Hi Jian,

On Thu, Oct 29, 2020 at 06:13:07PM -0700, 'Jian Cai' via Clang Built Linux wrote:

Thanks @Nick Desaulniers ndesaulniers@google.com and @Sasha Levin sashal@kernel.org for the tips. For this particular change, it seems we do not need to backport all the dependencies (if they have not been merged into 5.4 stable). @Greg KH gregkh@linuxfoundation.org, please find the custom backport as below. It has passed all the tests on ChromeOS ( http://crrev.com/c/2504570).

Thanks, Jian

The below patch won't apply because it appears to be copy pasted into this message:

Applying: Backport 44623b2818f4a442726639572f44fd9b6d0ef68c to kernel 5.4 error: git diff header lacks filename information when removing 1 leading pathname component (line 6) Patch failed at 0001 Backport 44623b2818f4a442726639572f44fd9b6d0ef68c to kernel 5.4 hint: Use 'git am --show-current-patch=diff' to see the failed patch When you have resolved this problem, run "git am --continue". If you prefer to skip this patch, run "git am --skip" instead. To restore the original branch and stop patching, run "git am --abort".

I would recommend resending the patch with git send-email or attaching the patch file created by 'git format-patch -1' to a future email for proper application.

From 60891062750a39d8bba9710d500e381a26c11f75 Mon Sep 17 00:00:00 2001 From: Jian Cai jiancai@google.com Date: Thu, 29 Oct 2020 17:49:39 -0700

Authorship and date should be fixed to retain the information of the original commit.

It is trivial to just redo the cherry-pick to fix that information in this instance but this is the command I usually run for more non-trivial backports that I have already done:

$ git commit -s --amend -C <sha> --date "$(git show -s --format=%ai <sha>)"

This should allow you to retain the commit message of the original message along with the author's date.

Subject: [PATCH] crypto: x86/crc32c - fix building with clang ias

commit 44623b2818f4a442726639572f44fd9b6d0ef68c upstream

The clang integrated assembler complains about movzxw:

arch/x86/crypto/crc32c-pcl-intel-asm_64.S:173:2: error: invalid instruction mnemonic 'movzxw'

It seems that movzwq is the mnemonic that it expects instead, and this is what objdump prints when disassembling the file.

NOTE: this is a custom backport as the surrounding code has been changed upstream.

A note of this nature is traditionally placed after the signoffs of the original patch like my example below:

Fixes: 6a8ce1ef3940 ("crypto: crc32c - Optimize CRC32C calculation with PCLMULQDQ instruction") Signed-off-by: Arnd Bergmann arnd@arndb.de Reviewed-by: Nathan Chancellor natechancellor@gmail.com Signed-off-by: Herbert Xu herbert@gondor.apana.org.au

[jc: Backport to 5.4]

Signed-off-by: Jian Cai caij2003@gmail.com

I usually like to notate why the patch did not apply cleanly so that it is easier for others to audit, such as:

[jc: Fixed conflicts due to lack of 34fdce6981b969]

That is merely a suggestion, not required by any means.

Otherwise, the backport seems obvious fine to me.

Cheers, Nathan

---

arch/x86/crypto/crc32c-pcl-intel-asm_64.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/crypto/crc32c-pcl-intel-asm_64.S b/arch/x86/crypto/crc32c-pcl-intel-asm_64.S index d9b734d0c8cc..3c6e01520a97 100644 --- a/arch/x86/crypto/crc32c-pcl-intel-asm_64.S +++ b/arch/x86/crypto/crc32c-pcl-intel-asm_64.S @@ -170,7 +170,7 @@ continue_block:

## branch into array lea jump_table(%rip), bufp

• movzxw (bufp, %rax, 2), len

• movzwq (bufp, %rax, 2), len lea crc_array(%rip), bufp lea (bufp, len, 1), bufp JMP_NOSPEC bufp

-- 2.29.1.341.ge80a0c044ae-goog