* Re: [PATCH] x86-64: Fix the tcb field load for x32 [BZ #31185]
[not found] <20231221034212.2608829-1-hjl.tools@gmail.com>
@ 2023-12-21 16:10 ` H.J. Lu
0 siblings, 0 replies; only message in thread
From: H.J. Lu @ 2023-12-21 16:10 UTC (permalink / raw)
To: libc-alpha, Libc-stable Mailing List, Noah Goldstein
On Wed, Dec 20, 2023 at 7:42 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> _dl_tlsdesc_undefweak and _dl_tlsdesc_dynamic access the thread pointer
> via the tcb field in TCB:
>
> _dl_tlsdesc_undefweak:
> _CET_ENDBR
> movq 8(%rax), %rax
> subq %fs:0, %rax
> ret
>
> _dl_tlsdesc_dynamic:
> ...
> subq %fs:0, %rax
> movq -8(%rsp), %rdi
> ret
>
> Since the tcb field in TCB is a pointer, %fs:0 is a 32-bit location,
> not 64-bit. It should use "sub %fs:0, %RAX_LP" instead. Since
> _dl_tlsdesc_undefweak returns ptrdiff_t and _dl_make_tlsdesc_dynamic
> returns void *, RAX_LP is appropriate here for x32 and x86-64. This
> fixes BZ #31185.
> ---
> sysdeps/x86_64/dl-tlsdesc.S | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/sysdeps/x86_64/dl-tlsdesc.S b/sysdeps/x86_64/dl-tlsdesc.S
> index c4823547d7..4579424bf7 100644
> --- a/sysdeps/x86_64/dl-tlsdesc.S
> +++ b/sysdeps/x86_64/dl-tlsdesc.S
> @@ -61,7 +61,7 @@ _dl_tlsdesc_return:
> _dl_tlsdesc_undefweak:
> _CET_ENDBR
> movq 8(%rax), %rax
> - subq %fs:0, %rax
> + sub %fs:0, %RAX_LP
> ret
> cfi_endproc
> .size _dl_tlsdesc_undefweak, .-_dl_tlsdesc_undefweak
> @@ -116,7 +116,7 @@ _dl_tlsdesc_dynamic:
> addq TLSDESC_MODOFF(%rdi), %rax
> .Lret:
> movq -16(%rsp), %rsi
> - subq %fs:0, %rax
> + sub %fs:0, %RAX_LP
> movq -8(%rsp), %rdi
> ret
> .Lslow:
> --
> 2.43.0
>
I will check it in tomorrow and back it to release branches later.
Thanks.
--
H.J.
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