Glibc 2.18 was changed by
commit ecbf434213c0333d81706074e4d107ac45011635
Author: Andreas Jaeger <a...@suse.de>
Date: Wed May 15 20:20:54 2013 +0200
Reserve new TLS field for x86 and x86_64
[BZ #10686]
* sysdeps/x86_64/tls.h (struct tcbhead_t): Add __private_ss
field.
* sysdeps/i386/tls.h (struct tcbhead_t): Likewise.
to reduce the size of __private_tm to make room for __private_ss, which
was supposed to be used for TARGET_THREAD_SPLIT_STACK_OFFSET:
typedef struct
{
void *tcb; /* Pointer to the TCB. Not necessarily the
thread descriptor used by libpthread. */
dtv_t *dtv;
void *self; /* Pointer to the thread descriptor. */
int multiple_threads;
uintptr_t sysinfo;
uintptr_t stack_guard;
uintptr_t pointer_guard;
int gscope_flag;
int __glibc_reserved1;
/* Reservation of some values for the TM ABI. */
void *__private_tm[4];
/* GCC split stack support. */
void *__private_ss;
} tcbhead_t;
But the offset of __private_ss for i386 was mistakenly set to 0x30,
instead of 0x34 and libgcc/config/i386/morestack.S has:
cmpl %gs:0x30,%eax # See if we have enough space.
movl %eax,%gs:0x30 # Save the new stack boundary.
movl %eax,%gs:0x30 # Save the new stack boundary.
movl %ecx,%gs:0x30 # Save new stack boundary.
movl %eax,%gs:0x30
movl %gs:0x30,%eax
movl %eax,%gs:0x30
Since update TARGET_THREAD_SPLIT_STACK_OFFSET changes split stack ABI,
glibc 2.28 has been changed by
commit 0221ce2a90be2d40fc90f0b5dcec77a1ec013f53
Author: H.J. Lu <hjl.to...@gmail.com>
Date: Tue Jun 12 06:23:28 2018 -0700
i386: Change offset of __private_ss to 0x30 [BZ #23250]
to match GCC:
typedef struct
{
void *tcb; /* Pointer to the TCB. Not necessarily the
thread descriptor used by libpthread. */
dtv_t *dtv;
void *self; /* Pointer to the thread descriptor. */
int multiple_threads;
uintptr_t sysinfo;
uintptr_t stack_guard;
uintptr_t pointer_guard;
int gscope_flag;
int __glibc_reserved1;
/* Reservation of some values for the TM ABI. */
void *__private_tm[3];
/* GCC split stack support. */
void *__private_ss;
void *__glibc_reserved2;
} tcbhead_t;
I am going to check it in as an obvious patch.
Thanks.
H.J.
----
PR target/85990
* config/i386/gnu-user.h (TARGET_THREAD_SPLIT_STACK_OFFSET):
Update comments.
* config/i386/gnu-user64.h (TARGET_THREAD_SPLIT_STACK_OFFSET):
Likewise.
---
gcc/config/i386/gnu-user.h | 2 +-
gcc/config/i386/gnu-user64.h | 4 +++-
2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/gcc/config/i386/gnu-user.h b/gcc/config/i386/gnu-user.h
index d1dad685e72..56449a5439e 100644
--- a/gcc/config/i386/gnu-user.h
+++ b/gcc/config/i386/gnu-user.h
@@ -134,6 +134,6 @@ along with GCC; see the file COPYING3. If not see
/* i386 glibc provides __stack_chk_guard in %gs:0x14. */
#define TARGET_THREAD_SSP_OFFSET 0x14
-/* We steal the last transactional memory word. */
+/* i386 glibc provides __private_ss in %gs:0x30. */
#define TARGET_THREAD_SPLIT_STACK_OFFSET 0x30
#endif
diff --git a/gcc/config/i386/gnu-user64.h b/gcc/config/i386/gnu-user64.h
index 491416fec0c..f7a68fdecf0 100644
--- a/gcc/config/i386/gnu-user64.h
+++ b/gcc/config/i386/gnu-user64.h
@@ -86,7 +86,9 @@ see the files COPYING3 and COPYING.RUNTIME respectively. If
not, see
#define TARGET_THREAD_SSP_OFFSET \
(TARGET_64BIT ? (TARGET_X32 ? 0x18 : 0x28) : 0x14)
-/* We steal the last transactional memory word. */
+/* i386 glibc provides __private_ss in %gs:0x30.
+ x32 glibc provides it in %fs:0x40.
+ x86_64 glibc provides it in %fs:0x70. */
#define TARGET_THREAD_SPLIT_STACK_OFFSET \
(TARGET_64BIT ? (TARGET_X32 ? 0x40 : 0x70) : 0x30)
#endif
--
2.17.1
