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dwarf: Account for multiple CFA for args_size

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It is possible to have multiple CFA_args_size adjustments for a single
frame.  If the CFA_args_size adjustment is immediately following the
return from a function which can raise an exception, it is possible to
incorrectly adjust the stack pointer.  Consider the following:

  ...
  .cfi_escape 0x2e, 0x00
  call f
.Ltmp:
  .cfi_escape 0x2e, 0x10
  lea label@GOTOFF(%ebx), %eax
  ...

Because we process the CFI program up to and *INCLUDING* IP, where the
IP is the RA, we would process the associated DW_CFA_GNU_args_size for
the post-call instruction.  The result would be a DW_CFA_GNU_args_size
of 0x10 rather than 0x00, resulting in an incorrect stack adjustment.
Handle this by processing the CFI operation but not adjusting the state
record unless we are below the current IP.
This commit is contained in:
Saleem Abdulrasool 2017-01-18 13:56:19 -08:00 committed by Dave Watson
parent 9e97c9b17a
commit e9e8ed73e3
1 changed files with 5 additions and 2 deletions
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7
src/dwarf/Gparser.c
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@ -356,8 +356,11 @@ run_cfi_program (struct dwarf_cursor *c, dwarf_state_record_t *sr,
case DW_CFA_GNU_args_size:
if ((ret = dwarf_read_uleb128 (as, a, addr, &val, arg)) < 0)
goto fail;
sr->args_size = val;
Debug (15, "CFA_GNU_args_size %lu\n", (long) val);
if (curr_ip < ip)
{
sr->args_size = val;
Debug (15, "CFA_GNU_args_size %lu\n", (long) val);
}
break;
case DW_CFA_GNU_negative_offset_extended: