2022-03-22 12:20:32

by Peter Zijlstra

Subject: [PATCH 1/2] x86/chacha20: Avoid spurious jumps to other functions

The chacha_Nblock_xor_avx512vl() functions all have their own,
identical, .LdoneN label, however in one particular spot {2,4} jump to
the 8 version instead of their own. Resulting in:

arch/x86/crypto/chacha-x86_64.o: warning: objtool: chacha_2block_xor_avx512vl() falls through to next function chacha_8block_xor_avx512vl()
arch/x86/crypto/chacha-x86_64.o: warning: objtool: chacha_4block_xor_avx512vl() falls through to next function chacha_8block_xor_avx512vl()

Make each function consistently use its own done label.

Reported-by: Stephen Rothwell <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
---
arch/x86/crypto/chacha-avx512vl-x86_64.S | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/x86/crypto/chacha-avx512vl-x86_64.S
+++ b/arch/x86/crypto/chacha-avx512vl-x86_64.S
@@ -172,7 +172,7 @@ SYM_FUNC_START(chacha_2block_xor_avx512v
# xor remaining bytes from partial register into output
mov %rcx,%rax
and $0xf,%rcx
- jz .Ldone8
+ jz .Ldone2
mov %rax,%r9
and $~0xf,%r9

@@ -438,7 +438,7 @@ SYM_FUNC_START(chacha_4block_xor_avx512v
# xor remaining bytes from partial register into output
mov %rcx,%rax
and $0xf,%rcx
- jz .Ldone8
+ jz .Ldone4
mov %rax,%r9
and $~0xf,%r9

2022-03-22 14:15:11

by Martin Willi

Subject: Re: [PATCH 1/2] x86/chacha20: Avoid spurious jumps to other functions

> The chacha_Nblock_xor_avx512vl() functions all have their own,
> identical, .LdoneN label, however in one particular spot {2,4} jump
> to the 8 version instead of their own. [...]
>
> Make each function consistently use its own done label.

Reviewed-by: Martin Willi <[email protected]>

2022-03-25 15:25:59

by Herbert Xu

Subject: Re: [PATCH 1/2] x86/chacha20: Avoid spurious jumps to other functions

On Tue, Mar 22, 2022 at 12:48:10PM +0100, Peter Zijlstra wrote:
> The chacha_Nblock_xor_avx512vl() functions all have their own,
> identical, .LdoneN label, however in one particular spot {2,4} jump to
> the 8 version instead of their own. Resulting in:
>
> arch/x86/crypto/chacha-x86_64.o: warning: objtool: chacha_2block_xor_avx512vl() falls through to next function chacha_8block_xor_avx512vl()
> arch/x86/crypto/chacha-x86_64.o: warning: objtool: chacha_4block_xor_avx512vl() falls through to next function chacha_8block_xor_avx512vl()
>
> Make each function consistently use its own done label.
>
> Reported-by: Stephen Rothwell <[email protected]>
> Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
> ---
> arch/x86/crypto/chacha-avx512vl-x86_64.S | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)

Patch applied. Thanks.
--
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt