gdb/ChangeLog:

* solib-svr4.h (struct link_map_offsets): Add l_ld_offset and
l_ld_size fields.
* solib-svr4.c (struct lm_info): Add l_addr field.
(LM_ADDR_FROM_LINK_MAP): Renamed from LM_ADDR.
(HAS_LM_DYNAMIC_FROM_LINK_MAP): New.
(LM_DYNAMIC_FROM_LINK_MAP): New.
(LM_ADDR_CHECK): New.  Use it instead of LM_ADDR.
(svr4_current_sos): Initialize l_addr.  Adjust.
(svr4_relocate_section_addresses): Adjust.
(svr4_ilp32_fetch_link_map_offsets): Define new members.
(svr4_lp64_fetch_link_map_offsets): Likewise.
* solib-legacy.c (legacy_svr4_fetch_link_map_offsets): Likewise.
* mipsnbsd-tdep.c (mipsnbsd_ilp32_fetch_link_map_offsets): Likewise.
(mipsnbsd_lp64_fetch_link_map_offsets): Likewise.
* Makefile.in (solib-svr4.o): Depend on $(elf_bfd_h).
gdb/testsuite/ChangeLog:
* gdb.base/prelink.exp: New test.
* gdb.base/prelink.c, gdb.base/prelink-lib.c: New sources.

1 files changed, 108 insertions, 5 deletions

diff --git a/gdb/solib-svr4.c b/gdb/solib-svr4.c
index caadb4a26d6..7d740a33b40 100644
--- a/gdb/solib-svr4.c
+++ b/gdb/solib-svr4.c
@@ -42,6 +42,7 @@
 #include "solib-svr4.h"
 
 #include "bfd-target.h"
+#include "elf-bfd.h"
 #include "exec.h"
 
 static struct link_map_offsets *svr4_fetch_link_map_offsets (void);
@@ -59,6 +60,13 @@ struct lm_info
        rather than void *, so that we may use byte offsets to find the
        various fields without the need for a cast.  */
     gdb_byte *lm;
+
+    /* Amount by which addresses in the binary should be relocated to
+       match the inferior.  This could most often be taken directly
+       from lm, but when prelinking is involved and the prelink base
+       address changes, we may need a different offset, we want to
+       warn about the difference and compute it only once.  */
+    CORE_ADDR l_addr;
   };
 
 /* On SVR4 systems, a list of symbols in the dynamic linker where
@@ -127,14 +135,101 @@ static char *main_name_list[] =
 /* link map access functions */
 
 static CORE_ADDR
-LM_ADDR (struct so_list *so)
+LM_ADDR_FROM_LINK_MAP (struct so_list *so)
 {
   struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
 
-  return (CORE_ADDR) extract_signed_integer (so->lm_info->lm + lmo->l_addr_offset, 
+  return (CORE_ADDR) extract_signed_integer (so->lm_info->lm
+					     + lmo->l_addr_offset,
 					     lmo->l_addr_size);
 }
 
+static int
+HAS_LM_DYNAMIC_FROM_LINK_MAP ()
+{
+  struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
+
+  return (lmo->l_ld_size != 0);
+}
+
+static CORE_ADDR
+LM_DYNAMIC_FROM_LINK_MAP (struct so_list *so)
+{
+  struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
+
+  gdb_assert (lmo->l_ld_size != 0);
+
+  return (CORE_ADDR) extract_signed_integer (so->lm_info->lm
+					     + lmo->l_ld_offset,
+					     lmo->l_ld_size);
+}
+
+static CORE_ADDR
+LM_ADDR_CHECK (struct so_list *so, bfd *abfd)
+{
+  if (so->lm_info->l_addr == (CORE_ADDR)-1)
+    {
+      struct bfd_section *dyninfo_sect;
+      CORE_ADDR l_addr, l_dynaddr, dynaddr, align = 0x1000;
+
+      l_addr = LM_ADDR_FROM_LINK_MAP (so);
+
+      if (! abfd || ! HAS_LM_DYNAMIC_FROM_LINK_MAP ())
+	goto set_addr;
+
+      l_dynaddr = LM_DYNAMIC_FROM_LINK_MAP (so);
+
+      dyninfo_sect = bfd_get_section_by_name (abfd, ".dynamic");
+      if (dyninfo_sect == NULL)
+	goto set_addr;
+
+      dynaddr = bfd_section_vma (abfd, dyninfo_sect);
+
+      if (dynaddr + l_addr != l_dynaddr)
+	{
+	  warning (_(".dynamic section for \"%s\" "
+		     "is not at the expected address"), so->so_name);
+
+	  if (bfd_get_flavour (abfd) == bfd_target_elf_flavour)
+	    {
+	      Elf_Internal_Ehdr *ehdr = elf_tdata (abfd)->elf_header;
+	      Elf_Internal_Phdr *phdr = elf_tdata (abfd)->phdr;
+	      int i;
+
+	      align = 1;
+
+	      for (i = 0; i < ehdr->e_phnum; i++)
+		if (phdr[i].p_type == PT_LOAD && phdr[i].p_align > align)
+		  align = phdr[i].p_align;
+	    }
+
+	  /* Turn it into a mask.  */
+	  align--;
+
+	  /* If the changes match the alignment requirements, we
+	     assume we're using a core file that was generated by the
+	     same binary, just prelinked with a different base offset.
+	     If it doesn't match, we may have a different binary, the
+	     same binary with the dynamic table loaded at an unrelated
+	     location, or anything, really.  To avoid regressions,
+	     don't adjust the base offset in the latter case, although
+	     odds are that, if things really changed, debugging won't
+	     quite work.  */
+	  if ((l_addr & align) == 0 && ((dynaddr - l_dynaddr) & align) == 0)
+	    {
+	      l_addr = l_dynaddr - dynaddr;
+	      warning (_("difference appears to be caused by prelink, "
+			 "adjusting expectations"));
+	    }
+	}
+
+    set_addr:
+      so->lm_info->l_addr = l_addr;
+    }
+
+  return so->lm_info->l_addr;
+}
+
 static CORE_ADDR
 LM_NEXT (struct so_list *so)
 {
@@ -649,6 +744,8 @@ svr4_current_sos (void)
 	    free_so (new);
 	  else
 	    {
+	      new->lm_info->l_addr = (CORE_ADDR)-1;
+
 	      new->next = 0;
 	      *link_ptr = new;
 	      link_ptr = &new->next;
@@ -912,7 +1009,7 @@ enable_break (void)
 	  if (strcmp (buf, so->so_original_name) == 0)
 	    {
 	      load_addr_found = 1;
-	      load_addr = LM_ADDR (so);
+	      load_addr = LM_ADDR_CHECK (so, tmp_bfd);
 	      break;
 	    }
 	  so = so->next;
@@ -1272,8 +1369,10 @@ static void
 svr4_relocate_section_addresses (struct so_list *so,
                                  struct section_table *sec)
 {
-  sec->addr    = svr4_truncate_ptr (sec->addr    + LM_ADDR (so));
-  sec->endaddr = svr4_truncate_ptr (sec->endaddr + LM_ADDR (so));
+  sec->addr    = svr4_truncate_ptr (sec->addr    + LM_ADDR_CHECK (so,
+								  sec->bfd));
+  sec->endaddr = svr4_truncate_ptr (sec->endaddr + LM_ADDR_CHECK (so,
+								  sec->bfd));
 }
 
 
@@ -1362,6 +1461,8 @@ svr4_ilp32_fetch_link_map_offsets (void)
       lmo.l_addr_size = 4;
       lmo.l_name_offset = 4;
       lmo.l_name_size = 4;
+      lmo.l_ld_offset = 8;
+      lmo.l_ld_size = 4;
       lmo.l_next_offset = 12;
       lmo.l_next_size = 4;
       lmo.l_prev_offset = 16;
@@ -1395,6 +1496,8 @@ svr4_lp64_fetch_link_map_offsets (void)
       lmo.l_addr_size = 8;
       lmo.l_name_offset = 8;
       lmo.l_name_size = 8;
+      lmo.l_ld_offset = 16;
+      lmo.l_ld_size = 8;
       lmo.l_next_offset = 24;
       lmo.l_next_size = 8;
       lmo.l_prev_offset = 32;