bfd/dwarf: Improve use of previously loaded dwarf information

When parsing DWARF data in order to report file/line type error messages
we perform section placement to make section addresses unique within
relocatable object files.

Currently, if we reuse previously loaded (and cached) dwarf data then we
neglect to perform section placement, the result is that the section
addresses will not be unique, and we might, incorrectly associate an
address with the wrong debug information, and so report an incorrect
file and line number.

Further we neglect to check that that bfd for which we are looking up
debug information is actually the bfd for which the previous debug
information was loaded, it is possible that we will reuse previously
loaded debug information for a different bfd.

And finally, due to following of gnu_debuglink links in one bfd to
another, the process of checking that the cached debug information is
valid requires us to track the original bfd in the cached debug
information.  The original debug information here is either the bfd that
we're interested in, not the bfd we finally load the debug information
from.

bfd/ChangeLog:

	* dwarf2.c (struct dwarf2_debug): Add orig_bfd member.
	(_bfd_dwarf2_slurp_debug_info): If stashed debug information does
	not match current bfd, then reload debug information.  Record bfd
	we're loading debug info for in the stash.  If we have debug
	informatin in the cache then perform section placement before
	returning.

ld/ChangeLog:

	* testsuite/ld-elf/dwarf.exp (build_tests): Add new tests.
	* testsuite/ld-elf/dwarf2.err: New file.
	* testsuite/ld-elf/dwarf2a.c: New file.
	* testsuite/ld-elf/dwarf2b.c: New file.
	* testsuite/ld-elf/dwarf3.c: New file.
	* testsuite/ld-elf/dwarf3.err: New file.

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 0c45c44bfed94f00d93f043e8a521e7cf270c234..01314bda146263b08391c0143a6bbad7b3aca8c5 100644 (file)
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,12 @@
+2017-02-16  Andrew Burgess  <andrew.burgess@embecosm.com>
+
+       * dwarf2.c (struct dwarf2_debug): Add orig_bfd member.
+       (_bfd_dwarf2_slurp_debug_info): If stashed debug information does
+       not match current bfd, then reload debug information.  Record bfd
+       we're loading debug info for in the stash.  If we have debug
+       informatin in the cache then perform section placement before
+       returning.
+
 2017-02-16  Alan Modra  <amodra@gmail.com>
 
        PR 21000

diff --git a/bfd/dwarf2.c b/bfd/dwarf2.c
index 6b111d3d7a0d2bb89e76f6c2d626f38cb1a23e00..03447a908a5337b543c64849ffb086183ba0ae6d 100644 (file)
--- a/bfd/dwarf2.c
+++ b/bfd/dwarf2.c
@@ -100,6 +100,12 @@ struct dwarf2_debug
   /* Pointer to the end of the .debug_info section memory buffer.  */
   bfd_byte *info_ptr_end;
 
+  /* Pointer to the original bfd for which debug was loaded.  This is what
+     we use to compare and so check that the cached debug data is still
+     valid - it saves having to possibly dereference the gnu_debuglink each
+     time.  */
+  bfd *orig_bfd;
+
   /* Pointer to the bfd, section and address of the beginning of the
      section.  The bfd might be different than expected because of
      gnu_debuglink sections.  */
@@ -3897,8 +3903,20 @@ _bfd_dwarf2_slurp_debug_info (bfd *abfd, bfd *debug_bfd,
 
   if (stash != NULL)
     {
-      if (section_vma_same (abfd, stash))
-       return TRUE;
+      if (stash->orig_bfd == abfd
+          && section_vma_same (abfd, stash))
+        {
+          /* Check that we did previously find some debug information
+             before attempting to make use of it.  */
+          if (stash->bfd_ptr != NULL)
+            {
+              if (do_place && !place_sections (abfd, stash))
+                return FALSE;
+              return TRUE;
+            }
+
+          return FALSE;
+        }
       _bfd_dwarf2_cleanup_debug_info (abfd, pinfo);
       memset (stash, 0, amt);
     }
@@ -3908,6 +3926,7 @@ _bfd_dwarf2_slurp_debug_info (bfd *abfd, bfd *debug_bfd,
       if (! stash)
        return FALSE;
     }
+  stash->orig_bfd = abfd;
   stash->debug_sections = debug_sections;
   stash->syms = symbols;
   if (!save_section_vma (abfd, stash))

diff --git a/ld/ChangeLog b/ld/ChangeLog
index 8d493737e3d79dadbc0c1726f1b159bf756e9d55..696e08afffb5e1bcfa847e91e19fce01c4c63837 100644 (file)
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -1,3 +1,12 @@
+2017-02-16  Andrew Burgess  <andrew.burgess@embecosm.com>
+
+       * testsuite/ld-elf/dwarf.exp (build_tests): Add new tests.
+       * testsuite/ld-elf/dwarf2.err: New file.
+       * testsuite/ld-elf/dwarf2a.c: New file.
+       * testsuite/ld-elf/dwarf2b.c: New file.
+       * testsuite/ld-elf/dwarf3.c: New file.
+       * testsuite/ld-elf/dwarf3.err: New file.
+
 2017-02-16  Andrew Burgess  <andrew.burgess@embecosm.com>
 
        * testsuite/lib/ld-lib.exp (run_cc_link_tests): Add warning,

diff --git a/ld/testsuite/ld-elf/dwarf.exp b/ld/testsuite/ld-elf/dwarf.exp
index 529ebccd505d73d2bf4b9e27b516742e0c353cf8..25b0c9d47637c7f7dd0b73c5d38525f66b984a42 100644 (file)
--- a/ld/testsuite/ld-elf/dwarf.exp
+++ b/ld/testsuite/ld-elf/dwarf.exp
@@ -49,6 +49,12 @@ set build_tests {
   {"Build libdwarf1.so"
    "-s -shared" "-fPIC -g -feliminate-dwarf2-dups"
    {dwarf1.c} {} "libdwarf1.so"}
+  {"DWARF parse during linker error"
+   "" "-fno-toplevel-reorder"
+   {dwarf2a.c dwarf2b.c} {{error_output "dwarf2.err"}} "dwarf2.x"}
+  {"Handle no DWARF information"
+   "" "-g0"
+   {dwarf3.c} {{error_output "dwarf3.err"}} "dwarf3.x"}
 }
 
 set run_tests {

diff --git a/ld/testsuite/ld-elf/dwarf2.err b/ld/testsuite/ld-elf/dwarf2.err
new file mode 100644 (file)
index 0000000..872d282
--- /dev/null
+++ b/ld/testsuite/ld-elf/dwarf2.err
@@ -0,0 +1,4 @@
+tmpdir/dwarf2b\.o:\(\.data\+0x0\): multiple definition of `global_var'
+tmpdir/dwarf2a\.o:\(\.data\+0x0\): first defined here
+tmpdir/dwarf2b\.o:\(\.data\+0x4\): multiple definition of `other_var'
+tmpdir/dwarf2a\.o:\(\.data\+0x4\): first defined here

diff --git a/ld/testsuite/ld-elf/dwarf2a.c b/ld/testsuite/ld-elf/dwarf2a.c
new file mode 100644 (file)
index 0000000..1de5794
--- /dev/null
+++ b/ld/testsuite/ld-elf/dwarf2a.c
@@ -0,0 +1,8 @@
+int global_var = 3;
+int other_var = 4;
+
+int
+function (void)
+{
+  return 0;
+}

diff --git a/ld/testsuite/ld-elf/dwarf2b.c b/ld/testsuite/ld-elf/dwarf2b.c
new file mode 100644 (file)
index 0000000..c557978
--- /dev/null
+++ b/ld/testsuite/ld-elf/dwarf2b.c
@@ -0,0 +1,10 @@
+int global_var = 4;
+int other_var = 2;
+
+extern int function (void);
+
+int
+main ()
+{
+  return function ();
+}

diff --git a/ld/testsuite/ld-elf/dwarf3.c b/ld/testsuite/ld-elf/dwarf3.c
new file mode 100644 (file)
index 0000000..054eb9b
--- /dev/null
+++ b/ld/testsuite/ld-elf/dwarf3.c
@@ -0,0 +1,13 @@
+/* This test is actually used to test for a segfault that came from the bfd
+   dwarf parsing code in the case when there is _no_ dwarf info.  */
+
+extern void bar (int a);
+
+int
+main ()
+{
+  bar (1);
+  bar (2);
+
+  return 0;
+}

diff --git a/ld/testsuite/ld-elf/dwarf3.err b/ld/testsuite/ld-elf/dwarf3.err
new file mode 100644 (file)
index 0000000..6027431
--- /dev/null
+++ b/ld/testsuite/ld-elf/dwarf3.err
@@ -0,0 +1,4 @@
+.*/dwarf3\.o: In function `main':
+.*dwarf3.c:\(\.text.*\+0x[0-9a-f]+\): undefined reference to `bar'
+.*dwarf3.c:\(\.text.*\+0x[0-9a-f]+\): undefined reference to `bar'
+#...
\ No newline at end of file