commit a75a02a696f9f869d77b17b99964823aa8833a8b

Author: Szabolcs Nagy <szabolcs.nagy@arm.com>

Date:   Thu Feb 11 11:58:20 2021 +0000

    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

diff --git a/sysdeps/i386/dl-tlsdesc.S b/sysdeps/i386/dl-tlsdesc.S

index 128f0af3188f46bb..22ecb2c6adc6cc6e 100644

--- a/sysdeps/i386/dl-tlsdesc.S

+++ b/sysdeps/i386/dl-tlsdesc.S

@@ -138,159 +138,3 @@ _dl_tlsdesc_dynamic:

 	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

diff --git a/sysdeps/i386/dl-tlsdesc.h b/sysdeps/i386/dl-tlsdesc.h

index c8a1e056150dc418..1a1a22c303baf85b 100644

--- a/sysdeps/i386/dl-tlsdesc.h

+++ b/sysdeps/i386/dl-tlsdesc.h

@@ -43,11 +43,7 @@ struct tlsdesc_dynamic_arg

 extern ptrdiff_t attribute_hidden __attribute__ ((regparm (1)))

   _dl_tlsdesc_return (struct tlsdesc *),

-  _dl_tlsdesc_undefweak (struct tlsdesc *),

-  _dl_tlsdesc_resolve_abs_plus_addend (struct tlsdesc *),

-  _dl_tlsdesc_resolve_rel (struct tlsdesc *),

-  _dl_tlsdesc_resolve_rela (struct tlsdesc *),

-  _dl_tlsdesc_resolve_hold (struct tlsdesc *);

+  _dl_tlsdesc_undefweak (struct tlsdesc *);

 # ifdef SHARED

 extern void *_dl_make_tlsdesc_dynamic (struct link_map *map,

diff --git a/sysdeps/i386/tlsdesc.c b/sysdeps/i386/tlsdesc.c

index 82fa8a1d35fd1912..1b4227c8381e1b3d 100644

--- a/sysdeps/i386/tlsdesc.c

+++ b/sysdeps/i386/tlsdesc.c

@@ -16,242 +16,13 @@

    License along with the GNU C Library; if not, see

    <http://www.gnu.org/licenses/>.  */

-#include <link.h>

 #include <ldsodefs.h>

-#include <elf/dynamic-link.h>

 #include <tls.h>

 #include <dl-tlsdesc.h>

 #include <dl-unmap-segments.h>

+#define _dl_tlsdesc_resolve_hold 0

 #include <tlsdeschtab.h>

-/* The following 4 functions take an entry_check_offset argument.

-   It's computed by the caller as an offset between its entry point

-   and the call site, such that by adding the built-in return address

-   that is implicitly passed to the function with this offset, we can

-   easily obtain the caller's entry point to compare with the entry

-   point given in the TLS descriptor.  If it's changed, we want to

-   return immediately.  */

-

-/* This function is used to lazily resolve TLS_DESC REL relocations

-   that reference the *ABS* segment in their own link maps.  The

-   argument is the addend originally stored there.  */

-

-void

-__attribute__ ((regparm (3))) attribute_hidden

-_dl_tlsdesc_resolve_abs_plus_addend_fixup (struct tlsdesc volatile *td,

-					   struct link_map *l,

-					   ptrdiff_t entry_check_offset)

-{

-  ptrdiff_t addend = (ptrdiff_t) td->arg;

-

-  if (_dl_tlsdesc_resolve_early_return_p (td, __builtin_return_address (0)

-					  - entry_check_offset))

-    return;

-

-#ifndef SHARED

-  CHECK_STATIC_TLS (l, l);

-#else

-  if (!TRY_STATIC_TLS (l, l))

-    {

-      td->arg = _dl_make_tlsdesc_dynamic (l, addend);

-      td->entry = _dl_tlsdesc_dynamic;

-    }

-  else

-#endif

-    {

-      td->arg = (void*) (addend - l->l_tls_offset);

-      td->entry = _dl_tlsdesc_return;

-    }

-

-  _dl_tlsdesc_wake_up_held_fixups ();

-}

-

-/* This function is used to lazily resolve TLS_DESC REL relocations

-   that originally had zero addends.  The argument location, that

-   originally held the addend, is used to hold a pointer to the

-   relocation, but it has to be restored before we call the function

-   that applies relocations.  */

-

-void

-__attribute__ ((regparm (3))) attribute_hidden

-_dl_tlsdesc_resolve_rel_fixup (struct tlsdesc volatile *td,

-			       struct link_map *l,

-			       ptrdiff_t entry_check_offset)

-{

-  const ElfW(Rel) *reloc = td->arg;

-

-  if (_dl_tlsdesc_resolve_early_return_p (td, __builtin_return_address (0)

-					  - entry_check_offset))

-    return;

-

-  /* The code below was borrowed from _dl_fixup(),

-     except for checking for STB_LOCAL.  */

-  const ElfW(Sym) *const symtab

-    = (const void *) D_PTR (l, l_info[DT_SYMTAB]);

-  const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);

-  const ElfW(Sym) *sym = &symtab[ELFW(R_SYM) (reloc->r_info)];

-  lookup_t result;

-

-   /* Look up the target symbol.  If the normal lookup rules are not

-      used don't look in the global scope.  */

-  if (ELFW(ST_BIND) (sym->st_info) != STB_LOCAL

-      && __builtin_expect (ELFW(ST_VISIBILITY) (sym->st_other), 0) == 0)

-    {

-      const struct r_found_version *version = NULL;

-

-      if (l->l_info[VERSYMIDX (DT_VERSYM)] != NULL)

-	{

-	  const ElfW(Half) *vernum =

-	    (const void *) D_PTR (l, l_info[VERSYMIDX (DT_VERSYM)]);

-	  ElfW(Half) ndx = vernum[ELFW(R_SYM) (reloc->r_info)] & 0x7fff;

-	  version = &l->l_versions[ndx];

-	  if (version->hash == 0)

-	    version = NULL;

-	}

-

-      result = _dl_lookup_symbol_x (strtab + sym->st_name, l, &sym,

-				    l->l_scope, version, ELF_RTYPE_CLASS_PLT,

-				    DL_LOOKUP_ADD_DEPENDENCY, NULL);

-    }

-  else

-    {

-      /* We already found the symbol.  The module (and therefore its load

-	 address) is also known.  */

-      result = l;

-    }

-

-  if (!sym)

-    {

-      td->arg = 0;

-      td->entry = _dl_tlsdesc_undefweak;

-    }

-  else

-    {

-#  ifndef SHARED

-      CHECK_STATIC_TLS (l, result);

-#  else

-      if (!TRY_STATIC_TLS (l, result))

-	{

-	  td->arg = _dl_make_tlsdesc_dynamic (result, sym->st_value);

-	  td->entry = _dl_tlsdesc_dynamic;

-	}

-      else

-#  endif

-	{

-	  td->arg = (void*)(sym->st_value - result->l_tls_offset);

-	  td->entry = _dl_tlsdesc_return;

-	}

-    }

-

-  _dl_tlsdesc_wake_up_held_fixups ();

-}

-

-/* This function is used to lazily resolve TLS_DESC RELA relocations.

-   The argument location is used to hold a pointer to the relocation.  */

-

-void

-__attribute__ ((regparm (3))) attribute_hidden

-_dl_tlsdesc_resolve_rela_fixup (struct tlsdesc volatile *td,

-				struct link_map *l,

-				ptrdiff_t entry_check_offset)

-{

-  const ElfW(Rela) *reloc = td->arg;

-

-  if (_dl_tlsdesc_resolve_early_return_p (td, __builtin_return_address (0)

-					  - entry_check_offset))

-    return;

-

-  /* The code below was borrowed from _dl_fixup(),

-     except for checking for STB_LOCAL.  */

-  const ElfW(Sym) *const symtab

-    = (const void *) D_PTR (l, l_info[DT_SYMTAB]);

-  const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);

-  const ElfW(Sym) *sym = &symtab[ELFW(R_SYM) (reloc->r_info)];

-  lookup_t result;

-

-   /* Look up the target symbol.  If the normal lookup rules are not

-      used don't look in the global scope.  */

-  if (ELFW(ST_BIND) (sym->st_info) != STB_LOCAL

-      && __builtin_expect (ELFW(ST_VISIBILITY) (sym->st_other), 0) == 0)

-    {

-      const struct r_found_version *version = NULL;

-

-      if (l->l_info[VERSYMIDX (DT_VERSYM)] != NULL)

-	{

-	  const ElfW(Half) *vernum =

-	    (const void *) D_PTR (l, l_info[VERSYMIDX (DT_VERSYM)]);

-	  ElfW(Half) ndx = vernum[ELFW(R_SYM) (reloc->r_info)] & 0x7fff;

-	  version = &l->l_versions[ndx];

-	  if (version->hash == 0)

-	    version = NULL;

-	}

-

-      result = _dl_lookup_symbol_x (strtab + sym->st_name, l, &sym,

-				    l->l_scope, version, ELF_RTYPE_CLASS_PLT,

-				    DL_LOOKUP_ADD_DEPENDENCY, NULL);

-    }

-  else

-    {

-      /* We already found the symbol.  The module (and therefore its load

-	 address) is also known.  */

-      result = l;

-    }

-

-  if (!sym)

-    {

-      td->arg = (void*) reloc->r_addend;

-      td->entry = _dl_tlsdesc_undefweak;

-    }

-  else

-    {

-#  ifndef SHARED

-      CHECK_STATIC_TLS (l, result);

-#  else

-      if (!TRY_STATIC_TLS (l, result))

-	{

-	  td->arg = _dl_make_tlsdesc_dynamic (result, sym->st_value

-					      + reloc->r_addend);

-	  td->entry = _dl_tlsdesc_dynamic;

-	}

-      else

-#  endif

-	{

-	  td->arg = (void*) (sym->st_value - result->l_tls_offset

-			     + reloc->r_addend);

-	  td->entry = _dl_tlsdesc_return;

-	}

-    }

-

-  _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__ ((regparm (3))) attribute_hidden

-_dl_tlsdesc_resolve_hold_fixup (struct tlsdesc volatile *td,

-				struct link_map *l __attribute__((__unused__)),

-				ptrdiff_t entry_check_offset)

-{

-  /* Maybe we're lucky and can return early.  */

-  if (__builtin_return_address (0) - entry_check_offset != 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.  */