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[PATCH] AMD64, Prologue: Recognize stack decrementation as prologue operation.
- From: Bernhard Heckel <bernhard dot heckel at intel dot com>
- To: qiyaoltc at gmail dot com
- Cc: gdb-patches at sourceware dot org, Bernhard Heckel <bernhard dot heckel at intel dot com>
- Date: Thu, 1 Dec 2016 15:16:44 +0100
- Subject: [PATCH] AMD64, Prologue: Recognize stack decrementation as prologue operation.
- Authentication-results: sourceware.org; auth=none
Some compiler decrement stack pointer within the prologue
sequence in order to reserve memory for local variables.
Recognize this subtraction to stop at the very end of the
prologue.
2016-10-20 Bernhard Heckel <bernhard.heckel@intel.com>
gdb/Changelog:
amd64-tdep.c (amd64_analyze_prologue): Recognize stack decrementation
as prologue operation.
---
gdb/amd64-tdep.c | 30 ++++++++++++++++++++++++++++++
1 file changed, 30 insertions(+)
diff --git a/gdb/amd64-tdep.c b/gdb/amd64-tdep.c
index a3a1fde..795d78e 100644
--- a/gdb/amd64-tdep.c
+++ b/gdb/amd64-tdep.c
@@ -2283,6 +2283,12 @@ amd64_analyze_prologue (struct gdbarch *gdbarch,
/* Ditto for movl %esp, %ebp. */
static const gdb_byte mov_esp_ebp_1[2] = { 0x89, 0xe5 };
static const gdb_byte mov_esp_ebp_2[2] = { 0x8b, 0xec };
+ /* Ditto for subtraction on the stack pointer. */
+ static const gdb_byte sub_rsp_imm8[3] = { 0x48, 0x83, 0xec };
+ static const gdb_byte sub_rsp_imm32[3] = { 0x48, 0x81, 0xec };
+ /* Ditto for subtraction on the stack pointer. */
+ static const gdb_byte sub_esp_imm8[2] = { 0x83, 0xec };
+ static const gdb_byte sub_esp_imm32[2] = { 0x81, 0xec };
gdb_byte buf[3];
gdb_byte op;
@@ -2316,6 +2322,18 @@ amd64_analyze_prologue (struct gdbarch *gdbarch,
{
/* OK, we actually have a frame. */
cache->frameless_p = 0;
+
+ /* Some compiler do subtraction on the stack pointer
+ to reserve memory for local variables.
+ Two common variants exist to do so. */
+ read_code (pc + 4, buf, 3);
+ if (memcmp (buf, sub_rsp_imm8, 3) == 0)
+ /* Operand is 1 byte. */
+ return pc + 8;
+ else if (memcmp (buf, sub_rsp_imm32, 3) == 0)
+ /* Operand is 4 bytes. */
+ return pc + 11;
+
return pc + 4;
}
@@ -2327,6 +2345,18 @@ amd64_analyze_prologue (struct gdbarch *gdbarch,
{
/* OK, we actually have a frame. */
cache->frameless_p = 0;
+
+ /* Some compiler do subtraction on the stack pointer
+ to reserve memory for local variables.
+ Two common variants exist to do so. */
+ read_code (pc + 3, buf, 2);
+ if (memcmp (buf, sub_esp_imm8, 2) == 0)
+ /* Operand is 1 byte. */
+ return pc + 6;
+ else if (memcmp (buf, sub_esp_imm32, 2) == 0)
+ /* Operand is 4 bytes. */
+ return pc + 9;
+
return pc + 3;
}
}
--
2.7.1.339.g0233b80