Add the running kernel's build ID to the stacktrace information header. This makes it simpler for developers to locate the vmlinux with full debug info for a particular kernel stacktrace. Combined with scripts/decode_stracktrace.sh a developer can download the correct vmlinux from a debuginfod server and find the exact line number and file for the functions in a stacktrace.
This is especially useful for pstore or crash debugging where the kernel crashes and the recovery kernel may be different or the debug symbols don't exist on the device due to space concerns. The stacktrace can be analyzed after the crash with the matching vmlinux to 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] 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] direct_entry+0x16c/0x1b4 [lkdtm] 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 ]--- The hex string aa23f7a1231c229de205662d5a9e0d4c580f19a1 is the build ID, following the kernel version number. Cc: Jiri Olsa <[email protected]> Cc: Alexei Starovoitov <[email protected]> Cc: Jessica Yu <[email protected]> Cc: Evan Green <[email protected]> Cc: Hsin-Yi Wang <[email protected]> Signed-off-by: Stephen Boyd <[email protected]> --- lib/dump_stack.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/lib/dump_stack.c b/lib/dump_stack.c index f5a33b6f773f..a13f3ea218d3 100644 --- a/lib/dump_stack.c +++ b/lib/dump_stack.c @@ -5,6 +5,7 @@ */ #include <linux/kernel.h> +#include <linux/buildid.h> #include <linux/export.h> #include <linux/sched.h> #include <linux/sched/debug.h> @@ -45,13 +46,13 @@ void __init dump_stack_set_arch_desc(const char *fmt, ...) */ void dump_stack_print_info(const char *log_lvl) { - printk("%sCPU: %d PID: %d Comm: %.20s %s%s %s %.*s\n", + printk("%sCPU: %d PID: %d Comm: %.20s %s%s %s %.*s %s\n", log_lvl, raw_smp_processor_id(), current->pid, current->comm, kexec_crash_loaded() ? "Kdump: loaded " : "", print_tainted(), init_utsname()->release, (int)strcspn(init_utsname()->version, " "), - init_utsname()->version); + init_utsname()->version, vmlinux_build_id()); if (dump_stack_arch_desc_str[0] != '\0') printk("%sHardware name: %s\n", -- https://chromeos.dev
