author: Michael Ellerman <mpe@ellerman.id.au> 2019-03-22 23:37:24 +1100
committer: Michael Ellerman <mpe@ellerman.id.au> 2019-03-25 23:33:26 +1100
commit: d9470757398a700d9450a43508000bcfd010c7a4
parent: 8c2ffd9174779014c3fe1f96d9dc3641d9175f00
Commit Summary:
Diffstat:
1 file changed, 13 insertions, 4 deletions
diff --git a/arch/powerpc/lib/memcmp_64.S b/arch/powerpc/lib/memcmp_64.S
index 844d8e774492..b7f6f6e0b6e8 100644
--- a/arch/powerpc/lib/memcmp_64.S
+++ b/arch/powerpc/lib/memcmp_64.S
@@ -215,11 +215,20 @@ _GLOBAL_TOC(memcmp)
beq .Lzero
.Lcmp_rest_lt8bytes:
- /* Here we have only less than 8 bytes to compare with. at least s1
- * Address is aligned with 8 bytes.
- * The next double words are load and shift right with appropriate
- * bits.
+ /*
+ * Here we have less than 8 bytes to compare. At least s1 is aligned to
+ * 8 bytes, but s2 may not be. We must make sure s2 + 7 doesn't cross a
+ * page boundary, otherwise we might read past the end of the buffer and
+ * trigger a page fault. We use 4K as the conservative minimum page
+ * size. If we detect that case we go to the byte-by-byte loop.
+ *
+ * Otherwise the next double word is loaded from s1 and s2, and shifted
+ * right to compare the appropriate bits.
*/
+ clrldi r6,r4,(64-12) // r6 = r4 & 0xfff
+ cmpdi r6,0xff8
+ bgt .Lshort
+
subfic r6,r5,8
slwi r6,r6,3
LD rA,0,r3