Re: [linux-next:master 3857/7963] arch/x86/crypto/sm4-aesni-avx-asm_64.o: warning: objtool: sm4_aesni_avx_crypt8()+0x8: sibling call from callable instruction with modified stack frame

[Arnd Bergmann <arnd@kernel.org>]

On Sun, Aug 15, 2021 at 9:41 PM kernel test robot <lkp@intel.com> wrote:
>
> CC: Linux Memory Management List <linux-mm@kvack.org>
> TO: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
> CC: Herbert Xu <herbert@gondor.apana.org.au>
>
> Hi Tianjia,
>
> First bad commit (maybe != root cause):
>
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> head:   4b358aabb93a2c654cd1dcab1a25a589f6e2b153
> commit: a7ee22ee1445c7fdb00ab80116bb9710ca86a860 [3857/7963] crypto: x86/sm4 - add AES-NI/AVX/x86_64 implementation
> config: x86_64-randconfig-r024-20210816 (attached as .config)
> compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 7776b19eed44906e9973bfb240b6279d6feaab41)
> reproduce (this is a W=1 build):
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=a7ee22ee1445c7fdb00ab80116bb9710ca86a860
>         git remote add linux-next https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
>         git fetch --no-tags linux-next master
>         git checkout a7ee22ee1445c7fdb00ab80116bb9710ca86a860
>         # save the attached .config to linux build tree
>         mkdir build_dir
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross O=build_dir ARCH=x86_64 SHELL=/bin/bash arch/x86/
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
>
> All warnings (new ones prefixed by >>):
>
> >> arch/x86/crypto/sm4-aesni-avx-asm_64.o: warning: objtool: sm4_aesni_avx_crypt8()+0x8: sibling call from callable instruction with modified stack frame

I see the same thing in my randconfig builds using gcc. This is an
assembler file,
my interpretation is that objtool has found an actual code bug:

.macro FRAME_BEGIN
        push %_ASM_BP
        _ASM_MOV %_ASM_SP, %_ASM_BP
.endm
.macro FRAME_END
        pop %_ASM_BP
.endm

SYM_FUNC_START(sm4_aesni_avx_crypt8)
        /* input:
         *      %rdi: round key array, CTX
         *      %rsi: dst (1..8 blocks)
         *      %rdx: src (1..8 blocks)
         *      %rcx: num blocks (1..8)
         */
        FRAME_BEGIN

        cmpq $5, %rcx;
        jb sm4_aesni_avx_crypt4;
        ....

SYM_FUNC_START(sm4_aesni_avx_crypt4)
        /* input:
         *      %rdi: round key array, CTX
         *      %rsi: dst (1..4 blocks)
         *      %rdx: src (1..4 blocks)
         *      %rcx: num blocks (1..4)
         */
        FRAME_BEGIN
        ...
        FRAME_END
        ret;
SYM_FUNC_END(sm4_aesni_avx_crypt4)


sm4_aesni_avx_crypt8() starts a frame and conditionally branches to
sm4_aesni_avx_crypt4(), which starts another frame and returns from
that without cleaning up the parent frame.

        Arnd