PowerPC64 thread-safe stubs not needed for iplt
I was looking at a current glibc using objdump today and saw an odd plt call stub. 0000000000044d80 <00000033.plt_call.__strchrnul>: 44d80: f8 41 00 28 std r2,40(r1) 44d84: e9 82 8c f8 ld r12,-29448(r2) 44d88: 7d 89 03 a6 mtctr r12 44d8c: e8 42 8d 00 ld r2,-29440(r2) 44d90: 28 22 00 00 cmpldi r2,0 44d94: 4c e2 04 20 bnectr+ 44d98: 48 13 84 f0 b 17d288 <realloc@plt> What? It doesn't branch to __strchrnul@plt on finding a zero r2? Turns out this isn't a real problem since the stub is for loading an ifunc, so will not be lazily resolved and thus r2 will never be zero. Of course, that means the thread-safety check is unnecessary. I also tweak the special __tls_get_addr_opt call stub here, to restore r2 immediately after the call. Not doing that might affect eh_frame unwinding. * elf64-ppc.c (plt_stub_size, build_plt_stub): Don't build thread-safe stubs for iplt. (build_tls_get_addr_stub): Restore r2 immediately after call.
This commit is contained in:
parent
cf424aef0a
commit
bd4d2eaad0
|
@ -1,3 +1,9 @@
|
|||
2015-02-26 Alan Modra <amodra@gmail.com>
|
||||
|
||||
* elf64-ppc.c (plt_stub_size, build_plt_stub): Don't build
|
||||
thread-safe stubs for iplt.
|
||||
(build_tls_get_addr_stub): Restore r2 immediately after call.
|
||||
|
||||
2015-02-26 Terry Guo <terry.guo@arm.com>
|
||||
|
||||
* elf32-arm.c (elf32_arm_merge_eabi_attributes): Update how we
|
||||
|
|
|
@ -10220,7 +10220,10 @@ plt_stub_size (struct ppc_link_hash_table *htab,
|
|||
size += 4;
|
||||
if (htab->params->plt_static_chain)
|
||||
size += 4;
|
||||
if (htab->params->plt_thread_safe)
|
||||
if (htab->params->plt_thread_safe
|
||||
&& htab->elf.dynamic_sections_created
|
||||
&& stub_entry->h != NULL
|
||||
&& stub_entry->h->elf.dynindx != -1)
|
||||
size += 8;
|
||||
if (PPC_HA (off + 8 + 8 * htab->params->plt_static_chain) != PPC_HA (off))
|
||||
size += 4;
|
||||
|
@ -10260,16 +10263,18 @@ build_plt_stub (struct ppc_link_hash_table *htab,
|
|||
bfd *obfd = htab->params->stub_bfd;
|
||||
bfd_boolean plt_load_toc = htab->opd_abi;
|
||||
bfd_boolean plt_static_chain = htab->params->plt_static_chain;
|
||||
bfd_boolean plt_thread_safe = htab->params->plt_thread_safe;
|
||||
bfd_boolean plt_thread_safe = (htab->params->plt_thread_safe
|
||||
&& htab->elf.dynamic_sections_created
|
||||
&& stub_entry->h != NULL
|
||||
&& stub_entry->h->elf.dynindx != -1);
|
||||
bfd_boolean use_fake_dep = plt_thread_safe;
|
||||
bfd_vma cmp_branch_off = 0;
|
||||
|
||||
if (!ALWAYS_USE_FAKE_DEP
|
||||
&& plt_load_toc
|
||||
&& plt_thread_safe
|
||||
&& !(stub_entry->h != NULL
|
||||
&& (stub_entry->h == htab->tls_get_addr_fd
|
||||
|| stub_entry->h == htab->tls_get_addr)
|
||||
&& !((stub_entry->h == htab->tls_get_addr_fd
|
||||
|| stub_entry->h == htab->tls_get_addr)
|
||||
&& !htab->params->no_tls_get_addr_opt))
|
||||
{
|
||||
bfd_vma pltoff = stub_entry->plt_ent->plt.offset & ~1;
|
||||
|
@ -10462,8 +10467,8 @@ build_tls_get_addr_stub (struct ppc_link_hash_table *htab,
|
|||
p = build_plt_stub (htab, stub_entry, p, offset, r);
|
||||
bfd_put_32 (obfd, BCTRL, p - 4);
|
||||
|
||||
bfd_put_32 (obfd, LD_R11_0R1 + STK_LINKER (htab), p), p += 4;
|
||||
bfd_put_32 (obfd, LD_R2_0R1 + STK_TOC (htab), p), p += 4;
|
||||
bfd_put_32 (obfd, LD_R11_0R1 + STK_LINKER (htab), p), p += 4;
|
||||
bfd_put_32 (obfd, MTLR_R11, p), p += 4;
|
||||
bfd_put_32 (obfd, BLR, p), p += 4;
|
||||
|
||||
|
|
Loading…
Reference in New Issue