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* i386-tdep.c (i386_skip_noop): New function. 

(i386_analyze_prologue): Call i386_skip_noop function.
This commit is contained in:
Pierre Muller 2008-01-25 17:24:49 +00:00
parent 6e3d6dc1ed
commit e11481da79
2 changed files with 51 additions and 0 deletions
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5
gdb/ChangeLog
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@ -1,3 +1,8 @@
2008-01-25 Pierre Muller <muller@ics.u-strasbg.fr>
* i386-tdep.c (i386_skip_noop): New function.
(i386_analyze_prologue): Call i386_skip_noop function.
2008-01-24 Michael Snyder <msnyder@specifix.com>
* procfs.c (procfs_xfer_partial): Comment, cut/paste error.

46
gdb/i386-tdep.c
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@ -632,6 +632,51 @@ struct i386_insn i386_frame_setup_skip_insns[] =
{ 0 }
};
/* Check whether PC points to a no-op instruction. */
static CORE_ADDR
i386_skip_noop (CORE_ADDR pc)
{
gdb_byte op;
int check = 1;
read_memory_nobpt (pc, &op, 1);
while (check)
{
check = 0;
/* Ignore `nop' instruction. */
if (op == 0x90)
{
pc += 1;
read_memory_nobpt (pc, &op, 1);
check = 1;
}
/* Ignore no-op instruction `mov %edi, %edi'.
Microsoft system dlls often start with
a `mov %edi,%edi' instruction.
The 5 bytes before the function start are
filled with `nop' instructions.
This pattern can be used for hot-patching:
The `mov %edi, %edi' instruction can be replaced by a
near jump to the location of the 5 `nop' instructions
which can be replaced by a 32-bit jump to anywhere
in the 32-bit address space. */
else if (op == 0x8b)
{
read_memory_nobpt (pc + 1, &op, 1);
if (op == 0xff)
{
pc += 2;
read_memory_nobpt (pc, &op, 1);
check = 1;
}
}
}
return pc;
}
/* Check whether PC points at a code that sets up a new stack frame.
If so, it updates CACHE and returns the address of the first
instruction after the sequence that sets up the frame or LIMIT,
@ -817,6 +862,7 @@ static CORE_ADDR
i386_analyze_prologue (CORE_ADDR pc, CORE_ADDR current_pc,
struct i386_frame_cache *cache)
{
pc = i386_skip_noop (pc);
pc = i386_follow_jump (pc);
pc = i386_analyze_struct_return (pc, current_pc, cache);
pc = i386_skip_probe (pc);