Fix false match of non-build-id disk library to build-id memory library.

this patch:
	Use DT_DEBUG library search first.
	8ff862960efb648cdff647d7fad1be5acffe9b11
	[patch 2/2] Fix loading core files without build-ids
	https://lists.fedorahosted.org/pipermail/elfutils-devel/2013-April/003031.html
	[patch 2/2 v2] Fix loading core files without build-ids
	https://lists.fedorahosted.org/pipermail/elfutils-devel/2013-May/003065.html

has PASS->FAIL regression on CentOS-5 for run-unstrip-n.sh:

-actual on CentOS-5
+expected by testcase

-0xf77b3000+0x822c - /lib/librt.so.1 - librt.so.1
-0xf7603000+0x15c5c4 - /lib/libc.so.6 - libc.so.6
-0xf75e9000+0x191e4 - /lib/libpthread.so.0 - libpthread.so.0
-0xf77d7000+0x1c670 - /lib/ld-linux.so.2 - ld-linux.so.2
 0x8048000+0x2000 f1c600bc36cb91bf01f9a63a634ecb79aa4c3199@0x8048178 . - [exe]
+0xf75e9000+0x1a000 29a103420abe341e92072fb14274e250e4072148@0xf75e9164 - - libpthread.so.0
+0xf7603000+0x1b0000 0b9bf374699e141e5dfc14757ff42b8c2373b4de@0xf7603184 - - libc.so.6
+0xf77b3000+0x9000 c6c5b5e35ab9589d4762ac85b4bd56b1b2720e37@0xf77b3164 - - librt.so.1
 0xf77d6000+0x1000 676560b1b765cde9c2e53f134f4ee354ea894747@0xf77d6210 . - linux-gate.so.1
+0xf77d7000+0x21000 6d2cb32650054f1c176d01d48713a4a5e5e84c1a@0xf77d7124 - - ld-linux.so.2

Therefore elfutils now incorrectly matches on-disk file without build-id to an
in-core (in-memory) file with build-id.

In fact due to its known FIXME:
                    This verification gives false positive if in-core ELF had
                    build-id but on-disk ELF does not have any.  But we cannot
                    reliably find ELF header and/or the ELF build id just from
                    the link map (and checking core segments is also not
                    reliable).  */

So it probably should not be so ignorable as I did, one may want to analyze
build-id core files on CentOS-5, not sure.  In fact it can be fixed, when we
find in dwfl_segment_report_module a module with build-id with conflicts in
its address range with existing non-build-id dwfl_link_map_report module we
should prefer the build-id module instead.

The problem is that once Dwfl_Module is added to Dwfl it cannot be easily
removed.

Originally elfutils called dwfl_segment_report_module first and then
dwfl_link_map_report.

Currently the order is dwfl_link_map_report and then
dwfl_segment_report_module only for modules missing from dwfl_link_map_report.

Patch below unfortunately needs bidirectional negotiation between the two
functions, therefore dwfl_link_map_report now no longer adds Dwfl_Modules to
Dwfl but it only stores information about them to r_debug_info_module.
This information is filtered then by dwfl_segment_report_module and only
filtered r_debug_info_module entries get finally added to Dwfl
(in dwfl_core_file_report).

NT_FILE would make all this magic easy but it is true that on CentOS-5 it
definitely does not exist.

libdwfl/
2013-07-23  Jan Kratochvil  <[email protected]>

	* core-file.c (clear_r_debug_info): Close also ELF and FD.
	(dwfl_core_file_report): Call __libdwfl_report_elf for
	R_DEBUG_INFO.MODULE.
	* dwfl_report_elf.c (__libdwfl_elf_address_range): New function from
	code of ...
	(__libdwfl_report_elf): ... this function.  Call it.
	* dwfl_segment_report_module.c: Include unistd.h.
	(dwfl_segment_report_module): Use basename for MODULE->NAME.
	Clear MODULE if it has no build-id and we have segment with build-id.
	Ignore this segment only if MODULE still contains valid ELF.
	* libdwflP.h (__libdwfl_elf_address_range): New declaration.
	(struct r_debug_info_module): New fields fd, elf, l_addr, start, end
	and disk_file_has_build_id.
	(dwfl_link_map_report): Extend the comment.
	* link_map.c (report_r_debug): Extend the comment.  Always fill in new
	r_debug_info_module.  Initialize also the new r_debug_info_module
	fields.  Remove one FIXME comment.  Call __libdwfl_elf_address_range
	instead of __libdwfl_report_elf when R_DEBUG_INFO is not NULL.

tests/
2013-07-23  Jan Kratochvil  <[email protected]>

	* run-unstrip-n.sh (test-core.*): Ignore libc.so.6 entry and order of
	the entries.

Signed-off-by: Jan Kratochvil <[email protected]>

1 files changed, 55 insertions, 28 deletions

diff --git a/libdwfl/link_map.c b/libdwfl/link_map.c
index fecf616d..65e1c3a6 100644
--- a/libdwfl/link_map.c
+++ b/libdwfl/link_map.c
@@ -224,7 +224,9 @@ addrsize (uint_fast8_t elfclass)
 
 /* Report a module for each struct link_map in the linked list at r_map
    in the struct r_debug at R_DEBUG_VADDR.  For r_debug_info description
-   see dwfl_link_map_report in libdwflP.h.
+   see dwfl_link_map_report in libdwflP.h.  If R_DEBUG_INFO is not NULL then no
+   modules get added to DWFL, caller has to add them from filled in
+   R_DEBUG_INFO.
 
    For each link_map entry, if an existing module resides at its address,
    this just modifies that module's name and suggested file name.  If
@@ -355,6 +357,28 @@ report_r_debug (uint_fast8_t elfclass, uint_fast8_t elfdata,
       if (iterations == 1 && dwfl->executable_for_core != NULL)
 	name = dwfl->executable_for_core;
 
+      struct r_debug_info_module *r_debug_info_module = NULL;
+      if (r_debug_info != NULL)
+	{
+	  /* Save link map information about valid shared library (or
+	     executable) which has not been found on disk.  */
+	  const char *name1 = name == NULL ? "" : name;
+	  r_debug_info_module = malloc (sizeof (*r_debug_info_module)
+					+ strlen (name1) + 1);
+	  if (r_debug_info_module == NULL)
+	    return release_buffer (result);
+	  r_debug_info_module->fd = -1;
+	  r_debug_info_module->elf = NULL;
+	  r_debug_info_module->l_addr = l_addr;
+	  r_debug_info_module->l_ld = l_ld;
+	  r_debug_info_module->start = 0;
+	  r_debug_info_module->end = 0;
+	  r_debug_info_module->disk_file_has_build_id = false;
+	  strcpy (r_debug_info_module->name, name1);
+	  r_debug_info_module->next = r_debug_info->module;
+	  r_debug_info->module = r_debug_info_module;
+	}
+
       Dwfl_Module *mod = NULL;
       if (name != NULL)
 	{
@@ -374,19 +398,15 @@ report_r_debug (uint_fast8_t elfclass, uint_fast8_t elfdata,
 
 		  /* FIXME: Bias L_ADDR should be computed from the prelink
 		     state in memory (when the file got loaded), not against
-		     the current on-disk file state as is computed below.
-
-		     This verification gives false positive if in-core ELF had
-		     build-id but on-disk ELF does not have any.  But we cannot
-		     reliably find ELF header and/or the ELF build id just from
-		     the link map (and checking core segments is also not
-		     reliable).  */
+		     the current on-disk file state as is computed below.  */
 
 		  if (__libdwfl_find_elf_build_id (NULL, elf, &build_id_bits,
 						   &build_id_elfaddr,
 						   &build_id_len) > 0
 		      && build_id_elfaddr != 0)
 		    {
+		      if (r_debug_info_module != NULL)
+			r_debug_info_module->disk_file_has_build_id = true;
 		      GElf_Addr build_id_vaddr = build_id_elfaddr + l_addr;
 		      release_buffer (0);
 		      int segndx = INTUSE(dwfl_addrsegment) (dwfl,
@@ -410,31 +430,38 @@ report_r_debug (uint_fast8_t elfclass, uint_fast8_t elfdata,
 		    }
 
 		  if (valid)
-		    // XXX hook for sysroot
-		    mod = __libdwfl_report_elf (dwfl, basename (name), name,
-						fd, elf, l_addr, true, true);
-		  if (mod == NULL)
 		    {
-		      elf_end (elf);
-		      close (fd);
+		      if (r_debug_info_module == NULL)
+			{
+			  // XXX hook for sysroot
+			  mod = __libdwfl_report_elf (dwfl, basename (name),
+						      name, fd, elf, l_addr,
+						      true, true);
+			  if (mod != NULL)
+			    {
+			      elf = NULL;
+			      fd = -1;
+			    }
+			}
+		      else if (__libdwfl_elf_address_range (elf, l_addr, true,
+							    true, NULL, NULL,
+						    &r_debug_info_module->start,
+						    &r_debug_info_module->end,
+							    NULL, NULL))
+			{
+			  r_debug_info_module->elf = elf;
+			  r_debug_info_module->fd = fd;
+			  elf = NULL;
+			  fd = -1;
+			}
 		    }
+		  if (elf != NULL)
+		    elf_end (elf);
+		  if (fd != -1)
+		    close (fd);
 		}
 	    }
 	}
-      if (r_debug_info != NULL && mod == NULL)
-	{
-	  /* Save link map information about valid shared library (or
-	     executable) which has not been found on disk.  */
-	  const char *base = name == NULL ? "" : basename (name);
-	  struct r_debug_info_module *module;
-	  module = malloc (sizeof (*module) + strlen (base) + 1);
-	  if (module == NULL)
-	    return release_buffer (result);
-	  module->l_ld = l_ld;
-	  strcpy (module->name, base);
-	  module->next = r_debug_info->module;
-	  r_debug_info->module = module;
-	}
 
       if (mod != NULL)
 	{