Re: [PATCH 00/21] objtool: vmlinux.o and CLANG LTO support

[Sedat Dilek <sedat.dilek@gmail.com>]

On Fri, Jan 15, 2021 at 5:51 AM Sedat Dilek <sedat.dilek@gmail.com> wrote:
>
> On Thu, Jan 14, 2021 at 8:40 PM Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> >
> > Add support for proper vmlinux.o validation, which will be needed for
> > Sami's upcoming x86 LTO set.  (And vmlinux validation is the future for
> > objtool anyway, for other reasons.)
> >
> > This isn't 100% done -- most notably, crypto still needs to be supported
> > -- but I think this gets us most of the way there.
> >
> > This can also be found at
> >
> >   git://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux.git objtool-vmlinux
> >
> > And for more testing it can be combined with Sami's x86 LTO patches:
> >
> >   https://github.com/samitolvanen/linux clang-lto
> >
> >
> >
> > Josh Poimboeuf (21):
> >   objtool: Fix seg fault in BT_FUNC() with fake jump
> >   objtool: Fix error handling for STD/CLD warnings
> >   objtool: Fix retpoline detection in asm code
> >   objtool: Fix ".cold" section suffix check for newer versions of GCC
> >   objtool: Support retpoline jump detection for vmlinux.o
> >   x86/ftrace: Add UNWIND_HINT_FUNC annotation for ftrace_stub
> >   objtool: Assume only ELF functions do sibling calls
> >   objtool: Add asm version of STACK_FRAME_NON_STANDARD
> >   objtool: Combine UNWIND_HINT_RET_OFFSET and UNWIND_HINT_FUNC
> >   objtool: Add xen_start_kernel() to noreturn list
> >   objtool: Move unsuffixed symbol conversion to a helper function
> >   objtool: Add CONFIG_CFI_CLANG support
> >   x86/xen: Support objtool validation in xen-asm.S
> >   x86/xen: Support objtool vmlinux.o validation in xen-head.S
> >   x86/xen/pvh: Convert indirect jump to retpoline
> >   x86/ftrace: Support objtool vmlinux.o validation in ftrace_64.S
> >   x86/acpi: Convert indirect jump to retpoline
> >   x86/acpi: Support objtool validation in wakeup_64.S
> >   x86/power: Convert indirect jumps to retpolines
> >   x86/power: Move restore_registers() to top of the file
> >   x86/power: Support objtool validation in hibernate_asm_64.S
> >
> >  arch/x86/include/asm/unwind_hints.h |  13 +---
> >  arch/x86/kernel/acpi/Makefile       |   1 -
> >  arch/x86/kernel/acpi/wakeup_64.S    |   5 +-
> >  arch/x86/kernel/ftrace_64.S         |   8 +--
> >  arch/x86/lib/retpoline.S            |   2 +-
> >  arch/x86/platform/pvh/head.S        |   3 +-
> >  arch/x86/power/Makefile             |   1 -
> >  arch/x86/power/hibernate_asm_64.S   | 105 ++++++++++++++--------------
> >  arch/x86/xen/Makefile               |   1 -
> >  arch/x86/xen/xen-asm.S              |  29 +++++---
> >  arch/x86/xen/xen-head.S             |   5 +-
> >  include/linux/objtool.h             |  13 +++-
> >  tools/include/linux/objtool.h       |  13 +++-
> >  tools/objtool/arch/x86/decode.c     |   4 +-
> >  tools/objtool/arch/x86/special.c    |   2 +-
> >  tools/objtool/check.c               |  91 +++++++++++++-----------
> >  tools/objtool/check.h               |  12 +++-
> >  tools/objtool/elf.c                 |  87 +++++++++++++++++------
> >  tools/objtool/elf.h                 |   2 +-
> >  19 files changed, 241 insertions(+), 156 deletions(-)
> >
> > --
> > 2.29.2
> >
>
> I tried this series on top of clang-cfi and it segfaults here.
>
> + info OBJTOOL vmlinux.o
> + [  != silent_ ]
> + printf   %-7s %s\n OBJTOOL vmlinux.o
>  OBJTOOL vmlinux.o
> + tools/objtool/objtool orc generate --duplicate --mcount --vmlinux
> --no-fp --no-unreachable --retpoline --uaccess vmlinux.o
> Segmentation fault
> + on_exit
> + [ 139 -ne 0 ]
> + cleanup
> + rm -f .btf.*
> + rm -f .tmp_System.map
> + rm -f .tmp_initcalls.lds
> + rm -f .tmp_symversions.lds
> + rm -f .tmp_vmlinux*
> + rm -f System.map
> + rm -f vmlinux
> + rm -f vmlinux.o
> make[3]: *** [Makefile:1213: vmlinux] Error 139
>

I re-tried with the latest clang-lto Git and switched to Debian's LLVM-11.0.1.
This build was successful.
No objtool-vmlinux warnings observed.

In the next step I try with my selfmade LLVM-11.1.0-rc1 (to see if it's broken).

- Sedat