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https://sourceware.org/git/glibc.git
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i386: Remove lazy tlsdesc relocation related code
Like in commit e75711ebfa976d5468ec292282566a18b07e4d67 for x86_64, remove unused lazy tlsdesc relocation processing code: _dl_tlsdesc_resolve_abs_plus_addend _dl_tlsdesc_resolve_rel _dl_tlsdesc_resolve_rela _dl_tlsdesc_resolve_hold
This commit is contained in:
Szabolcs Nagy
parent
fb33cc1b06
commit
14e2476505
@ -134,159 +134,3 @@ _dl_tlsdesc_dynamic:
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cfi_endproc
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.size _dl_tlsdesc_dynamic, .-_dl_tlsdesc_dynamic
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#endif /* SHARED */
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/* This function is a wrapper for a lazy resolver for TLS_DESC
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REL relocations that reference the *ABS* segment in their own
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link maps. %ebx points to the caller's GOT. %eax points to a
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TLS descriptor, such that 0(%eax) holds the address of the
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resolver wrapper itself (unless some other thread beat us to
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it) and 4(%eax) holds the addend in the relocation.
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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_abs_plus_addend
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.global _dl_tlsdesc_resolve_abs_plus_addend
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.type _dl_tlsdesc_resolve_abs_plus_addend,@function
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cfi_startproc
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.align 16
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_dl_tlsdesc_resolve_abs_plus_addend:
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0:
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_CET_ENDBR
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pushl %eax
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cfi_adjust_cfa_offset (4)
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pushl %ecx
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cfi_adjust_cfa_offset (4)
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pushl %edx
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cfi_adjust_cfa_offset (4)
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movl $1f - 0b, %ecx
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movl 4(%ebx), %edx
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call _dl_tlsdesc_resolve_abs_plus_addend_fixup
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1:
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popl %edx
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cfi_adjust_cfa_offset (-4)
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popl %ecx
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cfi_adjust_cfa_offset (-4)
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popl %eax
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cfi_adjust_cfa_offset (-4)
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jmp *(%eax)
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cfi_endproc
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.size _dl_tlsdesc_resolve_abs_plus_addend, .-_dl_tlsdesc_resolve_abs_plus_addend
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/* This function is a wrapper for a lazy resolver for TLS_DESC
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REL relocations that had zero addends. %ebx points to the
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caller's GOT. %eax points to a TLS descriptor, such that
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0(%eax) holds the address of the resolver wrapper itself
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(unless some other thread beat us to it) and 4(%eax) holds a
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pointer to the relocation.
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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_rel
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.global _dl_tlsdesc_resolve_rel
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.type _dl_tlsdesc_resolve_rel,@function
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cfi_startproc
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.align 16
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_dl_tlsdesc_resolve_rel:
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0:
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_CET_ENDBR
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pushl %eax
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cfi_adjust_cfa_offset (4)
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pushl %ecx
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cfi_adjust_cfa_offset (4)
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pushl %edx
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cfi_adjust_cfa_offset (4)
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movl $1f - 0b, %ecx
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movl 4(%ebx), %edx
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call _dl_tlsdesc_resolve_rel_fixup
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1:
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popl %edx
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cfi_adjust_cfa_offset (-4)
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popl %ecx
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cfi_adjust_cfa_offset (-4)
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popl %eax
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cfi_adjust_cfa_offset (-4)
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jmp *(%eax)
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cfi_endproc
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.size _dl_tlsdesc_resolve_rel, .-_dl_tlsdesc_resolve_rel
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/* This function is a wrapper for a lazy resolver for TLS_DESC
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RELA relocations. %ebx points to the caller's GOT. %eax
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points to a TLS descriptor, such that 0(%eax) holds the
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address of the resolver wrapper itself (unless some other
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thread beat us to it) and 4(%eax) holds a pointer to the
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relocation.
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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 16
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_dl_tlsdesc_resolve_rela:
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0:
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_CET_ENDBR
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pushl %eax
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cfi_adjust_cfa_offset (4)
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pushl %ecx
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cfi_adjust_cfa_offset (4)
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pushl %edx
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cfi_adjust_cfa_offset (4)
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movl $1f - 0b, %ecx
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movl 4(%ebx), %edx
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call _dl_tlsdesc_resolve_rela_fixup
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1:
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popl %edx
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cfi_adjust_cfa_offset (-4)
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popl %ecx
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cfi_adjust_cfa_offset (-4)
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popl %eax
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cfi_adjust_cfa_offset (-4)
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jmp *(%eax)
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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 16
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_dl_tlsdesc_resolve_hold:
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0:
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_CET_ENDBR
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pushl %eax
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cfi_adjust_cfa_offset (4)
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pushl %ecx
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cfi_adjust_cfa_offset (4)
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pushl %edx
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cfi_adjust_cfa_offset (4)
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movl $1f - 0b, %ecx
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movl 4(%ebx), %edx
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call _dl_tlsdesc_resolve_hold_fixup
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1:
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popl %edx
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cfi_adjust_cfa_offset (-4)
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popl %ecx
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cfi_adjust_cfa_offset (-4)
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popl %eax
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cfi_adjust_cfa_offset (-4)
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jmp *(%eax)
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cfi_endproc
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.size _dl_tlsdesc_resolve_hold, .-_dl_tlsdesc_resolve_hold
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@ -43,11 +43,7 @@ struct tlsdesc_dynamic_arg
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extern ptrdiff_t attribute_hidden __attribute__ ((regparm (1)))
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_dl_tlsdesc_return (struct tlsdesc *),
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_dl_tlsdesc_undefweak (struct tlsdesc *),
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_dl_tlsdesc_resolve_abs_plus_addend (struct tlsdesc *),
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_dl_tlsdesc_resolve_rel (struct tlsdesc *),
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_dl_tlsdesc_resolve_rela (struct tlsdesc *),
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_dl_tlsdesc_resolve_hold (struct tlsdesc *);
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_dl_tlsdesc_undefweak (struct tlsdesc *);
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# ifdef SHARED
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extern void *_dl_make_tlsdesc_dynamic (struct link_map *map,
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@ -16,242 +16,13 @@
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License along with the GNU C Library; if not, see
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<https://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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/* The following 4 functions take an entry_check_offset argument.
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It's computed by the caller as an offset between its entry point
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and the call site, such that by adding the built-in return address
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that is implicitly passed to the function with this offset, we can
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easily obtain the caller's entry point to compare with the entry
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point given in the TLS descriptor. If it's changed, we want to
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return immediately. */
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/* This function is used to lazily resolve TLS_DESC REL relocations
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that reference the *ABS* segment in their own link maps. The
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argument is the addend originally stored there. */
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void
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__attribute__ ((regparm (3))) attribute_hidden
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_dl_tlsdesc_resolve_abs_plus_addend_fixup (struct tlsdesc volatile *td,
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struct link_map *l,
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ptrdiff_t entry_check_offset)
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{
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ptrdiff_t addend = (ptrdiff_t) td->arg;
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if (_dl_tlsdesc_resolve_early_return_p (td, __builtin_return_address (0)
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- entry_check_offset))
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return;
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#ifndef SHARED
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CHECK_STATIC_TLS (l, l);
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#else
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if (!TRY_STATIC_TLS (l, l))
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{
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td->arg = _dl_make_tlsdesc_dynamic (l, addend);
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td->entry = _dl_tlsdesc_dynamic;
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}
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else
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#endif
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{
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td->arg = (void*) (addend - l->l_tls_offset);
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td->entry = _dl_tlsdesc_return;
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}
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_dl_tlsdesc_wake_up_held_fixups ();
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}
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/* This function is used to lazily resolve TLS_DESC REL relocations
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that originally had zero addends. The argument location, that
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originally held the addend, is used to hold a pointer to the
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relocation, but it has to be restored before we call the function
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that applies relocations. */
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void
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__attribute__ ((regparm (3))) attribute_hidden
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_dl_tlsdesc_resolve_rel_fixup (struct tlsdesc volatile *td,
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struct link_map *l,
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ptrdiff_t entry_check_offset)
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{
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const ElfW(Rel) *reloc = td->arg;
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if (_dl_tlsdesc_resolve_early_return_p (td, __builtin_return_address (0)
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- entry_check_offset))
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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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td->arg = 0;
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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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td->arg = _dl_make_tlsdesc_dynamic (result, sym->st_value);
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td->entry = _dl_tlsdesc_dynamic;
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}
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else
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# endif
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{
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td->arg = (void*)(sym->st_value - result->l_tls_offset);
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td->entry = _dl_tlsdesc_return;
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}
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}
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_dl_tlsdesc_wake_up_held_fixups ();
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}
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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__ ((regparm (3))) attribute_hidden
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_dl_tlsdesc_resolve_rela_fixup (struct tlsdesc volatile *td,
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struct link_map *l,
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ptrdiff_t entry_check_offset)
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{
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const ElfW(Rela) *reloc = td->arg;
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if (_dl_tlsdesc_resolve_early_return_p (td, __builtin_return_address (0)
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- entry_check_offset))
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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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td->arg = (void*) reloc->r_addend;
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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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td->arg = _dl_make_tlsdesc_dynamic (result, sym->st_value
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+ reloc->r_addend);
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td->entry = _dl_tlsdesc_dynamic;
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}
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else
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# endif
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{
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td->arg = (void*) (sym->st_value - result->l_tls_offset
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+ reloc->r_addend);
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td->entry = _dl_tlsdesc_return;
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}
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}
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_dl_tlsdesc_wake_up_held_fixups ();
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}
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/* This function is used to avoid busy waiting for other threads to
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complete the lazy relocation. Once another thread wins the race to
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relocate a TLS descriptor, it sets the descriptor up such that this
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function is called to wait until the resolver releases the
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lock. */
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void
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__attribute__ ((regparm (3))) attribute_hidden
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_dl_tlsdesc_resolve_hold_fixup (struct tlsdesc volatile *td,
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struct link_map *l __attribute__((__unused__)),
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ptrdiff_t entry_check_offset)
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{
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/* Maybe we're lucky and can return early. */
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if (__builtin_return_address (0) - entry_check_offset != td->entry)
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return;
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/* Locking here will stop execution until the running resolver runs
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_dl_tlsdesc_wake_up_held_fixups(), releasing the lock.
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FIXME: We'd be better off waiting on a condition variable, such
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that we didn't have to hold the lock throughout the relocation
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processing. */
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__rtld_lock_lock_recursive (GL(dl_load_lock));
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__rtld_lock_unlock_recursive (GL(dl_load_lock));
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}
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/* Unmap the dynamic object, but also release its TLS descriptor table
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if there is one. */
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