[patch] solib-svr4.c - allow reading linkmap info from core without executable

Aleksandar Ristovski
2009-05-29T20:42:17Z

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Hello,

This small patch allows solib-svr4.c to attempt to read
linkmap info from core file when executable binary is not given.

e.g.:
$ gdb --core testsuite/gdb.base/bigcore.corefile
...
(gdb) info sharedlibrary
No shared libraries loaded at this time.
(gdb)

after patch:

$ ./gdb --nx --core testsuite/gdb.base/bigcore.corefile
GNU gdb (GDB) 6.8.50.20090529-cvs
...
(gdb) info shared
From To Syms Read Shared Object Library
0x4cb3e470 0x4cb58844 No /lib/libm.so.6
0x4ca18dd0 0x4cafe490 No /lib/libc.so.6
0x4c9e5880 0x4c9fa8ef No /lib/ld-linux.so.2
(gdb)

Thanks,

--
Aleksandar Ristovski
QNX Software Systems

ChangeLog:

* solib-svr4.c (IGNORE_FIRST_LINK_MAP_ENTRY): Avoid
dereferencing NULL
pointer.
(locate_base): If exec_bfd is NULL, use core_bfd if.

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Index: gdb/solib-svr4.c
===================================================================
RCS file: /cvs/src/src/gdb/solib-svr4.c,v
retrieving revision 1.100
diff -u -p -r1.100 solib-svr4.c
--- gdb/solib-svr4.c 22 May 2009 23:49:13 -0000 1.100
+++ gdb/solib-svr4.c 29 May 2009 20:34:49 -0000
@@ -266,7 +266,7 @@ IGNORE_FIRST_LINK_MAP_ENTRY (struct so_l

/* Assume that everything is a library if the dynamic loader was loaded
late by a static executable. */
- if (bfd_get_section_by_name (exec_bfd, ".dynamic") == NULL)
+ if (exec_bfd && bfd_get_section_by_name (exec_bfd, ".dynamic") == NULL)
return 0;

return extract_typed_address (so->lm_info->lm + lmo->l_prev_offset,
@@ -826,8 +826,10 @@ locate_base (struct svr4_info *info)

if (info->debug_base == 0 && svr4_have_link_map_offsets ())
{
- if (exec_bfd != NULL
+ if ((exec_bfd != NULL
&& bfd_get_flavour (exec_bfd) == bfd_target_elf_flavour)
+ || (core_bfd != NULL
+ && bfd_get_flavour (core_bfd) == bfd_target_elf_flavour))
info->debug_base = elf_locate_base ();
}
return info->debug_base;