* [PATCH] x86-64: Fix the dtv field load for x32 [BZ #31184]
@ 2023-12-21 0:31 H.J. Lu
2023-12-21 16:08 ` H.J. Lu
0 siblings, 1 reply; 2+ messages in thread
From: H.J. Lu @ 2023-12-21 0:31 UTC (permalink / raw)
To: libc-alpha
On x32, I got
FAIL: elf/tst-tlsgap
$ gdb elf/tst-tlsgap
...
open tst-tlsgap-mod1.so
Thread 2 "tst-tlsgap" received signal SIGSEGV, Segmentation fault.
[Switching to LWP 2268754]
_dl_tlsdesc_dynamic () at ../sysdeps/x86_64/dl-tlsdesc.S:108
108 movq (%rsi), %rax
(gdb) p/x $rsi
$4 = 0xf7dbf9005655fb18
(gdb)
This is caused by
_dl_tlsdesc_dynamic:
_CET_ENDBR
/* Preserve call-clobbered registers that we modify.
We need two scratch regs anyway. */
movq %rsi, -16(%rsp)
movq %fs:DTV_OFFSET, %rsi
Since the dtv field in TCB is a pointer, %fs:DTV_OFFSET is a 32-bit
location, not 64-bit. Load the dtv field to RSI_LP instead of rsi.
This fixes BZ #31184.
---
sysdeps/x86_64/dl-tlsdesc.S | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/sysdeps/x86_64/dl-tlsdesc.S b/sysdeps/x86_64/dl-tlsdesc.S
index 5593897e29..c4823547d7 100644
--- a/sysdeps/x86_64/dl-tlsdesc.S
+++ b/sysdeps/x86_64/dl-tlsdesc.S
@@ -102,7 +102,7 @@ _dl_tlsdesc_dynamic:
/* Preserve call-clobbered registers that we modify.
We need two scratch regs anyway. */
movq %rsi, -16(%rsp)
- movq %fs:DTV_OFFSET, %rsi
+ mov %fs:DTV_OFFSET, %RSI_LP
movq %rdi, -8(%rsp)
movq TLSDESC_ARG(%rax), %rdi
movq (%rsi), %rax
--
2.43.0
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] x86-64: Fix the dtv field load for x32 [BZ #31184]
2023-12-21 0:31 [PATCH] x86-64: Fix the dtv field load for x32 [BZ #31184] H.J. Lu
@ 2023-12-21 16:08 ` H.J. Lu
0 siblings, 0 replies; 2+ messages in thread
From: H.J. Lu @ 2023-12-21 16:08 UTC (permalink / raw)
To: libc-alpha, Libc-stable Mailing List
On Wed, Dec 20, 2023 at 4:31 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On x32, I got
>
> FAIL: elf/tst-tlsgap
>
> $ gdb elf/tst-tlsgap
> ...
> open tst-tlsgap-mod1.so
>
> Thread 2 "tst-tlsgap" received signal SIGSEGV, Segmentation fault.
> [Switching to LWP 2268754]
> _dl_tlsdesc_dynamic () at ../sysdeps/x86_64/dl-tlsdesc.S:108
> 108 movq (%rsi), %rax
> (gdb) p/x $rsi
> $4 = 0xf7dbf9005655fb18
> (gdb)
>
> This is caused by
>
> _dl_tlsdesc_dynamic:
> _CET_ENDBR
> /* Preserve call-clobbered registers that we modify.
> We need two scratch regs anyway. */
> movq %rsi, -16(%rsp)
> movq %fs:DTV_OFFSET, %rsi
>
> Since the dtv field in TCB is a pointer, %fs:DTV_OFFSET is a 32-bit
> location, not 64-bit. Load the dtv field to RSI_LP instead of rsi.
> This fixes BZ #31184.
> ---
> sysdeps/x86_64/dl-tlsdesc.S | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/sysdeps/x86_64/dl-tlsdesc.S b/sysdeps/x86_64/dl-tlsdesc.S
> index 5593897e29..c4823547d7 100644
> --- a/sysdeps/x86_64/dl-tlsdesc.S
> +++ b/sysdeps/x86_64/dl-tlsdesc.S
> @@ -102,7 +102,7 @@ _dl_tlsdesc_dynamic:
> /* Preserve call-clobbered registers that we modify.
> We need two scratch regs anyway. */
> movq %rsi, -16(%rsp)
> - movq %fs:DTV_OFFSET, %rsi
> + mov %fs:DTV_OFFSET, %RSI_LP
> movq %rdi, -8(%rsp)
> movq TLSDESC_ARG(%rax), %rdi
> movq (%rsi), %rax
> --
> 2.43.0
>
I will check it in tomorrow and back it to release branches later.
Thanks.
--
H.J.
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2023-12-21 0:31 [PATCH] x86-64: Fix the dtv field load for x32 [BZ #31184] H.J. Lu
2023-12-21 16:08 ` H.J. Lu
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