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powerpc: Avoid unaligned loads and stores in boot memcpy code

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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>
This commit is contained in:
Paul Mackerras 2006-01-14 15:06:51 +11:00
parent 66a45dd362
commit b4e7de0f35
1 changed files with 17 additions and 3 deletions
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20
arch/powerpc/boot/string.S
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@ -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