PATCH: Check DS segment register for x32 process

H.J. Lu
2012-05-11T19:31:29Z

Hi,

This patch checks DS segment register for x32 process. Tested on
Linux/x86-64. OK to install?

Thanks.

H.J.
---
* amd64-linux-nat.c (AMD64_LINUX_X32_DS): New.
(amd64_linux_read_description): Check DS segment register for
x32 process.

diff --git a/gdb/amd64-linux-nat.c b/gdb/amd64-linux-nat.c
index 3be8404..97c9a49 100644
--- a/gdb/amd64-linux-nat.c
+++ b/gdb/amd64-linux-nat.c
@@ -756,16 +945,23 @@ amd64_linux_siginfo_fixup (siginfo_t *native, gdb_byte *inf, int direction)
Value of CS segment register:
1. 64bit process: 0x33.
2. 32bit process: 0x23.
+
+ Value of DS segment register:
+ 1. LP64 process: 0x0.
+ 2. X32 process: 0x2b.
*/

#define AMD64_LINUX_USER64_CS 0x33
+#define AMD64_LINUX_X32_DS 0x2b

static const struct target_desc *
amd64_linux_read_description (struct target_ops *ops)
{
unsigned long cs;
+ unsigned long ds;
int tid;
int is_64bit;
+ int is_x32;
static uint64_t xcr0;

/* GNU/Linux LWP ID's are process ID's. */
@@ -782,6 +978,18 @@ amd64_linux_read_description (struct target_ops *ops)

is_64bit = cs == AMD64_LINUX_USER64_CS;

+ /* Get DS register. */
+ errno = 0;
+ ds = ptrace (PTRACE_PEEKUSER, tid,
+ offsetof (struct user_regs_struct, ds), 0);
+ if (errno != 0)
+ perror_with_name (_("Couldn't get DS register"));
+
+ is_x32 = ds == AMD64_LINUX_X32_DS;
+
+ if (sizeof (void *) == 4 && is_64bit && !is_x32)
+ error (_("Can't debug 64-bit process with 32-bit GDB"));
+
if (have_ptrace_getregset == -1)
{
uint64_t xstateregs[(I386_XSTATE_SSE_SIZE / sizeof (uint64_t))];
@@ -809,14 +1017,24 @@ amd64_linux_read_description (struct target_ops *ops)
&& (xcr0 & I386_XSTATE_AVX_MASK) == I386_XSTATE_AVX_MASK)
{
if (is_64bit)
- return tdesc_amd64_avx_linux;
+ {
+ if (is_x32)
+ return tdesc_x32_avx_linux;
+ else
+ return tdesc_amd64_avx_linux;
+ }
else
return tdesc_i386_avx_linux;
}
else
{
if (is_64bit)
- return tdesc_amd64_linux;
+ {
+ if (is_x32)
+ return tdesc_x32_linux;
+ else
+ return tdesc_amd64_linux;
+ }
else
return tdesc_i386_linux;
}