[Bug corefiles/27689] FAIL: gdb.base/gcore-tls-pie.exp: x/i $pc

["vries at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=27689

--- Comment #1 from Tom de Vries <vries at gcc dot gnu.org> ---
(In reply to Tom de Vries from comment #0)
> warning: core file may not match specified executable file.^M

I looked into this warning.  It's due to a mismatch in buildid, which is caused
by incorrect reading of the buildid for the core.

We're trying to read the following 3 notes from the core:
...
                      04 00 00 00  10 00 00 00 01 00 00 00  |o.2.............|
00000770  47 4e 55 00 00 00 00 00  03 00 00 00 02 00 00 00  |GNU.............|
00000780  00 00 00 00

                       00 00 00 00

                                   04 00 00 00 20 00 00 00  |............ ...|
00000790  05 00 00 00 47 4e 55 00  02 80 00 c0 04 00 00 00  |....GNU.........|
000007a0  01 00 00 00 00 00 00 00  01 00 01 c0 04 00 00 00  |................|
000007b0  01 00 00 00 00 00 00 00

                                   04 00 00 00 14 00 00 00  |................|
000007c0  03 00 00 00 47 4e 55 00  79 c4 e9 5a c4 c0 5c ce  |....GNU.y..Z..\.|
000007d0  95 e9 38 e2 13 58 41 4e  2e fa 5f c7
...

[ Note format: First word is name size (4 in all cases), second words is data
size (0x10, 0x20 and 0x14), third word is type (1,5,3, see NT_GNU constants in
include/elf/common.h), then there's the name, "GNU\0", followed by the data. ]

First we have a NT_GNU_ABI_TAG note, then a NT_GNU_PROPERTY_TYPE_0 note, then a
NT_GNU_BUILD_ID note.

However, the NT_GNU_PROPERTY_TYPE_0 note has alignment 8:
... 
  [Nr] Name              Type            Address          Off    Size   ES Flg
Lk Inf Al
  ...
  [16] .note.gnu.property NOTE            0000000000000000 000390 000030 00   A
 0   0  8
...
to it doesn't start immediately after the NT_GNU_ABI_TAG note, instead we have
4 bytes padding (00 00 00 00).

The padding throws off the note reader in bfd, so the last two notes are not
read correctly.

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