From: H.J. Lu <hjl.tools@gmail.com>
Date: Thu, 21 Dec 2023 03:42:12 +0000 (-0800)
Subject: x86-64: Fix the tcb field load for x32 [BZ #31185]
X-Git-Tag: glibc-2.39~168
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=81be2a61dafc168327c1639e97b6dae128c7ccf3;p=thirdparty%2Fglibc.git

x86-64: Fix the tcb field load for x32 [BZ #31185]

_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.
---

diff --git a/sysdeps/x86_64/dl-tlsdesc.S b/sysdeps/x86_64/dl-tlsdesc.S
index c4823547d7b..4579424bf7e 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: