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jump_label: Disable jump labels in __exit code

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With the following commit:

  333522447063 ("jump_label: Explicitly disable jump labels in __init code")

... we explicitly disabled jump labels in __init code, so they could be
detected and not warned about in the following commit:

  dc1dd184c2f0 ("jump_label: Warn on failed jump_label patching attempt")

In-kernel __exit code has the same issue.  It's never used, so it's
freed along with the rest of initmem.  But jump label entries in __exit
code aren't explicitly disabled, so we get the following warning when
enabling pr_debug() in __exit code:

  can't patch jump_label at dmi_sysfs_exit+0x0/0x2d
  WARNING: CPU: 0 PID: 22572 at kernel/jump_label.c:376 __jump_label_update+0x9d/0xb0

Fix the warning by disabling all jump labels in initmem (which includes
both __init and __exit code).

Reported-and-tested-by: Li Wang <liwang@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Jason Baron <jbaron@akamai.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: dc1dd184c2f0 ("jump_label: Warn on failed jump_label patching attempt")
Link: http://lkml.kernel.org/r/7121e6e595374f06616c505b6e690e275c0054d1.1521483452.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Change-Id: I6009e2dee9a8401e61736fbebf76445f7de35a8e
This commit is contained in:
Josh Poimboeuf 2018-03-19 13:18:57 -05:00 • committed by Michael Bestas
commit 052d89b469
3 changed files with 7 additions and 6 deletions
Download patch file Download diff file Expand all files Collapse all files

4
include/linux/jump_label.h
View file

@ -136,7 +136,7 @@ extern struct jump_entry __start___jump_table[];
extern struct jump_entry __stop___jump_table[];
extern void jump_label_init(void);
extern void jump_label_invalidate_init(void);
extern void jump_label_invalidate_initmem(void);
extern void jump_label_lock(void);
extern void jump_label_unlock(void);
extern void arch_jump_label_transform(struct jump_entry *entry,
@ -180,7 +180,7 @@ static __always_inline void jump_label_init(void)
static_key_initialized = true;
}
static inline void jump_label_invalidate_init(void) {}
static inline void jump_label_invalidate_initmem(void) {}
static __always_inline bool static_key_false(struct static_key *key)
{

2
init/main.c
View file

@ -955,7 +955,7 @@ static int __ref kernel_init(void *unused)
kernel_init_freeable();
/* need to finish all async __init code before freeing the memory */
async_synchronize_full();
jump_label_invalidate_init();
jump_label_invalidate_initmem();
free_initmem();
mark_readonly();
system_state = SYSTEM_RUNNING;

7
kernel/jump_label.c
View file

@ -15,6 +15,7 @@
#include <linux/static_key.h>
#include <linux/jump_label_ratelimit.h>
#include <linux/bug.h>
#include <asm/sections.h>
#ifdef HAVE_JUMP_LABEL
@ -328,15 +329,15 @@ void __init jump_label_init(void)
jump_label_unlock();
}
/* Disable any jump label entries in __init code */
void __init jump_label_invalidate_init(void)
/* Disable any jump label entries in __init/__exit code */
void __init jump_label_invalidate_initmem(void)
{
struct jump_entry *iter_start = __start___jump_table;
struct jump_entry *iter_stop = __stop___jump_table;
struct jump_entry *iter;
for (iter = iter_start; iter < iter_stop; iter++) {
if (init_kernel_text(iter->code))
if (init_section_contains((void *)(unsigned long)iter->code, 1))
iter->code = 0;
}
}