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Message-ID: <20170914210031.3sdhhi2xrvgmse5j@treble> Date: Thu, 14 Sep 2017 16:00:31 -0500 From: Josh Poimboeuf <jpoimboe@...hat.com> To: Arnd Bergmann <arnd@...db.de> Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Subject: Re: "objtool orc" creates invalid file arch/x86/kernel/time.o On Sun, Sep 10, 2017 at 10:38:58PM +0200, Arnd Bergmann wrote: > Hi Josh, > > I have a randconfig build that produces a link error: > > built-in.o: member arch/x86/kernel/time.o in archive is not an object > > I've traced it down to the "objtool orc generate" command that appears > to corrupt the file, by running the same commands that 'make' calls: Thanks, I was able to recreate with your config. I'll post the patch soon (here's the preview): --- From: Josh Poimboeuf <jpoimboe@...hat.com> Subject: [PATCH] objtool: Fix object file corruption Arnd Bergmann reported that a randconfig build was failing with the following link error: built-in.o: member arch/x86/kernel/time.o in archive is not an object It turns out the link failed because the time.o file had been corrupted by objtool: nm: arch/x86/kernel/time.o: File format not recognized In certain rare cases, when a .o file's ORC table is very small, the .data section size doesn't change because it's page aligned. Because all the existing sections haven't changed size, libelf doesn't detect any section header changes, and so it doesn't update the section header table properly. Instead it writes junk in the section header entries for the new ORC sections. Make sure libelf properly updates the section header table by setting the ELF_F_DIRTY flag in the top level elf struct. Reported-by: Arnd Bergmann <arnd@...db.de> Fixes: 627fce14809b ("objtool: Add ORC unwind table generation") Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com> --- tools/objtool/elf.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c index 6e9f980a7d26..780d02af957d 100644 --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -561,6 +561,7 @@ int elf_write(struct elf *elf) struct section *sec; Elf_Scn *s; + /* Update section headers for changed sections: */ list_for_each_entry(sec, &elf->sections, list) { if (sec->changed) { s = elf_getscn(elf->elf, sec->idx); @@ -568,13 +569,17 @@ int elf_write(struct elf *elf) WARN_ELF("elf_getscn"); return -1; } - if (!gelf_update_shdr (s, &sec->sh)) { + if (!gelf_update_shdr(s, &sec->sh)) { WARN_ELF("gelf_update_shdr"); return -1; } } } + /* Make sure the new section header entries get updated properly. */ + elf_flagelf(elf->elf, ELF_C_SET, ELF_F_DIRTY); + + /* Write all changes to the file. */ if (elf_update(elf->elf, ELF_C_WRITE) < 0) { WARN_ELF("elf_update"); return -1; -- 2.13.5
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