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/* Thread-local storage handling in the ELF dynamic linker. i386 version.
Copyright (C) 2004-2021 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 */
/* This function is a wrapper for a lazy resolver for TLS_DESC
REL relocations that reference the *ABS* segment in their own
link maps. %ebx points to the caller's GOT. %eax points to a
TLS descriptor, such that 0(%eax) holds the address of the
resolver wrapper itself (unless some other thread beat us to
it) and 4(%eax) holds the addend in the relocation.
When the actual resolver returns, it will have adjusted the
TLS descriptor such that we can tail-call it for it to return
the TP offset of the symbol. */
.hidden _dl_tlsdesc_resolve_abs_plus_addend
.global _dl_tlsdesc_resolve_abs_plus_addend
.type _dl_tlsdesc_resolve_abs_plus_addend,@function
cfi_startproc
.align 16
_dl_tlsdesc_resolve_abs_plus_addend:
0:
_CET_ENDBR
pushl %eax
cfi_adjust_cfa_offset (4)
pushl %ecx
cfi_adjust_cfa_offset (4)
pushl %edx
cfi_adjust_cfa_offset (4)
movl $1f - 0b, %ecx
movl 4(%ebx), %edx
call _dl_tlsdesc_resolve_abs_plus_addend_fixup
1:
popl %edx
cfi_adjust_cfa_offset (-4)
popl %ecx
cfi_adjust_cfa_offset (-4)
popl %eax
cfi_adjust_cfa_offset (-4)
jmp *(%eax)
cfi_endproc
.size _dl_tlsdesc_resolve_abs_plus_addend, .-_dl_tlsdesc_resolve_abs_plus_addend
/* This function is a wrapper for a lazy resolver for TLS_DESC
REL relocations that had zero addends. %ebx points to the
caller's GOT. %eax points to a TLS descriptor, such that
0(%eax) holds the address of the resolver wrapper itself
(unless some other thread beat us to it) and 4(%eax) holds a
pointer to the relocation.
When the actual resolver returns, it will have adjusted the
TLS descriptor such that we can tail-call it for it to return
the TP offset of the symbol. */
.hidden _dl_tlsdesc_resolve_rel
.global _dl_tlsdesc_resolve_rel
.type _dl_tlsdesc_resolve_rel,@function
cfi_startproc
.align 16
_dl_tlsdesc_resolve_rel:
0:
_CET_ENDBR
pushl %eax
cfi_adjust_cfa_offset (4)
pushl %ecx
cfi_adjust_cfa_offset (4)
pushl %edx
cfi_adjust_cfa_offset (4)
movl $1f - 0b, %ecx
movl 4(%ebx), %edx
call _dl_tlsdesc_resolve_rel_fixup
1:
popl %edx
cfi_adjust_cfa_offset (-4)
popl %ecx
cfi_adjust_cfa_offset (-4)
popl %eax
cfi_adjust_cfa_offset (-4)
jmp *(%eax)
cfi_endproc
.size _dl_tlsdesc_resolve_rel, .-_dl_tlsdesc_resolve_rel
/* This function is a wrapper for a lazy resolver for TLS_DESC
RELA relocations. %ebx points to the caller's GOT. %eax
points to a TLS descriptor, such that 0(%eax) holds the
address of the resolver wrapper itself (unless some other
thread beat us to it) and 4(%eax) holds a pointer to the
relocation.
When the actual resolver returns, it will have adjusted the
TLS descriptor such that we can tail-call it for it to return
the TP offset of the symbol. */
.hidden _dl_tlsdesc_resolve_rela
.global _dl_tlsdesc_resolve_rela
.type _dl_tlsdesc_resolve_rela,@function
cfi_startproc
.align 16
_dl_tlsdesc_resolve_rela:
0:
_CET_ENDBR
pushl %eax
cfi_adjust_cfa_offset (4)
pushl %ecx
cfi_adjust_cfa_offset (4)
pushl %edx
cfi_adjust_cfa_offset (4)
movl $1f - 0b, %ecx
movl 4(%ebx), %edx
call _dl_tlsdesc_resolve_rela_fixup
1:
popl %edx
cfi_adjust_cfa_offset (-4)
popl %ecx
cfi_adjust_cfa_offset (-4)
popl %eax
cfi_adjust_cfa_offset (-4)
jmp *(%eax)
cfi_endproc
.size _dl_tlsdesc_resolve_rela, .-_dl_tlsdesc_resolve_rela
/* This function is a placeholder for lazy resolving of TLS
relocations. Once some thread starts resolving a TLS
relocation, it sets up the TLS descriptor to use this
resolver, such that other threads that would attempt to
resolve it concurrently may skip the call to the original lazy
resolver and go straight to a condition wait.
When the actual resolver returns, it will have adjusted the
TLS descriptor such that we can tail-call it for it to return
the TP offset of the symbol. */
.hidden _dl_tlsdesc_resolve_hold
.global _dl_tlsdesc_resolve_hold
.type _dl_tlsdesc_resolve_hold,@function
cfi_startproc
.align 16
_dl_tlsdesc_resolve_hold:
0:
_CET_ENDBR
pushl %eax
cfi_adjust_cfa_offset (4)
pushl %ecx
cfi_adjust_cfa_offset (4)
pushl %edx
cfi_adjust_cfa_offset (4)
movl $1f - 0b, %ecx
movl 4(%ebx), %edx
call _dl_tlsdesc_resolve_hold_fixup
1:
popl %edx
cfi_adjust_cfa_offset (-4)
popl %ecx
cfi_adjust_cfa_offset (-4)
popl %eax
cfi_adjust_cfa_offset (-4)
jmp *(%eax)
cfi_endproc
.size _dl_tlsdesc_resolve_hold, .-_dl_tlsdesc_resolve_hold
|
