diff mbox series

[13/15] x86_64: Remove lazy tlsdesc relocation related code

Message ID 59686e4319f63d809adfb03cd7fbd0d0bb323b70.1613390045.git.szabolcs.nagy@arm.com
State New
Headers show
Series Dynamic TLS related data race fixes | expand

Commit Message

Szabolcs Nagy Feb. 15, 2021, 12:02 p.m. UTC
_dl_tlsdesc_resolve_rela and _dl_tlsdesc_resolve_hold are only used for
lazy tlsdesc relocation processing which is no longer supported.
---
 sysdeps/x86_64/dl-tlsdesc.S | 104 ----------------------------------
 sysdeps/x86_64/dl-tlsdesc.h |   4 +-
 sysdeps/x86_64/tlsdesc.c    | 109 +-----------------------------------
 3 files changed, 2 insertions(+), 215 deletions(-)
diff mbox series

Patch

diff --git a/sysdeps/x86_64/dl-tlsdesc.S b/sysdeps/x86_64/dl-tlsdesc.S
index 1d055adadd..ca9236bed8 100644
--- a/sysdeps/x86_64/dl-tlsdesc.S
+++ b/sysdeps/x86_64/dl-tlsdesc.S
@@ -144,107 +144,3 @@  _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 d134b3f4db..03d5ac7a54 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 4083849f22..ecf864d6ee 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
    <https://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.  */