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authorAlan Modra <amodra@gmail.com>2018-01-13 18:53:41 +1030
committerAlan Modra <amodra@gmail.com>2018-01-17 18:51:04 +1030
commit9e390558cef76767a98123994c422d0642d86cf8 (patch)
treefa46b2f2c764e30be6e6e512fe29a01de0b4ad04 /ld/emultempl/ppc32elf.em
parent78742b93a5fef4b88b1391817e7bcc6738000044 (diff)
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PowerPC PLT stub tidy
This is in preparation for the next patch adding Spectre variant 2 mitigation for PowerPC and PowerPC64. Besides tidying code involved in stub output (to reduce the number of places where bctr is output), the patch adds some user visible features: 1) PowerPC64 ELFv2 global entry stubs now are aligned under the control of --plt-align, with a default alignment of 32 bytes. 2) PowerPC64 __glink_PLTresolve is no longer padded out with nops. 3) PowerPC32 PLT stubs are aligned under the control of --plt-align, with the default alignment being 16 bytes as before. 4) The PowerPC32 branch/nop table emitted before __glink_PLTresolve is now smaller in many cases. It was sized incorrectly when the __tls_get_addr_opt stub was used, and unnecessarily included space for local ifuncs. bfd/ * elf32-ppc.c (GLINK_ENTRY_SIZE): Add parameters, handle __tls_get_addr_opt, and alignment sizing. (TLS_GET_ADDR_GLINK_SIZE): Delete. (is_nonpic_glink_stub): Don't use GLINK_ENTRY_SIZE. (ppc_elf_get_synthetic_symtab): Recognize stubs spaced at 4, 6, or 8 insns. (ppc_elf_link_hash_table_create): Init new ppc_elf_params field. (allocate_dynrelocs): Use new GLINK_ENTRY_SIZE. (ppc_elf_size_dynamic_sections): Likewise. Size branch table by PLT reloc count. (write_glink_stub): Handle __tls_get_addr_opt stub. Pad out to size given by GLINK_ENTRY_SIZE. (ppc_elf_relocate_section): Adjust write_glink_stub call. (ppc_elf_finish_dynamic_symbol): Likewise. (ppc_elf_finish_dynamic_sections): Write PLTresolve without using insn array since so many need rewriting. * elf32-ppc.h (struct ppc_elf_params): Add plt_stub_align. * elf64-ppc.c (GLINK_PLTRESOLVE_SIZE): Rename from GLINK_CALL_STUB_SIZE. Add htab param and evaluate to size without nops. Adjust all uses. (ppc64_elf_get_synthetic_symtab): Don't use GLINK_CALL_STUB_SIZE in glink_vma calculation. (struct ppc_link_hash_table): Add global_entry section pointer. (create_linkage_sections): Create separate section for global entry stubs. (PPC_LO, PPC_HI, PPC_HA): Move earlier. (size_global_entry_stubs): Handle sizing for aligned stubs. (ppc64_elf_size_dynamic_sections): Handle global_entry alloc, and don't stash end of glink branch table in rawsize. (ppc_build_one_stub): Rewrite stub size calculations. (build_global_entry_stubs): Use new section. (ppc64_elf_build_stubs): Don't pad __glink_PLTresolve with nops. Build lazy link stubs out to end of section. Build global entry stubs in new section. gold/ * options.h (plt_align): Support for PowerPC32 too. * powerpc.cc (Stub_table::stub_align): Heed --plt-align for 32-bit. (Stub_table::plt_call_size, branch_stub_size): Tidy. (Stub_table::plt_call_align): Implement using stub_align. (Output_data_glink::global_entry_align): New function. (Output_data_glink::global_entry_off): New function. (Output_data_glink::global_entry_address): Use global_entry_off. (Output_data_glink::pltresolve_size): New function, replacing pltresolve_size_ constant. Update all uses. (Output_data_glink::add_global_entry): Align offset. (Output_data_glink::set_final_data_size): Use global_entry_align. (Stub_table::do_write): Don't pad __glink_PLTrelsolve with nops. Tidy stub output. Use global_entry_off. ld/ * emultempl/ppc32elf.em (params): Init new field. (enum ppc32_opt): New enum to define OPTION_* values. Add OPTION_PLT_ALIGN and OPTION_NO_PLT_ALIGN. (PARSE_AND_LIST_LONGOPTS): Handle new options. (PARSE_AND_LIST_ARGS_CASES): Likewise. (PARSE_AND_LIST_OPTIONS): Likewise. Break up help output. * emultempl/ppc64elf.em (ppc_add_stub_section): Init alignment correctly for negative --plt-stub-align. * testsuite/ld-powerpc/elfv2exe.d, * testsuite/ld-powerpc/elfv2so.d, * testsuite/ld-powerpc/relbrlt.d, * testsuite/ld-powerpc/relbrlt.s, * testsuite/ld-powerpc/tlsexe.d, * testsuite/ld-powerpc/tlsexe.r, * testsuite/ld-powerpc/tlsexe32.d, * testsuite/ld-powerpc/tlsexe32.g, * testsuite/ld-powerpc/tlsexe32.r, * testsuite/ld-powerpc/tlsexetoc.d, * testsuite/ld-powerpc/tlsexetoc.r, * testsuite/ld-powerpc/tlsopt5_32.d, * testsuite/ld-powerpc/tlsso.d, * testsuite/ld-powerpc/tlstocso.d: Update for changed stub order.
Diffstat (limited to 'ld/emultempl/ppc32elf.em')
-rw-r--r--ld/emultempl/ppc32elf.em86
1 files changed, 64 insertions, 22 deletions
diff --git a/ld/emultempl/ppc32elf.em b/ld/emultempl/ppc32elf.em
index 6852e9b..70dd5a0 100644
--- a/ld/emultempl/ppc32elf.em
+++ b/ld/emultempl/ppc32elf.em
@@ -38,7 +38,8 @@ static int notlsopt = 0;
/* Choose the correct place for .got. */
static int old_got = 0;
-static struct ppc_elf_params params = { PLT_UNSET, -1, 0, 0, 0, 0, 0, 0, 0 };
+static struct ppc_elf_params params = { PLT_UNSET, 0, -1,
+ 0, 0, 0, 0, 0, 0, 0 };
static void
ppc_after_open_output (void)
@@ -239,17 +240,22 @@ fi
# parse_args and list_options functions.
#
PARSE_AND_LIST_PROLOGUE=${PARSE_AND_LIST_PROLOGUE}'
-#define OPTION_NO_TLS_OPT 321
-#define OPTION_NO_TLS_GET_ADDR_OPT (OPTION_NO_TLS_OPT + 1)
-#define OPTION_NEW_PLT (OPTION_NO_TLS_GET_ADDR_OPT + 1)
-#define OPTION_OLD_PLT (OPTION_NEW_PLT + 1)
-#define OPTION_OLD_GOT (OPTION_OLD_PLT + 1)
-#define OPTION_STUBSYMS (OPTION_OLD_GOT + 1)
-#define OPTION_NO_STUBSYMS (OPTION_STUBSYMS + 1)
-#define OPTION_PPC476_WORKAROUND (OPTION_NO_STUBSYMS + 1)
-#define OPTION_NO_PPC476_WORKAROUND (OPTION_PPC476_WORKAROUND + 1)
-#define OPTION_NO_PICFIXUP (OPTION_NO_PPC476_WORKAROUND + 1)
-#define OPTION_VLE_RELOC_FIXUP (OPTION_NO_PICFIXUP + 1)
+enum ppc32_opt
+{
+ OPTION_NO_TLS_OPT = 321,
+ OPTION_NO_TLS_GET_ADDR_OPT,
+ OPTION_NEW_PLT,
+ OPTION_OLD_PLT,
+ OPTION_PLT_ALIGN,
+ OPTION_NO_PLT_ALIGN,
+ OPTION_OLD_GOT,
+ OPTION_STUBSYMS,
+ OPTION_NO_STUBSYMS,
+ OPTION_PPC476_WORKAROUND,
+ OPTION_NO_PPC476_WORKAROUND,
+ OPTION_NO_PICFIXUP,
+ OPTION_VLE_RELOC_FIXUP
+};
'
PARSE_AND_LIST_LONGOPTS=${PARSE_AND_LIST_LONGOPTS}'
@@ -261,6 +267,8 @@ if test -z "$VXWORKS_BASE_EM_FILE" ; then
PARSE_AND_LIST_LONGOPTS=${PARSE_AND_LIST_LONGOPTS}'
{ "secure-plt", no_argument, NULL, OPTION_NEW_PLT },
{ "bss-plt", no_argument, NULL, OPTION_OLD_PLT },
+ { "plt-align", no_argument, NULL, OPTION_PLT_ALIGN },
+ { "no-plt-align", no_argument, NULL, OPTION_NO_PLT_ALIGN },
{ "sdata-got", no_argument, NULL, OPTION_OLD_GOT },'
fi
PARSE_AND_LIST_LONGOPTS=${PARSE_AND_LIST_LONGOPTS}'
@@ -272,21 +280,47 @@ PARSE_AND_LIST_LONGOPTS=${PARSE_AND_LIST_LONGOPTS}'
PARSE_AND_LIST_OPTIONS=${PARSE_AND_LIST_OPTIONS}'
fprintf (file, _("\
- --emit-stub-syms Label linker stubs with a symbol.\n\
- --no-emit-stub-syms Don'\''t label linker stubs with a symbol.\n\
- --no-tls-optimize Don'\''t try to optimize TLS accesses.\n\
- --no-tls-get-addr-optimize Don'\''t use a special __tls_get_addr call.\n'
+ --emit-stub-syms Label linker stubs with a symbol.\n"
+ ));
+ fprintf (file, _("\
+ --no-emit-stub-syms Don'\''t label linker stubs with a symbol.\n"
+ ));
+ fprintf (file, _("\
+ --no-tls-optimize Don'\''t try to optimize TLS accesses.\n"
+ ));
+ fprintf (file, _("\
+ --no-tls-get-addr-optimize Don'\''t use a special __tls_get_addr call.\n"
+ ));'
if test -z "$VXWORKS_BASE_EM_FILE" ; then
PARSE_AND_LIST_OPTIONS=${PARSE_AND_LIST_OPTIONS}'\
- --secure-plt Use new-style PLT if possible.\n\
- --bss-plt Force old-style BSS PLT.\n\
- --sdata-got Force GOT location just before .sdata.\n'
+ fprintf (file, _("\
+ --secure-plt Use new-style PLT if possible.\n"
+ ));
+ fprintf (file, _("\
+ --bss-plt Force old-style BSS PLT.\n"
+ ));
+ fprintf (file, _("\
+ --plt-align Align PLT call stubs to fit cache lines.\n"
+ ));
+ fprintf (file, _("\
+ --no-plt-align Dont'\''t align individual PLT call stubs.\n"
+ ));
+ fprintf (file, _("\
+ --sdata-got Force GOT location just before .sdata.\n"
+ ));'
fi
PARSE_AND_LIST_OPTIONS=${PARSE_AND_LIST_OPTIONS}'\
+ fprintf (file, _("\
--ppc476-workaround [=pagesize]\n\
- Avoid a cache bug on ppc476.\n\
- --no-ppc476-workaround Disable workaround.\n\
- --no-pic-fixup Don'\''t edit non-pic to pic.\n\
+ Avoid a cache bug on ppc476.\n"
+ ));
+ fprintf (file, _("\
+ --no-ppc476-workaround Disable workaround.\n"
+ ));
+ fprintf (file, _("\
+ --no-pic-fixup Don'\''t edit non-pic to pic.\n"
+ ));
+ fprintf (file, _("\
--vle-reloc-fixup Correct old object file 16A/16D relocation.\n"
));
'
@@ -316,6 +350,14 @@ PARSE_AND_LIST_ARGS_CASES=${PARSE_AND_LIST_ARGS_CASES}'
params.plt_style = PLT_OLD;
break;
+ case OPTION_PLT_ALIGN:
+ params.plt_stub_align = 5;
+ break;
+
+ case OPTION_NO_PLT_ALIGN:
+ params.plt_stub_align = 0;
+ break;
+
case OPTION_OLD_GOT:
old_got = 1;
break;