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linux/arch/sparc/lib/NG2memcpy.S
Rob Gardner a7c5724b5c sparc64: fix FP corruption in user copy functions 
Short story: Exception handlers used by some copy_to_user() and
copy_from_user() functions do not diligently clean up floating point
register usage, and this can result in a user process seeing invalid
values in floating point registers. This sometimes makes the process
fail.

Long story: Several cpu-specific (NG4, NG2, U1, U3) memcpy functions
use floating point registers and VIS alignaddr/faligndata to
accelerate data copying when source and dest addresses don't align
well. Linux uses a lazy scheme for saving floating point registers; It
is not done upon entering the kernel since it's a very expensive
operation. Rather, it is done only when needed. If the kernel ends up
not using FP regs during the course of some trap or system call, then
it can return to user space without saving or restoring them.

The various memcpy functions begin their FP code with VISEntry (or a
variation thereof), which saves the FP regs. They conclude their FP
code with VISExit (or a variation) which essentially marks the FP regs
"clean", ie, they contain no unsaved values. fprs.FPRS_FEF is turned
off so that a lazy restore will be triggered when/if the user process
accesses floating point regs again.

The bug is that the user copy variants of memcpy, copy_from_user() and
copy_to_user(), employ an exception handling mechanism to detect faults
when accessing user space addresses, and when this handler is invoked,
an immediate return from the function is forced, and VISExit is not
executed, thus leaving the fprs register in an indeterminate state,
but often with fprs.FPRS_FEF set and one or more dirty bits. This
results in a return to user space with invalid values in the FP regs,
and since fprs.FPRS_FEF is on, no lazy restore occurs.

This bug affects copy_to_user() and copy_from_user() for NG4, NG2,
U3, and U1. All are fixed by using a new exception handler for those
loads and stores that are done during the time between VISEnter and
VISExit.

n.b. In NG4memcpy, the problematic code can be triggered by a copy
size greater than 128 bytes and an unaligned source address.  This bug
is known to be the cause of random user process memory corruptions
while perf is running with the callgraph option (ie, perf record -g).
This occurs because perf uses copy_from_user() to read user stacks,
and may fault when it follows a stack frame pointer off to an
invalid page. Validation checks on the stack address just obscure
the underlying problem.

Signed-off-by: Rob Gardner <rob.gardner@oracle.com>
Signed-off-by: Dave Aldridge <david.j.aldridge@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-12-24 12:13:18 -05:00

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/* NG2memcpy.S: Niagara-2 optimized memcpy.
*
* Copyright (C) 2007 David S. Miller (davem@davemloft.net)
*/
#ifdef __KERNEL__
#include <asm/visasm.h>
#include <asm/asi.h>
#define GLOBAL_SPARE %g7
#else
#define ASI_PNF 0x82
#define ASI_BLK_P 0xf0
#define ASI_BLK_INIT_QUAD_LDD_P 0xe2
#define FPRS_FEF 0x04
#ifdef MEMCPY_DEBUG
#define VISEntryHalf rd %fprs, %o5; wr %g0, FPRS_FEF, %fprs; \
clr %g1; clr %g2; clr %g3; clr %g5; subcc %g0, %g0, %g0;
#define VISExitHalf and %o5, FPRS_FEF, %o5; wr %o5, 0x0, %fprs
#else
#define VISEntryHalf rd %fprs, %o5; wr %g0, FPRS_FEF, %fprs
#define VISExitHalf and %o5, FPRS_FEF, %o5; wr %o5, 0x0, %fprs
#endif
#define GLOBAL_SPARE %g5
#endif
#ifndef STORE_ASI
#ifndef SIMULATE_NIAGARA_ON_NON_NIAGARA
#define STORE_ASI ASI_BLK_INIT_QUAD_LDD_P
#else
#define STORE_ASI 0x80 /* ASI_P */
#endif
#endif
#ifndef EX_LD
#define EX_LD(x) x
#endif
#ifndef EX_LD_FP
#define EX_LD_FP(x) x
#endif
#ifndef EX_ST
#define EX_ST(x) x
#endif
#ifndef EX_ST_FP
#define EX_ST_FP(x) x
#endif
#ifndef EX_RETVAL
#define EX_RETVAL(x) x
#endif
#ifndef LOAD
#define LOAD(type,addr,dest) type [addr], dest
#endif
#ifndef LOAD_BLK
#define LOAD_BLK(addr,dest) ldda [addr] ASI_BLK_P, dest
#endif
#ifndef STORE
#ifndef MEMCPY_DEBUG
#define STORE(type,src,addr) type src, [addr]
#else
#define STORE(type,src,addr) type##a src, [addr] 0x80
#endif
#endif
#ifndef STORE_BLK
#define STORE_BLK(src,addr) stda src, [addr] ASI_BLK_P
#endif
#ifndef STORE_INIT
#define STORE_INIT(src,addr) stxa src, [addr] STORE_ASI
#endif
#ifndef FUNC_NAME
#define FUNC_NAME NG2memcpy
#endif
#ifndef PREAMBLE
#define PREAMBLE
#endif
#ifndef XCC
#define XCC xcc
#endif
#define FREG_FROB(x0, x1, x2, x3, x4, x5, x6, x7, x8) \
faligndata %x0, %x1, %f0; \
faligndata %x1, %x2, %f2; \
faligndata %x2, %x3, %f4; \
faligndata %x3, %x4, %f6; \
faligndata %x4, %x5, %f8; \
faligndata %x5, %x6, %f10; \
faligndata %x6, %x7, %f12; \
faligndata %x7, %x8, %f14;
#define FREG_MOVE_1(x0) \
fsrc2 %x0, %f0;
#define FREG_MOVE_2(x0, x1) \
fsrc2 %x0, %f0; \
fsrc2 %x1, %f2;
#define FREG_MOVE_3(x0, x1, x2) \
fsrc2 %x0, %f0; \
fsrc2 %x1, %f2; \
fsrc2 %x2, %f4;
#define FREG_MOVE_4(x0, x1, x2, x3) \
fsrc2 %x0, %f0; \
fsrc2 %x1, %f2; \
fsrc2 %x2, %f4; \
fsrc2 %x3, %f6;
#define FREG_MOVE_5(x0, x1, x2, x3, x4) \
fsrc2 %x0, %f0; \
fsrc2 %x1, %f2; \
fsrc2 %x2, %f4; \
fsrc2 %x3, %f6; \
fsrc2 %x4, %f8;
#define FREG_MOVE_6(x0, x1, x2, x3, x4, x5) \
fsrc2 %x0, %f0; \
fsrc2 %x1, %f2; \
fsrc2 %x2, %f4; \
fsrc2 %x3, %f6; \
fsrc2 %x4, %f8; \
fsrc2 %x5, %f10;
#define FREG_MOVE_7(x0, x1, x2, x3, x4, x5, x6) \
fsrc2 %x0, %f0; \
fsrc2 %x1, %f2; \
fsrc2 %x2, %f4; \
fsrc2 %x3, %f6; \
fsrc2 %x4, %f8; \
fsrc2 %x5, %f10; \
fsrc2 %x6, %f12;
#define FREG_MOVE_8(x0, x1, x2, x3, x4, x5, x6, x7) \
fsrc2 %x0, %f0; \
fsrc2 %x1, %f2; \
fsrc2 %x2, %f4; \
fsrc2 %x3, %f6; \
fsrc2 %x4, %f8; \
fsrc2 %x5, %f10; \
fsrc2 %x6, %f12; \
fsrc2 %x7, %f14;
#define FREG_LOAD_1(base, x0) \
EX_LD_FP(LOAD(ldd, base + 0x00, %x0))
#define FREG_LOAD_2(base, x0, x1) \
EX_LD_FP(LOAD(ldd, base + 0x00, %x0)); \
EX_LD_FP(LOAD(ldd, base + 0x08, %x1));
#define FREG_LOAD_3(base, x0, x1, x2) \
EX_LD_FP(LOAD(ldd, base + 0x00, %x0)); \
EX_LD_FP(LOAD(ldd, base + 0x08, %x1)); \
EX_LD_FP(LOAD(ldd, base + 0x10, %x2));
#define FREG_LOAD_4(base, x0, x1, x2, x3) \
EX_LD_FP(LOAD(ldd, base + 0x00, %x0)); \
EX_LD_FP(LOAD(ldd, base + 0x08, %x1)); \
EX_LD_FP(LOAD(ldd, base + 0x10, %x2)); \
EX_LD_FP(LOAD(ldd, base + 0x18, %x3));
#define FREG_LOAD_5(base, x0, x1, x2, x3, x4) \
EX_LD_FP(LOAD(ldd, base + 0x00, %x0)); \
EX_LD_FP(LOAD(ldd, base + 0x08, %x1)); \
EX_LD_FP(LOAD(ldd, base + 0x10, %x2)); \
EX_LD_FP(LOAD(ldd, base + 0x18, %x3)); \
EX_LD_FP(LOAD(ldd, base + 0x20, %x4));
#define FREG_LOAD_6(base, x0, x1, x2, x3, x4, x5) \
EX_LD_FP(LOAD(ldd, base + 0x00, %x0)); \
EX_LD_FP(LOAD(ldd, base + 0x08, %x1)); \
EX_LD_FP(LOAD(ldd, base + 0x10, %x2)); \
EX_LD_FP(LOAD(ldd, base + 0x18, %x3)); \
EX_LD_FP(LOAD(ldd, base + 0x20, %x4)); \
EX_LD_FP(LOAD(ldd, base + 0x28, %x5));
#define FREG_LOAD_7(base, x0, x1, x2, x3, x4, x5, x6) \
EX_LD_FP(LOAD(ldd, base + 0x00, %x0)); \
EX_LD_FP(LOAD(ldd, base + 0x08, %x1)); \
EX_LD_FP(LOAD(ldd, base + 0x10, %x2)); \
EX_LD_FP(LOAD(ldd, base + 0x18, %x3)); \
EX_LD_FP(LOAD(ldd, base + 0x20, %x4)); \
EX_LD_FP(LOAD(ldd, base + 0x28, %x5)); \
EX_LD_FP(LOAD(ldd, base + 0x30, %x6));
.register %g2,#scratch
.register %g3,#scratch
.text
.align 64
.globl FUNC_NAME
.type FUNC_NAME,#function
FUNC_NAME: /* %o0=dst, %o1=src, %o2=len */
srlx %o2, 31, %g2
cmp %g2, 0
tne %xcc, 5
PREAMBLE
mov %o0, %o3
cmp %o2, 0
be,pn %XCC, 85f
or %o0, %o1, GLOBAL_SPARE
cmp %o2, 16
blu,a,pn %XCC, 80f
or GLOBAL_SPARE, %o2, GLOBAL_SPARE
/* 2 blocks (128 bytes) is the minimum we can do the block
* copy with. We need to ensure that we'll iterate at least
* once in the block copy loop. At worst we'll need to align
* the destination to a 64-byte boundary which can chew up
* to (64 - 1) bytes from the length before we perform the
* block copy loop.
*
* However, the cut-off point, performance wise, is around
* 4 64-byte blocks.
*/
cmp %o2, (4 * 64)
blu,pt %XCC, 75f
andcc GLOBAL_SPARE, 0x7, %g0
/* %o0: dst
* %o1: src
* %o2: len (known to be >= 128)
*
* The block copy loops can use %o4, %g2, %g3 as
* temporaries while copying the data. %o5 must
* be preserved between VISEntryHalf and VISExitHalf
*/
LOAD(prefetch, %o1 + 0x000, #one_read)
LOAD(prefetch, %o1 + 0x040, #one_read)
LOAD(prefetch, %o1 + 0x080, #one_read)
/* Align destination on 64-byte boundary. */
andcc %o0, (64 - 1), %o4
be,pt %XCC, 2f
sub %o4, 64, %o4
sub %g0, %o4, %o4 ! bytes to align dst
sub %o2, %o4, %o2
1: subcc %o4, 1, %o4
EX_LD(LOAD(ldub, %o1, %g1))
EX_ST(STORE(stb, %g1, %o0))
add %o1, 1, %o1
bne,pt %XCC, 1b
add %o0, 1, %o0
2:
/* Clobbers o5/g1/g2/g3/g7/icc/xcc. We must preserve
* o5 from here until we hit VISExitHalf.
*/
VISEntryHalf
membar #Sync
alignaddr %o1, %g0, %g0
add %o1, (64 - 1), %o4
andn %o4, (64 - 1), %o4
andn %o2, (64 - 1), %g1
sub %o2, %g1, %o2
and %o1, (64 - 1), %g2
add %o1, %g1, %o1
sub %o0, %o4, %g3
brz,pt %g2, 190f
cmp %g2, 32
blu,a 5f
cmp %g2, 16
cmp %g2, 48
blu,a 4f
cmp %g2, 40
cmp %g2, 56
blu 170f
nop
ba,a,pt %xcc, 180f
4: /* 32 <= low bits < 48 */
blu 150f
nop
ba,a,pt %xcc, 160f
5: /* 0 < low bits < 32 */
blu,a 6f
cmp %g2, 8
cmp %g2, 24
blu 130f
nop
ba,a,pt %xcc, 140f
6: /* 0 < low bits < 16 */
bgeu 120f
nop
/* fall through for 0 < low bits < 8 */
110: sub %o4, 64, %g2
EX_LD_FP(LOAD_BLK(%g2, %f0))
1: EX_ST_FP(STORE_INIT(%g0, %o4 + %g3))
EX_LD_FP(LOAD_BLK(%o4, %f16))
FREG_FROB(f0, f2, f4, f6, f8, f10, f12, f14, f16)
EX_ST_FP(STORE_BLK(%f0, %o4 + %g3))
FREG_MOVE_8(f16, f18, f20, f22, f24, f26, f28, f30)
subcc %g1, 64, %g1
add %o4, 64, %o4
bne,pt %xcc, 1b
LOAD(prefetch, %o4 + 64, #one_read)
ba,pt %xcc, 195f
nop
120: sub %o4, 56, %g2
FREG_LOAD_7(%g2, f0, f2, f4, f6, f8, f10, f12)
1: EX_ST_FP(STORE_INIT(%g0, %o4 + %g3))
EX_LD_FP(LOAD_BLK(%o4, %f16))
FREG_FROB(f0, f2, f4, f6, f8, f10, f12, f16, f18)
EX_ST_FP(STORE_BLK(%f0, %o4 + %g3))
FREG_MOVE_7(f18, f20, f22, f24, f26, f28, f30)
subcc %g1, 64, %g1
add %o4, 64, %o4
bne,pt %xcc, 1b
LOAD(prefetch, %o4 + 64, #one_read)
ba,pt %xcc, 195f
nop
130: sub %o4, 48, %g2
FREG_LOAD_6(%g2, f0, f2, f4, f6, f8, f10)
1: EX_ST_FP(STORE_INIT(%g0, %o4 + %g3))
EX_LD_FP(LOAD_BLK(%o4, %f16))
FREG_FROB(f0, f2, f4, f6, f8, f10, f16, f18, f20)
EX_ST_FP(STORE_BLK(%f0, %o4 + %g3))
FREG_MOVE_6(f20, f22, f24, f26, f28, f30)
subcc %g1, 64, %g1
add %o4, 64, %o4
bne,pt %xcc, 1b
LOAD(prefetch, %o4 + 64, #one_read)
ba,pt %xcc, 195f
nop
140: sub %o4, 40, %g2
FREG_LOAD_5(%g2, f0, f2, f4, f6, f8)
1: EX_ST_FP(STORE_INIT(%g0, %o4 + %g3))
EX_LD_FP(LOAD_BLK(%o4, %f16))
FREG_FROB(f0, f2, f4, f6, f8, f16, f18, f20, f22)
EX_ST_FP(STORE_BLK(%f0, %o4 + %g3))
FREG_MOVE_5(f22, f24, f26, f28, f30)
subcc %g1, 64, %g1
add %o4, 64, %o4
bne,pt %xcc, 1b
LOAD(prefetch, %o4 + 64, #one_read)
ba,pt %xcc, 195f
nop
150: sub %o4, 32, %g2
FREG_LOAD_4(%g2, f0, f2, f4, f6)
1: EX_ST_FP(STORE_INIT(%g0, %o4 + %g3))
EX_LD_FP(LOAD_BLK(%o4, %f16))
FREG_FROB(f0, f2, f4, f6, f16, f18, f20, f22, f24)
EX_ST_FP(STORE_BLK(%f0, %o4 + %g3))
FREG_MOVE_4(f24, f26, f28, f30)
subcc %g1, 64, %g1
add %o4, 64, %o4
bne,pt %xcc, 1b
LOAD(prefetch, %o4 + 64, #one_read)
ba,pt %xcc, 195f
nop
160: sub %o4, 24, %g2
FREG_LOAD_3(%g2, f0, f2, f4)
1: EX_ST_FP(STORE_INIT(%g0, %o4 + %g3))
EX_LD_FP(LOAD_BLK(%o4, %f16))
FREG_FROB(f0, f2, f4, f16, f18, f20, f22, f24, f26)
EX_ST_FP(STORE_BLK(%f0, %o4 + %g3))
FREG_MOVE_3(f26, f28, f30)
subcc %g1, 64, %g1
add %o4, 64, %o4
bne,pt %xcc, 1b
LOAD(prefetch, %o4 + 64, #one_read)
ba,pt %xcc, 195f
nop
170: sub %o4, 16, %g2
FREG_LOAD_2(%g2, f0, f2)
1: EX_ST_FP(STORE_INIT(%g0, %o4 + %g3))
EX_LD_FP(LOAD_BLK(%o4, %f16))
FREG_FROB(f0, f2, f16, f18, f20, f22, f24, f26, f28)
EX_ST_FP(STORE_BLK(%f0, %o4 + %g3))
FREG_MOVE_2(f28, f30)
subcc %g1, 64, %g1
add %o4, 64, %o4
bne,pt %xcc, 1b
LOAD(prefetch, %o4 + 64, #one_read)
ba,pt %xcc, 195f
nop
180: sub %o4, 8, %g2
FREG_LOAD_1(%g2, f0)
1: EX_ST_FP(STORE_INIT(%g0, %o4 + %g3))
EX_LD_FP(LOAD_BLK(%o4, %f16))
FREG_FROB(f0, f16, f18, f20, f22, f24, f26, f28, f30)
EX_ST_FP(STORE_BLK(%f0, %o4 + %g3))
FREG_MOVE_1(f30)
subcc %g1, 64, %g1
add %o4, 64, %o4
bne,pt %xcc, 1b
LOAD(prefetch, %o4 + 64, #one_read)
ba,pt %xcc, 195f
nop
190:
1: EX_ST_FP(STORE_INIT(%g0, %o4 + %g3))
subcc %g1, 64, %g1
EX_LD_FP(LOAD_BLK(%o4, %f0))
EX_ST_FP(STORE_BLK(%f0, %o4 + %g3))
add %o4, 64, %o4
bne,pt %xcc, 1b
LOAD(prefetch, %o4 + 64, #one_read)
195:
add %o4, %g3, %o0
membar #Sync
VISExitHalf
/* %o2 contains any final bytes still needed to be copied
* over. If anything is left, we copy it one byte at a time.
*/
brz,pt %o2, 85f
sub %o0, %o1, GLOBAL_SPARE
ba,a,pt %XCC, 90f
.align 64
75: /* 16 < len <= 64 */
bne,pn %XCC, 75f
sub %o0, %o1, GLOBAL_SPARE
72:
andn %o2, 0xf, %o4
and %o2, 0xf, %o2
1: subcc %o4, 0x10, %o4
EX_LD(LOAD(ldx, %o1, %o5))
add %o1, 0x08, %o1
EX_LD(LOAD(ldx, %o1, %g1))
sub %o1, 0x08, %o1
EX_ST(STORE(stx, %o5, %o1 + GLOBAL_SPARE))
add %o1, 0x8, %o1
EX_ST(STORE(stx, %g1, %o1 + GLOBAL_SPARE))
bgu,pt %XCC, 1b
add %o1, 0x8, %o1
73: andcc %o2, 0x8, %g0
be,pt %XCC, 1f
nop
sub %o2, 0x8, %o2
EX_LD(LOAD(ldx, %o1, %o5))
EX_ST(STORE(stx, %o5, %o1 + GLOBAL_SPARE))
add %o1, 0x8, %o1
1: andcc %o2, 0x4, %g0
be,pt %XCC, 1f
nop
sub %o2, 0x4, %o2
EX_LD(LOAD(lduw, %o1, %o5))
EX_ST(STORE(stw, %o5, %o1 + GLOBAL_SPARE))
add %o1, 0x4, %o1
1: cmp %o2, 0
be,pt %XCC, 85f
nop
ba,pt %xcc, 90f
nop
75:
andcc %o0, 0x7, %g1
sub %g1, 0x8, %g1
be,pn %icc, 2f
sub %g0, %g1, %g1
sub %o2, %g1, %o2
1: subcc %g1, 1, %g1
EX_LD(LOAD(ldub, %o1, %o5))
EX_ST(STORE(stb, %o5, %o1 + GLOBAL_SPARE))
bgu,pt %icc, 1b
add %o1, 1, %o1
2: add %o1, GLOBAL_SPARE, %o0
andcc %o1, 0x7, %g1
bne,pt %icc, 8f
sll %g1, 3, %g1
cmp %o2, 16
bgeu,pt %icc, 72b
nop
ba,a,pt %xcc, 73b
8: mov 64, GLOBAL_SPARE
andn %o1, 0x7, %o1
EX_LD(LOAD(ldx, %o1, %g2))
sub GLOBAL_SPARE, %g1, GLOBAL_SPARE
andn %o2, 0x7, %o4
sllx %g2, %g1, %g2
1: add %o1, 0x8, %o1
EX_LD(LOAD(ldx, %o1, %g3))
subcc %o4, 0x8, %o4
srlx %g3, GLOBAL_SPARE, %o5
or %o5, %g2, %o5
EX_ST(STORE(stx, %o5, %o0))
add %o0, 0x8, %o0
bgu,pt %icc, 1b
sllx %g3, %g1, %g2
srl %g1, 3, %g1
andcc %o2, 0x7, %o2
be,pn %icc, 85f
add %o1, %g1, %o1
ba,pt %xcc, 90f
sub %o0, %o1, GLOBAL_SPARE
.align 64
80: /* 0 < len <= 16 */
andcc GLOBAL_SPARE, 0x3, %g0
bne,pn %XCC, 90f
sub %o0, %o1, GLOBAL_SPARE
1:
subcc %o2, 4, %o2
EX_LD(LOAD(lduw, %o1, %g1))
EX_ST(STORE(stw, %g1, %o1 + GLOBAL_SPARE))
bgu,pt %XCC, 1b
add %o1, 4, %o1
85: retl
mov EX_RETVAL(%o3), %o0
.align 32
90:
subcc %o2, 1, %o2
EX_LD(LOAD(ldub, %o1, %g1))
EX_ST(STORE(stb, %g1, %o1 + GLOBAL_SPARE))
bgu,pt %XCC, 90b
add %o1, 1, %o1
retl
mov EX_RETVAL(%o3), %o0
.size FUNC_NAME, .-FUNC_NAME
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