linux/lib/buildid.c

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// SPDX-License-Identifier: GPL-2.0
#include <linux/buildid.h>
buildid: stash away kernels build ID on init Parse the kernel's build ID at initialization so that other code can print a hex format string representation of the running kernel's build ID. This will be used in the kdump and dump_stack code so that developers can easily locate the vmlinux debug symbols for a crash/stacktrace. [swboyd@chromium.org: fix implicit declaration of init_vmlinux_build_id()] Link: https://lkml.kernel.org/r/CAE-0n51UjTbay8N9FXAyE7_aR2+ePrQnKSRJ0gbmRsXtcLBVaw@mail.gmail.com Link: https://lkml.kernel.org/r/20210511003845.2429846-4-swboyd@chromium.org Signed-off-by: Stephen Boyd <swboyd@chromium.org> Acked-by: Baoquan He <bhe@redhat.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Jessica Yu <jeyu@kernel.org> Cc: Evan Green <evgreen@chromium.org> Cc: Hsin-Yi Wang <hsinyi@chromium.org> Cc: Dave Young <dyoung@redhat.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Cc: Matthew Wilcox <willy@infradead.org> Cc: Petr Mladek <pmladek@suse.com> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Sasha Levin <sashal@kernel.org> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-07-08 01:09:13 +00:00
#include <linux/cache.h>
#include <linux/elf.h>
#include <linux/kernel.h>
#include <linux/pagemap.h>
#define BUILD_ID 3
/*
* Parse build id from the note segment. This logic can be shared between
* 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are
* identical.
*/
static int parse_build_id_buf(unsigned char *build_id,
__u32 *size,
const void *note_start,
Elf32_Word note_size)
{
Elf32_Word note_offs = 0, new_offs;
while (note_offs + sizeof(Elf32_Nhdr) < note_size) {
Elf32_Nhdr *nhdr = (Elf32_Nhdr *)(note_start + note_offs);
if (nhdr->n_type == BUILD_ID &&
nhdr->n_namesz == sizeof("GNU") &&
buildid: only consider GNU notes for build ID parsing Patch series "Add build ID to stacktraces", v6. This series adds the kernel's build ID[1] to the stacktrace header printed in oops messages, warnings, etc. and the build ID for any module that appears in the stacktrace after the module name. The goal is to make the stacktrace more self-contained and descriptive by including the relevant build IDs in the kernel logs when something goes wrong. This can be used by post processing tools like script/decode_stacktrace.sh and kernel developers to easily locate the debug info associated with a kernel crash and line up what line and file things started falling apart at. To show how this can be used I've included a patch to decode_stacktrace.sh that downloads the debuginfo from a debuginfod server. This also includes some patches to make the buildid.c file use more const arguments and consolidate logic into buildid.c from kdump. These are left to the end as they were mostly cleanup patches. Here's an example lkdtm stacktrace on arm64. WARNING: CPU: 4 PID: 3255 at drivers/misc/lkdtm/bugs.c:83 lkdtm_WARNING+0x28/0x30 [lkdtm] Modules linked in: lkdtm rfcomm algif_hash algif_skcipher af_alg xt_cgroup uinput xt_MASQUERADE CPU: 4 PID: 3255 Comm: bash Not tainted 5.11 #3 aa23f7a1231c229de205662d5a9e0d4c580f19a1 Hardware name: Google Lazor (rev3+) with KB Backlight (DT) pstate: 00400009 (nzcv daif +PAN -UAO -TCO BTYPE=--) pc : lkdtm_WARNING+0x28/0x30 [lkdtm] lr : lkdtm_do_action+0x24/0x40 [lkdtm] sp : ffffffc0134fbca0 x29: ffffffc0134fbca0 x28: ffffff92d53ba240 x27: 0000000000000000 x26: 0000000000000000 x25: 0000000000000000 x24: ffffffe3622352c0 x23: 0000000000000020 x22: ffffffe362233366 x21: ffffffe3622352e0 x20: ffffffc0134fbde0 x19: 0000000000000008 x18: 0000000000000000 x17: ffffff929b6536fc x16: 0000000000000000 x15: 0000000000000000 x14: 0000000000000012 x13: ffffffe380ed892c x12: ffffffe381d05068 x11: 0000000000000000 x10: 0000000000000000 x9 : 0000000000000001 x8 : ffffffe362237000 x7 : aaaaaaaaaaaaaaaa x6 : 0000000000000000 x5 : 0000000000000000 x4 : 0000000000000001 x3 : 0000000000000008 x2 : ffffff93fef25a70 x1 : ffffff93fef15788 x0 : ffffffe3622352e0 Call trace: lkdtm_WARNING+0x28/0x30 [lkdtm ed5019fdf5e53be37cb1ba7899292d7e143b259e] direct_entry+0x16c/0x1b4 [lkdtm ed5019fdf5e53be37cb1ba7899292d7e143b259e] full_proxy_write+0x74/0xa4 vfs_write+0xec/0x2e8 ksys_write+0x84/0xf0 __arm64_sys_write+0x24/0x30 el0_svc_common+0xf4/0x1c0 do_el0_svc_compat+0x28/0x3c el0_svc_compat+0x10/0x1c el0_sync_compat_handler+0xa8/0xcc el0_sync_compat+0x178/0x180 ---[ end trace 3d95032303e59e68 ]--- This patch (of 13): Some kernel elf files have various notes that also happen to have an elf note type of '3', which matches NT_GNU_BUILD_ID but the note name isn't "GNU". For example, this note trips up the existing logic: Owner Data size Description Xen 0x00000008 Unknown note type: (0x00000003) description data: 00 00 00 ffffff80 ffffffff ffffffff ffffffff ffffffff Let's make sure that it is a GNU note when parsing the build ID so that we can use this function to parse a vmlinux's build ID too. Link: https://lkml.kernel.org/r/20210511003845.2429846-1-swboyd@chromium.org Link: https://lkml.kernel.org/r/20210511003845.2429846-2-swboyd@chromium.org Fixes: bd7525dacd7e ("bpf: Move stack_map_get_build_id into lib") Signed-off-by: Stephen Boyd <swboyd@chromium.org> Reported-by: Petr Mladek <pmladek@suse.com> Tested-by: Petr Mladek <pmladek@suse.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Jessica Yu <jeyu@kernel.org> Cc: Evan Green <evgreen@chromium.org> Cc: Hsin-Yi Wang <hsinyi@chromium.org> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Dave Young <dyoung@redhat.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Cc: Matthew Wilcox <willy@infradead.org> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Sasha Levin <sashal@kernel.org> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-07-08 01:09:06 +00:00
!strcmp((char *)(nhdr + 1), "GNU") &&
nhdr->n_descsz > 0 &&
nhdr->n_descsz <= BUILD_ID_SIZE_MAX) {
memcpy(build_id,
note_start + note_offs +
ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),
nhdr->n_descsz);
memset(build_id + nhdr->n_descsz, 0,
BUILD_ID_SIZE_MAX - nhdr->n_descsz);
if (size)
*size = nhdr->n_descsz;
return 0;
}
new_offs = note_offs + sizeof(Elf32_Nhdr) +
ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4);
if (new_offs <= note_offs) /* overflow */
break;
note_offs = new_offs;
}
return -EINVAL;
}
static inline int parse_build_id(const void *page_addr,
unsigned char *build_id,
__u32 *size,
const void *note_start,
Elf32_Word note_size)
{
/* check for overflow */
if (note_start < page_addr || note_start + note_size < note_start)
return -EINVAL;
/* only supports note that fits in the first page */
if (note_start + note_size > page_addr + PAGE_SIZE)
return -EINVAL;
return parse_build_id_buf(build_id, size, note_start, note_size);
}
/* Parse build ID from 32-bit ELF */
static int get_build_id_32(const void *page_addr, unsigned char *build_id,
__u32 *size)
{
Elf32_Ehdr *ehdr = (Elf32_Ehdr *)page_addr;
Elf32_Phdr *phdr;
int i;
/*
* FIXME
* Neither ELF spec nor ELF loader require that program headers
* start immediately after ELF header.
*/
if (ehdr->e_phoff != sizeof(Elf32_Ehdr))
return -EINVAL;
/* only supports phdr that fits in one page */
if (ehdr->e_phnum >
(PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr))
return -EINVAL;
phdr = (Elf32_Phdr *)(page_addr + sizeof(Elf32_Ehdr));
for (i = 0; i < ehdr->e_phnum; ++i) {
if (phdr[i].p_type == PT_NOTE &&
!parse_build_id(page_addr, build_id, size,
page_addr + phdr[i].p_offset,
phdr[i].p_filesz))
return 0;
}
return -EINVAL;
}
/* Parse build ID from 64-bit ELF */
static int get_build_id_64(const void *page_addr, unsigned char *build_id,
__u32 *size)
{
Elf64_Ehdr *ehdr = (Elf64_Ehdr *)page_addr;
Elf64_Phdr *phdr;
int i;
/*
* FIXME
* Neither ELF spec nor ELF loader require that program headers
* start immediately after ELF header.
*/
if (ehdr->e_phoff != sizeof(Elf64_Ehdr))
return -EINVAL;
/* only supports phdr that fits in one page */
if (ehdr->e_phnum >
(PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr))
return -EINVAL;
phdr = (Elf64_Phdr *)(page_addr + sizeof(Elf64_Ehdr));
for (i = 0; i < ehdr->e_phnum; ++i) {
if (phdr[i].p_type == PT_NOTE &&
!parse_build_id(page_addr, build_id, size,
page_addr + phdr[i].p_offset,
phdr[i].p_filesz))
return 0;
}
return -EINVAL;
}
/*
* Parse build ID of ELF file mapped to vma
* @vma: vma object
* @build_id: buffer to store build id, at least BUILD_ID_SIZE long
* @size: returns actual build id size in case of success
*
* Return: 0 on success, -EINVAL otherwise
*/
int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,
__u32 *size)
{
Elf32_Ehdr *ehdr;
struct page *page;
void *page_addr;
int ret;
/* only works for page backed storage */
if (!vma->vm_file)
return -EINVAL;
page = find_get_page(vma->vm_file->f_mapping, 0);
if (!page)
return -EFAULT; /* page not mapped */
ret = -EINVAL;
page_addr = kmap_local_page(page);
ehdr = (Elf32_Ehdr *)page_addr;
/* compare magic x7f "ELF" */
if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0)
goto out;
/* only support executable file and shared object file */
if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
goto out;
if (ehdr->e_ident[EI_CLASS] == ELFCLASS32)
ret = get_build_id_32(page_addr, build_id, size);
else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
ret = get_build_id_64(page_addr, build_id, size);
out:
kunmap_local(page_addr);
put_page(page);
return ret;
}
/**
* build_id_parse_buf - Get build ID from a buffer
* @buf: ELF note section(s) to parse
* @buf_size: Size of @buf in bytes
* @build_id: Build ID parsed from @buf, at least BUILD_ID_SIZE_MAX long
*
* Return: 0 on success, -EINVAL otherwise
*/
int build_id_parse_buf(const void *buf, unsigned char *build_id, u32 buf_size)
{
return parse_build_id_buf(build_id, NULL, buf, buf_size);
}
buildid: stash away kernels build ID on init Parse the kernel's build ID at initialization so that other code can print a hex format string representation of the running kernel's build ID. This will be used in the kdump and dump_stack code so that developers can easily locate the vmlinux debug symbols for a crash/stacktrace. [swboyd@chromium.org: fix implicit declaration of init_vmlinux_build_id()] Link: https://lkml.kernel.org/r/CAE-0n51UjTbay8N9FXAyE7_aR2+ePrQnKSRJ0gbmRsXtcLBVaw@mail.gmail.com Link: https://lkml.kernel.org/r/20210511003845.2429846-4-swboyd@chromium.org Signed-off-by: Stephen Boyd <swboyd@chromium.org> Acked-by: Baoquan He <bhe@redhat.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Jessica Yu <jeyu@kernel.org> Cc: Evan Green <evgreen@chromium.org> Cc: Hsin-Yi Wang <hsinyi@chromium.org> Cc: Dave Young <dyoung@redhat.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Cc: Matthew Wilcox <willy@infradead.org> Cc: Petr Mladek <pmladek@suse.com> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Sasha Levin <sashal@kernel.org> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-07-08 01:09:13 +00:00
#if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID) || IS_ENABLED(CONFIG_VMCORE_INFO)
buildid: stash away kernels build ID on init Parse the kernel's build ID at initialization so that other code can print a hex format string representation of the running kernel's build ID. This will be used in the kdump and dump_stack code so that developers can easily locate the vmlinux debug symbols for a crash/stacktrace. [swboyd@chromium.org: fix implicit declaration of init_vmlinux_build_id()] Link: https://lkml.kernel.org/r/CAE-0n51UjTbay8N9FXAyE7_aR2+ePrQnKSRJ0gbmRsXtcLBVaw@mail.gmail.com Link: https://lkml.kernel.org/r/20210511003845.2429846-4-swboyd@chromium.org Signed-off-by: Stephen Boyd <swboyd@chromium.org> Acked-by: Baoquan He <bhe@redhat.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Jessica Yu <jeyu@kernel.org> Cc: Evan Green <evgreen@chromium.org> Cc: Hsin-Yi Wang <hsinyi@chromium.org> Cc: Dave Young <dyoung@redhat.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Cc: Matthew Wilcox <willy@infradead.org> Cc: Petr Mladek <pmladek@suse.com> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Sasha Levin <sashal@kernel.org> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-07-08 01:09:13 +00:00
unsigned char vmlinux_build_id[BUILD_ID_SIZE_MAX] __ro_after_init;
/**
* init_vmlinux_build_id - Compute and stash the running kernel's build ID
*/
void __init init_vmlinux_build_id(void)
{
extern const void __start_notes;
extern const void __stop_notes;
buildid: stash away kernels build ID on init Parse the kernel's build ID at initialization so that other code can print a hex format string representation of the running kernel's build ID. This will be used in the kdump and dump_stack code so that developers can easily locate the vmlinux debug symbols for a crash/stacktrace. [swboyd@chromium.org: fix implicit declaration of init_vmlinux_build_id()] Link: https://lkml.kernel.org/r/CAE-0n51UjTbay8N9FXAyE7_aR2+ePrQnKSRJ0gbmRsXtcLBVaw@mail.gmail.com Link: https://lkml.kernel.org/r/20210511003845.2429846-4-swboyd@chromium.org Signed-off-by: Stephen Boyd <swboyd@chromium.org> Acked-by: Baoquan He <bhe@redhat.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Jessica Yu <jeyu@kernel.org> Cc: Evan Green <evgreen@chromium.org> Cc: Hsin-Yi Wang <hsinyi@chromium.org> Cc: Dave Young <dyoung@redhat.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Cc: Matthew Wilcox <willy@infradead.org> Cc: Petr Mladek <pmladek@suse.com> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Sasha Levin <sashal@kernel.org> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-07-08 01:09:13 +00:00
unsigned int size = &__stop_notes - &__start_notes;
build_id_parse_buf(&__start_notes, vmlinux_build_id, size);
}
dump_stack: add vmlinux build ID to stack traces Add the running kernel's build ID[1] to the stacktrace information header. This makes it simpler for developers to locate the vmlinux with full debuginfo for a particular kernel stacktrace. Combined with scripts/decode_stracktrace.sh, a developer can download the correct vmlinux from a debuginfod[2] server and find the exact file and line number for the functions plus offsets in a stacktrace. This is especially useful for pstore crash debugging where the kernel crashes are recorded in the pstore logs and the recovery kernel is different or the debuginfo doesn't exist on the device due to space concerns (the data can be large and a security concern). The stacktrace can be analyzed after the crash by using the build ID to find the matching vmlinux and understand where in the function something went wrong. Example stacktrace from lkdtm: WARNING: CPU: 4 PID: 3255 at drivers/misc/lkdtm/bugs.c:83 lkdtm_WARNING+0x28/0x30 [lkdtm] Modules linked in: lkdtm rfcomm algif_hash algif_skcipher af_alg xt_cgroup uinput xt_MASQUERADE CPU: 4 PID: 3255 Comm: bash Not tainted 5.11 #3 aa23f7a1231c229de205662d5a9e0d4c580f19a1 Hardware name: Google Lazor (rev3+) with KB Backlight (DT) pstate: 00400009 (nzcv daif +PAN -UAO -TCO BTYPE=--) pc : lkdtm_WARNING+0x28/0x30 [lkdtm] The hex string aa23f7a1231c229de205662d5a9e0d4c580f19a1 is the build ID, following the kernel version number. Put it all behind a config option, STACKTRACE_BUILD_ID, so that kernel developers can remove this information if they decide it is too much. Link: https://lkml.kernel.org/r/20210511003845.2429846-5-swboyd@chromium.org Link: https://fedoraproject.org/wiki/Releases/FeatureBuildId [1] Link: https://sourceware.org/elfutils/Debuginfod.html [2] Signed-off-by: Stephen Boyd <swboyd@chromium.org> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Jessica Yu <jeyu@kernel.org> Cc: Evan Green <evgreen@chromium.org> Cc: Hsin-Yi Wang <hsinyi@chromium.org> Cc: Petr Mladek <pmladek@suse.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Dave Young <dyoung@redhat.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Sasha Levin <sashal@kernel.org> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-07-08 01:09:17 +00:00
#endif