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authorAlan Modra <amodra@gmail.com>2012-01-11 09:28:45 +0000
committerAlan Modra <amodra@gmail.com>2012-01-11 09:28:45 +0000
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parent313a658140f4e578ca376be3e3cf68ff561d3979 (diff)
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* elf64-ppc.c: Define more insns used in plt call stubs. (ppc64_elf_brtaken_reloc): Assume isa version 2 or above. (ppc64_elf_relocate_section): Likewise. (enum ppc_stub_type): Add ppc_stub_plt_call_r2save. (struct ppc_link_hash_table): Increase size of stub_count array. Add plt_stub_align and plt_thread_safe. (ALWAYS_USE_FAKE_DEP, ALWAYS_EMIT_R2SAVE): Define. (plt_stub_size, plt_stub_pad): New functions. (build_plt_stub): Emit barriers for power7 thread safety. Don't emit needless save of r2. (build_tls_get_addr_stub): Adjust params. (ppc_build_one_stub): Handle ppc_stub_plt_call_r2save and aligning plt stubs. Adjust build_*plt_stub calls. (ppc_size_one_stub): Similarly. (ppc64_elf_size_stubs): Accept plt_thread_safe and plt_stub_align params. Choose default for plt_thread_safe based on existence of calls to thread creation functions. Modify plt_call to plt_call_r2save when no tocsave reloc found. Align tail of stub sections. (ppc64_elf_build_stubs): Align tail of stub sections. Adjust output of stub statistics. (ppc64_elf_relocate_section): Handle ppc_stub_plt_call_r2save. * elf64-ppc.h (ppc64_elf_size_stubs): Update prototype. ld/ * emultempl/ppc64elf.em (PARSE_AND_LIST_PROLOGUE, PARSE_AND_LIST_LONGOPTS, PARSE_AND_LIST_OPTIONS, PARSE_AND_LIST_ARGS_CASES): Handle --{no-,}plt-thread-safe and --{no-,}plt-align. (plt_thread_safe, plt_stub_align): New vars. (gld${EMULATION_NAME}_after_allocation): Pass them to ppc64_elf_size_stubs. Align stub sections according to plt_stub_align. * ld.texinfo: Document new command line options, and an old undocumented option.
Diffstat (limited to 'ld/ld.texinfo')
-rw-r--r--ld/ld.texinfo52
1 files changed, 50 insertions, 2 deletions
diff --git a/ld/ld.texinfo b/ld/ld.texinfo
index 592e38c..6c74ff5 100644
--- a/ld/ld.texinfo
+++ b/ld/ld.texinfo
@@ -1,7 +1,7 @@
\input texinfo
@setfilename ld.info
@c Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
-@c 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011
+@c 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012
@c Free Software Foundation, Inc.
@syncodeindex ky cp
@c man begin INCLUDE
@@ -6710,7 +6710,9 @@ optimization.
@cindex PowerPC64 multi-TOC
@kindex --no-multi-toc
@item --no-multi-toc
-By default, PowerPC64 GCC generates code for a TOC model where TOC
+If given any toc option besides @code{-mcmodel=medium} or
+@code{-mcmodel=large}, PowerPC64 GCC generates code for a TOC model
+where TOC
entries are accessed with a 16-bit offset from r2. This limits the
total TOC size to 64K. PowerPC64 @command{ld} extends this limit by
grouping code sections such that each group uses less than 64K for its
@@ -6719,6 +6721,52 @@ calls. @command{ld} does not split apart input sections, so cannot
help if a single input file has a @code{.toc} section that exceeds
64K, most likely from linking multiple files with @command{ld -r}.
Use this option to turn off this feature.
+
+@cindex PowerPC64 TOC sorting
+@kindex --no-toc-sort
+@item --no-toc-sort
+By default, @command{ld} sorts TOC sections so that those whose file
+happens to have a section called @code{.init} or @code{.fini} are
+placed first, followed by TOC sections referenced by code generated
+with PowerPC64 gcc's @code{-mcmodel=small}, and lastly TOC sections
+referenced only by code generated with PowerPC64 gcc's
+@code{-mcmodel=medium} or @code{-mcmodel=large} options. Doing this
+results in better TOC grouping for multi-TOC. Use this option to turn
+off this feature.
+
+@cindex PowerPC64 PLT stub alignment
+@kindex --plt-align
+@kindex --no-plt-align
+@item --plt-align
+@itemx --no-plt-align
+Use these options to control whether individual PLT call stubs are
+aligned to a 32-byte boundary, or to the specified power of two
+boundary when using @code{--plt-align=}. By default PLT call stubs
+are packed tightly.
+
+@cindex PowerPC64 PLT call stub static chain
+@kindex --plt-static-chain
+@kindex --no-plt-static-chain
+@item --plt-static-chain
+@itemx --no-plt-static-chain
+Use these options to control whether PLT call stubs load the static
+chain pointer (r11). @code{ld} defaults to not loading the static
+chain since there is never any need to do so on a PLT call.
+
+@cindex PowerPC64 PLT call stub thread safety
+@kindex --plt-thread-safe
+@kindex --no-plt-thread-safe
+@item --plt-thread-safe
+@itemx --no-thread-safe
+With power7's weakly ordered memory model, it is possible when using
+lazy binding for ld.so to update a plt entry in one thread and have
+another thread see the individual plt entry words update in the wrong
+order, despite ld.so carefully writing in the correct order and using
+memory write barriers. To avoid this we need some sort of read
+barrier in the call stub, or use LD_BIND_NOW=1. By default, @code{ld}
+looks for calls to commonly used functions that create threads, and if
+seen, adds the necessary barriers. Use these options to change the
+default behaviour.
@end table
@ifclear GENERIC