Re: [PATCH] Skip VDSO when reading SO list

Jan Kratochvil
2013-09-20T13:15:58Z

On Mon, 19 Aug 2013 16:44:13 +0200, Andreas Arnez wrote:
> 2013-08-19 Andreas Arnez <arnez@linux.vnet.ibm.com>
>
> * solib-svr4.c (svr4_read_so_list): Skip the VDSO when reading
vDSO
> link map entries.

Could you include here the testcase from:
http://pkgs.fedoraproject.org/cgit/gdb.git/tree/gdb-core-open-vdso-warning.patch

> Index: gdb/gdb/solib-svr4.c
> ===================================================================
> --- gdb.orig/gdb/solib-svr4.c
> +++ gdb/gdb/solib-svr4.c
> @@ -1310,6 +1310,7 @@ static int
> svr4_read_so_list (CORE_ADDR lm, CORE_ADDR prev_lm,
> struct so_list ***link_ptr_ptr, int ignore_first)
> {
> + struct so_list *first = NULL;
> CORE_ADDR next_lm;
>
> for (; lm != 0; prev_lm = lm, lm = next_lm)
> @@ -1349,10 +1350,22 @@ svr4_read_so_list (CORE_ADDR lm, CORE_AD
> {
> struct svr4_info *info = get_svr4_info ();
>
> + first = new;
> info->main_lm_addr = new->lm_info->lm_addr;
> do_cleanups (old_chain);
> continue;
> }
> +
> + /* The l_name of a VDSO sometimes lies in read-only memory that
vDSO
> + is excluded from a core dump. In order to avoid the "can't
> + read pathname" warning, we try to identify the VDSO. One
vDSO
> + criteria is that the l_name address matches that of the main
> + executable. */
> + if (first && new->lm_info->l_name == first->lm_info->l_name)

Here should be also '&& ignore_first'.

> + {
> + do_cleanups (old_chain);
> + continue;
> + }

And move this block below so that the condition is evaluated only if
target_read_string has really failed.

The purpose is that no workarounds should complicate the code in the case the
system components are already bug-free (after glibc gets fixed).

>
> /* Extract this shared object's name. */
> target_read_string (new->lm_info->l_name, &buffer,

Please make one new post after the updates.

Thanks,
Jan