[Crash-utility] [RFC PATCH 16/16] Fix compare_syms() not to put a text symbol out of range

[lijiang]

On Thu, May 25, 2023 at 4:02 PM HAGIO KAZUHITO(萩尾 一仁) <k-hagio-ab at nec.com>
wrote:

> From: Kazuhito Hagio <k-hagio-ab at nec.com>
>
> Without the patch, a __pfx symbol having the same address as its module
> text pseudo symbol is located at before the pseudo symbol and it is not
> displayed by "sym" command, after loading module symbols.  For example,
>
>   crash> sym -m dm_mod | head -n 3
>   ffffffffc07e8000 MODULE TEXT START: dm_mod
>   ffffffffc07e8000 (T) __pfx_dm_send_uevents
>   ffffffffc07e8010 (T) dm_send_uevents
>   crash> mod -s dm_mod
>   crash> sym -m dm_mod | head -n 3
>   ffffffffc07e8000 MODULE TEXT START: dm_mod
>   ffffffffc07e8010 (T) dm_send_uevents
>   ffffffffc07e81a0 (T) __pfx_dm_path_uevent
>   crash> set debug 1
>   crash> help -s
>   ...
>           loaded_objfile: 54dd800
>     ffffffffc07e8000  __pfx_dm_send_uevents     << out of MOD_TEXT range
>     ffffffffc07e8000  _MODULE_TEXT_START_dm_mod
>     ffffffffc07e8010  dm_send_uevents
>     ffffffffc07e81a0  __pfx_dm_path_uevent
>
> Signed-off-by: Kazuhito Hagio <k-hagio-ab at nec.com>
> ---
>  symbols.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/symbols.c b/symbols.c
> index a1e54c6f9f98..7153bf9a2dc1 100644
> --- a/symbols.c
> +++ b/symbols.c
> @@ -3433,7 +3433,8 @@ compare_syms(const void *v1, const void *v2)
>                         return -1;
>                 if (STRNEQ(s2->name, "__insmod"))
>                         return 1;
> -               if (STRNEQ(s2->name, "_MODULE_START_"))
> +               if (MODULE_MEM_START(s2, MOD_TEXT) ||
> +                   STRNEQ(s2->name, "_MODULE_START_"))
>

You are right. They have different *PSEUDO* symbol names:
_MODULE_TEXT_START_xxx and _MODULE_START_xxx.

And we also need to check for similar cases in all patches.

Thanks.
Lianbo

                        return 1;
>                 /* Get pseudo section name. */
>                 if (MODULE_SECTION_START(s1))
> --
> 2.31.1
>
>
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