Re: [PATCH v2 03/12] dump_stack: Add vmlinux build ID to stack traces

[Andy Shevchenko]

On Tue, Mar 23, 2021 at 07:04:34PM -0700, Stephen Boyd wrote:
> 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:

Can we drop the noise from the example and leave only important part(s)?

>  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.

-- 
With Best Regards,
Andy Shevchenko