Messages in this thread | | | Date | Wed, 3 Jan 2018 07:59:24 -0600 | From | Josh Poimboeuf <> | Subject | Re: objtool segfault with ORC unwinder enabled |
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On Wed, Jan 03, 2018 at 01:22:07PM +0100, Markus wrote: > On Wed, Jan 03, 2018 at 12:19:41 CET Greg Kroah-Hartman wrote: > > On Wed, Jan 03, 2018 at 11:49:08AM +0100, Markus wrote: > > > Hello! > > > > > > ORC unwinder is enabled in stable for wider testing but still at least one > > > bug is open: > > > https://bugzilla.kernel.org/show_bug.cgi?id=197035 > > > > Random web links on mailing lists don't help much, please put the > > information here in the email. > > Its not a random web link. Its the official kernel.org bugtracker. But nobody > seems to be looking at it. > > > > objtool will segfault because a NULL pointer is dereferenced. > > > > And how are you reproducing this? > > Just building the kernel with ORC enabled. > (At least for me. Using framepointers compiles, enabling ORC again breaks it.) > gcc 6.4.0 (In bug report others were tested as well.) > elfutils 0.170 > What else may be interesting? > > > > Is a NULL pointer sym valid? > > > If a NULL pointer is invalid, it has to be checked why it is sometimes > > > NULL. > > What .config is triggering this problem? > See attachment. > > > And does this show up on 4.14.11, and 4.15-rc6? > Both: yes. > > /tools/objtool/objtool orc generate --no-fp "arch/x86/kernel/irq.o" > > => segfault. > > Changing CFLAGS for objtool to O1 and starting from gdb: > > (gdb) r orc generate --no-fp "arch/x86/kernel/irq.o" > Starting program: tools/objtool/objtool orc generate --no-fp "arch/x86/kernel/ > irq.o" > > Program received signal SIGSEGV, Segmentation fault. > 0x000055555555e06c in elf_rebuild_rela_section (sec=sec@entry=0x7ffff690d010) > at elf.c:554 > 554 relas[idx].r_info = GELF_R_INFO(rela->sym->idx, rela- > >type); > (gdb) bt > #0 0x000055555555e06c in elf_rebuild_rela_section > (sec=sec@entry=0x7ffff690d010) at elf.c:554 > #1 0x000055555555d0aa in create_orc_sections (file=file@entry=0x7ffffff7d740) > at orc_gen.c:210 > #2 0x000055555555c146 in check (_objname=<optimized out>, _no_fp=<optimized > out>, no_unreachable=<optimized out>, orc=orc@entry=true) at check.c:1971 > #3 0x000055555555811f in cmd_orc (argc=<optimized out>, argv=0x7fffffffd8d8) > at builtin-orc.c:54 > #4 0x000055555555f490 in handle_internal_command (argv=0x7fffffffd8d0, > argc=4) at objtool.c:108 > #5 main (argc=4, argv=0x7fffffffd8d0) at objtool.c:131 > (gdb) p rela->sym > $1 = (struct symbol *) 0x0
Hi Markus,
I'm unable to recreate. Can you attach one of the .o files (like the above irq.o)?
-- Josh
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