Spectre v1, as kernel code can speculatively run with
+a user GS.
+
+Spectre variant 2 (Branch Target Injection)
+-------------------------------------------
+
+The branch target injection attack takes advantage of speculative
+execution of indirect branches :ref:`[3] <spec_ref3>`.  The indirect
+branch predictors inside the processor used to guess the target of
+indirect branches can be influenced by an attacker, causing gadget code
+to be speculatively executed, thus exposing sensitive data touched by
+the victim. The side effects left in the CPU's caches during speculative
+execution can be measured to infer data values.
+
+.. _poison_btb:
+
+In Spectre variant 2 attacks, the attacker can steer speculative indirect
+branches in the victim to gadget code by poisoning the branch target
+buffer of a CPU used for predicting indirect branch addresses. Such
+poisoning could be done by indirect branching into existing code,
+with the address offset of the indirect branch under the attacker's
+control. Since the branch prediction on impacted hardware does not
+fully disambiguate branch address and uses the offset for prediction,
+this could cause privileged code's indirect branch to jump to a gadget
+code with the same offset.
+
+The most useful gadgets take an attacker-controlled input parameter (such
+as a register value) so that the memory read can be controlled. Gadgets
+without input parameters might be possible, but the attacker would have
+very little control over what memory can be read, reducing the risk of
+the attack revealing useful data.
+
+One other variant 2 attack vector is for the attacker to poison the
+return stack buffer (RSB) :ref:`[13] <spec_ref13>` to cause speculative
+subroutine return instruction execution to go to a gadget.  An attacker's
+imbalanced subroutine call instructions might "poison" entries in the
+return stack buffer which are later consumed by a victim's subroutine
+return instructions.  This attack can be mitigated by flushing the return
+stack buffer on context switch, or virtual machine (VM) exit.
+
+On systems with simultaneous multi-threading (SMT), attacks are possible
+from the sibling thread, as level 1 cache and branch target buffer
+(BTB) may be shared between hardware threads in a CPU core.  A malicious
+program running on the sibling thread may influence its peer's BTB to
+steer its indirect branch speculations to gadget code, and measure the
+speculative execution's side effects left in level 1 cache to infer the
+victim's data.
+
+Yet another variant 2 attack vector is for the attacker to poison the
+Branch History Buffer (BHB) to speculatively steer an indirect branch
+to a specific Branch Target Buffer (BTB) entry, even if the entry isn't
+associated with the source address of the indirect branch. Specifically,
+the BHB might be shared across privilege levels even in the presence of
+Enhanced IBRS.
+
+Currently the only known real-world BHB attack vector is via
+unprivileged eBPF. Therefore, it's highly recommended to not enable
+unprivileged eBPF, especially when eIBRS is used (without retpolines).
+For a full mitigation against BHB attacks, it's recommended to use
+retpolines (or eIBRS combined with retpolines).
+
+Attack scenarios
+----------------
+
+The following list of attack scenarios have been anticipated, but may
+not cover all possible attack vectors.
+
+1. A user process attacking the kernel
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Spectre variant 1
+~~~~~~~~~~~~~~~~~
+
+   The attacker passes a parameter to the kernel via a register or
+   via a known address in memory during a syscall. Such parameter may
+   be used later by the kernel as an index to an array or to derive
+   a pointer for a Spectre variant 1 attack.  The index or pointer
+   is invalid, but bound checks are bypassed in the code branch taken
+   for speculative execution. This could cause privileged memory to be
+   accessed and leaked.
+
+   For kernel code that has been identified where data pointers could
+   potentially be influenced for Spectre attacks, new "nospec" accessor
+   macros are used to prevent speculative loading of data.
+
+Spectre variant 1 (swapgs)
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+   An attacker can train the branch predictor to speculatively skip the
+   swapgs path for an interrupt or exception.  If they initialize
+   the GS register to a user-space value, if the swapgs is speculatively
+   skipped, subsequent GS-related percpu accesses in the speculation
+   window will be done with the attacker-controlled GS value.  This
+   could cause privileged memory to be accessed and leaked.
+
+   For example:
+
+   ::
+
+     if (coming from user space)
+         swapgs
+     mov %gs:<percpu_offset>, %reg
+     mov (%reg), %reg1
+
+   When coming from user space, the CPU can speculatively skip the
+   swapgs, and then do a speculative percpu load using the user GS
+   value.  So the user can speculatively force a read of any kernel
+   value.  If a gadget exists which uses the percpu value as an address
+   in another load/store, then the contents of the kernel value may
+   become visible via an L1 side channel attack.
+
+   A similar attack exists when coming from kernel space.  The CPU can
+   speculatively do the swapgs, causing the user GS to get used for the
+   rest of the speculative window.
+
+Spectre variant 2
+~~~~~~~~~~~~~~~~~
+
+   A spectre variant 2 attacker can :ref:`poison <poison_btb>` the branch
+   target buffer (BTB) before issuing syscall to launch an attack.
+   After entering the kernel, the kernel could use the poisoned branch
+   target buffer on indirect jump and jump to gadget code in speculative
+   execution.
+
+   If an attacker tries to control the memory addresses leaked during
+   speculative execution, he would also need to pass a parameter to the
+   gadget, either through a register or a known address in memory. After
+   the gadget has executed, he can measure the side effect.
+
+   The kernel can protect itself against consuming poisoned branch
+   target buffer entries by using return trampolines (also known as
+   "retpoline") :ref:`[3] <spec_ref3>` :ref:`[9] <spec_ref9>` for all
+   indirect branches. Return trampolines trap speculative execution paths
+   to prevent jumping to gadget code during speculative execution.
+   x86 CPUs with Enhanced Indirect Branch Restricted Speculation
+   (Enhanced IBRS) available in hardware should use the feature to
+   mitigate Spectre variant 2 instead of retpoline. Enhanced IBRS is
+   more efficient than retpoline.
+
+   There may be gadget code in firmware which could be exploited with
+   Spectre variant 2 attack by a rogue user process. To mitigate such
+   attacks on x86, Indirect Branch Restricted Speculation (IBRS) feature
+   is turned on before the kernel invokes any firmware code.
+
+2. A user process attacking another user process
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+   A malicious user process can try to attack another user process,
+   either via a context switch on the same hardware thread, or from the
+   sibling hyperthread sharing a physical processor core on simultaneous
+   multi-threading (SMT) system.
+
+   Spectre variant 1 attacks generally require passing parameters
+   between the processes, which needs a data passing relationship, such
+   as remote procedure calls (RPC).  Those parameters are used in gadget
+   code to derive invalid data pointers accessing privileged memory in
+   the attacked process.
+
+   Spectre variant 2 attacks can be launched from a rogue process by
+   :ref:`poisoning <poison_btb>` the branch target buffer.  This can
+   influence the indirect branch targets for a victim process that either
+   runs later on the same hardware thread, or running concurrently on
+   a sibling hardware thread sharing the same physical core.
+
+   A user process can protect itself against Spectre variant 2 attacks
+   by using the prctl() syscall to disable indirect branch speculation
+   for itself.  An administrator can also cordon off an unsafe process
+   from polluting the branch target buffer by disabling the process's
+   indirect branch speculation. This comes with a performance cost
+   from not using indirect branch speculation and clearing the branch
+   target buffer.  When SMT is enabled on x86, for a process that has
+   indirect branch speculation disabled, Single Threaded Indirect Branch
+   Predictors (STIBP) :ref:`[4] <spec_ref4>` are turned on to prevent the
+   sibling thread from controlling branch target buffer.  In addition,
+   the Indirect Branch Prediction Barrier (IBPB) is issued to clear the
+   branch target buffer when context switching to and from such process.
+
+   On x86, the return stack buffer is stuffed on context switch.
+   This prevents the branch target buffer from being used for branch
+   prediction when the return stack buffer underflows while switching to
+   a deeper call stack. Any poisoned entries in the return stack buffer
+   left by the previous process will also be cleared.
+
+   User programs should use address space randomization to make attacks
+   more difficult (Set /proc/sys/kernel/randomize_va_space = 1 or 2).
+
+3. A virtualized guest attacking the host
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+   The attack mechanism is similar to how user processes attack the
+   kernel.  The kernel is entered via hyper-calls or other virtualization
+   exit paths.
+
+   For Spectre variant 1 attacks, rogue guests can pass parameters
+   (e.g. in registers) via hyper-calls to derive invalid pointers to
+   speculate into privileged memory after entering the kernel.  For places
+   where such kernel code has been identified, nospec accessor macros
+   are used to stop speculative memory access.
+
+   For Spectre variant 2 attacks, rogue guests can :ref:`poison
+   <poison_btb>` the branch target buffer or return stack buffer, causing
+   the kernel to jump to gadget code in the speculative execution paths.
+
+   To mitigate variant 2, the host kernel can use return trampolines
+   for indirect branches to bypass the poisoned branch target buffer,
+   and flushing the return stack buffer on VM exit.  This prevents rogue
+   guests from affecting indirect branching in the host kernel.
+
+   To protect host processes from rogue guests, host processes can have
+   indirect branch speculation disabled via prctl().  The branch target
+   buffer is cleared before context switching to such processes.
+
+4. A virtualized guest attacking other guest
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+   A rogue guest may attack another guest to get data accessible by the
+   other guest.
+
+   Spectre variant 1 attacks are possible if parameters can be passed
+   between guests.  This may be done via mechanisms such as shared memory
+   or message passing.  Such parameters could be used to derive data
+   pointers to privileged data in guest.  The privileged data could be
+   accessed by gadget code in the victim's speculation paths.
+
+   Spectre variant 2 attacks can be launched from a rogue guest by
+   :ref:`poisoning <poison_btb>` the branch target buffer or the return
+   stack buffer. Such poisoned entries could be used to influence
+   speculation execution paths in the victim guest.
+
+   Linux kernel mitigates attacks to other guests running in the same
+   CPU hardware thread by flushing the return stack buffer on VM exit,
+   and clearing the branch target buffer before switching to a new guest.
+
+   If SMT is used, Spectre variant 2 attacks from an untrusted guest
+   in the sibling hyperthread can be mitigated by the administrator,
+   by turning off the unsafe guest's indirect branch speculation via
+   prctl().  A guest can also protect itself by turning on microcode
+   based mitigations (such as IBPB or STIBP on x86) within the guest.
+
+.. _spectre_sys_info:
+
+Spectre system information
+--------------------------
+
+The Linux kernel provides a sysfs interface to enumerate the current
+mitigation status of the system for Spectre: whether the system is
+vulnerable, and which mitigations are active.
+
+The sysfs file showing Spectre variant 1 mitigation status is:
+
+   /sys/devices/system/cpu/vulnerabilities/spectre_v1
+
+The possible values in this file are:
+
+  .. list-table::
+
+     * - 'Not affected'
+       - The processor is not vulnerable.
+     * - 'Vulnerable: __user pointer sanitization and usercopy barriers only; no swapgs barriers'
+       - The swapgs protections are disabled; otherwise it has
+         protection in the kernel on a case by case base with explicit
+         pointer sanitation and usercopy LFENCE barriers.
+     * - 'Mitigation: usercopy/swapgs barriers and __user pointer sanitization'
+       - Protection in the kernel on a case by case base with explicit
+         pointer sanitation, usercopy LFENCE barriers, and swapgs LFENCE
+         barriers.
+
+However, the protections are put in place on a case by case basis,
+and there is no guarantee that all possible attack vectors for Spectre
+variant 1 are covered.
+
+The spectre_v2 kernel file reports if the kernel has been compiled with
+retpoline mitigation or if the CPU has hardware mitigation, and if the
+CPU has support for additional process-specific mitigation.
+
+This file also reports CPU features enabled by microcode to mitigate
+attack between user processes:
+
+1. Indirect Branch Prediction Barrier (IBPB) to add additional
+   isolation between processes of different users.
+2. Single Thread Indirect Branch Predictors (STIBP) to add additional
+   isolation between CPU threads running on the same core.
+
+These CPU features may impact performance when used and can be enabled
+per process on a case-by-case base.
+
+The sysfs file showing Spectre variant 2 mitigation status is:
+
+   /sys/devices/system/cpu/vulnerabilities/spectre_v2
+
+The possible values in this file are:
+
+  - Kernel status:
+
+  ========================================  =================================
+  'Not affected'                            The processor is not vulnerable
+  'Mitigation: None'                        Vulnerable, no mitigation
+  'Mitigation: Retpolines'                  Use Retpoline thunks
+  'Mitigation: LFENCE'                      Use LFENCE instructions
+  'Mitigation: Enhanced IBRS'               Hardware-focused mitigation
+  'Mitigation: Enhanced IBRS + Retpolines'  Hardware-focused + Retpolines
+  'Mitigation: Enhanced IBRS + LFENCE'      Hardware-focused + LFENCE
+  ========================================  =================================
+
+  - Firmware status: Show if Indirect Branch Restricted Speculation (IBRS) is
+    used to protect against Spectre variant 2 attacks when calling firmware (x86 only).
+
+  ========== =============================================================
+  'IBRS_FW'  Protection against user program attacks when calling firmware
+  ========== =============================================================
+
+  - Indirect branch prediction barrier (IBPB) status for protection between
+    processes of different users. This feature can be controlled through
+    prctl() per process, or through kernel command line options. This is
+    an x86 only feature. For more details see below.
+
+  ===================   ========================================================
+  'IBPB: disabled'      IBPB unused
+  'IBPB: always-on'     Use IBPB on all tasks
+  'IBPB: conditional'   Use IBPB on SECCOMP or indirect branch restricted tasks
+  ===================   ========================================================
+
+  - Single threaded indirect branch prediction (STIBP) status for protection
+    between different hyper threads. This feature can be controlled through
+    prctl per process, or through kernel command line options. This is x86
+    only feature. For more details see below.
+
+  ====================  ========================================================
+  'STIBP: disabled'     STIBP unused
+  'STIBP: forced'       Use STIBP on all tasks
+  'STIBP: conditional'  Use STIBP on SECCOMP or indirect branch restricted tasks
+  ====================  ========================================================
+
+  - Return stack buffer (RSB) protection status:
+
+  =============   ===========================================
+  'RSB filling'   Protection of RSB on context switch enabled
+  =============   ===========================================
+
+Full mitigation might require a microcode update from the CPU
+vendor. When the necessary microcode is not available, the kernel will
+report vulnerability.
+
+Turning on mitigation for Spectre variant 1 and Spectre variant 2
+-----------------------------------------------------------------
+
+1. Kernel mitigation
+^^^^^^^^^^^^^^^^^^^^
+
+Spectre variant 1
+~~~~~~~~~~~~~~~~~
+
+   For the Spectre variant 1, vulnerable kernel code (as determined
+   by code audit or scanning tools) is annotated on a case by case
+   basis to use nospec accessor macros for bounds clipping :ref:`[2]
+   <spec_ref2>` to avoid any usable disclosure gadgets. However, it may
+   not cover all attack vectors for Spectre variant 1.
+
+   Copy-from-user code has an LFENCE barrier to prevent the access_ok()
+   check from being mis-speculated.  The barrier is done by the
+   barrier_nospec() macro.
+
+   For the swapgs variant of Spectre variant 1, LFENCE barriers are
+   added to interrupt, exception and NMI entry where needed.  These
+   barriers are done by the FENCE_SWAPGS_KERNEL_ENTRY and
+   FENCE_SWAPGS_USER_ENTRY macros.
+
+Spectre variant 2
+~~~~~~~~~~~~~~~~~
+
+   For Spectre variant 2 mitigation, the compiler turns indirect calls or
+   jumps in the kernel into equivalent return trampolines (retpolines)
+   :ref:`[3] <spec_ref3>` :ref:`[9] <spec_ref9>` to go to the target
+   addresses.  Speculative execution paths under retpolines are trapped
+   in an infinite loop to prevent any speculative execution jumping to
+   a gadget.
+
+   To turn on retpoline mitigation on a vulnerable CPU, the kernel
+   needs to be compiled with a gcc compiler that supports the
+   -mindirect-branch=thunk-extern -mindirect-branch-register options.
+   If the kernel is compiled with a Clang compiler, the compiler needs
+   to support -mretpoline-external-thunk option.  The kernel config
+   CONFIG_RETPOLINE needs to be turned on, and the CPU needs to run with
+   the latest updated microcode.
+
+   On Intel Skylake-era systems the mitigation covers most, but not all,
+   cases. See :ref:`[3] <spec_ref3>` for more details.
+
+   On CPUs with hardware mitigation for Spectre variant 2 (e.g. Enhanced
+   IBRS on x86), retpoline is automatically disabled at run time.
+
+   The retpoline mitigation is turned on by default on vulnerable
+   CPUs. It can be forced on or off by the administrator
+   via the kernel command line and sysfs control files. See
+   :ref:`spectre_mitigation_control_command_line`.
+
+   On x86, indirect branch restricted speculation is turned on by default
+   before invoking any firmware code to prevent Spectre variant 2 exploits
+   using the firmware.
+
+   Using kernel address space randomization (CONFIG_RANDOMIZE_BASE=y
+   and CONFIG_SLAB_FREELIST_RANDOM=y in the kernel configuration) makes
+   attacks on the kernel generally more difficult.
+
+2. User program mitigation
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+   User programs can mitigate Spectre variant 1 using LFENCE or "bounds
+   clipping". For more details see :ref:`[2] <spec_ref2>`.
+
+   For Spectre variant 2 mitigation, individual user programs
+   can be compiled with return trampolines for indirect branches.
+   This protects them from consuming poisoned entries in the branch
+   target buffer left by malicious software.  Alternatively, the
+   programs can disable their indirect branch speculation via prctl()
+   (See Documentation/spec_ctrl.txt).
+   On x86, this will turn on STIBP to guard against attacks from the
+   sibling thread when the user program is running, and use IBPB to
+   flush the branch target buffer when switching to/from the program.
+
+   Restricting indirect branch speculation on a user program will
+   also prevent the program from launching a variant 2 attack
+   on x86.  All sand-boxed SECCOMP programs have indirect branch
+   speculation restricted by default.  Administrators can change
+   that behavior via the kernel command line and sysfs control files.
+   See :ref:`spectre_mitigation_control_command_line`.
+
+   Programs that disable their indirect branch speculation will have
+   more overhead and run slower.
+
+   User programs should use address space randomization
+   (/proc/sys/kernel/randomize_va_space = 1 or 2) to make attacks more
+   difficult.
+
+3. VM mitigation
+^^^^^^^^^^^^^^^^
+
+   Within the kernel, Spectre variant 1 attacks from rogue guests are
+   mitigated on a case by case basis in VM exit paths. Vulnerable code
+   uses nospec accessor macros for "bounds clipping", to avoid any
+   usable disclosure gadgets.  However, this may not cover all variant
+   1 attack vectors.
+
+   For Spectre variant 2 attacks from rogue guests to the kernel, the
+   Linux kernel uses retpoline or Enhanced IBRS to prevent consumption of
+   poisoned entries in branch target buffer left by rogue guests.  It also
+   flushes the return stack buffer on every VM exit to prevent a return
+   stack buffer underflow so poisoned branch target buffer could be used,
+   or attacker guests leaving poisoned entries in the return stack buffer.
+
+   To mitigate guest-to-guest attacks in the same CPU hardware thread,
+   the branch target buffer is sanitized by flushing before switching
+   to a new guest on a CPU.
+
+   The above mitigations are turned on by default on vulnerable CPUs.
+
+   To mitigate guest-to-guest attacks from sibling thread when SMT is
+   in use, an untrusted guest running in the sibling thread can have
+   its indirect branch speculation disabled by administrator via prctl().
+
+   The kernel also allows guests to use any microcode based mitigation
+   they choose to use (such as IBPB or STIBP on x86) to protect themselves.
+
+.. _spectre_mitigation_control_command_line:
+
+Mitigation control on the kernel command line
+---------------------------------------------
+
+Spectre variant 2 mitigation can be disabled or force enabled at the
+kernel command line.
+
+	nospectre_v1
+
+		[X86,PPC] Disable mitigations for Spectre Variant 1
+		(bounds check bypass). With this option data leaks are
+		possible in the system.
+
+	nospectre_v2
+
+		[X86] Disable all mitigations for the Spectre variant 2
+		(indirect branch prediction) vulnerability. System may
+		allow data leaks with this option, which is equivalent
+		to spectre_v2=off.
+
+
+        spectre_v2=
+
+		[X86] Control mitigation of Spectre variant 2
+		(indirect branch speculation) vulnerability.
+		The default operation protects the kernel from
+		user space attacks.
+
+		on
+			unconditionally enable, implies
+			spectre_v2_user=on
+		off
+			unconditionally disable, implies
+		        spectre_v2_user=off
+		auto
+			kernel detects whether your CPU model is
+		        vulnerable
+
+		Selecting 'on' will, and 'auto' may, choose a
+		mitigation method at run time according to the
+		CPU, the available microcode, the setting of the
+		CONFIG_RETPOLINE configuration option, and the
+		compiler with which the kernel was built.
+
+		Selecting 'on' will also enable the mitigation
+		against user space to user space task attacks.
+
+		Selecting 'off' will disable both the kernel and
+		the user space protections.
+
+		Specific mitigations can also be selected manually:
+
+                retpoline               auto pick between generic,lfence
+                retpoline,generic       Retpolines
+                retpoline,lfence        LFENCE; indirect branch
+                retpoline,amd           alias for retpoline,lfence
+                eibrs                   enhanced IBRS
+                eibrs,retpoline         enhanced IBRS + Retpolines
+                eibrs,lfence            enhanced IBRS + LFENCE
+
+		Not specifying this option is equivalent to
+		spectre_v2=auto.
+
+For user space mitigation:
+
+        spectre_v2_user=
+
+		[X86] Control mitigation of Spectre variant 2
+		(indirect branch speculation) vulnerability between
+		user space tasks
+
+		on
+			Unconditionally enable mitigations. Is
+			enforced by spectre_v2=on
+
+		off
+			Unconditionally disable mitigations. Is
+			enforced by spectre_v2=off
+
+		prctl
+			Indirect branch speculation is enabled,
+			but mitigation can be enabled via prctl
+			per thread. The mitigation control state
+			is inherited on fork.
+
+		prctl,ibpb
+			Like "prctl" above, but only STIBP is
+			controlled per thread. IBPB is issued
+			always when switching between different user
+			space processes.
+
+		seccomp
+			Same as "prctl" above, but all seccomp
+			threads will enable the mitigation unless
+			they explicitly opt out.
+
+		seccomp,ibpb
+			Like "seccomp" above, but only STIBP is
+			controlled per thread. IBPB is issued
+			always when switching between different
+			user space processes.
+
+		auto
+			Kernel selects the mitigation depending on
+			the available CPU features and vulnerability.
+
+		Default mitigation:
+		If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl"
+
+		Not specifying this option is equivalent to
+		spectre_v2_user=auto.
+
+		In general the kernel by default selects
+		reasonable mitigations for the current CPU. To
+		disable Spectre variant 2 mitigations, boot with
+		spectre_v2=off. Spectre variant 1 mitigations
+		cannot be disabled.
+
+Mitigation selection guide
+--------------------------
+
+1. Trusted userspace
+^^^^^^^^^^^^^^^^^^^^
+
+   If all userspace applications are from trusted sources and do not
+   execute externally supplied untrusted code, then the mitigations can
+   be disabled.
+
+2. Protect sensitive programs
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+   For security-sensitive programs that have secrets (e.g. crypto
+   keys), protection against Spectre variant 2 can be put in place by
+   disabling indirect branch speculation when the program is running
+   (See Documentation/spec_ctrl.txt).
+
+3. Sandbox untrusted programs
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+   Untrusted programs that could be a source of attacks can be cordoned
+   off by disabling their indirect branch speculation when they are run
+   (See Documentation/spec_ctrl.txt).
+   This prevents untrusted programs from polluting the branch target
+   buffer.  All programs running in SECCOMP sandboxes have indirect
+   branch speculation restricted by default. This behavior can be
+   changed via the kernel command line and sysfs control files. See
+   :ref:`spectre_mitigation_control_command_line`.
+
+3. High security mode
+^^^^^^^^^^^^^^^^^^^^^
+
+   All Spectre variant 2 mitigations can be forced on
+   at boot time for all programs (See the "on" option in
+   :ref:`spectre_mitigation_control_command_line`).  This will add
+   overhead as indirect branch speculations for all programs will be
+   restricted.
+
+   On x86, branch target buffer will be flushed with IBPB when switching
+   to a new program. STIBP is left on all the time to protect programs
+   against variant 2 attacks originating from programs running on
+   sibling threads.
+
+   Alternatively, STIBP can be used only when running programs
+   whose indirect branch speculation is explicitly disabled,
+   while IBPB is still used all the time when switching to a new
+   program to clear the branch target buffer (See "ibpb" option in
+   :ref:`spectre_mitigation_control_command_line`).  This "ibpb" option
+   has less performance cost than the "on" option, which leaves STIBP
+   on all the time.
+
+References on Spectre
+---------------------
+
+Intel white papers:
+
+.. _spec_ref1:
+
+[1] `Intel analysis of speculative execution side channels <https://newsroom.intel.com/wp-content/uploads/sites/11/2018/01/Intel-Analysis-of-Speculative-Execution-Side-Channels.pdf>`_.
+
+.. _spec_ref2:
+
+[2] `Bounds check bypass <https://software.intel.com/security-software-guidance/software-guidance/bounds-check-bypass>`_.
+
+.. _spec_ref3:
+
+[3] `Deep dive: Retpoline: A branch target injection mitigation <https://software.intel.com/security-software-guidance/insights/deep-dive-retpoline-branch-target-injection-mitigation>`_.
+
+.. _spec_ref4:
+
+[4] `Deep Dive: Single Thread Indirect Branch Predictors <https://software.intel.com/security-software-guidance/insights/deep-dive-single-thread-indirect-branch-predictors>`_.
+
+AMD white papers:
+
+.. _spec_ref5:
+
+[5] `AMD64 technology indirect branch control extension <https://developer.amd.com/wp-content/resources/Architecture_Guidelines_Update_Indirect_Branch_Control.pdf>`_.
+
+.. _spec_ref6:
+
+[6] `Software techniques for managing speculation on AMD processors <https://developer.amd.com/wp-content/resources/Managing-Speculation-on-AMD-Processors.pdf>`_.
+
+ARM white papers:
+
+.. _spec_ref7:
+
+[7] `Cache speculation side-channels <https://developer.arm.com/support/arm-security-updates/speculative-processor-vulnerability/download-the-whitepaper>`_.
+
+.. _spec_ref8:
+
+[8] `Cache speculation issues update <https://developer.arm.com/support/arm-security-updates/speculative-processor-vulnerability/latest-updates/cache-speculation-issues-update>`_.
+
+Google white paper:
+
+.. _spec_ref9:
+
+[9] `Retpoline: a software construct for preventing branch-target-injection <https://support.google.com/faqs/answer/7625886>`_.
+
+MIPS white paper:
+
+.. _spec_ref10:
+
+[10] `MIPS: response on speculative execution and side channel vulnerabilities <https://www.mips.com/blog/mips-response-on-speculative-execution-and-side-channel-vulnerabilities/>`_.
+
+Academic papers:
+
+.. _spec_ref11:
+
+[11] `Spectre Attacks: Exploiting Speculative Execution <https://spectreattack.com/spectre.pdf>`_.
+
+.. _spec_ref12:
+
+[12] `NetSpectre: Read Arbitrary Memory over Network <https://arxiv.org/abs/1807.10535>`_.
+
+.. _spec_ref13:
+
+[13] `Spectre Returns! Speculation Attacks using the Return Stack Buffer <https://www.usenix.org/system/files/conference/woot18/woot18-paper-koruyeh.pdf>`_.
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@ -4198,8 +4198,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			Specific mitigations can also be selected manually:

 			retpoline	  - replace indirect branches
-			retpoline,generic - google's original retpoline
-			retpoline,amd     - AMD-specific minimal thunk
+			retpoline,generic - Retpolines
+			retpoline,lfence  - LFENCE; indirect branch
+			retpoline,amd     - alias for retpoline,lfence
+			eibrs		  - enhanced IBRS
+			eibrs,retpoline   - enhanced IBRS + Retpolines
+			eibrs,lfence      - enhanced IBRS + LFENCE

 			Not specifying this option is equivalent to
 			spectre_v2=auto.
--- a/2
+++ b/2
@ -1,6 +1,6 @@
 VERSION = 4
 PATCHLEVEL = 9
-SUBLEVEL = 305
+SUBLEVEL = 306
 EXTRAVERSION =
 NAME = Roaring Lionus

--- a/arch/arm/include/asm/assembler.h
+++ b/arch/arm/include/asm/assembler.h
@ -108,6 +108,16 @@
 	.endm
 #endif

+#if __LINUX_ARM_ARCH__ < 7
+	.macro	dsb, args
+	mcr	p15, 0, r0, c7, c10, 4
+	.endm
+
+	.macro	isb, args
+	mcr	p15, 0, r0, c7, c5, 4
+	.endm
+#endif
+
 	.macro asm_trace_hardirqs_off, save=1
 #if defined(CONFIG_TRACE_IRQFLAGS)
 	.if \save
--- a/arch/arm/include/asm/spectre.h
+++ b/arch/arm/include/asm/spectre.h
@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef __ASM_SPECTRE_H
+#define __ASM_SPECTRE_H
+
+enum {
+	SPECTRE_UNAFFECTED,
+	SPECTRE_MITIGATED,
+	SPECTRE_VULNERABLE,
+};
+
+enum {
+	__SPECTRE_V2_METHOD_BPIALL,
+	__SPECTRE_V2_METHOD_ICIALLU,
+	__SPECTRE_V2_METHOD_SMC,
+	__SPECTRE_V2_METHOD_HVC,
+	__SPECTRE_V2_METHOD_LOOP8,
+};
+
+enum {
+	SPECTRE_V2_METHOD_BPIALL = BIT(__SPECTRE_V2_METHOD_BPIALL),
+	SPECTRE_V2_METHOD_ICIALLU = BIT(__SPECTRE_V2_METHOD_ICIALLU),
+	SPECTRE_V2_METHOD_SMC = BIT(__SPECTRE_V2_METHOD_SMC),
+	SPECTRE_V2_METHOD_HVC = BIT(__SPECTRE_V2_METHOD_HVC),
+	SPECTRE_V2_METHOD_LOOP8 = BIT(__SPECTRE_V2_METHOD_LOOP8),
+};
+
+void spectre_v2_update_state(unsigned int state, unsigned int methods);
+
+int spectre_bhb_update_vectors(unsigned int method);
+
+#endif
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@ -100,4 +100,6 @@ endif

 obj-$(CONFIG_HAVE_ARM_SMCCC)	+= smccc-call.o

+obj-$(CONFIG_GENERIC_CPU_VULNERABILITIES) += spectre.o
+
 extra-y := $(head-y) vmlinux.lds
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@ -1036,12 +1036,11 @@ vector_\name:
 	sub	lr, lr, #\correction
 	.endif

-	@
-	@ Save r0, lr_<exception> (parent PC) and spsr_<exception>
-	@ (parent CPSR)
-	@
+	@ Save r0, lr_<exception> (parent PC)
 	stmia	sp, {r0, lr}		@ save r0, lr
-	mrs	lr, spsr
+
+	@ Save spsr_<exception> (parent CPSR)
+2:	mrs	lr, spsr
 	str	lr, [sp, #8]		@ save spsr

 	@
@ -1062,6 +1061,44 @@ vector_\name:
 	movs	pc, lr			@ branch to handler in SVC mode
 ENDPROC(vector_\name)

+#ifdef CONFIG_HARDEN_BRANCH_HISTORY
+	.subsection 1
+	.align 5
+vector_bhb_loop8_\name:
+	.if \correction
+	sub	lr, lr, #\correction
+	.endif
+
+	@ Save r0, lr_<exception> (parent PC)
+	stmia	sp, {r0, lr}
+
+	@ bhb workaround
+	mov	r0, #8
+1:	b	. + 4
+	subs	r0, r0, #1
+	bne	1b
+	dsb
+	isb
+	b	2b
+ENDPROC(vector_bhb_loop8_\name)
+
+vector_bhb_bpiall_\name:
+	.if \correction
+	sub	lr, lr, #\correction
+	.endif
+
+	@ Save r0, lr_<exception> (parent PC)
+	stmia	sp, {r0, lr}
+
+	@ bhb workaround
+	mcr	p15, 0, r0, c7, c5, 6	@ BPIALL
+	@ isb not needed due to "movs pc, lr" in the vector stub
+	@ which gives a "context synchronisation".
+	b	2b
+ENDPROC(vector_bhb_bpiall_\name)
+	.previous
+#endif
+
 	.align	2
 	@ handler addresses follow this label
 1:
@ -1070,6 +1107,10 @@ ENDPROC(vector_\name)
 	.section .stubs, "ax", %progbits
 	@ This must be the first word
 	.word	vector_swi
+#ifdef CONFIG_HARDEN_BRANCH_HISTORY
+	.word	vector_bhb_loop8_swi
+	.word	vector_bhb_bpiall_swi
+#endif

 vector_rst:
 ARM(	swi	SYS_ERROR0	)
@ -1184,8 +1225,10 @@ vector_addrexcptn:
 * FIQ "NMI" handler
 *-----------------------------------------------------------------------------
 * Handle a FIQ using the SVC stack allowing FIQ act like NMI on x86
- * systems.
+ * systems. This must be the last vector stub, so lets place it in its own
+ * subsection.
 */
+	.subsection 2
 	vector_stub	fiq, FIQ_MODE, 4

 	.long	__fiq_usr			@  0  (USR_26 / USR_32)
@ -1218,6 +1261,30 @@ vector_addrexcptn:
 	W(b)	vector_irq
 	W(b)	vector_fiq

+#ifdef CONFIG_HARDEN_BRANCH_HISTORY
+	.section .vectors.bhb.loop8, "ax", %progbits
+.L__vectors_bhb_loop8_start:
+	W(b)	vector_rst
+	W(b)	vector_bhb_loop8_und
+	W(ldr)	pc, .L__vectors_bhb_loop8_start + 0x1004
+	W(b)	vector_bhb_loop8_pabt
+	W(b)	vector_bhb_loop8_dabt
+	W(b)	vector_addrexcptn
+	W(b)	vector_bhb_loop8_irq
+	W(b)	vector_bhb_loop8_fiq
+
+	.section .vectors.bhb.bpiall, "ax", %progbits
+.L__vectors_bhb_bpiall_start:
+	W(b)	vector_rst
+	W(b)	vector_bhb_bpiall_und
+	W(ldr)	pc, .L__vectors_bhb_bpiall_start + 0x1008
+	W(b)	vector_bhb_bpiall_pabt
+	W(b)	vector_bhb_bpiall_dabt
+	W(b)	vector_addrexcptn
+	W(b)	vector_bhb_bpiall_irq
+	W(b)	vector_bhb_bpiall_fiq
+#endif
+
 	.data

 	.globl	cr_alignment
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@ -152,6 +152,29 @@ ENDPROC(ret_from_fork)
 *-----------------------------------------------------------------------------
 */

+	.align	5
+#ifdef CONFIG_HARDEN_BRANCH_HISTORY
+ENTRY(vector_bhb_loop8_swi)
+	sub	sp, sp, #PT_REGS_SIZE
+	stmia	sp, {r0 - r12}
+	mov	r8, #8
+1:	b	2f
+2:	subs	r8, r8, #1
+	bne	1b
+	dsb
+	isb
+	b	3f
+ENDPROC(vector_bhb_loop8_swi)
+
+	.align	5
+ENTRY(vector_bhb_bpiall_swi)
+	sub	sp, sp, #PT_REGS_SIZE
+	stmia	sp, {r0 - r12}
+	mcr	p15, 0, r8, c7, c5, 6	@ BPIALL
+	isb
+	b	3f
+ENDPROC(vector_bhb_bpiall_swi)
+#endif
 	.align	5
 ENTRY(vector_swi)
 #ifdef CONFIG_CPU_V7M
@ -159,6 +182,7 @@ ENTRY(vector_swi)
 #else
 	sub	sp, sp, #PT_REGS_SIZE
 	stmia	sp, {r0 - r12}			@ Calling r0 - r12
+3:
 ARM(	add	r8, sp, #S_PC		)
 ARM(	stmdb	r8, {sp, lr}^		)	@ Calling sp, lr
 THUMB(	mov	r8, sp			)
--- a/arch/arm/kernel/spectre.c
+++ b/arch/arm/kernel/spectre.c
@ -0,0 +1,71 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/bpf.h>
+#include <linux/cpu.h>
+#include <linux/device.h>
+
+#include <asm/spectre.h>
+
+static bool _unprivileged_ebpf_enabled(void)
+{
+#ifdef CONFIG_BPF_SYSCALL
+	return !sysctl_unprivileged_bpf_disabled;
+#else
+	return false;
+#endif
+}
+
+ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr,
+			    char *buf)
+{
+	return sprintf(buf, "Mitigation: __user pointer sanitization\n");
+}
+
+static unsigned int spectre_v2_state;
+static unsigned int spectre_v2_methods;
+
+void spectre_v2_update_state(unsigned int state, unsigned int method)
+{
+	if (state > spectre_v2_state)
+		spectre_v2_state = state;
+	spectre_v2_methods |= method;
+}
+
+ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr,
+			    char *buf)
+{
+	const char *method;
+
+	if (spectre_v2_state == SPECTRE_UNAFFECTED)
+		return sprintf(buf, "%s\n", "Not affected");
+
+	if (spectre_v2_state != SPECTRE_MITIGATED)
+		return sprintf(buf, "%s\n", "Vulnerable");
+
+	if (_unprivileged_ebpf_enabled())
+		return sprintf(buf, "Vulnerable: Unprivileged eBPF enabled\n");
+
+	switch (spectre_v2_methods) {
+	case SPECTRE_V2_METHOD_BPIALL:
+		method = "Branch predictor hardening";
+		break;
+
+	case SPECTRE_V2_METHOD_ICIALLU:
+		method = "I-cache invalidation";
+		break;
+
+	case SPECTRE_V2_METHOD_SMC:
+	case SPECTRE_V2_METHOD_HVC:
+		method = "Firmware call";
+		break;
+
+	case SPECTRE_V2_METHOD_LOOP8:
+		method = "History overwrite";
+		break;
+
+	default:
+		method = "Multiple mitigations";
+		break;
+	}
+
+	return sprintf(buf, "Mitigation: %s\n", method);
+}
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@ -31,6 +31,7 @@
 #include <linux/atomic.h>
 #include <asm/cacheflush.h>
 #include <asm/exception.h>
+#include <asm/spectre.h>
 #include <asm/unistd.h>
 #include <asm/traps.h>
 #include <asm/ptrace.h>
@ -819,10 +820,59 @@ static inline void __init kuser_init(void *vectors)
 }
 #endif

+#ifndef CONFIG_CPU_V7M
+static void copy_from_lma(void *vma, void *lma_start, void *lma_end)
+{
+	memcpy(vma, lma_start, lma_end - lma_start);
+}
+
+static void flush_vectors(void *vma, size_t offset, size_t size)
+{
+	unsigned long start = (unsigned long)vma + offset;
+	unsigned long end = start + size;
+
+	flush_icache_range(start, end);
+}
+
+#ifdef CONFIG_HARDEN_BRANCH_HISTORY
+int spectre_bhb_update_vectors(unsigned int method)
+{
+	extern char __vectors_bhb_bpiall_start[], __vectors_bhb_bpiall_end[];
+	extern char __vectors_bhb_loop8_start[], __vectors_bhb_loop8_end[];
+	void *vec_start, *vec_end;
+
+	if (system_state >= SYSTEM_RUNNING) {
+		pr_err("CPU%u: Spectre BHB workaround too late - system vulnerable\n",
+		       smp_processor_id());
+		return SPECTRE_VULNERABLE;
+	}
+
+	switch (method) {
+	case SPECTRE_V2_METHOD_LOOP8:
+		vec_start = __vectors_bhb_loop8_start;
+		vec_end = __vectors_bhb_loop8_end;
+		break;
+
+	case SPECTRE_V2_METHOD_BPIALL:
+		vec_start = __vectors_bhb_bpiall_start;
+		vec_end = __vectors_bhb_bpiall_end;
+		break;
+
+	default:
+		pr_err("CPU%u: unknown Spectre BHB state %d\n",
+		       smp_processor_id(), method);
+		return SPECTRE_VULNERABLE;
+	}
+
+	copy_from_lma(vectors_page, vec_start, vec_end);
+	flush_vectors(vectors_page, 0, vec_end - vec_start);
+
+	return SPECTRE_MITIGATED;
+}
+#endif
+
 void __init early_trap_init(void *vectors_base)
 {
-#ifndef CONFIG_CPU_V7M
-	unsigned long vectors = (unsigned long)vectors_base;
 	extern char __stubs_start[], __stubs_end[];
 	extern char __vectors_start[], __vectors_end[];
 	unsigned i;
@ -843,17 +893,20 @@ void __init early_trap_init(void *vectors_base)
 	 * into the vector page, mapped at 0xffff0000, and ensure these
 	 * are visible to the instruction stream.
 	 */
-	memcpy((void *)vectors, __vectors_start, __vectors_end - __vectors_start);
-	memcpy((void *)vectors + 0x1000, __stubs_start, __stubs_end - __stubs_start);
+	copy_from_lma(vectors_base, __vectors_start, __vectors_end);
+	copy_from_lma(vectors_base + 0x1000, __stubs_start, __stubs_end);

 	kuser_init(vectors_base);

-	flush_icache_range(vectors, vectors + PAGE_SIZE * 2);
+	flush_vectors(vectors_base, 0, PAGE_SIZE * 2);
+}
 #else /* ifndef CONFIG_CPU_V7M */
+void __init early_trap_init(void *vectors_base)
+{
 	/*
 	 * on V7-M there is no need to copy the vector table to a dedicated
 	 * memory area. The address is configurable and so a table in the kernel
 	 * image can be used.
 	 */
-#endif
 }
+#endif
--- a/arch/arm/kernel/vmlinux-xip.lds.S
+++ b/arch/arm/kernel/vmlinux-xip.lds.S
@ -12,6 +12,19 @@
 #include <asm/memory.h>
 #include <asm/page.h>

+/*
+ * ld.lld does not support NOCROSSREFS:
+ * https://github.com/ClangBuiltLinux/linux/issues/1609
+ */
+#ifdef CONFIG_LD_IS_LLD
+#define NOCROSSREFS
+#endif
+
+/* Set start/end symbol names to the LMA for the section */
+#define ARM_LMA(sym, section)						\
+	sym##_start = LOADADDR(section);				\
+	sym##_end = LOADADDR(section) + SIZEOF(section)
+
 #define PROC_INFO							\
 	. = ALIGN(4);							\
 	VMLINUX_SYMBOL(__proc_info_begin) = .;				\
@ -148,19 +161,31 @@ SECTIONS
 	 * The vectors and stubs are relocatable code, and the
 	 * only thing that matters is their relative offsets
 	 */
-	__vectors_start = .;
-	.vectors 0xffff0000 : AT(__vectors_start) {
-		*(.vectors)
+	__vectors_lma = .;
+	OVERLAY 0xffff0000 : NOCROSSREFS AT(__vectors_lma) {
+		.vectors {
+			*(.vectors)
+		}
+		.vectors.bhb.loop8 {
+			*(.vectors.bhb.loop8)
+		}
+		.vectors.bhb.bpiall {
+			*(.vectors.bhb.bpiall)
+		}
 	}
-	. = __vectors_start + SIZEOF(.vectors);
-	__vectors_end = .;
+	ARM_LMA(__vectors, .vectors);
+	ARM_LMA(__vectors_bhb_loop8, .vectors.bhb.loop8);
+	ARM_LMA(__vectors_bhb_bpiall, .vectors.bhb.bpiall);
+	. = __vectors_lma + SIZEOF(.vectors) +
+		SIZEOF(.vectors.bhb.loop8) +
+		SIZEOF(.vectors.bhb.bpiall);

-	__stubs_start = .;
-	.stubs ADDR(.vectors) + 0x1000 : AT(__stubs_start) {
+	__stubs_lma = .;
+	.stubs ADDR(.vectors) + 0x1000 : AT(__stubs_lma) {
 		*(.stubs)
 	}
-	. = __stubs_start + SIZEOF(.stubs);
-	__stubs_end = .;
+	ARM_LMA(__stubs, .stubs);
+	. = __stubs_lma + SIZEOF(.stubs);

 	PROVIDE(vector_fiq_offset = vector_fiq - ADDR(.vectors));

--- a/arch/arm/kernel/vmlinux.lds.S
+++ b/arch/arm/kernel/vmlinux.lds.S
@ -14,6 +14,19 @@
 #include <asm/page.h>
 #include <asm/pgtable.h>

+/*
+ * ld.lld does not support NOCROSSREFS:
+ * https://github.com/ClangBuiltLinux/linux/issues/1609
+ */
+#ifdef CONFIG_LD_IS_LLD
+#define NOCROSSREFS
+#endif
+
+/* Set start/end symbol names to the LMA for the section */
+#define ARM_LMA(sym, section)						\
+	sym##_start = LOADADDR(section);				\
+	sym##_end = LOADADDR(section) + SIZEOF(section)
+
 #define PROC_INFO							\
 	. = ALIGN(4);							\
 	VMLINUX_SYMBOL(__proc_info_begin) = .;				\
@ -169,19 +182,31 @@ SECTIONS
 	 * The vectors and stubs are relocatable code, and the
 	 * only thing that matters is their relative offsets
 	 */
-	__vectors_start = .;
-	.vectors 0xffff0000 : AT(__vectors_start) {
-		*(.vectors)
+	__vectors_lma = .;
+	OVERLAY 0xffff0000 : NOCROSSREFS AT(__vectors_lma) {
+		.vectors {
+			*(.vectors)
+		}
+		.vectors.bhb.loop8 {
+			*(.vectors.bhb.loop8)
+		}
+		.vectors.bhb.bpiall {
+			*(.vectors.bhb.bpiall)
+		}
 	}
-	. = __vectors_start + SIZEOF(.vectors);
-	__vectors_end = .;
+	ARM_LMA(__vectors, .vectors);
+	ARM_LMA(__vectors_bhb_loop8, .vectors.bhb.loop8);
+	ARM_LMA(__vectors_bhb_bpiall, .vectors.bhb.bpiall);
+	. = __vectors_lma + SIZEOF(.vectors) +
+		SIZEOF(.vectors.bhb.loop8) +
+		SIZEOF(.vectors.bhb.bpiall);

-	__stubs_start = .;
-	.stubs ADDR(.vectors) + 0x1000 : AT(__stubs_start) {
+	__stubs_lma = .;
+	.stubs ADDR(.vectors) + 0x1000 : AT(__stubs_lma) {
 		*(.stubs)
 	}
-	. = __stubs_start + SIZEOF(.stubs);
-	__stubs_end = .;
+	ARM_LMA(__stubs, .stubs);
+	. = __stubs_lma + SIZEOF(.stubs);

 	PROVIDE(vector_fiq_offset = vector_fiq - ADDR(.vectors));

--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@ -803,6 +803,7 @@ config CPU_BPREDICT_DISABLE

 config CPU_SPECTRE
 	bool
+	select GENERIC_CPU_VULNERABILITIES

 config HARDEN_BRANCH_PREDICTOR
 	bool "Harden the branch predictor against aliasing attacks" if EXPERT
@ -823,6 +824,16 @@ config HARDEN_BRANCH_PREDICTOR

 	   If unsure, say Y.

+config HARDEN_BRANCH_HISTORY
+	bool "Harden Spectre style attacks against branch history" if EXPERT
+	depends on CPU_SPECTRE
+	default y
+	help
+	  Speculation attacks against some high-performance processors can
+	  make use of branch history to influence future speculation. When
+	  taking an exception, a sequence of branches overwrites the branch
+	  history, or branch history is invalidated.
+
 config TLS_REG_EMUL
 	bool
 	select NEED_KUSER_HELPERS
--- a/arch/arm/mm/proc-v7-bugs.c
+++ b/arch/arm/mm/proc-v7-bugs.c
@ -7,8 +7,36 @@
 #include <asm/cp15.h>
 #include <asm/cputype.h>
 #include <asm/proc-fns.h>
+#include <asm/spectre.h>
 #include <asm/system_misc.h>

+#ifdef CONFIG_ARM_PSCI
+#define SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED	1
+static int __maybe_unused spectre_v2_get_cpu_fw_mitigation_state(void)
+{
+	struct arm_smccc_res res;
+
+	arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
+			     ARM_SMCCC_ARCH_WORKAROUND_1, &res);
+
+	switch ((int)res.a0) {
+	case SMCCC_RET_SUCCESS:
+		return SPECTRE_MITIGATED;
+
+	case SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED:
+		return SPECTRE_UNAFFECTED;
+
+	default:
+		return SPECTRE_VULNERABLE;
+	}
+}
+#else
+static int __maybe_unused spectre_v2_get_cpu_fw_mitigation_state(void)
+{
+	return SPECTRE_VULNERABLE;
+}
+#endif
+
 #ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
 DEFINE_PER_CPU(harden_branch_predictor_fn_t, harden_branch_predictor_fn);

@ -37,13 +65,61 @@ static void __maybe_unused call_hvc_arch_workaround_1(void)
 	arm_smccc_1_1_hvc(ARM_SMCCC_ARCH_WORKAROUND_1, NULL);
 }

-static void cpu_v7_spectre_init(void)
+static unsigned int spectre_v2_install_workaround(unsigned int method)
 {
 	const char *spectre_v2_method = NULL;
 	int cpu = smp_processor_id();

 	if (per_cpu(harden_branch_predictor_fn, cpu))
-		return;
+		return SPECTRE_MITIGATED;
+
+	switch (method) {
+	case SPECTRE_V2_METHOD_BPIALL:
+		per_cpu(harden_branch_predictor_fn, cpu) =
+			harden_branch_predictor_bpiall;
+		spectre_v2_method = "BPIALL";
+		break;
+
+	case SPECTRE_V2_METHOD_ICIALLU:
+		per_cpu(harden_branch_predictor_fn, cpu) =
+			harden_branch_predictor_iciallu;
+		spectre_v2_method = "ICIALLU";
+		break;
+
+	case SPECTRE_V2_METHOD_HVC:
+		per_cpu(harden_branch_predictor_fn, cpu) =
+			call_hvc_arch_workaround_1;
+		cpu_do_switch_mm = cpu_v7_hvc_switch_mm;
+		spectre_v2_method = "hypervisor";
+		break;
+
+	case SPECTRE_V2_METHOD_SMC:
+		per_cpu(harden_branch_predictor_fn, cpu) =
+			call_smc_arch_workaround_1;
+		cpu_do_switch_mm = cpu_v7_smc_switch_mm;
+		spectre_v2_method = "firmware";
+		break;
+	}
+
+	if (spectre_v2_method)
+		pr_info("CPU%u: Spectre v2: using %s workaround\n",
+			smp_processor_id(), spectre_v2_method);
+
+	return SPECTRE_MITIGATED;
+}
+#else
+static unsigned int spectre_v2_install_workaround(unsigned int method)
+{
+	pr_info("CPU%u: Spectre V2: workarounds disabled by configuration\n",
+		smp_processor_id());
+
+	return SPECTRE_VULNERABLE;
+}
+#endif
+
+static void cpu_v7_spectre_v2_init(void)
+{
+	unsigned int state, method = 0;

 	switch (read_cpuid_part()) {
 	case ARM_CPU_PART_CORTEX_A8:
@ -52,29 +128,32 @@ static void cpu_v7_spectre_init(void)
 	case ARM_CPU_PART_CORTEX_A17:
 	case ARM_CPU_PART_CORTEX_A73:
 	case ARM_CPU_PART_CORTEX_A75:
-		per_cpu(harden_branch_predictor_fn, cpu) =
-			harden_branch_predictor_bpiall;
-		spectre_v2_method = "BPIALL";
+		state = SPECTRE_MITIGATED;
+		method = SPECTRE_V2_METHOD_BPIALL;
 		break;

 	case ARM_CPU_PART_CORTEX_A15:
 	case ARM_CPU_PART_BRAHMA_B15:
-		per_cpu(harden_branch_predictor_fn, cpu) =
-			harden_branch_predictor_iciallu;
-		spectre_v2_method = "ICIALLU";
+		state = SPECTRE_MITIGATED;
+		method = SPECTRE_V2_METHOD_ICIALLU;
 		break;

-#ifdef CONFIG_ARM_PSCI
 	default:
 		/* Other ARM CPUs require no workaround */
-		if (read_cpuid_implementor() == ARM_CPU_IMP_ARM)
+		if (read_cpuid_implementor() == ARM_CPU_IMP_ARM) {
+			state = SPECTRE_UNAFFECTED;
 			break;
+		}
 		/* fallthrough */
-		/* Cortex A57/A72 require firmware workaround */
+	/* Cortex A57/A72 require firmware workaround */
 	case ARM_CPU_PART_CORTEX_A57:
 	case ARM_CPU_PART_CORTEX_A72: {
 		struct arm_smccc_res res;

+		state = spectre_v2_get_cpu_fw_mitigation_state();
+		if (state != SPECTRE_MITIGATED)
+			break;
+
 		if (psci_ops.smccc_version == SMCCC_VERSION_1_0)
 			break;

@ -84,10 +163,7 @@ static void cpu_v7_spectre_init(void)
 					  ARM_SMCCC_ARCH_WORKAROUND_1, &res);
 			if ((int)res.a0 != 0)
 				break;
-			per_cpu(harden_branch_predictor_fn, cpu) =
-				call_hvc_arch_workaround_1;
-			cpu_do_switch_mm = cpu_v7_hvc_switch_mm;
-			spectre_v2_method = "hypervisor";
+			method = SPECTRE_V2_METHOD_HVC;
 			break;

 		case PSCI_CONDUIT_SMC:
@ -95,29 +171,97 @@ static void cpu_v7_spectre_init(void)
 					  ARM_SMCCC_ARCH_WORKAROUND_1, &res);
 			if ((int)res.a0 != 0)
 				break;
-			per_cpu(harden_branch_predictor_fn, cpu) =
-				call_smc_arch_workaround_1;
-			cpu_do_switch_mm = cpu_v7_smc_switch_mm;
-			spectre_v2_method = "firmware";
+			method = SPECTRE_V2_METHOD_SMC;
 			break;

 		default:
+			state = SPECTRE_VULNERABLE;
 			break;
 		}
 	}
-#endif
 	}

-	if (spectre_v2_method)
-		pr_info("CPU%u: Spectre v2: using %s workaround\n",
-			smp_processor_id(), spectre_v2_method);
+	if (state == SPECTRE_MITIGATED)
+		state = spectre_v2_install_workaround(method);
+
+	spectre_v2_update_state(state, method);
+}
+
+#ifdef CONFIG_HARDEN_BRANCH_HISTORY
+static int spectre_bhb_method;
+
+static const char *spectre_bhb_method_name(int method)
+{
+	switch (method) {
+	case SPECTRE_V2_METHOD_LOOP8:
+		return "loop";
+
+	case SPECTRE_V2_METHOD_BPIALL:
+		return "BPIALL";
+
+	default:
+		return "unknown";
+	}
+}
+
+static int spectre_bhb_install_workaround(int method)
+{
+	if (spectre_bhb_method != method) {
+		if (spectre_bhb_method) {
+			pr_err("CPU%u: Spectre BHB: method disagreement, system vulnerable\n",
+			       smp_processor_id());
+
+			return SPECTRE_VULNERABLE;
+		}
+
+		if (spectre_bhb_update_vectors(method) == SPECTRE_VULNERABLE)
+			return SPECTRE_VULNERABLE;
+
+		spectre_bhb_method = method;
+	}
+
+	pr_info("CPU%u: Spectre BHB: using %s workaround\n",
+		smp_processor_id(), spectre_bhb_method_name(method));
+
+	return SPECTRE_MITIGATED;
 }
 #else
-static void cpu_v7_spectre_init(void)
+static int spectre_bhb_install_workaround(int method)
 {
+	return SPECTRE_VULNERABLE;
 }
 #endif

+static void cpu_v7_spectre_bhb_init(void)
+{
+	unsigned int state, method = 0;
+
+	switch (read_cpuid_part()) {
+	case ARM_CPU_PART_CORTEX_A15:
+	case ARM_CPU_PART_BRAHMA_B15:
+	case ARM_CPU_PART_CORTEX_A57:
+	case ARM_CPU_PART_CORTEX_A72:
+		state = SPECTRE_MITIGATED;
+		method = SPECTRE_V2_METHOD_LOOP8;
+		break;
+
+	case ARM_CPU_PART_CORTEX_A73:
+	case ARM_CPU_PART_CORTEX_A75:
+		state = SPECTRE_MITIGATED;
+		method = SPECTRE_V2_METHOD_BPIALL;
+		break;
+
+	default:
+		state = SPECTRE_UNAFFECTED;
+		break;
+	}
+
+	if (state == SPECTRE_MITIGATED)
+		state = spectre_bhb_install_workaround(method);
+
+	spectre_v2_update_state(state, method);
+}
+
 static __maybe_unused bool cpu_v7_check_auxcr_set(bool *warned,
 						  u32 mask, const char *msg)
 {
@ -146,16 +290,17 @@ static bool check_spectre_auxcr(bool *warned, u32 bit)
 void cpu_v7_ca8_ibe(void)
 {
 	if (check_spectre_auxcr(this_cpu_ptr(&spectre_warned), BIT(6)))
-		cpu_v7_spectre_init();
+		cpu_v7_spectre_v2_init();
 }

 void cpu_v7_ca15_ibe(void)
 {
 	if (check_spectre_auxcr(this_cpu_ptr(&spectre_warned), BIT(0)))
-		cpu_v7_spectre_init();
+		cpu_v7_spectre_v2_init();
 }

 void cpu_v7_bugs_init(void)
 {
-	cpu_v7_spectre_init();
+	cpu_v7_spectre_v2_init();
+	cpu_v7_spectre_bhb_init();
 }
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@ -417,10 +417,6 @@ config RETPOLINE
 	  branches. Requires a compiler with -mindirect-branch=thunk-extern
 	  support for full protection. The kernel may run slower.

-	  Without compiler support, at least indirect branches in assembler
-	  code are eliminated. Since this includes the syscall entry path,
-	  it is not entirely pointless.
-
 if X86_32
 config X86_EXTENDED_PLATFORM
 	bool "Support for extended (non-PC) x86 platforms"
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@ -223,9 +223,7 @@ ifdef CONFIG_RETPOLINE
    RETPOLINE_CFLAGS_CLANG := -mretpoline-external-thunk

    RETPOLINE_CFLAGS += $(call cc-option,$(RETPOLINE_CFLAGS_GCC),$(call cc-option,$(RETPOLINE_CFLAGS_CLANG)))
-    ifneq ($(RETPOLINE_CFLAGS),)
-        KBUILD_CFLAGS += $(RETPOLINE_CFLAGS) -DRETPOLINE
-    endif
+    KBUILD_CFLAGS += $(RETPOLINE_CFLAGS)
 endif

 archscripts: scripts_basic
@ -241,6 +239,13 @@ archprepare:
 ifeq ($(CONFIG_KEXEC_FILE),y)
 	$(Q)$(MAKE) $(build)=arch/x86/purgatory arch/x86/purgatory/kexec-purgatory.c
 endif
+ifdef CONFIG_RETPOLINE
+ifeq ($(RETPOLINE_CFLAGS),)
+	@echo "You are building kernel with non-retpoline compiler." >&2
+	@echo "Please update your compiler." >&2
+	@false
+endif
+endif

 ###
 # Kernel objects
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@ -195,7 +195,7 @@
 #define X86_FEATURE_FENCE_SWAPGS_USER	( 7*32+10) /* "" LFENCE in user entry SWAPGS path */
 #define X86_FEATURE_FENCE_SWAPGS_KERNEL	( 7*32+11) /* "" LFENCE in kernel entry SWAPGS path */
 #define X86_FEATURE_RETPOLINE	( 7*32+12) /* "" Generic Retpoline mitigation for Spectre variant 2 */
-#define X86_FEATURE_RETPOLINE_AMD ( 7*32+13) /* "" AMD Retpoline mitigation for Spectre variant 2 */
+#define X86_FEATURE_RETPOLINE_LFENCE	( 7*32+13) /* "" Use LFENCE for Spectre variant 2 */

 #define X86_FEATURE_MSR_SPEC_CTRL ( 7*32+16) /* "" MSR SPEC_CTRL is implemented */
 #define X86_FEATURE_SSBD	( 7*32+17) /* Speculative Store Bypass Disable */
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@ -119,7 +119,7 @@
 	ANNOTATE_NOSPEC_ALTERNATIVE
 	ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; jmp *\reg),	\
 		__stringify(RETPOLINE_JMP \reg), X86_FEATURE_RETPOLINE,	\
-		__stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *\reg), X86_FEATURE_RETPOLINE_AMD
+		__stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *\reg), X86_FEATURE_RETPOLINE_LFENCE
 #else
 	jmp	*\reg
 #endif
@ -130,7 +130,7 @@
 	ANNOTATE_NOSPEC_ALTERNATIVE
 	ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; call *\reg),	\
 		__stringify(RETPOLINE_CALL \reg), X86_FEATURE_RETPOLINE,\
-		__stringify(lfence; ANNOTATE_RETPOLINE_SAFE; call *\reg), X86_FEATURE_RETPOLINE_AMD
+		__stringify(lfence; ANNOTATE_RETPOLINE_SAFE; call *\reg), X86_FEATURE_RETPOLINE_LFENCE
 #else
 	call	*\reg
 #endif
@ -164,29 +164,35 @@
 	_ASM_PTR " 999b\n\t"					\
 	".popsection\n\t"

-#if defined(CONFIG_X86_64) && defined(RETPOLINE)
+#ifdef CONFIG_RETPOLINE
+#ifdef CONFIG_X86_64

 /*
- * Since the inline asm uses the %V modifier which is only in newer GCC,
- * the 64-bit one is dependent on RETPOLINE not CONFIG_RETPOLINE.
+ * Inline asm uses the %V modifier which is only in newer GCC
+ * which is ensured when CONFIG_RETPOLINE is defined.
 */
 # define CALL_NOSPEC						\
 	ANNOTATE_NOSPEC_ALTERNATIVE				\
-	ALTERNATIVE(						\
+	ALTERNATIVE_2(						\
 	ANNOTATE_RETPOLINE_SAFE					\
 	"call *%[thunk_target]\n",				\
 	"call __x86_indirect_thunk_%V[thunk_target]\n",		\
-	X86_FEATURE_RETPOLINE)
+	X86_FEATURE_RETPOLINE,					\
+	"lfence;\n"						\
+	ANNOTATE_RETPOLINE_SAFE					\
+	"call *%[thunk_target]\n",				\
+	X86_FEATURE_RETPOLINE_LFENCE)
 # define THUNK_TARGET(addr) [thunk_target] "r" (addr)

-#elif defined(CONFIG_X86_32) && defined(CONFIG_RETPOLINE)
+#else /* CONFIG_X86_32 */
 /*
 * For i386 we use the original ret-equivalent retpoline, because
 * otherwise we'll run out of registers. We don't care about CET
 * here, anyway.
 */
 # define CALL_NOSPEC						\
-	ALTERNATIVE(						\
+	ANNOTATE_NOSPEC_ALTERNATIVE				\
+	ALTERNATIVE_2(						\
 	ANNOTATE_RETPOLINE_SAFE					\
 	"call *%[thunk_target]\n",				\
 	"       jmp    904f;\n"					\
@ -201,9 +207,14 @@
 	"       ret;\n"						\
 	"       .align 16\n"					\
 	"904:	call   901b;\n",				\
-	X86_FEATURE_RETPOLINE)
+	X86_FEATURE_RETPOLINE,					\
+	"lfence;\n"						\
+	ANNOTATE_RETPOLINE_SAFE					\
+	"call *%[thunk_target]\n",				\
+	X86_FEATURE_RETPOLINE_LFENCE)

 # define THUNK_TARGET(addr) [thunk_target] "rm" (addr)
+#endif
 #else /* No retpoline for C / inline asm */
 # define CALL_NOSPEC "call *%[thunk_target]\n"
 # define THUNK_TARGET(addr) [thunk_target] "rm" (addr)
@ -212,11 +223,11 @@
 /* The Spectre V2 mitigation variants */
 enum spectre_v2_mitigation {
 	SPECTRE_V2_NONE,
-	SPECTRE_V2_RETPOLINE_MINIMAL,
-	SPECTRE_V2_RETPOLINE_MINIMAL_AMD,
-	SPECTRE_V2_RETPOLINE_GENERIC,
-	SPECTRE_V2_RETPOLINE_AMD,
-	SPECTRE_V2_IBRS_ENHANCED,
+	SPECTRE_V2_RETPOLINE,
+	SPECTRE_V2_LFENCE,
+	SPECTRE_V2_EIBRS,
+	SPECTRE_V2_EIBRS_RETPOLINE,
+	SPECTRE_V2_EIBRS_LFENCE,
 };

 /* The indirect branch speculation control variants */
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@ -30,6 +30,7 @@
 #include <asm/cacheflush.h>
 #include <asm/intel-family.h>
 #include <asm/e820.h>
+#include <linux/bpf.h>

 #include "cpu.h"

@ -585,7 +586,7 @@ static enum spectre_v2_user_mitigation spectre_v2_user_stibp __ro_after_init =
 static enum spectre_v2_user_mitigation spectre_v2_user_ibpb __ro_after_init =
 	SPECTRE_V2_USER_NONE;

-#ifdef RETPOLINE
+#ifdef CONFIG_RETPOLINE
 static bool spectre_v2_bad_module;

 bool retpoline_module_ok(bool has_retpoline)
@ -606,6 +607,32 @@ static inline const char *spectre_v2_module_string(void)
 static inline const char *spectre_v2_module_string(void) { return ""; }
 #endif

+#define SPECTRE_V2_LFENCE_MSG "WARNING: LFENCE mitigation is not recommended for this CPU, data leaks possible!\n"
+#define SPECTRE_V2_EIBRS_EBPF_MSG "WARNING: Unprivileged eBPF is enabled with eIBRS on, data leaks possible via Spectre v2 BHB attacks!\n"
+#define SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG "WARNING: Unprivileged eBPF is enabled with eIBRS+LFENCE mitigation and SMT, data leaks possible via Spectre v2 BHB attacks!\n"
+
+#ifdef CONFIG_BPF_SYSCALL
+void unpriv_ebpf_notify(int new_state)
+{
+	if (new_state)
+		return;
+
+	/* Unprivileged eBPF is enabled */
+
+	switch (spectre_v2_enabled) {
+	case SPECTRE_V2_EIBRS:
+		pr_err(SPECTRE_V2_EIBRS_EBPF_MSG);
+		break;
+	case SPECTRE_V2_EIBRS_LFENCE:
+		if (sched_smt_active())
+			pr_err(SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG);
+		break;
+	default:
+		break;
+	}
+}
+#endif
+
 static inline bool match_option(const char *arg, int arglen, const char *opt)
 {
 	int len = strlen(opt);
@ -620,7 +647,10 @@ enum spectre_v2_mitigation_cmd {
 	SPECTRE_V2_CMD_FORCE,
 	SPECTRE_V2_CMD_RETPOLINE,
 	SPECTRE_V2_CMD_RETPOLINE_GENERIC,
-	SPECTRE_V2_CMD_RETPOLINE_AMD,
+	SPECTRE_V2_CMD_RETPOLINE_LFENCE,
+	SPECTRE_V2_CMD_EIBRS,
+	SPECTRE_V2_CMD_EIBRS_RETPOLINE,
+	SPECTRE_V2_CMD_EIBRS_LFENCE,
 };

 enum spectre_v2_user_cmd {
@ -693,6 +723,13 @@ spectre_v2_parse_user_cmdline(enum spectre_v2_mitigation_cmd v2_cmd)
 	return SPECTRE_V2_USER_CMD_AUTO;
 }

+static inline bool spectre_v2_in_eibrs_mode(enum spectre_v2_mitigation mode)
+{
+	return (mode == SPECTRE_V2_EIBRS ||
+		mode == SPECTRE_V2_EIBRS_RETPOLINE ||
+		mode == SPECTRE_V2_EIBRS_LFENCE);
+}
+
 static void __init
 spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd)
 {
@ -755,10 +792,12 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd)
 	}

 	/*
-	 * If enhanced IBRS is enabled or SMT impossible, STIBP is not
+	 * If no STIBP, enhanced IBRS is enabled or SMT impossible, STIBP is not
 	 * required.
 	 */
-	if (!smt_possible || spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
+	if (!boot_cpu_has(X86_FEATURE_STIBP) ||
+	    !smt_possible ||
+	    spectre_v2_in_eibrs_mode(spectre_v2_enabled))
 		return;

 	/*
@ -770,12 +809,6 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd)
 	    boot_cpu_has(X86_FEATURE_AMD_STIBP_ALWAYS_ON))
 		mode = SPECTRE_V2_USER_STRICT_PREFERRED;

-	/*
-	 * If STIBP is not available, clear the STIBP mode.
-	 */
-	if (!boot_cpu_has(X86_FEATURE_STIBP))
-		mode = SPECTRE_V2_USER_NONE;
-
 	spectre_v2_user_stibp = mode;

 set_mode:
@ -784,11 +817,11 @@ set_mode:

 static const char * const spectre_v2_strings[] = {
 	[SPECTRE_V2_NONE]			= "Vulnerable",
-	[SPECTRE_V2_RETPOLINE_MINIMAL]		= "Vulnerable: Minimal generic ASM retpoline",
-	[SPECTRE_V2_RETPOLINE_MINIMAL_AMD]	= "Vulnerable: Minimal AMD ASM retpoline",
-	[SPECTRE_V2_RETPOLINE_GENERIC]		= "Mitigation: Full generic retpoline",
-	[SPECTRE_V2_RETPOLINE_AMD]		= "Mitigation: Full AMD retpoline",
-	[SPECTRE_V2_IBRS_ENHANCED]		= "Mitigation: Enhanced IBRS",
+	[SPECTRE_V2_RETPOLINE]			= "Mitigation: Retpolines",
+	[SPECTRE_V2_LFENCE]			= "Mitigation: LFENCE",
+	[SPECTRE_V2_EIBRS]			= "Mitigation: Enhanced IBRS",
+	[SPECTRE_V2_EIBRS_LFENCE]		= "Mitigation: Enhanced IBRS + LFENCE",
+	[SPECTRE_V2_EIBRS_RETPOLINE]		= "Mitigation: Enhanced IBRS + Retpolines",
 };

 static const struct {
@ -799,8 +832,12 @@ static const struct {
 	{ "off",		SPECTRE_V2_CMD_NONE,		  false },
 	{ "on",			SPECTRE_V2_CMD_FORCE,		  true  },
 	{ "retpoline",		SPECTRE_V2_CMD_RETPOLINE,	  false },
-	{ "retpoline,amd",	SPECTRE_V2_CMD_RETPOLINE_AMD,	  false },
+	{ "retpoline,amd",	SPECTRE_V2_CMD_RETPOLINE_LFENCE,  false },
+	{ "retpoline,lfence",	SPECTRE_V2_CMD_RETPOLINE_LFENCE,  false },
 	{ "retpoline,generic",	SPECTRE_V2_CMD_RETPOLINE_GENERIC, false },
+	{ "eibrs",		SPECTRE_V2_CMD_EIBRS,		  false },
+	{ "eibrs,lfence",	SPECTRE_V2_CMD_EIBRS_LFENCE,	  false },
+	{ "eibrs,retpoline",	SPECTRE_V2_CMD_EIBRS_RETPOLINE,	  false },
 	{ "auto",		SPECTRE_V2_CMD_AUTO,		  false },
 };

@ -810,11 +847,6 @@ static void __init spec_v2_print_cond(const char *reason, bool secure)
 		pr_info("%s selected on command line.\n", reason);
 }

-static inline bool retp_compiler(void)
-{
-	return __is_defined(RETPOLINE);
-}
-
 static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
 {
 	enum spectre_v2_mitigation_cmd cmd = SPECTRE_V2_CMD_AUTO;
@ -842,16 +874,30 @@ static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
 	}

 	if ((cmd == SPECTRE_V2_CMD_RETPOLINE ||
-	     cmd == SPECTRE_V2_CMD_RETPOLINE_AMD ||
-	     cmd == SPECTRE_V2_CMD_RETPOLINE_GENERIC) &&
+	     cmd == SPECTRE_V2_CMD_RETPOLINE_LFENCE ||
+	     cmd == SPECTRE_V2_CMD_RETPOLINE_GENERIC ||
+	     cmd == SPECTRE_V2_CMD_EIBRS_LFENCE ||
+	     cmd == SPECTRE_V2_CMD_EIBRS_RETPOLINE) &&
 	    !IS_ENABLED(CONFIG_RETPOLINE)) {
-		pr_err("%s selected but not compiled in. Switching to AUTO select\n", mitigation_options[i].option);
+		pr_err("%s selected but not compiled in. Switching to AUTO select\n",
+		       mitigation_options[i].option);
 		return SPECTRE_V2_CMD_AUTO;
 	}

-	if (cmd == SPECTRE_V2_CMD_RETPOLINE_AMD &&
-	    boot_cpu_data.x86_vendor != X86_VENDOR_AMD) {
-		pr_err("retpoline,amd selected but CPU is not AMD. Switching to AUTO select\n");
+	if ((cmd == SPECTRE_V2_CMD_EIBRS ||
+	     cmd == SPECTRE_V2_CMD_EIBRS_LFENCE ||
+	     cmd == SPECTRE_V2_CMD_EIBRS_RETPOLINE) &&
+	    !boot_cpu_has(X86_FEATURE_IBRS_ENHANCED)) {
+		pr_err("%s selected but CPU doesn't have eIBRS. Switching to AUTO select\n",
+		       mitigation_options[i].option);
+		return SPECTRE_V2_CMD_AUTO;
+	}
+
+	if ((cmd == SPECTRE_V2_CMD_RETPOLINE_LFENCE ||
+	     cmd == SPECTRE_V2_CMD_EIBRS_LFENCE) &&
+	    !boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) {
+		pr_err("%s selected, but CPU doesn't have a serializing LFENCE. Switching to AUTO select\n",
+		       mitigation_options[i].option);
 		return SPECTRE_V2_CMD_AUTO;
 	}

@ -860,6 +906,16 @@ static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
 	return cmd;
 }

+static enum spectre_v2_mitigation __init spectre_v2_select_retpoline(void)
+{
+	if (!IS_ENABLED(CONFIG_RETPOLINE)) {
+		pr_err("Kernel not compiled with retpoline; no mitigation available!");
+		return SPECTRE_V2_NONE;
+	}
+
+	return SPECTRE_V2_RETPOLINE;
+}
+
 static void __init spectre_v2_select_mitigation(void)
 {
 	enum spectre_v2_mitigation_cmd cmd = spectre_v2_parse_cmdline();
@ -880,50 +936,64 @@ static void __init spectre_v2_select_mitigation(void)
 	case SPECTRE_V2_CMD_FORCE:
 	case SPECTRE_V2_CMD_AUTO:
 		if (boot_cpu_has(X86_FEATURE_IBRS_ENHANCED)) {
-			mode = SPECTRE_V2_IBRS_ENHANCED;
-			/* Force it so VMEXIT will restore correctly */
-			x86_spec_ctrl_base |= SPEC_CTRL_IBRS;
-			wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
-			goto specv2_set_mode;
+			mode = SPECTRE_V2_EIBRS;
+			break;
 		}
-		if (IS_ENABLED(CONFIG_RETPOLINE))
-			goto retpoline_auto;
+
+		mode = spectre_v2_select_retpoline();
 		break;
-	case SPECTRE_V2_CMD_RETPOLINE_AMD:
-		if (IS_ENABLED(CONFIG_RETPOLINE))
-			goto retpoline_amd;
+
+	case SPECTRE_V2_CMD_RETPOLINE_LFENCE:
+		pr_err(SPECTRE_V2_LFENCE_MSG);
+		mode = SPECTRE_V2_LFENCE;
 		break;
+
 	case SPECTRE_V2_CMD_RETPOLINE_GENERIC:
-		if (IS_ENABLED(CONFIG_RETPOLINE))
-			goto retpoline_generic;
+		mode = SPECTRE_V2_RETPOLINE;
 		break;
+
 	case SPECTRE_V2_CMD_RETPOLINE:
-		if (IS_ENABLED(CONFIG_RETPOLINE))
-			goto retpoline_auto;
+		mode = spectre_v2_select_retpoline();
+		break;
+
+	case SPECTRE_V2_CMD_EIBRS:
+		mode = SPECTRE_V2_EIBRS;
+		break;
+
+	case SPECTRE_V2_CMD_EIBRS_LFENCE:
+		mode = SPECTRE_V2_EIBRS_LFENCE;
+		break;
+
+	case SPECTRE_V2_CMD_EIBRS_RETPOLINE:
+		mode = SPECTRE_V2_EIBRS_RETPOLINE;
 		break;
 	}
-	pr_err("Spectre mitigation: kernel not compiled with retpoline; no mitigation available!");
-	return;

-retpoline_auto:
-	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
-	retpoline_amd:
-		if (!boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) {
-			pr_err("Spectre mitigation: LFENCE not serializing, switching to generic retpoline\n");
-			goto retpoline_generic;
-		}
-		mode = retp_compiler() ? SPECTRE_V2_RETPOLINE_AMD :
-					 SPECTRE_V2_RETPOLINE_MINIMAL_AMD;
-		setup_force_cpu_cap(X86_FEATURE_RETPOLINE_AMD);
+	if (mode == SPECTRE_V2_EIBRS && unprivileged_ebpf_enabled())
+		pr_err(SPECTRE_V2_EIBRS_EBPF_MSG);
+
+	if (spectre_v2_in_eibrs_mode(mode)) {
+		/* Force it so VMEXIT will restore correctly */
+		x86_spec_ctrl_base |= SPEC_CTRL_IBRS;
+		wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
+	}
+
+	switch (mode) {
+	case SPECTRE_V2_NONE:
+	case SPECTRE_V2_EIBRS:
+		break;
+
+	case SPECTRE_V2_LFENCE:
+	case SPECTRE_V2_EIBRS_LFENCE:
+		setup_force_cpu_cap(X86_FEATURE_RETPOLINE_LFENCE);
+		/* fallthrough */
+
+	case SPECTRE_V2_RETPOLINE:
+	case SPECTRE_V2_EIBRS_RETPOLINE:
 		setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
-	} else {
-	retpoline_generic:
-		mode = retp_compiler() ? SPECTRE_V2_RETPOLINE_GENERIC :
-					 SPECTRE_V2_RETPOLINE_MINIMAL;
-		setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
+		break;
 	}

-specv2_set_mode:
 	spectre_v2_enabled = mode;
 	pr_info("%s\n", spectre_v2_strings[mode]);

@ -949,7 +1019,7 @@ specv2_set_mode:
 	 * the CPU supports Enhanced IBRS, kernel might un-intentionally not
 	 * enable IBRS around firmware calls.
 	 */
-	if (boot_cpu_has(X86_FEATURE_IBRS) && mode != SPECTRE_V2_IBRS_ENHANCED) {
+	if (boot_cpu_has(X86_FEATURE_IBRS) && !spectre_v2_in_eibrs_mode(mode)) {
 		setup_force_cpu_cap(X86_FEATURE_USE_IBRS_FW);
 		pr_info("Enabling Restricted Speculation for firmware calls\n");
 	}
@ -1019,6 +1089,10 @@ void arch_smt_update(void)
 {
 	mutex_lock(&spec_ctrl_mutex);

+	if (sched_smt_active() && unprivileged_ebpf_enabled() &&
+	    spectre_v2_enabled == SPECTRE_V2_EIBRS_LFENCE)
+		pr_warn_once(SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG);
+
 	switch (spectre_v2_user_stibp) {
 	case SPECTRE_V2_USER_NONE:
 		break;
@ -1263,7 +1337,6 @@ static int ib_prctl_set(struct task_struct *task, unsigned long ctrl)
 		if (spectre_v2_user_ibpb == SPECTRE_V2_USER_NONE &&
 		    spectre_v2_user_stibp == SPECTRE_V2_USER_NONE)
 			return 0;
-
 		/*
 		 * With strict mode for both IBPB and STIBP, the instruction
 		 * code paths avoid checking this task flag and instead,
@ -1610,7 +1683,7 @@ static ssize_t tsx_async_abort_show_state(char *buf)

 static char *stibp_state(void)
 {
-	if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
+	if (spectre_v2_in_eibrs_mode(spectre_v2_enabled))
 		return "";

 	switch (spectre_v2_user_stibp) {
@ -1640,6 +1713,27 @@ static char *ibpb_state(void)
 	return "";
 }

+static ssize_t spectre_v2_show_state(char *buf)
+{
+	if (spectre_v2_enabled == SPECTRE_V2_LFENCE)
+		return sprintf(buf, "Vulnerable: LFENCE\n");
+
+	if (spectre_v2_enabled == SPECTRE_V2_EIBRS && unprivileged_ebpf_enabled())
+		return sprintf(buf, "Vulnerable: eIBRS with unprivileged eBPF\n");
+
+	if (sched_smt_active() && unprivileged_ebpf_enabled() &&
+	    spectre_v2_enabled == SPECTRE_V2_EIBRS_LFENCE)
+		return sprintf(buf, "Vulnerable: eIBRS+LFENCE with unprivileged eBPF and SMT\n");
+
+	return sprintf(buf, "%s%s%s%s%s%s\n",
+		       spectre_v2_strings[spectre_v2_enabled],
+		       ibpb_state(),
+		       boot_cpu_has(X86_FEATURE_USE_IBRS_FW) ? ", IBRS_FW" : "",
+		       stibp_state(),
+		       boot_cpu_has(X86_FEATURE_RSB_CTXSW) ? ", RSB filling" : "",
+		       spectre_v2_module_string());
+}
+
 static ssize_t srbds_show_state(char *buf)
 {
 	return sprintf(buf, "%s\n", srbds_strings[srbds_mitigation]);
@ -1662,12 +1756,7 @@ static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr
 		return sprintf(buf, "%s\n", spectre_v1_strings[spectre_v1_mitigation]);

 	case X86_BUG_SPECTRE_V2:
-		return sprintf(buf, "%s%s%s%s%s%s\n", spectre_v2_strings[spectre_v2_enabled],
-			       ibpb_state(),
-			       boot_cpu_has(X86_FEATURE_USE_IBRS_FW) ? ", IBRS_FW" : "",
-			       stibp_state(),
-			       boot_cpu_has(X86_FEATURE_RSB_CTXSW) ? ", RSB filling" : "",
-			       spectre_v2_module_string());
+		return spectre_v2_show_state(buf);

 	case X86_BUG_SPEC_STORE_BYPASS:
 		return sprintf(buf, "%s\n", ssb_strings[ssb_mode]);
--- a/Show more
+++ b/Show more