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authorHelge Deller <deller@gmx.de>2017-03-29 21:41:05 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-04-08 09:30:34 +0200
commit76343bfbcafa1b703b38746e8b39d15d31ab8957 (patch)
treecd46f740f41bde03ace1e1ec775c2ec4bf059e66 /arch/parisc/lib/lusercopy.S
parent99e354a59ac5e7920166e68903b4ad031ef933e3 (diff)
parisc: Fix access fault handling in pa_memcpy()
commit 554bfeceb8a22d448cd986fc9efce25e833278a1 upstream. pa_memcpy() is the major memcpy implementation in the parisc kernel which is used to do any kind of userspace/kernel memory copies. Al Viro noticed various bugs in the implementation of pa_mempcy(), most notably that in case of faults it may report back to have copied more bytes than it actually did. Fixing those bugs is quite hard in the C-implementation, because the compiler is messing around with the registers and we are not guaranteed that specific variables are always in the same processor registers. This makes proper fault handling complicated. This patch implements pa_memcpy() in assembler. That way we have correct fault handling and adding a 64-bit copy routine was quite easy. Runtime tested with 32- and 64bit kernels. Reported-by: Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by: John David Anglin <dave.anglin@bell.net> Signed-off-by: Helge Deller <deller@gmx.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/parisc/lib/lusercopy.S')
-rw-r--r--arch/parisc/lib/lusercopy.S318
1 files changed, 318 insertions, 0 deletions
diff --git a/arch/parisc/lib/lusercopy.S b/arch/parisc/lib/lusercopy.S
index 56845de6b5df..f01188c044ee 100644
--- a/arch/parisc/lib/lusercopy.S
+++ b/arch/parisc/lib/lusercopy.S
@@ -5,6 +5,8 @@
* Copyright (C) 2000 Richard Hirst <rhirst with parisc-linux.org>
* Copyright (C) 2001 Matthieu Delahaye <delahaym at esiee.fr>
* Copyright (C) 2003 Randolph Chung <tausq with parisc-linux.org>
+ * Copyright (C) 2017 Helge Deller <deller@gmx.de>
+ * Copyright (C) 2017 John David Anglin <dave.anglin@bell.net>
*
*
* This program is free software; you can redistribute it and/or modify
@@ -132,4 +134,320 @@ ENDPROC_CFI(lstrnlen_user)
.procend
+
+
+/*
+ * unsigned long pa_memcpy(void *dstp, const void *srcp, unsigned long len)
+ *
+ * Inputs:
+ * - sr1 already contains space of source region
+ * - sr2 already contains space of destination region
+ *
+ * Returns:
+ * - number of bytes that could not be copied.
+ * On success, this will be zero.
+ *
+ * This code is based on a C-implementation of a copy routine written by
+ * Randolph Chung, which in turn was derived from the glibc.
+ *
+ * Several strategies are tried to try to get the best performance for various
+ * conditions. In the optimal case, we copy by loops that copy 32- or 16-bytes
+ * at a time using general registers. Unaligned copies are handled either by
+ * aligning the destination and then using shift-and-write method, or in a few
+ * cases by falling back to a byte-at-a-time copy.
+ *
+ * Testing with various alignments and buffer sizes shows that this code is
+ * often >10x faster than a simple byte-at-a-time copy, even for strangely
+ * aligned operands. It is interesting to note that the glibc version of memcpy
+ * (written in C) is actually quite fast already. This routine is able to beat
+ * it by 30-40% for aligned copies because of the loop unrolling, but in some
+ * cases the glibc version is still slightly faster. This lends more
+ * credibility that gcc can generate very good code as long as we are careful.
+ *
+ * Possible optimizations:
+ * - add cache prefetching
+ * - try not to use the post-increment address modifiers; they may create
+ * additional interlocks. Assumption is that those were only efficient on old
+ * machines (pre PA8000 processors)
+ */
+
+ dst = arg0
+ src = arg1
+ len = arg2
+ end = arg3
+ t1 = r19
+ t2 = r20
+ t3 = r21
+ t4 = r22
+ srcspc = sr1
+ dstspc = sr2
+
+ t0 = r1
+ a1 = t1
+ a2 = t2
+ a3 = t3
+ a0 = t4
+
+ save_src = ret0
+ save_dst = ret1
+ save_len = r31
+
+ENTRY_CFI(pa_memcpy)
+ .proc
+ .callinfo NO_CALLS
+ .entry
+
+ /* Last destination address */
+ add dst,len,end
+
+ /* short copy with less than 16 bytes? */
+ cmpib,>>=,n 15,len,.Lbyte_loop
+
+ /* same alignment? */
+ xor src,dst,t0
+ extru t0,31,2,t1
+ cmpib,<>,n 0,t1,.Lunaligned_copy
+
+#ifdef CONFIG_64BIT
+ /* only do 64-bit copies if we can get aligned. */
+ extru t0,31,3,t1
+ cmpib,<>,n 0,t1,.Lalign_loop32
+
+ /* loop until we are 64-bit aligned */
+.Lalign_loop64:
+ extru dst,31,3,t1
+ cmpib,=,n 0,t1,.Lcopy_loop_16
+20: ldb,ma 1(srcspc,src),t1
+21: stb,ma t1,1(dstspc,dst)
+ b .Lalign_loop64
+ ldo -1(len),len
+
+ ASM_EXCEPTIONTABLE_ENTRY(20b,.Lcopy_done)
+ ASM_EXCEPTIONTABLE_ENTRY(21b,.Lcopy_done)
+
+ ldi 31,t0
+.Lcopy_loop_16:
+ cmpb,COND(>>=),n t0,len,.Lword_loop
+
+10: ldd 0(srcspc,src),t1
+11: ldd 8(srcspc,src),t2
+ ldo 16(src),src
+12: std,ma t1,8(dstspc,dst)
+13: std,ma t2,8(dstspc,dst)
+14: ldd 0(srcspc,src),t1
+15: ldd 8(srcspc,src),t2
+ ldo 16(src),src
+16: std,ma t1,8(dstspc,dst)
+17: std,ma t2,8(dstspc,dst)
+
+ ASM_EXCEPTIONTABLE_ENTRY(10b,.Lcopy_done)
+ ASM_EXCEPTIONTABLE_ENTRY(11b,.Lcopy16_fault)
+ ASM_EXCEPTIONTABLE_ENTRY(12b,.Lcopy_done)
+ ASM_EXCEPTIONTABLE_ENTRY(13b,.Lcopy_done)
+ ASM_EXCEPTIONTABLE_ENTRY(14b,.Lcopy_done)
+ ASM_EXCEPTIONTABLE_ENTRY(15b,.Lcopy16_fault)
+ ASM_EXCEPTIONTABLE_ENTRY(16b,.Lcopy_done)
+ ASM_EXCEPTIONTABLE_ENTRY(17b,.Lcopy_done)
+
+ b .Lcopy_loop_16
+ ldo -32(len),len
+
+.Lword_loop:
+ cmpib,COND(>>=),n 3,len,.Lbyte_loop
+20: ldw,ma 4(srcspc,src),t1
+21: stw,ma t1,4(dstspc,dst)
+ b .Lword_loop
+ ldo -4(len),len
+
+ ASM_EXCEPTIONTABLE_ENTRY(20b,.Lcopy_done)
+ ASM_EXCEPTIONTABLE_ENTRY(21b,.Lcopy_done)
+
+#endif /* CONFIG_64BIT */
+
+ /* loop until we are 32-bit aligned */
+.Lalign_loop32:
+ extru dst,31,2,t1
+ cmpib,=,n 0,t1,.Lcopy_loop_4
+20: ldb,ma 1(srcspc,src),t1
+21: stb,ma t1,1(dstspc,dst)
+ b .Lalign_loop32
+ ldo -1(len),len
+
+ ASM_EXCEPTIONTABLE_ENTRY(20b,.Lcopy_done)
+ ASM_EXCEPTIONTABLE_ENTRY(21b,.Lcopy_done)
+
+
+.Lcopy_loop_4:
+ cmpib,COND(>>=),n 15,len,.Lbyte_loop
+
+10: ldw 0(srcspc,src),t1
+11: ldw 4(srcspc,src),t2
+12: stw,ma t1,4(dstspc,dst)
+13: stw,ma t2,4(dstspc,dst)
+14: ldw 8(srcspc,src),t1
+15: ldw 12(srcspc,src),t2
+ ldo 16(src),src
+16: stw,ma t1,4(dstspc,dst)
+17: stw,ma t2,4(dstspc,dst)
+
+ ASM_EXCEPTIONTABLE_ENTRY(10b,.Lcopy_done)
+ ASM_EXCEPTIONTABLE_ENTRY(11b,.Lcopy8_fault)
+ ASM_EXCEPTIONTABLE_ENTRY(12b,.Lcopy_done)
+ ASM_EXCEPTIONTABLE_ENTRY(13b,.Lcopy_done)
+ ASM_EXCEPTIONTABLE_ENTRY(14b,.Lcopy_done)
+ ASM_EXCEPTIONTABLE_ENTRY(15b,.Lcopy8_fault)
+ ASM_EXCEPTIONTABLE_ENTRY(16b,.Lcopy_done)
+ ASM_EXCEPTIONTABLE_ENTRY(17b,.Lcopy_done)
+
+ b .Lcopy_loop_4
+ ldo -16(len),len
+
+.Lbyte_loop:
+ cmpclr,COND(<>) len,%r0,%r0
+ b,n .Lcopy_done
+20: ldb 0(srcspc,src),t1
+ ldo 1(src),src
+21: stb,ma t1,1(dstspc,dst)
+ b .Lbyte_loop
+ ldo -1(len),len
+
+ ASM_EXCEPTIONTABLE_ENTRY(20b,.Lcopy_done)
+ ASM_EXCEPTIONTABLE_ENTRY(21b,.Lcopy_done)
+
+.Lcopy_done:
+ bv %r0(%r2)
+ sub end,dst,ret0
+
+
+ /* src and dst are not aligned the same way. */
+ /* need to go the hard way */
+.Lunaligned_copy:
+ /* align until dst is 32bit-word-aligned */
+ extru dst,31,2,t1
+ cmpib,COND(=),n 0,t1,.Lcopy_dstaligned
+20: ldb 0(srcspc,src),t1
+ ldo 1(src),src
+21: stb,ma t1,1(dstspc,dst)
+ b .Lunaligned_copy
+ ldo -1(len),len
+
+ ASM_EXCEPTIONTABLE_ENTRY(20b,.Lcopy_done)
+ ASM_EXCEPTIONTABLE_ENTRY(21b,.Lcopy_done)
+
+.Lcopy_dstaligned:
+
+ /* store src, dst and len in safe place */
+ copy src,save_src
+ copy dst,save_dst
+ copy len,save_len
+
+ /* len now needs give number of words to copy */
+ SHRREG len,2,len
+
+ /*
+ * Copy from a not-aligned src to an aligned dst using shifts.
+ * Handles 4 words per loop.
+ */
+
+ depw,z src,28,2,t0
+ subi 32,t0,t0
+ mtsar t0
+ extru len,31,2,t0
+ cmpib,= 2,t0,.Lcase2
+ /* Make src aligned by rounding it down. */
+ depi 0,31,2,src
+
+ cmpiclr,<> 3,t0,%r0
+ b,n .Lcase3
+ cmpiclr,<> 1,t0,%r0
+ b,n .Lcase1
+.Lcase0:
+ cmpb,= %r0,len,.Lcda_finish
+ nop
+
+1: ldw,ma 4(srcspc,src), a3
+ ASM_EXCEPTIONTABLE_ENTRY(1b,.Lcda_rdfault)
+1: ldw,ma 4(srcspc,src), a0
+ ASM_EXCEPTIONTABLE_ENTRY(1b,.Lcda_rdfault)
+ b,n .Ldo3
+.Lcase1:
+1: ldw,ma 4(srcspc,src), a2
+ ASM_EXCEPTIONTABLE_ENTRY(1b,.Lcda_rdfault)
+1: ldw,ma 4(srcspc,src), a3
+ ASM_EXCEPTIONTABLE_ENTRY(1b,.Lcda_rdfault)
+ ldo -1(len),len
+ cmpb,=,n %r0,len,.Ldo0
+.Ldo4:
+1: ldw,ma 4(srcspc,src), a0
+ ASM_EXCEPTIONTABLE_ENTRY(1b,.Lcda_rdfault)
+ shrpw a2, a3, %sar, t0
+1: stw,ma t0, 4(dstspc,dst)
+ ASM_EXCEPTIONTABLE_ENTRY(1b,.Lcopy_done)
+.Ldo3:
+1: ldw,ma 4(srcspc,src), a1
+ ASM_EXCEPTIONTABLE_ENTRY(1b,.Lcda_rdfault)
+ shrpw a3, a0, %sar, t0
+1: stw,ma t0, 4(dstspc,dst)
+ ASM_EXCEPTIONTABLE_ENTRY(1b,.Lcopy_done)
+.Ldo2:
+1: ldw,ma 4(srcspc,src), a2
+ ASM_EXCEPTIONTABLE_ENTRY(1b,.Lcda_rdfault)
+ shrpw a0, a1, %sar, t0
+1: stw,ma t0, 4(dstspc,dst)
+ ASM_EXCEPTIONTABLE_ENTRY(1b,.Lcopy_done)
+.Ldo1:
+1: ldw,ma 4(srcspc,src), a3
+ ASM_EXCEPTIONTABLE_ENTRY(1b,.Lcda_rdfault)
+ shrpw a1, a2, %sar, t0
+1: stw,ma t0, 4(dstspc,dst)
+ ASM_EXCEPTIONTABLE_ENTRY(1b,.Lcopy_done)
+ ldo -4(len),len
+ cmpb,<> %r0,len,.Ldo4
+ nop
+.Ldo0:
+ shrpw a2, a3, %sar, t0
+1: stw,ma t0, 4(dstspc,dst)
+ ASM_EXCEPTIONTABLE_ENTRY(1b,.Lcopy_done)
+
+.Lcda_rdfault:
+.Lcda_finish:
+ /* calculate new src, dst and len and jump to byte-copy loop */
+ sub dst,save_dst,t0
+ add save_src,t0,src
+ b .Lbyte_loop
+ sub save_len,t0,len
+
+.Lcase3:
+1: ldw,ma 4(srcspc,src), a0
+ ASM_EXCEPTIONTABLE_ENTRY(1b,.Lcda_rdfault)
+1: ldw,ma 4(srcspc,src), a1
+ ASM_EXCEPTIONTABLE_ENTRY(1b,.Lcda_rdfault)
+ b .Ldo2
+ ldo 1(len),len
+.Lcase2:
+1: ldw,ma 4(srcspc,src), a1
+ ASM_EXCEPTIONTABLE_ENTRY(1b,.Lcda_rdfault)
+1: ldw,ma 4(srcspc,src), a2
+ ASM_EXCEPTIONTABLE_ENTRY(1b,.Lcda_rdfault)
+ b .Ldo1
+ ldo 2(len),len
+
+
+ /* fault exception fixup handlers: */
+#ifdef CONFIG_64BIT
+.Lcopy16_fault:
+10: b .Lcopy_done
+ std,ma t1,8(dstspc,dst)
+ ASM_EXCEPTIONTABLE_ENTRY(10b,.Lcopy_done)
+#endif
+
+.Lcopy8_fault:
+10: b .Lcopy_done
+ stw,ma t1,4(dstspc,dst)
+ ASM_EXCEPTIONTABLE_ENTRY(10b,.Lcopy_done)
+
+ .exit
+ENDPROC_CFI(pa_memcpy)
+ .procend
+
.end