commit 55c9f3238080e9aba733bc0902779c46cfa16446

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

Date:   Thu Feb 11 11:52:24 2021 +0000

    x86_64: Remove lazy tlsdesc relocation related code

    _dl_tlsdesc_resolve_rela and _dl_tlsdesc_resolve_hold are only used for

    lazy tlsdesc relocation processing which is no longer supported.

diff --git a/sysdeps/x86_64/dl-machine.h b/sysdeps/x86_64/dl-machine.h

index ef5740ba281c7282..b94d3b39ec1dca64 100644

--- a/sysdeps/x86_64/dl-machine.h

+++ b/sysdeps/x86_64/dl-machine.h

@@ -127,10 +127,6 @@ elf_machine_runtime_setup (struct link_map *l, int lazy, int profile)

 	}

     }

-  if (l->l_info[ADDRIDX (DT_TLSDESC_GOT)] && lazy)

-    *(ElfW(Addr)*)(D_PTR (l, l_info[ADDRIDX (DT_TLSDESC_GOT)]) + l->l_addr)

-      = (ElfW(Addr)) &_dl_tlsdesc_resolve_rela;

-

   return lazy;

 }

diff --git a/sysdeps/x86_64/dl-tlsdesc.S b/sysdeps/x86_64/dl-tlsdesc.S

index 80d771cd887dd626..77e78cf0a6d8babc 100644

--- a/sysdeps/x86_64/dl-tlsdesc.S

+++ b/sysdeps/x86_64/dl-tlsdesc.S

@@ -148,107 +148,3 @@ _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

-	RELA relocations.  The incoming 0(%rsp) points to the caller's

-	link map, pushed by the dynamic object's internal lazy TLS

-	resolver front-end before tail-calling us.  We need to pop it

-	ourselves.  %rax points to a TLS descriptor, such that 0(%rax)

-	holds the address of the internal resolver front-end (unless

-	some other thread beat us to resolving it) and 8(%rax) 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

-	/* The PLT entry will have pushed the link_map pointer.  */

-_dl_tlsdesc_resolve_rela:

-	_CET_ENDBR

-	cfi_adjust_cfa_offset (8)

-	/* Save all call-clobbered registers.  Add 8 bytes for push in

-	   the PLT entry to align the stack.  */

-	subq	$80, %rsp

-	cfi_adjust_cfa_offset (80)

-	movq	%rax, (%rsp)

-	movq	%rdi, 8(%rsp)

-	movq	%rax, %rdi	/* Pass tlsdesc* in %rdi.  */

-	movq	%rsi, 16(%rsp)

-	movq	80(%rsp), %rsi	/* Pass link_map* in %rsi.  */

-	movq	%r8, 24(%rsp)

-	movq	%r9, 32(%rsp)

-	movq	%r10, 40(%rsp)

-	movq	%r11, 48(%rsp)

-	movq	%rdx, 56(%rsp)

-	movq	%rcx, 64(%rsp)

-	call	_dl_tlsdesc_resolve_rela_fixup

-	movq	(%rsp), %rax

-	movq	8(%rsp), %rdi

-	movq	16(%rsp), %rsi

-	movq	24(%rsp), %r8

-	movq	32(%rsp), %r9

-	movq	40(%rsp), %r10

-	movq	48(%rsp), %r11

-	movq	56(%rsp), %rdx

-	movq	64(%rsp), %rcx

-	addq	$88, %rsp

-	cfi_adjust_cfa_offset (-88)

-	jmp	*(%rax)

-	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

-	/* Save all call-clobbered registers.  */

-	subq	$72, %rsp

-	cfi_adjust_cfa_offset (72)

-	movq	%rax, (%rsp)

-	movq	%rdi, 8(%rsp)

-	movq	%rax, %rdi	/* Pass tlsdesc* in %rdi.  */

-	movq	%rsi, 16(%rsp)

-	/* Pass _dl_tlsdesc_resolve_hold's address in %rsi.  */

-	leaq	. - _dl_tlsdesc_resolve_hold(%rip), %rsi

-	movq	%r8, 24(%rsp)

-	movq	%r9, 32(%rsp)

-	movq	%r10, 40(%rsp)

-	movq	%r11, 48(%rsp)

-	movq	%rdx, 56(%rsp)

-	movq	%rcx, 64(%rsp)

-	call	_dl_tlsdesc_resolve_hold_fixup

-1:

-	movq	(%rsp), %rax

-	movq	8(%rsp), %rdi

-	movq	16(%rsp), %rsi

-	movq	24(%rsp), %r8

-	movq	32(%rsp), %r9

-	movq	40(%rsp), %r10

-	movq	48(%rsp), %r11

-	movq	56(%rsp), %rdx

-	movq	64(%rsp), %rcx

-	addq	$72, %rsp

-	cfi_adjust_cfa_offset (-72)

-	jmp	*(%rax)

-	cfi_endproc

-	.size	_dl_tlsdesc_resolve_hold, .-_dl_tlsdesc_resolve_hold

diff --git a/sysdeps/x86_64/dl-tlsdesc.h b/sysdeps/x86_64/dl-tlsdesc.h

index 66e659bb5c7ede74..1cde1ee9664f4908 100644

--- a/sysdeps/x86_64/dl-tlsdesc.h

+++ b/sysdeps/x86_64/dl-tlsdesc.h

@@ -55,9 +55,7 @@ struct tlsdesc_dynamic_arg

 extern ptrdiff_t attribute_hidden

   _dl_tlsdesc_return(struct tlsdesc *on_rax),

-  _dl_tlsdesc_undefweak(struct tlsdesc *on_rax),

-  _dl_tlsdesc_resolve_rela(struct tlsdesc *on_rax),

-  _dl_tlsdesc_resolve_hold(struct tlsdesc *on_rax);

+  _dl_tlsdesc_undefweak(struct tlsdesc *on_rax);

 # ifdef SHARED

 extern void *_dl_make_tlsdesc_dynamic (struct link_map *map,

diff --git a/sysdeps/x86_64/tlsdesc.c b/sysdeps/x86_64/tlsdesc.c

index 302d097dbb0c4f1e..61a19ae26944c84f 100644

--- a/sysdeps/x86_64/tlsdesc.c

+++ b/sysdeps/x86_64/tlsdesc.c

@@ -16,120 +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 2 functions take a caller argument, that contains the

-   address expected to be in the TLS descriptor.  If it's changed, we

-   want to return immediately.  */

-

-/* 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_hidden

-_dl_tlsdesc_resolve_rela_fixup (struct tlsdesc volatile *td,

-				struct link_map *l)

-{

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

-

-  if (_dl_tlsdesc_resolve_early_return_p

-      (td, (void*)(D_PTR (l, l_info[ADDRIDX (DT_TLSDESC_PLT)]) + l->l_addr)))

-    return;

-

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

-  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_hidden

-_dl_tlsdesc_resolve_hold_fixup (struct tlsdesc volatile *td,

-				void *caller)

-{

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

-  if (caller != 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.  */