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| author | Alan Modra <amodra@gmail.com> | 2015-02-26 21:26:42 +1030 |
|---|---|---|
| committer | Alan Modra <amodra@gmail.com> | 2015-02-26 21:49:54 +1030 |
| commit | bd4d2eaad0f624bc47b2e27222480a44d1a48108 (patch) | |
| tree | 32e794259808ecc381c0bc30ae2ecf5485d3d43d | |
| parent | cf424aef0af89903abdd6c4e055684929e4990af (diff) | |
| download | gdb-bd4d2eaad0f624bc47b2e27222480a44d1a48108.zip gdb-bd4d2eaad0f624bc47b2e27222480a44d1a48108.tar.gz gdb-bd4d2eaad0f624bc47b2e27222480a44d1a48108.tar.bz2 | |
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.
| -rw-r--r-- | bfd/ChangeLog | 6 | ||||
| -rw-r--r-- | bfd/elf64-ppc.c | 17 |
2 files changed, 17 insertions, 6 deletions
diff --git a/bfd/ChangeLog b/bfd/ChangeLog index 01b2d68..c2f114a 100644 --- a/bfd/ChangeLog +++ b/bfd/ChangeLog @@ -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 diff --git a/bfd/elf64-ppc.c b/bfd/elf64-ppc.c index 1573e30..90c2cc0 100644 --- a/bfd/elf64-ppc.c +++ b/bfd/elf64-ppc.c @@ -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; |