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/* Thread-local storage handling in the ELF dynamic linker. i386 version.
Copyright (C) 2004-2023 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <sysdep.h>
#include <tls.h>
#include "tlsdesc.h"
.text
/* This function is used to compute the TP offset for symbols in
Static TLS, i.e., whose TP offset is the same for all
threads.
The incoming %eax points to the TLS descriptor, such that
0(%eax) points to _dl_tlsdesc_return itself, and 4(%eax) holds
the TP offset of the symbol corresponding to the object
denoted by the argument. */
.hidden _dl_tlsdesc_return
.global _dl_tlsdesc_return
.type _dl_tlsdesc_return,@function
cfi_startproc
.align 16
_dl_tlsdesc_return:
_CET_ENDBR
movl 4(%eax), %eax
ret
cfi_endproc
.size _dl_tlsdesc_return, .-_dl_tlsdesc_return
/* This function is used for undefined weak TLS symbols, for
which the base address (i.e., disregarding any addend) should
resolve to NULL.
%eax points to the TLS descriptor, such that 0(%eax) points to
_dl_tlsdesc_undefweak itself, and 4(%eax) holds the addend.
We return the addend minus the TP, such that, when the caller
adds TP, it gets the addend back. If that's zero, as usual,
that's most likely a NULL pointer. */
.hidden _dl_tlsdesc_undefweak
.global _dl_tlsdesc_undefweak
.type _dl_tlsdesc_undefweak,@function
cfi_startproc
.align 16
_dl_tlsdesc_undefweak:
_CET_ENDBR
movl 4(%eax), %eax
subl %gs:0, %eax
ret
cfi_endproc
.size _dl_tlsdesc_undefweak, .-_dl_tlsdesc_undefweak
#ifdef SHARED
.hidden _dl_tlsdesc_dynamic
.global _dl_tlsdesc_dynamic
.type _dl_tlsdesc_dynamic,@function
/* This function is used for symbols that need dynamic TLS.
%eax points to the TLS descriptor, such that 0(%eax) points to
_dl_tlsdesc_dynamic itself, and 4(%eax) points to a struct
tlsdesc_dynamic_arg object. It must return in %eax the offset
between the thread pointer and the object denoted by the
argument, without clobbering any registers.
The assembly code that follows is a rendition of the following
C code, hand-optimized a little bit.
ptrdiff_t
__attribute__ ((__regparm__ (1)))
_dl_tlsdesc_dynamic (struct tlsdesc *tdp)
{
struct tlsdesc_dynamic_arg *td = tdp->arg;
dtv_t *dtv = *(dtv_t **)((char *)__thread_pointer + DTV_OFFSET);
if (__builtin_expect (td->gen_count <= dtv[0].counter
&& (dtv[td->tlsinfo.ti_module].pointer.val
!= TLS_DTV_UNALLOCATED),
1))
return dtv[td->tlsinfo.ti_module].pointer.val + td->tlsinfo.ti_offset
- __thread_pointer;
return ___tls_get_addr (&td->tlsinfo) - __thread_pointer;
}
*/
cfi_startproc
.align 16
_dl_tlsdesc_dynamic:
_CET_ENDBR
/* Like all TLS resolvers, preserve call-clobbered registers.
We need two scratch regs anyway. */
subl $28, %esp
cfi_adjust_cfa_offset (28)
movl %ecx, 20(%esp)
movl %edx, 24(%esp)
movl TLSDESC_ARG(%eax), %eax
movl %gs:DTV_OFFSET, %edx
movl TLSDESC_GEN_COUNT(%eax), %ecx
cmpl (%edx), %ecx
ja .Lslow
movl TLSDESC_MODID(%eax), %ecx
movl (%edx,%ecx,8), %edx
cmpl $-1, %edx
je .Lslow
movl TLSDESC_MODOFF(%eax), %eax
addl %edx, %eax
.Lret:
movl 20(%esp), %ecx
subl %gs:0, %eax
movl 24(%esp), %edx
addl $28, %esp
cfi_adjust_cfa_offset (-28)
ret
.p2align 4,,7
.Lslow:
cfi_adjust_cfa_offset (28)
call HIDDEN_JUMPTARGET (___tls_get_addr)
jmp .Lret
cfi_endproc
.size _dl_tlsdesc_dynamic, .-_dl_tlsdesc_dynamic
#endif /* SHARED */
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