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

[Pedro Alves <pedro@codesourcery.com>]

On Friday 19 June 2009 17:03:24, Aleksandar Ristovski wrote:
> 
> Yes, it works:

Okay, I've applied it, as below.

> (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
                          ^^
                          ^^

IIRC, this is due to only pulling in symbols from shared
libraries automatically if there's an exec_bfd (post_create_inferior).
I think that if we audit all solib-*.c implementations to make sure
they won't crash or do something wild without an exec_bfd, we
could remove that restriction.

-- 
Pedro Alves

2009-06-20  Aleksandar Ristovski  <aristovski@qnx.com>
	    Pedro Alves  <pedro@codesourcery.com>

	* solib-svr4.c (IGNORE_FIRST_LINK_MAP_ENTRY): Avoid dereferencing
	NULL pointer.
	(scan_dyntag): Skip if input bfd isn't elf flavoured.
	(locate_base): Call elf_locate_base even without an exec_bfd.

---
 gdb/solib-svr4.c |   14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

Index: src/gdb/solib-svr4.c
===================================================================
--- src.orig/gdb/solib-svr4.c	2009-06-18 20:55:50.000000000 +0100
+++ src/gdb/solib-svr4.c	2009-06-18 22:25:11.000000000 +0100
@@ -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,
@@ -600,9 +600,13 @@ scan_dyntag (int dyntag, bfd *abfd, CORE
 
   if (abfd == NULL)
     return 0;
+
+  if (bfd_get_flavour (abfd) != bfd_target_elf_flavour)
+    return 0;
+
   arch_size = bfd_get_arch_size (abfd);
   if (arch_size == -1)
-   return 0;
+    return 0;
 
   /* Find the start address of the .dynamic section.  */
   sect = bfd_get_section_by_name (abfd, ".dynamic");
@@ -825,11 +829,7 @@ locate_base (struct svr4_info *info)
      though if we don't have some link map offsets to work with.  */
 
   if (info->debug_base == 0 && svr4_have_link_map_offsets ())
-    {
-      if (exec_bfd != NULL
-	  && bfd_get_flavour (exec_bfd) == bfd_target_elf_flavour)
-	info->debug_base = elf_locate_base ();
-    }
+    info->debug_base = elf_locate_base ();
   return info->debug_base;
 }