linux-kernel - [PATCH 06/13] x86/crypto/crc32c-pcl-intel: Standardize jump table

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Date:   Wed, 24 Feb 2021 10:29:19 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     x86@...nel.org, Herbert Xu <herbert@...dor.apana.org.au>
Cc:     linux-kernel@...r.kernel.org, Miroslav Benes <mbenes@...e.cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Eric Biggers <ebiggers@...gle.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        linux-crypto@...r.kernel.org,
        "David S . Miller" <davem@...emloft.net>
Subject: [PATCH 06/13] x86/crypto/crc32c-pcl-intel: Standardize jump table

Simplify the jump table code so that it resembles a compiler-generated
table.

This enables ORC unwinding by allowing objtool to follow all the
potential code paths.

Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 arch/x86/crypto/crc32c-pcl-intel-asm_64.S | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/arch/x86/crypto/crc32c-pcl-intel-asm_64.S b/arch/x86/crypto/crc32c-pcl-intel-asm_64.S
index 884dc767b051..ac1f303eed0f 100644
--- a/arch/x86/crypto/crc32c-pcl-intel-asm_64.S
+++ b/arch/x86/crypto/crc32c-pcl-intel-asm_64.S
@@ -53,7 +53,7 @@
 .endm
 
 .macro JMPTBL_ENTRY i
-.word crc_\i - crc_array
+.quad crc_\i
 .endm
 
 .macro JNC_LESS_THAN j
@@ -168,10 +168,7 @@ continue_block:
 	xor     crc2, crc2
 
 	## branch into array
-	lea	jump_table(%rip), %bufp
-	movzwq  (%bufp, %rax, 2), len
-	lea	crc_array(%rip), %bufp
-	lea     (%bufp, len, 1), %bufp
+	mov	jump_table(,%rax,8), %bufp
 	JMP_NOSPEC bufp
 
 	################################################################
-- 
2.29.2