linux-kernel - Re: [PATCH v6 22/25] x86/asm: annotate indirect jumps

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Date:   Tue, 20 Oct 2020 09:45:06 -0700
From:   Sami Tolvanen <samitolvanen@...gle.com>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Jann Horn <jannh@...gle.com>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Will Deacon <will@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        linux-arch <linux-arch@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-kbuild <linux-kbuild@...r.kernel.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        linux-pci@...r.kernel.org
Subject: Re: [PATCH v6 22/25] x86/asm: annotate indirect jumps

On Thu, Oct 15, 2020 at 1:39 PM Josh Poimboeuf <jpoimboe@...hat.com> wrote:
>
> On Thu, Oct 15, 2020 at 12:22:16PM +0200, Peter Zijlstra wrote:
> > On Thu, Oct 15, 2020 at 01:23:41AM +0200, Jann Horn wrote:
> >
> > > It would probably be good to keep LTO and non-LTO builds in sync about
> > > which files are subjected to objtool checks. So either you should be
> > > removing the OBJECT_FILES_NON_STANDARD annotations for anything that
> > > is linked into the main kernel (which would be a nice cleanup, if that
> > > is possible),
> >
> > This, I've had to do that for a number of files already for the limited
> > vmlinux.o passes we needed for noinstr validation.
>
> Getting rid of OBJECT_FILES_NON_STANDARD is indeed the end goal, though
> I'm not sure how practical that will be for some of the weirder edge
> case.
>
> On a related note, I have some old crypto cleanups which need dusting
> off.

Building allyesconfig with this series and LTO enabled, I still see
the following objtool warnings for vmlinux.o, grouped by source file:

arch/x86/entry/entry_64.S:
__switch_to_asm()+0x0: undefined stack state
.entry.text+0xffd: sibling call from callable instruction with
modified stack frame
.entry.text+0x48: stack state mismatch: cfa1=7-8 cfa2=-1+0

arch/x86/entry/entry_64_compat.S:
.entry.text+0x1754: unsupported instruction in callable function
.entry.text+0x1634: redundant CLD
.entry.text+0x15fd: stack state mismatch: cfa1=7-8 cfa2=-1+0
.entry.text+0x168c: stack state mismatch: cfa1=7-8 cfa2=-1+0

arch/x86/kernel/head_64.S:
.head.text+0xfb: unsupported instruction in callable function

arch/x86/kernel/acpi/wakeup_64.S:
do_suspend_lowlevel()+0x116: sibling call from callable instruction
with modified stack frame

arch/x86/crypto/camellia-aesni-avx2-asm_64.S:
camellia_cbc_dec_32way()+0xb3: stack state mismatch: cfa1=7+520 cfa2=7+8
camellia_ctr_32way()+0x1a: stack state mismatch: cfa1=7+520 cfa2=7+8

arch/x86/crypto/aesni-intel_avx-x86_64.S:
aesni_gcm_init_avx_gen2()+0x12: unsupported stack pointer realignment
aesni_gcm_enc_update_avx_gen2()+0x12: unsupported stack pointer realignment
aesni_gcm_dec_update_avx_gen2()+0x12: unsupported stack pointer realignment
aesni_gcm_finalize_avx_gen2()+0x12: unsupported stack pointer realignment
aesni_gcm_init_avx_gen4()+0x12: unsupported stack pointer realignment
aesni_gcm_enc_update_avx_gen4()+0x12: unsupported stack pointer realignment
aesni_gcm_dec_update_avx_gen4()+0x12: unsupported stack pointer realignment
aesni_gcm_finalize_avx_gen4()+0x12: unsupported stack pointer realignment

arch/x86/crypto/sha1_avx2_x86_64_asm.S:
sha1_transform_avx2()+0xc: unsupported stack pointer realignment

arch/x86/crypto/sha1_ni_asm.S:
sha1_ni_transform()+0x7: unsupported stack pointer realignment

arch/x86/crypto/sha256-avx2-asm.S:
sha256_transform_rorx()+0x13: unsupported stack pointer realignment

arch/x86/crypto/sha512-ssse3-asm.S:
sha512_transform_ssse3()+0x14: unsupported stack pointer realignment

arch/x86/crypto/sha512-avx-asm.S:
sha512_transform_avx()+0x14: unsupported stack pointer realignment

arch/x86/crypto/sha512-avx2-asm.S:
sha512_transform_rorx()+0x7: unsupported stack pointer realignment

arch/x86/lib/retpoline.S:
__x86_retpoline_rdi()+0x10: return with modified stack frame
__x86_retpoline_rdi()+0x0: stack state mismatch: cfa1=7+32 cfa2=7+8
__x86_retpoline_rdi()+0x0: stack state mismatch: cfa1=7+32 cfa2=-1+0

Josh, Peter, any thoughts on what would be the preferred way to fix
these, or how to tell objtool to ignore this code?

Sami