From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Date: Fri, 27 Mar 2015 17:27:14 +0000 (+0000)
Subject: MdePkg: fix ARM version of InternalMathSwapBytes64 ()
X-Git-Tag: edk2-stable201903~10122
X-Git-Url: https://git.proxmox.com/?p=mirror_edk2.git;a=commitdiff_plain;h=55f5af1871d07d62def7bafa20b4761cc8b66e7d

MdePkg: fix ARM version of InternalMathSwapBytes64 ()

The ARM asm implementation of InternalMathSwapBytes64 () does
interesting things if bit 7 of operand r1 (upper 32 bits of the
input value) is set. After the recursive swap, bit 7 ends up in
the sign bit position, after which it is right shifted with sign
extension, and or'ed with the upper half of the output value.

This means SwapBytes64 (0x00000080_00000000) returns an incorrect
value of 0xFFFFFFFF_80000000.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Ronald Cron <Ronald.Cron@arm.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17077 6f19259b-4bc3-4df7-8a09-765794883524
---

diff --git a/MdePkg/Library/BaseLib/Arm/Math64.S b/MdePkg/Library/BaseLib/Arm/Math64.S
index 4d97573920..e2512621fe 100755
--- a/MdePkg/Library/BaseLib/Arm/Math64.S
+++ b/MdePkg/Library/BaseLib/Arm/Math64.S
@@ -256,22 +256,14 @@ L30:
 	GCC_ASM_EXPORT(InternalMathSwapBytes64)
 
 ASM_PFX(InternalMathSwapBytes64):
-	@ args = 0, pretend = 0, frame = 0
-	@ frame_needed = 1, uses_anonymous_args = 0
-	stmfd	sp!, {r4, r5, r6, r7, lr}
-	add	r7, sp, #12
+	stmfd	sp!, {r4, r5, r7, lr}
 	mov	r5, r1
 	bl	ASM_PFX(SwapBytes32)
-	mov	r6, r0
+	mov	r4, r0
 	mov	r0, r5
 	bl	ASM_PFX(SwapBytes32)
-	mov	r4, r6
-	mov	r5, r4, asr #31
-	mov	r2, #0
-	mov	r1, r0, asr #31
-	orr	r0, r0, r2
-	orr	r1, r1, r4
-	ldmfd	sp!, {r4, r5, r6, r7, pc}
+	mov	r1, r4
+	ldmfd	sp!, {r4, r5, r7, pc}
 
 
 ASM_FUNCTION_REMOVE_IF_UNREFERENCED
\ No newline at end of file