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Re: [PATCH] Skip VDSO when reading SO list
- From: Andreas Arnez <arnez at linux dot vnet dot ibm dot com>
- To: Jan Kratochvil <jan dot kratochvil at redhat dot com>
- Cc: gdb-patches at sourceware dot org, Andreas Krebbel <krebbel at linux dot vnet dot ibm dot com>
- Date: Tue, 20 Aug 2013 13:44:18 +0200
- Subject: Re: [PATCH] Skip VDSO when reading SO list
- References: <87d2p9oi4i dot fsf at br87z6lw dot de dot ibm dot com> <20130819182907 dot GA2145 at host2 dot jankratochvil dot net>
Jan Kratochvil <jan.kratochvil@redhat.com> writes:
> On Mon, 19 Aug 2013 16:44:13 +0200, Andreas Arnez wrote:
>> On some Linux versions, the file name (l_name) of a VDSO's link map
>> entry lies in read-only memory that is excluded from a core dump.
>> When reading such a core dump, GDB complains:
>>
>> warning: Can't read pathname for load map: Input/output error.
>
> I believe the right fix is in glibc instead:
> [patch] Fix vDSO l_name for GDB's: Can't read pathname for load map:Input/output error.
> http://sourceware.org/ml/libc-alpha/2009-10/msg00001.html
> Message-ID: <20091004161706.GA27450@host0.dyn.jankratochvil.net>
>
> Could you verify it works for you so that we could possibly ping it?
This patch doesn't apply anymore, because the glibc code has been
restructured, e.g. the vdso logic is now separated out in
elf/setup-vdso.h.
Maybe the following patch would nowadays do the trick.
diff --git a/elf/dl-object.c b/elf/dl-object.c
index 0f594d2..de142de 100644
--- a/elf/dl-object.c
+++ b/elf/dl-object.c
@@ -62,6 +62,7 @@ _dl_new_object (char *realname, const char *libname, int type,
size_t libname_len = strlen (libname) + 1;
struct link_map *new;
struct libname_list *newname;
+ static char rw_empty_string[] = { 0 };
#ifdef SHARED
/* We create the map for the executable before we know whether we have
auditing libraries and if yes, how many. Assume the worst. */
@@ -88,7 +89,7 @@ _dl_new_object (char *realname, const char *libname, int type,
/* newname->next = NULL; We use calloc therefore not necessary. */
newname->dont_free = 1;
- new->l_name = realname;
+ new->l_name = *realname ? realname : rw_empty_string;
new->l_type = type;
/* If we set the bit now since we know it is never used we avoid
dirtying the cache line later. */