[tip: objtool/core] x86/crypto/crc32c-pcl-intel: Standardize jump table

[tip-bot2 for Josh Poimboeuf]

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     2b02ed55482a1c5c310a7f53707292fcf1601e7a
Gitweb:        https://git.kernel.org/tip/2b02ed55482a1c5c310a7f53707292fcf1601e7a
Author:        Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
AuthorDate:    Wed, 24 Feb 2021 10:29:19 -06:00
Committer:     Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
CommitterDate: Mon, 19 Apr 2021 12:36:34 -05:00

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@xxxxxxxxxx>
Tested-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Acked-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Tested-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Acked-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/5357a039def90b8ef6b5874ef12cda008ecf18ba.1614182415.git.jpoimboe@xxxxxxxxxx
---
 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 884dc76..ac1f303 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
 
 	################################################################