Messages in this thread | | | From | Matt Helsley <> | Subject | [RFC][PATCH 00/36] objtool: Make recordmcount a subcommand | Date | Fri, 10 Apr 2020 12:35:23 -0700 |
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recordmcount has its own ELF wrapper code and could utilize objtool's ELF code to more-portably handle architecture variations. This series makes recordmcount a subcommand of objtool.
The initial 5 patches make objtool compilable for more than x86. Unlike recordmcount the check command and orc tools are not currently checking other architectures so we need a way to cleanly build objtool for those architectures that don't support check / orc. I went with using weak symbols and added a "missing" architecture which can be used to indicate the tool is not implemented while avoiding the need for every architecture to explicitly specify which subcommands / features are not implemented. I'm curious if there are better approaches folks recommend though -- this is the one I landed on. The patches do not add HAVE_OBJTOOL to all architectures.
Note: I've been following some of the discussion around making check work for arm64. So I'd say this series moves check into arch/x86 to reflect its current status and demonstrates how a command relevant to a single arch could be handled -- not necessarily what will/should happen to check.
Subsequent patches, the bulk of the set, very gradually convert recordmcount to become a subcommand of objtool and then reuse parts of objtool's ELF code. recordmcount maps the file in and collects simple information it needs to append a section to the object file. The only part of the original file it modifies is the address of new section tables -- interestingly enough this resembles RCU in that we don't really trim the old tables so much as unlink them via one critical offset and then rely on future (tooling in this case) to drop the unused bits. So much of the recordmcount ELF code is only reading and walking the data structures to collect the mcount locations it records in a separate area of memory. This means it's safe to mix access to the mapped file with access to the objtool-style linked data structures as we gradually convert it to using only the linked data structures. Once the old ELF code is no longer in use we can drop it and use objtool to take over the task of writing the results without using the RCU-like trick any more.
Testing so far:
I've been using scripts to test compilation, execution of objtool, and mcount output for x86, ppc64le, arm64, s390, and sparc.
Matt Helsley (36): objtool: Exit successfully when requesting help objtool: Move struct objtool_file into arch-independent header objtool: Enable compilation of objtool for all architectures objtool: Report missing support for subcommands objtool: Add support for relocations without addends objtool: Prepare to merge recordmcount objtool: Make recordmcount into mcount subcmd objtool: recordmcount: Start using objtool's elf wrapper objtool: recordmcount: Search for __mcount_loc before walking the sections objtool: recordmcount: Convert do_func() relhdrs objtool: mcount: Remove unused fname parameter objtool: mcount: Use libelf for section header names objtool: mcount: Walk objtool Elf structs in find_secsym_ndx objtool: mcount: Use symbol structs to find mcount relocations objtool: mcount: Walk relocation lists objtool: mcount: Move get_mcountsym objtool: mcount: Replace MIPS offset types objtool: mcount: Move is_fake_mcount() objtool: mcount: Stop using ehdr in find_section_sym_index objtool: mcount: Move find_section_sym_index() objtool: mcount: Restrict using ehdr in append_func() objtool: mcount: Use objtool ELF to write objtool: mcount: Move nop_mcount() objtool: mcount: Move helpers out of ELF wrapper objtool: mcount: Move relocation entry size detection objtool: mcount: Only keep ELF file size objtool: mcount: Use ELF header from objtool objtool: mcount: Remove unused file mapping objtool: mcount: Reduce usage of _size wrapper objtool: mcount: Move mcount_adjust out of wrapper objtool: mcount: Pre-allocate new ELF sections objtool: mcount: Generic location and relocation table types objtool: mcount: Move sift_rel_mcount out of wrapper file objtool: mcount: Remove wrapper for ELF relocation type objtool: mcount: Remove wrapper double-include trick objtool: mcount: Remove wordsized endian wrappers
Documentation/dontdiff | 2 +- Documentation/trace/ftrace-design.rst | 4 +- Documentation/trace/ftrace.rst | 6 +- Makefile | 6 +- arch/arm64/include/asm/ftrace.h | 2 +- arch/x86/include/asm/ftrace.h | 2 +- kernel/trace/Kconfig | 2 +- scripts/.gitignore | 1 - scripts/Makefile | 1 - scripts/Makefile.build | 24 +- scripts/recordmcount.c | 663 -------------------- scripts/recordmcount.h | 606 ------------------ scripts/sorttable.h | 2 +- tools/objtool/.gitignore | 1 + tools/objtool/Build | 6 +- tools/objtool/Makefile | 1 + tools/objtool/arch/missing/Build | 4 + tools/objtool/arch/missing/check.c | 16 + tools/objtool/arch/missing/mcount.c | 16 + tools/objtool/arch/missing/orc_dump.c | 13 + tools/objtool/arch/missing/orc_gen.c | 16 + tools/objtool/arch/x86/Build | 4 + tools/objtool/{ => arch/x86}/arch.h | 42 +- tools/objtool/{ => arch/x86}/cfi.h | 0 tools/objtool/{ => arch/x86}/check.c | 11 +- tools/objtool/arch/x86/decode.c | 2 +- tools/objtool/{ => arch/x86}/orc_dump.c | 5 +- tools/objtool/{ => arch/x86}/orc_gen.c | 9 +- tools/objtool/{ => arch/x86}/special.c | 4 +- tools/objtool/{ => arch/x86}/special.h | 2 +- tools/objtool/builtin-check.c | 5 + tools/objtool/builtin-mcount.c | 56 ++ tools/objtool/builtin-orc.c | 9 +- tools/objtool/builtin.h | 4 + tools/objtool/check.h | 48 +- tools/objtool/elf.c | 60 +- tools/objtool/elf.h | 7 +- tools/objtool/mcount.h | 14 + tools/objtool/objtool.c | 40 +- tools/objtool/objtool.h | 20 + tools/objtool/orc.h | 3 +- tools/objtool/recordmcount.c | 682 +++++++++++++++++++++ {scripts => tools/objtool}/recordmcount.pl | 0 43 files changed, 1038 insertions(+), 1383 deletions(-) delete mode 100644 scripts/recordmcount.c delete mode 100644 scripts/recordmcount.h create mode 100644 tools/objtool/arch/missing/Build create mode 100644 tools/objtool/arch/missing/check.c create mode 100644 tools/objtool/arch/missing/mcount.c create mode 100644 tools/objtool/arch/missing/orc_dump.c create mode 100644 tools/objtool/arch/missing/orc_gen.c rename tools/objtool/{ => arch/x86}/arch.h (59%) rename tools/objtool/{ => arch/x86}/cfi.h (100%) rename tools/objtool/{ => arch/x86}/check.c (99%) rename tools/objtool/{ => arch/x86}/orc_dump.c (98%) rename tools/objtool/{ => arch/x86}/orc_gen.c (96%) rename tools/objtool/{ => arch/x86}/special.c (98%) rename tools/objtool/{ => arch/x86}/special.h (95%) create mode 100644 tools/objtool/builtin-mcount.c create mode 100644 tools/objtool/mcount.h create mode 100644 tools/objtool/objtool.h create mode 100644 tools/objtool/recordmcount.c rename {scripts => tools/objtool}/recordmcount.pl (100%)
-- 2.20.1
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