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[PATCHv2] Fix static TLS exhaustion by TLS descriptors


AArch64 presently defaults to use TLS descriptors, as opposed to
traditional dynamic TLS relocations, and has hit a bug in the copy-pasta
used in elf_machine_rel{,a} for all TLS descriptor implementations. When
a program calls dlopen() with R_AARCH64_TLSDESC relocs, we're consuming
static TLS until it's exhausted (presumably as an optimisation.)
However, this means that once our static TLS space is consumed,
attempting to dlopen() any shared object which contain an
R_AARCH64_TPREL reloc will fail, since we've exhausted all the space.

Instead, always use dynamic TLS for TLS descriptors, which lets us load
arbitrarily many proper dynamic TLS using shared objects, and allow the
static TLS fallback only in the non-SHARED case.

This issue is reproducible on x86_64, by specifying -mtls-dialect=gnu2
when building with gcc. I've written a test for this:
https://github.com/jkkm/test-tls_desc.git
Tweak DIALECT to be appropriate, and run ./test-tls_desc.sh, ./main
and it should fail with:
% ./test-tls_desc.sh; ./main
./tmp16.so: cannot allocate memory in static TLS block
./test-tls_desc.sh: line 18: 10141 Aborted                 (core dumped) ./main

2014-06-03  Kyle McMartin  <kyle@redhat.com>

        * sysdeps/aarch64/dl-machine.h (elf_machine_rela): Always
          allocate dynamic TLS space for TLS descriptors.
        * sysdeps/x86_64/dl-machine.h (elf_machine_rela): Ditto.
        * sysdeps/arm/dl-machine.h (elf_machine_rel): Ditto.
        * sysdeps/i386/dl-machine.h (elf_machine_rel): Ditto.

--- a/sysdeps/aarch64/dl-machine.h
+++ b/sysdeps/aarch64/dl-machine.h
@@ -295,7 +295,7 @@ elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,
 # ifndef SHARED
 		CHECK_STATIC_TLS (map, sym_map);
 # else
-		if (!TRY_STATIC_TLS (map, sym_map))
+		if (1)
 		  {
 		    td->arg = _dl_make_tlsdesc_dynamic
 		      (sym_map, sym->st_value + reloc->r_addend);
diff --git a/sysdeps/arm/dl-machine.h b/sysdeps/arm/dl-machine.h
index 899b256..f55a991 100644
--- a/sysdeps/arm/dl-machine.h
+++ b/sysdeps/arm/dl-machine.h
@@ -458,7 +458,7 @@ elf_machine_rel (struct link_map *map, const Elf32_Rel *reloc,
 #  ifndef SHARED
 		CHECK_STATIC_TLS (map, sym_map);
 #  else
-		if (!TRY_STATIC_TLS (map, sym_map))
+		if (1)
 		  {
 		    td->argument.pointer
 		      = _dl_make_tlsdesc_dynamic (sym_map, value);
diff --git a/sysdeps/i386/dl-machine.h b/sysdeps/i386/dl-machine.h
index 368bee2..b6b5802 100644
--- a/sysdeps/i386/dl-machine.h
+++ b/sysdeps/i386/dl-machine.h
@@ -394,7 +394,7 @@ elf_machine_rel (struct link_map *map, const Elf32_Rel *reloc,
 #  ifndef SHARED
 		CHECK_STATIC_TLS (map, sym_map);
 #  else
-		if (!TRY_STATIC_TLS (map, sym_map))
+		if (1)
 		  {
 		    td->arg = _dl_make_tlsdesc_dynamic
 		      (sym_map, sym->st_value + (ElfW(Word))td->arg);
diff --git a/sysdeps/x86_64/dl-machine.h b/sysdeps/x86_64/dl-machine.h
index 8df04a9..4ec4340 100644
--- a/sysdeps/x86_64/dl-machine.h
+++ b/sysdeps/x86_64/dl-machine.h
@@ -359,7 +359,7 @@ elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,
 #   ifndef SHARED
 		CHECK_STATIC_TLS (map, sym_map);
 #   else
-		if (!TRY_STATIC_TLS (map, sym_map))
+		if (1)
 		  {
 		    td->arg = _dl_make_tlsdesc_dynamic
 		      (sym_map, sym->st_value + reloc->r_addend);


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