diff --git a/Documentation/ABI/testing/sysfs-kernel-btf b/Documentation/ABI/testing/sysfs-kernel-btf new file mode 100644 index 000000000000..5390f8001f96 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-kernel-btf @@ -0,0 +1,17 @@ +What: /sys/kernel/btf +Date: Aug 2019 +KernelVersion: 5.5 +Contact: bpf@vger.kernel.org +Description: + Contains BTF type information and related data for kernel and + kernel modules. + +What: /sys/kernel/btf/kernel +Date: Aug 2019 +KernelVersion: 5.5 +Contact: bpf@vger.kernel.org +Description: + Read-only binary attribute exposing kernel's own BTF type + information with description of all internal kernel types. See + Documentation/bpf/btf.rst for detailed description of format + itself. diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile index 05e1bf69ece1..a461583367aa 100644 --- a/kernel/bpf/Makefile +++ b/kernel/bpf/Makefile @@ -21,3 +21,6 @@ obj-$(CONFIG_CGROUP_BPF) += cgroup.o ifeq ($(CONFIG_INET),y) obj-$(CONFIG_BPF_SYSCALL) += reuseport_array.o endif +ifeq ($(CONFIG_SYSFS),y) +obj-$(CONFIG_DEBUG_INFO_BTF) += sysfs_btf.o +endif diff --git a/kernel/bpf/sysfs_btf.c b/kernel/bpf/sysfs_btf.c new file mode 100644 index 000000000000..092e63b9758b --- /dev/null +++ b/kernel/bpf/sysfs_btf.c @@ -0,0 +1,51 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Provide kernel BTF information for introspection and use by eBPF tools. + */ +#include +#include +#include +#include +#include + +/* See scripts/link-vmlinux.sh, gen_btf() func for details */ +extern char __weak _binary__btf_kernel_bin_start[]; +extern char __weak _binary__btf_kernel_bin_end[]; + +static ssize_t +btf_kernel_read(struct file *file, struct kobject *kobj, + struct bin_attribute *bin_attr, + char *buf, loff_t off, size_t len) +{ + memcpy(buf, _binary__btf_kernel_bin_start + off, len); + return len; +} + +static struct bin_attribute bin_attr_btf_kernel __ro_after_init = { + .attr = { .name = "kernel", .mode = 0444, }, + .read = btf_kernel_read, +}; + +static struct kobject *btf_kobj; + +static int __init btf_kernel_init(void) +{ + int err; + + if (!_binary__btf_kernel_bin_start) + return 0; + + btf_kobj = kobject_create_and_add("btf", kernel_kobj); + if (IS_ERR(btf_kobj)) { + err = PTR_ERR(btf_kobj); + btf_kobj = NULL; + return err; + } + + bin_attr_btf_kernel.size = _binary__btf_kernel_bin_end - + _binary__btf_kernel_bin_start; + + return sysfs_create_bin_file(btf_kobj, &bin_attr_btf_kernel); +} + +subsys_initcall(btf_kernel_init); diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh index d7d8fce43eec..5ea28071844d 100644 --- a/scripts/link-vmlinux.sh +++ b/scripts/link-vmlinux.sh @@ -127,8 +127,8 @@ recordmcount() } # Link of vmlinux -# ${1} - optional extra .o files -# ${2} - output file +# ${1} - output file +# ${@:2} - optional extra .o files vmlinux_link() { local lds="${objtree}/${KBUILD_LDS}" @@ -144,28 +144,28 @@ vmlinux_link() fi if [[ -n "${CONFIG_THIN_ARCHIVES}" && -z "${CONFIG_LTO_CLANG}" ]]; then - objects="--whole-archive built-in.o ${1}" + objects="--whole-archive built-in.o ${@:2}" else objects="${KBUILD_VMLINUX_INIT} \ --start-group \ ${KBUILD_VMLINUX_MAIN} \ --end-group \ - ${1}" + ${@:2}" fi - ${ld} ${ldflags} -o ${2} -T ${lds} ${objects} + ${ld} ${ldflags} -o ${1} -T ${lds} ${objects} else if [ -n "${CONFIG_THIN_ARCHIVES}" ]; then - objects="-Wl,--whole-archive built-in.o ${1}" + objects="-Wl,--whole-archive built-in.o ${@:2}" else objects="${KBUILD_VMLINUX_INIT} \ -Wl,--start-group \ ${KBUILD_VMLINUX_MAIN} \ -Wl,--end-group \ - ${1}" + ${@:2}" fi - ${CC} ${CFLAGS_vmlinux} -o ${2} \ + ${CC} ${CFLAGS_vmlinux} -o ${1} \ -Wl,-T,${lds} \ ${objects} \ -lutil -lrt -lpthread @@ -174,23 +174,34 @@ vmlinux_link() } # generate .BTF typeinfo from DWARF debuginfo +# ${1} - vmlinux image +# ${2} - file to dump raw BTF data into gen_btf() { local pahole_ver; + local bin_arch if ! [ -x "$(command -v ${PAHOLE})" ]; then info "BTF" "${1}: pahole (${PAHOLE}) is not available" - return 0 + return 1 fi pahole_ver=$(${PAHOLE} --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/') if [ "${pahole_ver}" -lt "113" ]; then info "BTF" "${1}: pahole version $(${PAHOLE} --version) is too old, need at least v1.13" - return 0 + return 1 fi - info "BTF" ${1} + info "BTF" ${2} + vmlinux_link ${1} LLVM_OBJCOPY=${OBJCOPY} ${PAHOLE} -J ${1} + + # dump .BTF section into raw binary file to link with final vmlinux + bin_arch=$(${OBJDUMP} -f ${1} | grep architecture | \ + cut -d, -f1 | cut -d' ' -f2) + ${OBJCOPY} --dump-section .BTF=.btf.kernel.bin ${1} 2>/dev/null + ${OBJCOPY} -I binary -O ${CONFIG_OUTPUT_FORMAT} -B ${bin_arch} \ + --rename-section .data=.BTF .btf.kernel.bin ${2} } # Create ${2} .o file with all symbols from the ${1} object file @@ -264,6 +275,7 @@ sortextable() # Delete output files in case of error cleanup() { + rm -f .btf.* rm -f .old_version rm -f .tmp_System.map rm -f .tmp_kallsyms* @@ -356,6 +368,13 @@ if [ ! -z ${RTIC_MPGEN+x} ]; then KBUILD_VMLINUX_MAIN+=$RTIC_MP_O fi +btf_kernel_bin_o="" +if [ -n "${CONFIG_DEBUG_INFO_BTF}" ]; then + if gen_btf .tmp_vmlinux.btf .btf.kernel.bin.o ; then + btf_kernel_bin_o=.btf.kernel.bin.o + fi +fi + kallsymso="" kallsyms_vmlinux="" if [ -n "${CONFIG_KALLSYMS}" ]; then @@ -383,11 +402,11 @@ if [ -n "${CONFIG_KALLSYMS}" ]; then kallsyms_vmlinux=.tmp_vmlinux2 # step 1 - vmlinux_link "" .tmp_vmlinux1 - kallsyms .tmp_vmlinux1 .tmp_kallsyms1.o + vmlinux_link .tmp_vmlinux1 + kallsyms .tmp_vmlinux1 .tmp_kallsyms1.o ${btf_kernel_bin_o} # step 2 - vmlinux_link .tmp_kallsyms1.o .tmp_vmlinux2 + vmlinux_link .tmp_vmlinux2 .tmp_kallsyms1.o ${btf_kernel_bin_o} kallsyms .tmp_vmlinux2 .tmp_kallsyms2.o # step 2a @@ -395,7 +414,7 @@ if [ -n "${CONFIG_KALLSYMS}" ]; then kallsymso=.tmp_kallsyms3.o kallsyms_vmlinux=.tmp_vmlinux3 - vmlinux_link .tmp_kallsyms2.o .tmp_vmlinux3 + vmlinux_link .tmp_vmlinux2 .tmp_kallsyms1.o ${btf_kernel_bin_o} kallsyms .tmp_vmlinux3 .tmp_kallsyms3.o fi @@ -418,11 +437,7 @@ if [ ! -z ${RTIC_MP_O} ]; then fi info LD vmlinux -vmlinux_link "${kallsymso}" vmlinux - -if [ -n "${CONFIG_DEBUG_INFO_BTF}" ]; then - gen_btf vmlinux -fi +vmlinux_link vmlinux "${kallsymso}" "${btf_kernel_bin_o}" if [ -n "${CONFIG_BUILDTIME_EXTABLE_SORT}" ]; then info SORTEX vmlinux