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linux/arch/sparc/lib/NG4memcpy.S
David S. Miller 44922150d8 sparc64: Fix userspace FPU register corruptions. 
If we have a series of events from userpsace, with %fprs=FPRS_FEF,
like follows:

ETRAP
	ETRAP
		VIS_ENTRY(fprs=0x4)
		VIS_EXIT
		RTRAP (kernel FPU restore with fpu_saved=0x4)
	RTRAP

We will not restore the user registers that were clobbered by the FPU
using kernel code in the inner-most trap.

Traps allocate FPU save slots in the thread struct, and FPU using
sequences save the "dirty" FPU registers only.

This works at the initial trap level because all of the registers
get recorded into the top-level FPU save area, and we'll return
to userspace with the FPU disabled so that any FPU use by the user
will take an FPU disabled trap wherein we'll load the registers
back up properly.

But this is not how trap returns from kernel to kernel operate.

The simplest fix for this bug is to always save all FPU register state
for anything other than the top-most FPU save area.

Getting rid of the optimized inner-slot FPU saving code ends up
making VISEntryHalf degenerate into plain VISEntry.

Longer term we need to do something smarter to reinstate the partial
save optimizations.  Perhaps the fundament error is having trap entry
and exit allocate FPU save slots and restore register state.  Instead,
the VISEntry et al. calls should be doing that work.

This bug is about two decades old.

Reported-by: James Y Knight <jyknight@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-08-06 19:13:25 -07:00

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/* NG4memcpy.S: Niagara-4 optimized memcpy.
*
* Copyright (C) 2012 David S. Miller (davem@davemloft.net)
*/
#ifdef __KERNEL__
#include <asm/visasm.h>
#include <asm/asi.h>
#define GLOBAL_SPARE %g7
#else
#define ASI_BLK_INIT_QUAD_LDD_P 0xe2
#define FPRS_FEF 0x04
/* On T4 it is very expensive to access ASRs like %fprs and
* %asi, avoiding a read or a write can save ~50 cycles.
*/
#define FPU_ENTER \
rd %fprs, %o5; \
andcc %o5, FPRS_FEF, %g0; \
be,a,pn %icc, 999f; \
wr %g0, FPRS_FEF, %fprs; \
999:
#ifdef MEMCPY_DEBUG
#define VISEntryHalf FPU_ENTER; \
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 FPU_ENTER
#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
#if !defined(EX_LD) && !defined(EX_ST)
#define NON_USER_COPY
#endif
#ifndef EX_LD
#define EX_LD(x) x
#endif
#ifndef EX_ST
#define EX_ST(x) x
#endif
#ifndef EX_RETVAL
#define EX_RETVAL(x) x
#endif
#ifndef LOAD
#define LOAD(type,addr,dest) type [addr], 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] %asi
#endif
#endif
#ifndef STORE_INIT
#define STORE_INIT(src,addr) stxa src, [addr] STORE_ASI
#endif
#ifndef FUNC_NAME
#define FUNC_NAME NG4memcpy
#endif
#ifndef PREAMBLE
#define PREAMBLE
#endif
#ifndef XCC
#define XCC xcc
#endif
.register %g2,#scratch
.register %g3,#scratch
.text
.align 64
.globl FUNC_NAME
.type FUNC_NAME,#function
FUNC_NAME: /* %o0=dst, %o1=src, %o2=len */
#ifdef MEMCPY_DEBUG
wr %g0, 0x80, %asi
#endif
srlx %o2, 31, %g2
cmp %g2, 0
tne %XCC, 5
PREAMBLE
mov %o0, %o3
brz,pn %o2, .Lexit
cmp %o2, 3
ble,pn %icc, .Ltiny
cmp %o2, 19
ble,pn %icc, .Lsmall
or %o0, %o1, %g2
cmp %o2, 128
bl,pn %icc, .Lmedium
nop
.Llarge:/* len >= 0x80 */
/* First get dest 8 byte aligned. */
sub %g0, %o0, %g1
and %g1, 0x7, %g1
brz,pt %g1, 51f
sub %o2, %g1, %o2
1: EX_LD(LOAD(ldub, %o1 + 0x00, %g2))
add %o1, 1, %o1
subcc %g1, 1, %g1
add %o0, 1, %o0
bne,pt %icc, 1b
EX_ST(STORE(stb, %g2, %o0 - 0x01))
51: LOAD(prefetch, %o1 + 0x040, #n_reads_strong)
LOAD(prefetch, %o1 + 0x080, #n_reads_strong)
LOAD(prefetch, %o1 + 0x0c0, #n_reads_strong)
LOAD(prefetch, %o1 + 0x100, #n_reads_strong)
LOAD(prefetch, %o1 + 0x140, #n_reads_strong)
LOAD(prefetch, %o1 + 0x180, #n_reads_strong)
LOAD(prefetch, %o1 + 0x1c0, #n_reads_strong)
LOAD(prefetch, %o1 + 0x200, #n_reads_strong)
/* Check if we can use the straight fully aligned
* loop, or we require the alignaddr/faligndata variant.
*/
andcc %o1, 0x7, %o5
bne,pn %icc, .Llarge_src_unaligned
sub %g0, %o0, %g1
/* Legitimize the use of initializing stores by getting dest
* to be 64-byte aligned.
*/
and %g1, 0x3f, %g1
brz,pt %g1, .Llarge_aligned
sub %o2, %g1, %o2
1: EX_LD(LOAD(ldx, %o1 + 0x00, %g2))
add %o1, 8, %o1
subcc %g1, 8, %g1
add %o0, 8, %o0
bne,pt %icc, 1b
EX_ST(STORE(stx, %g2, %o0 - 0x08))
.Llarge_aligned:
/* len >= 0x80 && src 8-byte aligned && dest 8-byte aligned */
andn %o2, 0x3f, %o4
sub %o2, %o4, %o2
1: EX_LD(LOAD(ldx, %o1 + 0x00, %g1))
add %o1, 0x40, %o1
EX_LD(LOAD(ldx, %o1 - 0x38, %g2))
subcc %o4, 0x40, %o4
EX_LD(LOAD(ldx, %o1 - 0x30, %g3))
EX_LD(LOAD(ldx, %o1 - 0x28, GLOBAL_SPARE))
EX_LD(LOAD(ldx, %o1 - 0x20, %o5))
EX_ST(STORE_INIT(%g1, %o0))
add %o0, 0x08, %o0
EX_ST(STORE_INIT(%g2, %o0))
add %o0, 0x08, %o0
EX_LD(LOAD(ldx, %o1 - 0x18, %g2))
EX_ST(STORE_INIT(%g3, %o0))
add %o0, 0x08, %o0
EX_LD(LOAD(ldx, %o1 - 0x10, %g3))
EX_ST(STORE_INIT(GLOBAL_SPARE, %o0))
add %o0, 0x08, %o0
EX_LD(LOAD(ldx, %o1 - 0x08, GLOBAL_SPARE))
EX_ST(STORE_INIT(%o5, %o0))
add %o0, 0x08, %o0
EX_ST(STORE_INIT(%g2, %o0))
add %o0, 0x08, %o0
EX_ST(STORE_INIT(%g3, %o0))
add %o0, 0x08, %o0
EX_ST(STORE_INIT(GLOBAL_SPARE, %o0))
add %o0, 0x08, %o0
bne,pt %icc, 1b
LOAD(prefetch, %o1 + 0x200, #n_reads_strong)
membar #StoreLoad | #StoreStore
brz,pn %o2, .Lexit
cmp %o2, 19
ble,pn %icc, .Lsmall_unaligned
nop
ba,a,pt %icc, .Lmedium_noprefetch
.Lexit: retl
mov EX_RETVAL(%o3), %o0
.Llarge_src_unaligned:
#ifdef NON_USER_COPY
VISEntryHalfFast(.Lmedium_vis_entry_fail)
#else
VISEntryHalf
#endif
andn %o2, 0x3f, %o4
sub %o2, %o4, %o2
alignaddr %o1, %g0, %g1
add %o1, %o4, %o1
EX_LD(LOAD(ldd, %g1 + 0x00, %f0))
1: EX_LD(LOAD(ldd, %g1 + 0x08, %f2))
subcc %o4, 0x40, %o4
EX_LD(LOAD(ldd, %g1 + 0x10, %f4))
EX_LD(LOAD(ldd, %g1 + 0x18, %f6))
EX_LD(LOAD(ldd, %g1 + 0x20, %f8))
EX_LD(LOAD(ldd, %g1 + 0x28, %f10))
EX_LD(LOAD(ldd, %g1 + 0x30, %f12))
EX_LD(LOAD(ldd, %g1 + 0x38, %f14))
faligndata %f0, %f2, %f16
EX_LD(LOAD(ldd, %g1 + 0x40, %f0))
faligndata %f2, %f4, %f18
add %g1, 0x40, %g1
faligndata %f4, %f6, %f20
faligndata %f6, %f8, %f22
faligndata %f8, %f10, %f24
faligndata %f10, %f12, %f26
faligndata %f12, %f14, %f28
faligndata %f14, %f0, %f30
EX_ST(STORE(std, %f16, %o0 + 0x00))
EX_ST(STORE(std, %f18, %o0 + 0x08))
EX_ST(STORE(std, %f20, %o0 + 0x10))
EX_ST(STORE(std, %f22, %o0 + 0x18))
EX_ST(STORE(std, %f24, %o0 + 0x20))
EX_ST(STORE(std, %f26, %o0 + 0x28))
EX_ST(STORE(std, %f28, %o0 + 0x30))
EX_ST(STORE(std, %f30, %o0 + 0x38))
add %o0, 0x40, %o0
bne,pt %icc, 1b
LOAD(prefetch, %g1 + 0x200, #n_reads_strong)
#ifdef NON_USER_COPY
VISExitHalfFast
#else
VISExitHalf
#endif
brz,pn %o2, .Lexit
cmp %o2, 19
ble,pn %icc, .Lsmall_unaligned
nop
ba,a,pt %icc, .Lmedium_unaligned
#ifdef NON_USER_COPY
.Lmedium_vis_entry_fail:
or %o0, %o1, %g2
#endif
.Lmedium:
LOAD(prefetch, %o1 + 0x40, #n_reads_strong)
andcc %g2, 0x7, %g0
bne,pn %icc, .Lmedium_unaligned
nop
.Lmedium_noprefetch:
andncc %o2, 0x20 - 1, %o5
be,pn %icc, 2f
sub %o2, %o5, %o2
1: EX_LD(LOAD(ldx, %o1 + 0x00, %g1))
EX_LD(LOAD(ldx, %o1 + 0x08, %g2))
EX_LD(LOAD(ldx, %o1 + 0x10, GLOBAL_SPARE))
EX_LD(LOAD(ldx, %o1 + 0x18, %o4))
add %o1, 0x20, %o1
subcc %o5, 0x20, %o5
EX_ST(STORE(stx, %g1, %o0 + 0x00))
EX_ST(STORE(stx, %g2, %o0 + 0x08))
EX_ST(STORE(stx, GLOBAL_SPARE, %o0 + 0x10))
EX_ST(STORE(stx, %o4, %o0 + 0x18))
bne,pt %icc, 1b
add %o0, 0x20, %o0
2: andcc %o2, 0x18, %o5
be,pt %icc, 3f
sub %o2, %o5, %o2
1: EX_LD(LOAD(ldx, %o1 + 0x00, %g1))
add %o1, 0x08, %o1
add %o0, 0x08, %o0
subcc %o5, 0x08, %o5
bne,pt %icc, 1b
EX_ST(STORE(stx, %g1, %o0 - 0x08))
3: brz,pt %o2, .Lexit
cmp %o2, 0x04
bl,pn %icc, .Ltiny
nop
EX_LD(LOAD(lduw, %o1 + 0x00, %g1))
add %o1, 0x04, %o1
add %o0, 0x04, %o0
subcc %o2, 0x04, %o2
bne,pn %icc, .Ltiny
EX_ST(STORE(stw, %g1, %o0 - 0x04))
ba,a,pt %icc, .Lexit
.Lmedium_unaligned:
/* First get dest 8 byte aligned. */
sub %g0, %o0, %g1
and %g1, 0x7, %g1
brz,pt %g1, 2f
sub %o2, %g1, %o2
1: EX_LD(LOAD(ldub, %o1 + 0x00, %g2))
add %o1, 1, %o1
subcc %g1, 1, %g1
add %o0, 1, %o0
bne,pt %icc, 1b
EX_ST(STORE(stb, %g2, %o0 - 0x01))
2:
and %o1, 0x7, %g1
brz,pn %g1, .Lmedium_noprefetch
sll %g1, 3, %g1
mov 64, %g2
sub %g2, %g1, %g2
andn %o1, 0x7, %o1
EX_LD(LOAD(ldx, %o1 + 0x00, %o4))
sllx %o4, %g1, %o4
andn %o2, 0x08 - 1, %o5
sub %o2, %o5, %o2
1: EX_LD(LOAD(ldx, %o1 + 0x08, %g3))
add %o1, 0x08, %o1
subcc %o5, 0x08, %o5
srlx %g3, %g2, GLOBAL_SPARE
or GLOBAL_SPARE, %o4, GLOBAL_SPARE
EX_ST(STORE(stx, GLOBAL_SPARE, %o0 + 0x00))
add %o0, 0x08, %o0
bne,pt %icc, 1b
sllx %g3, %g1, %o4
srl %g1, 3, %g1
add %o1, %g1, %o1
brz,pn %o2, .Lexit
nop
ba,pt %icc, .Lsmall_unaligned
.Ltiny:
EX_LD(LOAD(ldub, %o1 + 0x00, %g1))
subcc %o2, 1, %o2
be,pn %icc, .Lexit
EX_ST(STORE(stb, %g1, %o0 + 0x00))
EX_LD(LOAD(ldub, %o1 + 0x01, %g1))
subcc %o2, 1, %o2
be,pn %icc, .Lexit
EX_ST(STORE(stb, %g1, %o0 + 0x01))
EX_LD(LOAD(ldub, %o1 + 0x02, %g1))
ba,pt %icc, .Lexit
EX_ST(STORE(stb, %g1, %o0 + 0x02))
.Lsmall:
andcc %g2, 0x3, %g0
bne,pn %icc, .Lsmall_unaligned
andn %o2, 0x4 - 1, %o5
sub %o2, %o5, %o2
1:
EX_LD(LOAD(lduw, %o1 + 0x00, %g1))
add %o1, 0x04, %o1
subcc %o5, 0x04, %o5
add %o0, 0x04, %o0
bne,pt %icc, 1b
EX_ST(STORE(stw, %g1, %o0 - 0x04))
brz,pt %o2, .Lexit
nop
ba,a,pt %icc, .Ltiny
.Lsmall_unaligned:
1: EX_LD(LOAD(ldub, %o1 + 0x00, %g1))
add %o1, 1, %o1
add %o0, 1, %o0
subcc %o2, 1, %o2
bne,pt %icc, 1b
EX_ST(STORE(stb, %g1, %o0 - 0x01))
ba,a,pt %icc, .Lexit
.size FUNC_NAME, .-FUNC_NAME
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