On Tue 2021-03-23 19:04:35, Stephen Boyd wrote:
> Let's make kernel stacktraces easier to identify by including the build
> ID[1] of a module if the stacktrace is printing a symbol from a module.
>
> Example:
>
> WARNING: CPU: 3 PID: 3373 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 hci_uart <modules trimmed>
> CPU: 3 PID: 3373 Comm: bash Not tainted 5.11 #12 a8c0d47f7051f3e6670ceaea724af66a39c6cec8
I tested it with "echo l >/proc/sysrq-trigger" and I got the following
output:
[ 71.905593] CPU: 0 PID: 1762 Comm: bash Kdump: loaded Not tainted 5.12.0-rc5-default+ #167 00000080ffffffff0000000000000000
00000000
It does not looks like an unique build-id.
Any idea what was going wrong?
> --- a/include/linux/kallsyms.h
> +++ b/include/linux/kallsyms.h
> @@ -91,6 +93,7 @@ const char *kallsyms_lookup(unsigned long addr,
>
> /* Look up a kernel symbol and return it in a text buffer. */
> extern int sprint_symbol(char *buffer, unsigned long address);
> +extern int sprint_symbol_stacktrace(char *buffer, unsigned long address);
> extern int sprint_symbol_no_offset(char *buffer, unsigned long address);
> extern int sprint_backtrace(char *buffer, unsigned long address);
Could we use a more clear name? It is hard to guess what is
the difference between sprint_*_stacktrace() and sprint_backtrace().
What about sprint_symbol_build_id() ?
> diff --git a/kernel/module.c b/kernel/module.c
> index 30479355ab85..9e9cb502fb33 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -2770,6 +2771,20 @@ static void add_kallsyms(struct module *mod, const struct load_info *info)
> }
> mod->core_kallsyms.num_symtab = ndst;
> }
> +
> +static void init_build_id(struct module *mod, const struct load_info *info)
> +{
> + const Elf_Shdr *sechdr;
> + unsigned int i;
> +
> + for (i = 0; i < info->hdr->e_shnum; i++) {
> + sechdr = &info->sechdrs[i];
> + if (!sect_empty(sechdr) && sechdr->sh_type == SHT_NOTE &&
> + !build_id_parse_buf((void *)sechdr->sh_addr, mod->build_id,
> + sechdr->sh_size))
> + break;
> + }
Just to be sure. Is this really reliable way how to find the build ID,
please?
> +}
> #else
> static inline void layout_symtab(struct module *mod, struct load_info *info)
> {
> @@ -2778,6 +2793,10 @@ static inline void layout_symtab(struct module *mod, struct load_info *info)
> static void add_kallsyms(struct module *mod, const struct load_info *info)
> {
> }
Best Regards,
Petr
