Re: [PATCH 5/5] Add x32 support to amd64_analyze_stack_align

H.J. Lu
2012-06-16T14:42:05Z

On Sat, Jun 16, 2012 at 4:27 AM, Mark Kettenis <mark.kettenis@xs4all.nl> wrote:
>> Date: Wed, 13 Jun 2012 16:08:25 -0700
>> From: "H.J. Lu" <hongjiu.lu@intel.com>
>>
>> Hi,
>>
>> This patch adds support to amd64_analyze_stack_align.  OK to install?
>
> Sorry, no.  I think this function is complex enough as it is now.
> Please create a seperate function for x32.  That may lead to some code
> duplication, but that is better than increasing the complexity of this
> already complex function.
>

This patch adds amd64_x32_analyze_stack_align and uses it
for x32. OK to install?

Thanks.

--
H.J.
---
* amd64-tdep.c (amd64_x32_analyze_stack_align): New function.
(amd64_analyze_prologue): Call amd64_x32_analyze_stack_align
for x32.

diff --git a/gdb/amd64-tdep.c b/gdb/amd64-tdep.c
index 27f115b..5424926 100644
--- a/gdb/amd64-tdep.c
+++ b/gdb/amd64-tdep.c
@@ -1861,6 +1861,188 @@ amd64_analyze_stack_align (CORE_ADDR pc,
CORE_ADDR current_pc,
return min (pc + offset + 2, current_pc);
}

+/* Similar to amd64_analyze_stack_align for x32. */
+
+static CORE_ADDR
+amd64_x32_analyze_stack_align (CORE_ADDR pc, CORE_ADDR current_pc,
+ struct amd64_frame_cache *cache)
+{
+ /* There are 2 code sequences to re-align stack before the frame
+ gets set up:
+
+ 1. Use a caller-saved saved register:
+
+ leaq 8(%rsp), %reg
+ andq $-XXX, %rsp
+ pushq -8(%reg)
+
+ or
+
+ [addr32] leal 8(%rsp), %reg
+ andl $-XXX, %esp
+ [addr32] pushq -8(%reg)
+
+ 2. Use a callee-saved saved register:
+
+ pushq %reg
+ leaq 16(%rsp), %reg
+ andq $-XXX, %rsp
+ pushq -8(%reg)
+
+ or
+
+ pushq %reg
+ [addr32] leal 16(%rsp), %reg
+ andl $-XXX, %esp
+ [addr32] pushq -8(%reg)
+
+ "andq $-XXX, %rsp" can be either 4 bytes or 7 bytes:
+
+ 0x48 0x83 0xe4 0xf0 andq $-16, %rsp
+ 0x48 0x81 0xe4 0x00 0xff 0xff 0xff andq $-256, %rsp
+
+ "andl $-XXX, %esp" can be either 3 bytes or 6 bytes:
+
+ 0x83 0xe4 0xf0 andl $-16, %esp
+ 0x81 0xe4 0x00 0xff 0xff 0xff andl $-256, %esp
+ */
+
+ gdb_byte buf[19];
+ int reg, r;
+ int offset, offset_and;
+
+ if (target_read_memory (pc, buf, sizeof buf))
+ return pc;
+
+ /* Skip optional addr32 prefix. */
+ offset = buf[0] == 0x67 ? 1 : 0;
+
+ /* Check caller-saved saved register. The first instruction has
+ to be "leaq 8(%rsp), %reg" or "leal 8(%rsp), %reg". */
+ if (((buf[offset] & 0xfb) == 0x48 || (buf[offset] & 0xfb) == 0x40)
+ && buf[offset + 1] == 0x8d
+ && buf[offset + 3] == 0x24
+ && buf[offset + 4] == 0x8)
+ {
+ /* MOD must be binary 10 and R/M must be binary 100. */
+ if ((buf[offset + 2] & 0xc7) != 0x44)
+ return pc;
+
+ /* REG has register number. */
+ reg = (buf[offset + 2] >> 3) & 7;
+
+ /* Check the REX.R bit. */
+ if ((buf[offset] & 0x4) != 0)
+ reg += 8;
+
+ offset += 5;
+ }
+ else
+ {
+ /* Check callee-saved saved register. The first instruction
+ has to be "pushq %reg". */
+ reg = 0;
+ if ((buf[offset] & 0xf6) == 0x40
+ && (buf[offset + 1] & 0xf8) == 0x50)
+ {
+ /* Check the REX.B bit. */
+ if ((buf[offset] & 1) != 0)
+ reg = 8;
+
+ offset += 1;
+ }
+ else if ((buf[offset] & 0xf8) != 0x50)
+ return pc;
+
+ /* Get register. */
+ reg += buf[offset] & 0x7;
+
+ offset++;
+
+ /* Skip optional addr32 prefix. */
+ if (buf[offset] == 0x67)
+ offset++;
+
+ /* The next instruction has to be "leaq 16(%rsp), %reg" or
+ "leal 16(%rsp), %reg". */
+ if (((buf[offset] & 0xfb) != 0x48 && (buf[offset] & 0xfb) != 0x40)
+ || buf[offset + 1] != 0x8d
+ || buf[offset + 3] != 0x24
+ || buf[offset + 4] != 0x10)
+ return pc;
+
+ /* MOD must be binary 10 and R/M must be binary 100. */
+ if ((buf[offset + 2] & 0xc7) != 0x44)
+ return pc;
+
+ /* REG has register number. */
+ r = (buf[offset + 2] >> 3) & 7;
+
+ /* Check the REX.R bit. */
+ if ((buf[offset] & 0x4) != 0)
+ r += 8;
+
+ /* Registers in pushq and leaq have to be the same. */
+ if (reg != r)
+ return pc;
+
+ offset += 5;
+ }
+
+ /* Rigister can't be %rsp nor %rbp. */
+ if (reg == 4 || reg == 5)
+ return pc;
+
+ /* The next instruction may be "andq $-XXX, %rsp" or
+ "andl $-XXX, %esp". */
+ if (buf[offset] != 0x48)
+ offset--;
+
+ if (buf[offset + 2] != 0xe4
+ || (buf[offset + 1] != 0x81 && buf[offset + 1] != 0x83))
+ return pc;
+
+ offset_and = offset;
+ offset += buf[offset + 1] == 0x81 ? 7 : 4;
+
+ /* Skip optional addr32 prefix. */
+ if (buf[offset] == 0x67)
+ offset++;
+
+ /* The next instruction has to be "pushq -8(%reg)". */
+ r = 0;
+ if (buf[offset] == 0xff)
+ offset++;
+ else if ((buf[offset] & 0xf6) == 0x40
+ && buf[offset + 1] == 0xff)
+ {
+ /* Check the REX.B bit. */
+ if ((buf[offset] & 0x1) != 0)
+ r = 8;
+ offset += 2;
+ }
+ else
+ return pc;
+
+ /* 8bit -8 is 0xf8. REG must be binary 110 and MOD must be binary
+ 01. */
+ if (buf[offset + 1] != 0xf8
+ || (buf[offset] & 0xf8) != 0x70)
+ return pc;
+
+ /* R/M has register. */
+ r += buf[offset] & 7;
+
+ /* Registers in leaq and pushq have to be the same. */
+ if (reg != r)
+ return pc;
+
+ if (current_pc > pc + offset_and)
+ cache->saved_sp_reg = amd64_arch_reg_to_regnum (reg);
+
+ return min (pc + offset + 2, current_pc);
+}
+
/* Do a limited analysis of the prologue at PC and update CACHE
accordingly. Bail out early if CURRENT_PC is reached. Return the
address where the analysis stopped.
@@ -1898,7 +2080,10 @@ amd64_analyze_prologue (struct gdbarch *gdbarch,
if (current_pc <= pc)
return current_pc;

- pc = amd64_analyze_stack_align (pc, current_pc, cache);
+ if (gdbarch_ptr_bit (gdbarch) == 32)
+ pc = amd64_x32_analyze_stack_align (pc, current_pc, cache);
+ else
+ pc = amd64_analyze_stack_align (pc, current_pc, cache);

op = read_memory_unsigned_integer (pc, 1, byte_order);