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Re: [PATCH] AMD64, Prologue: Recognize stack decrementation as prologue operation.
- From: Yao Qi <qiyaoltc at gmail dot com>
- To: Bernhard Heckel <bernhard dot heckel at intel dot com>
- Cc: gdb-patches at sourceware dot org
- Date: Fri, 2 Dec 2016 23:06:34 +0000
- Subject: Re: [PATCH] AMD64, Prologue: Recognize stack decrementation as prologue operation.
- Authentication-results: sourceware.org; auth=none
- References: <1480601804-3128-1-git-send-email-bernhard.heckel@intel.com>
On 16-12-01 15:16:44, Bernhard Heckel wrote:
> Some compiler decrement stack pointer within the prologue
As Luis reviewed, it is clear to mention the name of the compilers
here.
> 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
File name should be started with "*".
> 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
Please mention the name of the compilers here.
> + 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
Likewise.
> + 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;
> +
Could you add a unit test for this new prologue sequences? Like what we
did in this patch
https://sourceware.org/ml/gdb-patches/2016-12/msg00071.html Both x86_64
and x32 prologue should be tested, because your patch is for both of
them.
--
Yao