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Diffstat (limited to 'sysdeps/i386/dl-tlsdesc.S')
| -rw-r--r-- | sysdeps/i386/dl-tlsdesc.S | 290 |
1 files changed, 290 insertions, 0 deletions
diff --git a/sysdeps/i386/dl-tlsdesc.S b/sysdeps/i386/dl-tlsdesc.S new file mode 100644 index 0000000000..db5005d9f4 --- /dev/null +++ b/sysdeps/i386/dl-tlsdesc.S @@ -0,0 +1,290 @@ +/* Thread-local storage handling in the ELF dynamic linker. i386 version. + Copyright (C) 2004, 2005, 2008 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, write to the Free + Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA + 02111-1307 USA. */ + +#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: + 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: + 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: + /* 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) + movl %ebx, 16(%esp) + call __i686.get_pc_thunk.bx + addl $_GLOBAL_OFFSET_TABLE_, %ebx + call ___tls_get_addr@PLT + movl 16(%esp), %ebx + 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: + 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: + 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: + 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: + 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 |