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dwarves: Fixup sizeof(long double) in bits in base_type_name_to_size table 

We were erroneously setting it to 64 bits everywhere, i.e. 8 bytes, when
it in fact is 16 bytes, 128 bits, as we can see with:

  $ btfdiff libc-2.28.so.debug
  --- /tmp/btfdiff.dwarf.RuqA9q	2019-02-26 10:25:49.828150761 -0300
  +++ /tmp/btfdiff.btf.t3XqV6	2019-02-26 10:25:49.835150835 -0300
  @@ -461,9 +461,15 @@ struct La_x86_64_retval {
 	  uint64_t                   lrv_rdx;              /*     8     8 */
 	  La_x86_64_xmm              lrv_xmm0;             /*    16    16 */
 	  La_x86_64_xmm              lrv_xmm1;             /*    32    16 */
  -	long double                lrv_st0;              /*    48    16 */
  +	long double                lrv_st0;              /*    48     8 */
  +
  +	/* XXX 8 bytes hole, try to pack */
  +
 	  /* --- cacheline 1 boundary (64 bytes) --- */
  -	long double                lrv_st1;              /*    64    16 */
  +	long double                lrv_st1;              /*    64     8 */
  +
  +	/* XXX 8 bytes hole, try to pack */
  +
 	  La_x86_64_vector           lrv_vector0;          /*    80    64 */
 	  /* --- cacheline 2 boundary (128 bytes) was 16 bytes ago --- */
 	  La_x86_64_vector           lrv_vector1;          /*   144    64 */

And:

  $ cat long_double.c
  #include <stdio.h>

  int main(void)
  {
	  return printf("sizeof(long double)=%zd\n", sizeof(long double));
  }
  $ ./long_double
  sizeof(long double)=16
  $ file long_double
  long_double: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, BuildID[sha1]=c876603879d49905fbd7fc5907dc65ad3bca422f, not stripped
  $

So use sizeof to at least match the running machine, this is
insufficient for cross-platform analysis, so a new fix is needed to
cover those cases, this at least improves the current situation a bit.

Reported-by: Andrii Nakryiko <andriin@fb.com>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: Yonghong Song <yhs@fb.com>
link: https://lore.kernel.org/bpf/20190226131156.GA26786@kernel.org/
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Arnaldo Carvalho de Melo 2019-02-26 10:26:14 -03:00
parent 5081ed5070
commit be5173b4df
1 changed files with 2 additions and 2 deletions
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dwarves.c
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@ -168,8 +168,8 @@ static struct base_type_name_to_size {
{ .name = "double double", .size = 64, },
{ .name = "single float", .size = 32, },
{ .name = "float", .size = 32, },
{ .name = "long double", .size = 64, },
{ .name = "long double long double", .size = 64, },
{ .name = "long double", .size = sizeof(long double) * 8, },
{ .name = "long double long double", .size = sizeof(long double) * 8, },
{ .name = "__int128", .size = 128, },
{ .name = "unsigned __int128", .size = 128, },
{ .name = "__int128 unsigned", .size = 128, },