Re: __copy_tofrom_user fails on unaligned read faults
From: Dale Farnsworth <hidden>
Date: 2002-11-25 18:30:05
On Sat, Nov 23, 2002 at 12:03:36PM +1100, Paul Mackerras wrote:
Could you try this patch, please?
Your patch worked fine after I moved the read/write flag from r4 to r9. Here's the resultant patch. I'm happy with it. -Dale diff -u linuxppc_2_4_devel/arch/ppc/lib/string.S hxeb100/arch/ppc/lib/string.S
--- linuxppc_2_4_devel/arch/ppc/lib/string.S 2002-11-25 10:38:45.000000000 -0700
+++ hxeb100/arch/ppc/lib/string.S 2002-11-25 09:32:00.000000000 -0700@@ -504,18 +504,18 @@ blr /* read fault, initial single-byte copy */ -100: li r4,0 +100: li r9,0 b 90f /* write fault, initial single-byte copy */ -101: li r4,1 +101: li r9,1 90: subf r5,r8,r5 li r3,0 b 99f /* read fault, initial word copy */ -102: li r4,0 +102: li r9,0 b 91f /* write fault, initial word copy */ -103: li r4,1 +103: li r9,1 91: li r3,2 b 99f
@@ -539,38 +539,47 @@ #endif /* read fault in cacheline loop */ -104: li r4,0 +104: li r9,0 b 92f /* fault on dcbz (effectively a write fault) */ /* or write fault in cacheline loop */ -105: li r4,1 +105: li r9,1 92: li r3,LG_CACHELINE_BYTES b 99f /* read fault in final word loop */ -108: li r4,0 +108: li r9,0 b 93f /* write fault in final word loop */ -109: li r4,1 +109: li r9,1 93: andi. r5,r5,3 li r3,2 b 99f /* read fault in final byte loop */ -110: li r4,0 +110: li r9,0 b 94f /* write fault in final byte loop */ -111: li r4,1 +111: li r9,1 94: li r5,0 li r3,0 /* * At this stage the number of bytes not copied is - * r5 + (ctr << r3), and r4 is 0 for read or 1 for write. + * r5 + (ctr << r3), and r9 is 0 for read or 1 for write. */ 99: mfctr r0 slw r3,r0,r3 - add r3,r3,r5 - cmpwi 0,r4,0 + add. r3,r3,r5 + beq 120f /* shouldn't happen */ + cmpwi 0,r9,0 bne 120f -/* for read fault, clear out the destination: r3 bytes starting at 4(r6) */ +/* for a read fault, first try to continue the copy one byte at a time */ + mtctr r3 +130: lbz r0,4(r4) +131: stb r0,4(r6) + addi r4,r4,1 + addi r6,r6,1 + bdnz 130b +/* then clear out the destination: r3 bytes starting at 4(r6) */ +132: mfctr r3 srwi. r0,r3,2 li r9,0 mtctr r0
@@ -591,6 +600,8 @@ .long 31b,109b .long 40b,110b .long 41b,111b + .long 130b,132b + .long 131b,120b .long 112b,120b .long 114b,120b .text
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