powerpc: Avoid unaligned loads and stores in boot memcpy code (b4e7de0f) · Commits · 戴 / test

The 601 processor will generate an alignment exception for accesses which cross a page boundary. In the boot wrapper code, OF is still handling all exceptions, and it doesn't have an alignment exception handler that emulates the instruction and continues. This changes the memcpy and memmove routines in the boot wrapper to avoid doing unaligned accesses. If the source and destination are misaligned with respect to each other, we just copy one byte at a time. Signed-off-by:

Paul Mackerras <paulus@samba.org>

arch/powerpc/boot/string.S

+17 −3

Original line number	Diff line number	Diff line
		@@ -107,10 +107,12 @@ memcpy:
		rlwinm. r7,r5,32-3,3,31 /* r7 = r5 >> 3 */
		addi r6,r3,-4
		addi r4,r4,-4
		beq 2f /* if less than 8 bytes to do */
		beq 3f /* if less than 8 bytes to do */
		andi. r0,r6,3 /* get dest word aligned */
		mtctr r7
		bne 5f
		andi. r0,r4,3 /* check src word aligned too */
		bne 3f
		1: lwz r7,4(r4)
		lwzu r8,8(r4)
		stw r7,4(r6)
		@@ -132,6 +134,11 @@ memcpy:
		bdnz 4b
		blr
		5: subfic r0,r0,4
		cmpw cr1,r0,r5
		add r7,r0,r4
		andi. r7,r7,3 /* will source be word-aligned too? */
		ble cr1,3b
		bne 3b /* do byte-by-byte if not */
		mtctr r0
		6: lbz r7,4(r4)
		addi r4,r4,1
		@@ -149,10 +156,12 @@ backwards_memcpy:
		rlwinm. r7,r5,32-3,3,31 /* r7 = r5 >> 3 */
		add r6,r3,r5
		add r4,r4,r5
		beq 2f
		beq 3f
		andi. r0,r6,3
		mtctr r7
		bne 5f
		andi. r0,r4,3
		bne 3f
		1: lwz r7,-4(r4)
		lwzu r8,-8(r4)
		stw r7,-4(r6)
		@@ -171,7 +180,12 @@ backwards_memcpy:
		stbu r0,-1(r6)
		bdnz 4b
		blr
		5: mtctr r0
		5: cmpw cr1,r0,r5
		subf r7,r0,r4
		andi. r7,r7,3
		ble cr1,3b
		bne 3b
		mtctr r0
		6: lbzu r7,-1(r4)
		stbu r7,-1(r6)
		bdnz 6b

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