aarch64: Remove barriers from TLS descriptor functions
Remove ldar synchronization and most lazy TLSDESC initialization related code. * sysdeps/aarch64/dl-machine.h (elf_machine_runtime_setup): Remove DT_TLSDESC_GOT initialization. * sysdeps/aarch64/dl-tlsdesc.S (_dl_tlsdesc_return_lazy): Remove. (_dl_tlsdesc_resolve_rela): Likewise. (_dl_tlsdesc_resolve_hold): Likewise. (_dl_tlsdesc_undefweak): Remove ldar. (_dl_tlsdesc_dynamic): Likewise. * sysdeps/aarch64/dl-tlsdesc.h (_dl_tlsdesc_return_lazy): Remove. (_dl_tlsdesc_resolve_rela): Likewise. (_dl_tlsdesc_resolve_hold): Likewise. * sysdeps/aarch64/tlsdesc.c (_dl_tlsdesc_resolve_rela_fixup): Remove. (_dl_tlsdesc_resolve_hold_fixup): Likewise. (_dl_tlsdesc_resolve_rela): Likewise. (_dl_tlsdesc_resolve_hold): Likewise.
This commit is contained in:
Szabolcs Nagy
parent
b7cf203b5c
commit
91c5a366d8
17
ChangeLog
17
ChangeLog
@ -1,3 +1,20 @@
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2017-11-03 Szabolcs Nagy <szabolcs.nagy@arm.com>
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* sysdeps/aarch64/dl-machine.h (elf_machine_runtime_setup): Remove
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DT_TLSDESC_GOT initialization.
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* sysdeps/aarch64/dl-tlsdesc.S (_dl_tlsdesc_return_lazy): Remove.
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(_dl_tlsdesc_resolve_rela): Likewise.
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(_dl_tlsdesc_resolve_hold): Likewise.
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(_dl_tlsdesc_undefweak): Remove ldar.
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(_dl_tlsdesc_dynamic): Likewise.
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* sysdeps/aarch64/dl-tlsdesc.h (_dl_tlsdesc_return_lazy): Remove.
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(_dl_tlsdesc_resolve_rela): Likewise.
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(_dl_tlsdesc_resolve_hold): Likewise.
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* sysdeps/aarch64/tlsdesc.c (_dl_tlsdesc_resolve_rela_fixup): Remove.
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(_dl_tlsdesc_resolve_hold_fixup): Likewise.
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(_dl_tlsdesc_resolve_rela): Likewise.
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(_dl_tlsdesc_resolve_hold): Likewise.
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2017-11-03 Szabolcs Nagy <szabolcs.nagy@arm.com>
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* sysdeps/aarch64/dl-machine.h (elf_machine_lazy_rel): Do symbol
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@ -102,10 +102,6 @@ elf_machine_runtime_setup (struct link_map *l, int lazy, int profile)
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}
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}
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if (l->l_info[ADDRIDX (DT_TLSDESC_GOT)] && lazy)
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*(ElfW(Addr)*)(D_PTR (l, l_info[ADDRIDX (DT_TLSDESC_GOT)]) + l->l_addr)
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= (ElfW(Addr)) &_dl_tlsdesc_resolve_rela;
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return lazy;
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}
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@ -80,30 +80,6 @@ _dl_tlsdesc_return:
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cfi_endproc
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.size _dl_tlsdesc_return, .-_dl_tlsdesc_return
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/* Same as _dl_tlsdesc_return but with synchronization for
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lazy relocation.
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Prototype:
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_dl_tlsdesc_return_lazy (tlsdesc *) ;
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*/
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.hidden _dl_tlsdesc_return_lazy
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.global _dl_tlsdesc_return_lazy
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.type _dl_tlsdesc_return_lazy,%function
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cfi_startproc
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.align 2
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_dl_tlsdesc_return_lazy:
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/* The ldar here happens after the load from [x0] at the call site
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(that is generated by the compiler as part of the TLS access ABI),
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so it reads the same value (this function is the final value of
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td->entry) and thus it synchronizes with the release store to
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td->entry in _dl_tlsdesc_resolve_rela_fixup ensuring that the load
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from [x0,#PTR_SIZE] here happens after the initialization of td->arg. */
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DELOUSE (0)
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ldar PTR_REG (zr), [x0]
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ldr PTR_REG (0), [x0, #PTR_SIZE]
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RET
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cfi_endproc
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.size _dl_tlsdesc_return_lazy, .-_dl_tlsdesc_return_lazy
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/* Handler for undefined weak TLS symbols.
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Prototype:
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_dl_tlsdesc_undefweak (tlsdesc *);
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@ -121,14 +97,7 @@ _dl_tlsdesc_return_lazy:
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_dl_tlsdesc_undefweak:
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str x1, [sp, #-16]!
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cfi_adjust_cfa_offset (16)
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/* The ldar here happens after the load from [x0] at the call site
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(that is generated by the compiler as part of the TLS access ABI),
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so it reads the same value (this function is the final value of
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td->entry) and thus it synchronizes with the release store to
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td->entry in _dl_tlsdesc_resolve_rela_fixup ensuring that the load
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from [x0,#8] here happens after the initialization of td->arg. */
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DELOUSE (0)
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ldar PTR_REG (zr), [x0]
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ldr PTR_REG (0), [x0, #PTR_SIZE]
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mrs x1, tpidr_el0
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sub PTR_REG (0), PTR_REG (0), PTR_REG (1)
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@ -192,13 +161,6 @@ _dl_tlsdesc_dynamic:
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cfi_rel_offset (x4, 32+24)
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mrs x4, tpidr_el0
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/* The ldar here happens after the load from [x0] at the call site
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(that is generated by the compiler as part of the TLS access ABI),
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so it reads the same value (this function is the final value of
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td->entry) and thus it synchronizes with the release store to
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td->entry in _dl_tlsdesc_resolve_rela_fixup ensuring that the load
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from [x0,#PTR_SIZE] here happens after the initialization of td->arg. */
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ldar PTR_REG (zr), [x0]
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ldr PTR_REG (1), [x0,#TLSDESC_ARG]
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ldr PTR_REG (0), [x4,#TCBHEAD_DTV]
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ldr PTR_REG (3), [x1,#TLSDESC_GEN_COUNT]
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@ -276,168 +238,3 @@ _dl_tlsdesc_dynamic:
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.size _dl_tlsdesc_dynamic, .-_dl_tlsdesc_dynamic
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# undef NSAVEXREGPAIRS
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#endif
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/* This function is a wrapper for a lazy resolver for TLS_DESC
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RELA relocations.
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When the actual resolver returns, it will have adjusted the
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TLS descriptor such that we can tail-call it for it to return
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the TP offset of the symbol. */
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.hidden _dl_tlsdesc_resolve_rela
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.global _dl_tlsdesc_resolve_rela
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.type _dl_tlsdesc_resolve_rela,%function
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cfi_startproc
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.align 2
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_dl_tlsdesc_resolve_rela:
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#define NSAVEXREGPAIRS 9
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/* The tlsdesc PLT entry pushes x2 and x3 to the stack. */
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cfi_adjust_cfa_offset (16)
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cfi_rel_offset (x2, 0)
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cfi_rel_offset (x3, 8)
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stp x29, x30, [sp, #-(32+16*NSAVEXREGPAIRS)]!
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cfi_adjust_cfa_offset (32+16*NSAVEXREGPAIRS)
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cfi_rel_offset (x29, 0)
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cfi_rel_offset (x30, 8)
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mov x29, sp
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stp x1, x4, [sp, #32+16*0]
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stp x5, x6, [sp, #32+16*1]
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stp x7, x8, [sp, #32+16*2]
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stp x9, x10, [sp, #32+16*3]
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stp x11, x12, [sp, #32+16*4]
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stp x13, x14, [sp, #32+16*5]
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stp x15, x16, [sp, #32+16*6]
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stp x17, x18, [sp, #32+16*7]
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str x0, [sp, #32+16*8]
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cfi_rel_offset (x1, 32)
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cfi_rel_offset (x4, 32+8)
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cfi_rel_offset (x5, 32+16)
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cfi_rel_offset (x6, 32+16+8)
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cfi_rel_offset (x7, 32+16*2)
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cfi_rel_offset (x8, 32+16*2+8)
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cfi_rel_offset (x9, 32+16*3)
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cfi_rel_offset (x10, 32+16*3+8)
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cfi_rel_offset (x11, 32+16*4)
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cfi_rel_offset (x12, 32+16*4+8)
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cfi_rel_offset (x13, 32+16*5)
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cfi_rel_offset (x14, 32+16*5+8)
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cfi_rel_offset (x15, 32+16*6)
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cfi_rel_offset (x16, 32+16*6+8)
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cfi_rel_offset (x17, 32+16*7)
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cfi_rel_offset (x18, 32+16*7+8)
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cfi_rel_offset (x0, 32+16*8)
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SAVE_Q_REGISTERS
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DELOUSE (3)
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ldr PTR_REG (1), [x3, #PTR_SIZE]
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bl _dl_tlsdesc_resolve_rela_fixup
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RESTORE_Q_REGISTERS
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ldr x0, [sp, #32+16*8]
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DELOUSE (0)
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ldr PTR_REG (1), [x0]
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blr x1
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ldp x1, x4, [sp, #32+16*0]
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ldp x5, x6, [sp, #32+16*1]
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ldp x7, x8, [sp, #32+16*2]
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ldp x9, x10, [sp, #32+16*3]
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ldp x11, x12, [sp, #32+16*4]
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ldp x13, x14, [sp, #32+16*5]
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ldp x15, x16, [sp, #32+16*6]
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ldp x17, x18, [sp, #32+16*7]
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ldp x29, x30, [sp], #(32+16*NSAVEXREGPAIRS)
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cfi_adjust_cfa_offset (-32-16*NSAVEXREGPAIRS)
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cfi_restore (x29)
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cfi_restore (x30)
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ldp x2, x3, [sp], #16
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cfi_adjust_cfa_offset (-16)
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RET
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#undef NSAVEXREGPAIRS
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cfi_endproc
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.size _dl_tlsdesc_resolve_rela, .-_dl_tlsdesc_resolve_rela
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/* This function is a placeholder for lazy resolving of TLS
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relocations. Once some thread starts resolving a TLS
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relocation, it sets up the TLS descriptor to use this
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resolver, such that other threads that would attempt to
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resolve it concurrently may skip the call to the original lazy
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resolver and go straight to a condition wait.
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When the actual resolver returns, it will have adjusted the
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TLS descriptor such that we can tail-call it for it to return
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the TP offset of the symbol. */
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.hidden _dl_tlsdesc_resolve_hold
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.global _dl_tlsdesc_resolve_hold
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.type _dl_tlsdesc_resolve_hold,%function
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cfi_startproc
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.align 2
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_dl_tlsdesc_resolve_hold:
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#define NSAVEXREGPAIRS 10
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1:
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stp x29, x30, [sp, #-(32+16*NSAVEXREGPAIRS)]!
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cfi_adjust_cfa_offset (32+16*NSAVEXREGPAIRS)
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cfi_rel_offset (x29, 0)
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cfi_rel_offset (x30, 8)
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mov x29, sp
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stp x1, x2, [sp, #32+16*0]
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stp x3, x4, [sp, #32+16*1]
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stp x5, x6, [sp, #32+16*2]
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stp x7, x8, [sp, #32+16*3]
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stp x9, x10, [sp, #32+16*4]
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stp x11, x12, [sp, #32+16*5]
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stp x13, x14, [sp, #32+16*6]
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stp x15, x16, [sp, #32+16*7]
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stp x17, x18, [sp, #32+16*8]
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str x0, [sp, #32+16*9]
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cfi_rel_offset (x1, 32)
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cfi_rel_offset (x2, 32+8)
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cfi_rel_offset (x3, 32+16)
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cfi_rel_offset (x4, 32+16+8)
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cfi_rel_offset (x5, 32+16*2)
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cfi_rel_offset (x6, 32+16*2+8)
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cfi_rel_offset (x7, 32+16*3)
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cfi_rel_offset (x8, 32+16*3+8)
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cfi_rel_offset (x9, 32+16*4)
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cfi_rel_offset (x10, 32+16*4+8)
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cfi_rel_offset (x11, 32+16*5)
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cfi_rel_offset (x12, 32+16*5+8)
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cfi_rel_offset (x13, 32+16*6)
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cfi_rel_offset (x14, 32+16*6+8)
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cfi_rel_offset (x15, 32+16*7)
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cfi_rel_offset (x16, 32+16*7+8)
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cfi_rel_offset (x17, 32+16*8)
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cfi_rel_offset (x18, 32+16*8+8)
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cfi_rel_offset (x0, 32+16*9)
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SAVE_Q_REGISTERS
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adr x1, 1b
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bl _dl_tlsdesc_resolve_hold_fixup
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RESTORE_Q_REGISTERS
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ldr x0, [sp, #32+16*9]
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DELOUSE (0)
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ldr PTR_REG (1), [x0]
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blr x1
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ldp x1, x2, [sp, #32+16*0]
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ldp x3, x4, [sp, #32+16*1]
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ldp x5, x6, [sp, #32+16*2]
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ldp x7, x8, [sp, #32+16*3]
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ldp x9, x10, [sp, #32+16*4]
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ldp x11, x12, [sp, #32+16*5]
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ldp x13, x14, [sp, #32+16*6]
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ldp x15, x16, [sp, #32+16*7]
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ldp x17, x18, [sp, #32+16*8]
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ldp x29, x30, [sp], #(32+16*NSAVEXREGPAIRS)
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cfi_adjust_cfa_offset (-32-16*NSAVEXREGPAIRS)
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cfi_restore (x29)
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cfi_restore (x30)
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RET
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cfi_endproc
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.size _dl_tlsdesc_resolve_hold, .-_dl_tlsdesc_resolve_hold
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#undef NSAVEXREGPAIRS
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@ -45,18 +45,9 @@ struct tlsdesc_dynamic_arg
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extern ptrdiff_t attribute_hidden
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_dl_tlsdesc_return (struct tlsdesc *);
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extern ptrdiff_t attribute_hidden
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_dl_tlsdesc_return_lazy (struct tlsdesc *);
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extern ptrdiff_t attribute_hidden
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_dl_tlsdesc_undefweak (struct tlsdesc *);
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extern ptrdiff_t attribute_hidden
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_dl_tlsdesc_resolve_rela (struct tlsdesc *);
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extern ptrdiff_t attribute_hidden
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_dl_tlsdesc_resolve_hold (struct tlsdesc *);
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# ifdef SHARED
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extern void *_dl_make_tlsdesc_dynamic (struct link_map *, size_t);
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@ -18,137 +18,12 @@
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <link.h>
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#include <ldsodefs.h>
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#include <elf/dynamic-link.h>
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#include <tls.h>
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#include <dl-tlsdesc.h>
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#include <dl-unmap-segments.h>
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#define _dl_tlsdesc_resolve_hold 0
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#include <tlsdeschtab.h>
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#include <atomic.h>
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/* The following functions take an entry_check_offset argument. It's
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computed by the caller as an offset between its entry point and the
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call site, such that by adding the built-in return address that is
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implicitly passed to the function with this offset, we can easily
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obtain the caller's entry point to compare with the entry point
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given in the TLS descriptor. If it's changed, we want to return
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immediately. */
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/* This function is used to lazily resolve TLS_DESC RELA relocations.
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The argument location is used to hold a pointer to the relocation. */
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void
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attribute_hidden
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_dl_tlsdesc_resolve_rela_fixup (struct tlsdesc *td, struct link_map *l)
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{
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const ElfW(Rela) *reloc = atomic_load_relaxed (&td->arg);
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/* After GL(dl_load_lock) is grabbed only one caller can see td->entry in
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initial state in _dl_tlsdesc_resolve_early_return_p, other concurrent
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callers will return and retry calling td->entry. The updated td->entry
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synchronizes with the single writer so all read accesses here can use
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relaxed order. */
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if (_dl_tlsdesc_resolve_early_return_p
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(td, (void*)(D_PTR (l, l_info[ADDRIDX (DT_TLSDESC_PLT)]) + l->l_addr)))
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return;
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/* The code below was borrowed from _dl_fixup(),
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except for checking for STB_LOCAL. */
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const ElfW(Sym) *const symtab
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= (const void *) D_PTR (l, l_info[DT_SYMTAB]);
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const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);
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const ElfW(Sym) *sym = &symtab[ELFW(R_SYM) (reloc->r_info)];
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lookup_t result;
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/* Look up the target symbol. If the normal lookup rules are not
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used don't look in the global scope. */
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if (ELFW(ST_BIND) (sym->st_info) != STB_LOCAL
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&& __builtin_expect (ELFW(ST_VISIBILITY) (sym->st_other), 0) == 0)
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{
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const struct r_found_version *version = NULL;
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if (l->l_info[VERSYMIDX (DT_VERSYM)] != NULL)
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{
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const ElfW(Half) *vernum =
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(const void *) D_PTR (l, l_info[VERSYMIDX (DT_VERSYM)]);
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ElfW(Half) ndx = vernum[ELFW(R_SYM) (reloc->r_info)] & 0x7fff;
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version = &l->l_versions[ndx];
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if (version->hash == 0)
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version = NULL;
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}
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result = _dl_lookup_symbol_x (strtab + sym->st_name, l, &sym,
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l->l_scope, version, ELF_RTYPE_CLASS_PLT,
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DL_LOOKUP_ADD_DEPENDENCY, NULL);
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}
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else
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{
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/* We already found the symbol. The module (and therefore its load
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address) is also known. */
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result = l;
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}
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if (!sym)
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{
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atomic_store_relaxed (&td->arg, (void *) reloc->r_addend);
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/* This release store synchronizes with the ldar acquire load
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instruction in _dl_tlsdesc_undefweak. */
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atomic_store_release (&td->entry, _dl_tlsdesc_undefweak);
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}
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else
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{
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# ifndef SHARED
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CHECK_STATIC_TLS (l, result);
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# else
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if (!TRY_STATIC_TLS (l, result))
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{
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void *p = _dl_make_tlsdesc_dynamic (result, sym->st_value
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+ reloc->r_addend);
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atomic_store_relaxed (&td->arg, p);
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/* This release store synchronizes with the ldar acquire load
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instruction in _dl_tlsdesc_dynamic. */
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||||
atomic_store_release (&td->entry, _dl_tlsdesc_dynamic);
|
||||
}
|
||||
else
|
||||
# endif
|
||||
{
|
||||
void *p = (void*) (sym->st_value + result->l_tls_offset
|
||||
+ reloc->r_addend);
|
||||
atomic_store_relaxed (&td->arg, p);
|
||||
/* This release store synchronizes with the ldar acquire load
|
||||
instruction in _dl_tlsdesc_return_lazy. */
|
||||
atomic_store_release (&td->entry, _dl_tlsdesc_return_lazy);
|
||||
}
|
||||
}
|
||||
|
||||
_dl_tlsdesc_wake_up_held_fixups ();
|
||||
}
|
||||
|
||||
/* This function is used to avoid busy waiting for other threads to
|
||||
complete the lazy relocation. Once another thread wins the race to
|
||||
relocate a TLS descriptor, it sets the descriptor up such that this
|
||||
function is called to wait until the resolver releases the
|
||||
lock. */
|
||||
|
||||
void
|
||||
attribute_hidden
|
||||
_dl_tlsdesc_resolve_hold_fixup (struct tlsdesc *td, void *caller)
|
||||
{
|
||||
/* Maybe we're lucky and can return early. */
|
||||
if (caller != atomic_load_relaxed (&td->entry))
|
||||
return;
|
||||
|
||||
/* Locking here will stop execution until the running resolver runs
|
||||
_dl_tlsdesc_wake_up_held_fixups(), releasing the lock.
|
||||
|
||||
FIXME: We'd be better off waiting on a condition variable, such
|
||||
that we didn't have to hold the lock throughout the relocation
|
||||
processing. */
|
||||
__rtld_lock_lock_recursive (GL(dl_load_lock));
|
||||
__rtld_lock_unlock_recursive (GL(dl_load_lock));
|
||||
}
|
||||
|
||||
|
||||
/* Unmap the dynamic object, but also release its TLS descriptor table
|
||||
if there is one. */
|
||||
|
||||
Loading…
Reference in New Issue
Block a user