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[PATCH][binutils] Fix printing of .debug_str_offsets

Tom de Vries tdevries@suse.de
Thu Feb 11 13:58:26 GMT 2021 
Hi,

With exec:
...
$ clang -gdwarf-5 ./src/gdb/testsuite/gdb.dwarf2/fission-mix*.c
...
we have:
...
$ readelf -w a.out
  ...
Contents of the .debug_str_offsets section:

    Length: 0x24
    Version: 0x5
       Index   Offset [String]
           0      1d0 clang version 10.0.1
           1      1e6 src/gdb/testsuite/gdb.dwarf2/fission-mix-2.c
           2      213 /home/vries/gdb_versions/devel
           3      232 bar
           4      236 x
           5       61 int
           6      238 s
           7      23a func2
           8       2c ild/BUILD/glibc-2.26/csu
           9        5 sdeps/x86_64/start.S
          10      1d0 clang version 10.0.1
          11      240 src/gdb/testsuite/gdb.dwarf2/fission-mix.c
          12      213 /home/vries/gdb_versions/devel
          13      26b foo
          14      236 x
          15       61 int
          16      238 s
          17      26f func
          18      274 main
          19      279 arg
...

The section consists of two parts, one for each CU, each with a header, but
the printing only reads the first header as a header, and prints the second
header as:
...
           8       2c ild/BUILD/glibc-2.26/csu
           9        5 sdeps/x86_64/start.S
...

Fix this in display_debug_str_offsets such that we have:
...
           6      238 s
           7      23a func2
    Length: 0x2c
    Version: 0x5
       Index   Offset [String]
           0      1d0 clang version 10.0.1
           1      240 src/gdb/testsuite/gdb.dwarf2/fission-mix.c
...

OK for trunk?

Thanks,
- Tom

[binutils] Fix printing of .debug_str_offsets

binutils/ChangeLog:

2021-02-11  Tom de Vries  <tdevries@suse.de>

	* dwarf.c (display_debug_str_offsets): Handle multiple sets of
	entries.

---
 binutils/dwarf.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/binutils/dwarf.c b/binutils/dwarf.c
index c96613f37e6..e55a7daa8fe 100644
--- a/binutils/dwarf.c
+++ b/binutils/dwarf.c
@@ -7379,18 +7379,22 @@ display_debug_str_offsets (struct dwarf_section *section,
       else
 	entry_length = 4;
 
+      unsigned char *entries_end;
       if (length == 0)
 	{
 	  /* This is probably an old style .debug_str_offset section which
 	     just contains offsets and no header (and the first offset is 0).  */
 	  length = section->size;
 	  curr   = section->start;
+	  entries_end = end;
 
 	  printf (_("    Length: %#lx\n"), (unsigned long) length);
 	  printf (_("       Index   Offset [String]\n"));
 	}
       else
 	{
+	  entries_end = curr + length;
+
 	  int version;
 	  SAFE_BYTE_GET_AND_INC (version, curr, 2, end);
 	  if (version != 5)
@@ -7406,11 +7410,15 @@ display_debug_str_offsets (struct dwarf_section *section,
 	  printf (_("       Index   Offset [String]\n"));
 	}
 
-      for (idx = 0; length >= entry_length && curr < end; idx++)
+      for (idx = 0; curr < entries_end; idx++)
 	{
 	  dwarf_vma offset;
 	  const unsigned char * string;
 
+	  if (curr + entry_length > entries_end)
+	    /* Not enough space to read one entry_length, give up.  */
+	    return 0;
+
 	  SAFE_BYTE_GET_AND_INC (offset, curr, entry_length, end);
 	  if (dwo)
 	    string = (const unsigned char *)
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