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alistair23-linux/arch/mips/kernel/r4k_switch.S
Paul Burton c9017757c5 MIPS: init upper 64b of vector registers when MSA is first used 
When a task first makes use of MSA we need to ensure that the upper
64b of the vector registers are set to some value such that no
information can be leaked to it from the previous task to use MSA
context on the CPU. The architecture formerly specified that these
bits would be cleared to 0 when a scalar FP instructions wrote to the
aliased FP registers, which would have implicitly handled this as the
kernel restored scalar FP context. However more recent versions of the
specification now state that the value of the bits in such cases is
unpredictable. Initialise them explictly to be sure, and set all the
bits to 1 rather than 0 for consistency with the least significant
64b.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/7497/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
2014-08-02 00:06:44 +02:00

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/*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* Copyright (C) 1994, 1995, 1996, 1998, 1999, 2002, 2003 Ralf Baechle
* Copyright (C) 1996 David S. Miller (davem@davemloft.net)
* Copyright (C) 1994, 1995, 1996, by Andreas Busse
* Copyright (C) 1999 Silicon Graphics, Inc.
* Copyright (C) 2000 MIPS Technologies, Inc.
* written by Carsten Langgaard, carstenl@mips.com
*/
#include <asm/asm.h>
#include <asm/cachectl.h>
#include <asm/fpregdef.h>
#include <asm/mipsregs.h>
#include <asm/asm-offsets.h>
#include <asm/pgtable-bits.h>
#include <asm/regdef.h>
#include <asm/stackframe.h>
#include <asm/thread_info.h>
#include <asm/asmmacro.h>
/*
* Offset to the current process status flags, the first 32 bytes of the
* stack are not used.
*/
#define ST_OFF (_THREAD_SIZE - 32 - PT_SIZE + PT_STATUS)
#ifndef USE_ALTERNATE_RESUME_IMPL
/*
* task_struct *resume(task_struct *prev, task_struct *next,
* struct thread_info *next_ti, s32 fp_save)
*/
.align 5
LEAF(resume)
mfc0 t1, CP0_STATUS
LONG_S t1, THREAD_STATUS(a0)
cpu_save_nonscratch a0
LONG_S ra, THREAD_REG31(a0)
/*
* Check whether we need to save any FP context. FP context is saved
* iff the process has used the context with the scalar FPU or the MSA
* ASE in the current time slice, as indicated by _TIF_USEDFPU and
* _TIF_USEDMSA respectively. switch_to will have set fp_save
* accordingly to an FP_SAVE_ enum value.
*/
beqz a3, 2f
/*
* We do. Clear the saved CU1 bit for prev, such that next time it is
* scheduled it will start in userland with the FPU disabled. If the
* task uses the FPU then it will be enabled again via the do_cpu trap.
* This allows us to lazily restore the FP context.
*/
PTR_L t3, TASK_THREAD_INFO(a0)
LONG_L t0, ST_OFF(t3)
li t1, ~ST0_CU1
and t0, t0, t1
LONG_S t0, ST_OFF(t3)
/* Check whether we're saving scalar or vector context. */
bgtz a3, 1f
/* Save 128b MSA vector context + scalar FP control & status. */
cfc1 t1, fcr31
msa_save_all a0
sw t1, THREAD_FCR31(a0)
b 2f
1: /* Save 32b/64b scalar FP context. */
fpu_save_double a0 t0 t1 # c0_status passed in t0
# clobbers t1
2:
#if defined(CONFIG_CC_STACKPROTECTOR) && !defined(CONFIG_SMP)
PTR_LA t8, __stack_chk_guard
LONG_L t9, TASK_STACK_CANARY(a1)
LONG_S t9, 0(t8)
#endif
/*
* The order of restoring the registers takes care of the race
* updating $28, $29 and kernelsp without disabling ints.
*/
move $28, a2
cpu_restore_nonscratch a1
PTR_ADDU t0, $28, _THREAD_SIZE - 32
set_saved_sp t0, t1, t2
mfc0 t1, CP0_STATUS /* Do we really need this? */
li a3, 0xff01
and t1, a3
LONG_L a2, THREAD_STATUS(a1)
nor a3, $0, a3
and a2, a3
or a2, t1
mtc0 a2, CP0_STATUS
move v0, a0
jr ra
END(resume)
#endif /* USE_ALTERNATE_RESUME_IMPL */
/*
* Save a thread's fp context.
*/
LEAF(_save_fp)
#if defined(CONFIG_64BIT) || defined(CONFIG_CPU_MIPS32_R2)
mfc0 t0, CP0_STATUS
#endif
fpu_save_double a0 t0 t1 # clobbers t1
jr ra
END(_save_fp)
/*
* Restore a thread's fp context.
*/
LEAF(_restore_fp)
#if defined(CONFIG_64BIT) || defined(CONFIG_CPU_MIPS32_R2)
mfc0 t0, CP0_STATUS
#endif
fpu_restore_double a0 t0 t1 # clobbers t1
jr ra
END(_restore_fp)
#ifdef CONFIG_CPU_HAS_MSA
/*
* Save a thread's MSA vector context.
*/
LEAF(_save_msa)
msa_save_all a0
jr ra
END(_save_msa)
/*
* Restore a thread's MSA vector context.
*/
LEAF(_restore_msa)
msa_restore_all a0
jr ra
END(_restore_msa)
LEAF(_init_msa_upper)
msa_init_all_upper
jr ra
END(_init_msa_upper)
#endif
/*
* Load the FPU with signalling NANS. This bit pattern we're using has
* the property that no matter whether considered as single or as double
* precision represents signaling NANS.
*
* We initialize fcr31 to rounding to nearest, no exceptions.
*/
#define FPU_DEFAULT 0x00000000
LEAF(_init_fpu)
mfc0 t0, CP0_STATUS
li t1, ST0_CU1
or t0, t1
mtc0 t0, CP0_STATUS
enable_fpu_hazard
li t1, FPU_DEFAULT
ctc1 t1, fcr31
li t1, -1 # SNaN
#ifdef CONFIG_64BIT
sll t0, t0, 5
bgez t0, 1f # 16 / 32 register mode?
dmtc1 t1, $f1
dmtc1 t1, $f3
dmtc1 t1, $f5
dmtc1 t1, $f7
dmtc1 t1, $f9
dmtc1 t1, $f11
dmtc1 t1, $f13
dmtc1 t1, $f15
dmtc1 t1, $f17
dmtc1 t1, $f19
dmtc1 t1, $f21
dmtc1 t1, $f23
dmtc1 t1, $f25
dmtc1 t1, $f27
dmtc1 t1, $f29
dmtc1 t1, $f31
1:
#endif
#ifdef CONFIG_CPU_MIPS32
mtc1 t1, $f0
mtc1 t1, $f1
mtc1 t1, $f2
mtc1 t1, $f3
mtc1 t1, $f4
mtc1 t1, $f5
mtc1 t1, $f6
mtc1 t1, $f7
mtc1 t1, $f8
mtc1 t1, $f9
mtc1 t1, $f10
mtc1 t1, $f11
mtc1 t1, $f12
mtc1 t1, $f13
mtc1 t1, $f14
mtc1 t1, $f15
mtc1 t1, $f16
mtc1 t1, $f17
mtc1 t1, $f18
mtc1 t1, $f19
mtc1 t1, $f20
mtc1 t1, $f21
mtc1 t1, $f22
mtc1 t1, $f23
mtc1 t1, $f24
mtc1 t1, $f25
mtc1 t1, $f26
mtc1 t1, $f27
mtc1 t1, $f28
mtc1 t1, $f29
mtc1 t1, $f30
mtc1 t1, $f31
#ifdef CONFIG_CPU_MIPS32_R2
.set push
.set mips64r2
sll t0, t0, 5 # is Status.FR set?
bgez t0, 1f # no: skip setting upper 32b
mthc1 t1, $f0
mthc1 t1, $f1
mthc1 t1, $f2
mthc1 t1, $f3
mthc1 t1, $f4
mthc1 t1, $f5
mthc1 t1, $f6
mthc1 t1, $f7
mthc1 t1, $f8
mthc1 t1, $f9
mthc1 t1, $f10
mthc1 t1, $f11
mthc1 t1, $f12
mthc1 t1, $f13
mthc1 t1, $f14
mthc1 t1, $f15
mthc1 t1, $f16
mthc1 t1, $f17
mthc1 t1, $f18
mthc1 t1, $f19
mthc1 t1, $f20
mthc1 t1, $f21
mthc1 t1, $f22
mthc1 t1, $f23
mthc1 t1, $f24
mthc1 t1, $f25
mthc1 t1, $f26
mthc1 t1, $f27
mthc1 t1, $f28
mthc1 t1, $f29
mthc1 t1, $f30
mthc1 t1, $f31
1: .set pop
#endif /* CONFIG_CPU_MIPS32_R2 */
#else
.set arch=r4000
dmtc1 t1, $f0
dmtc1 t1, $f2
dmtc1 t1, $f4
dmtc1 t1, $f6
dmtc1 t1, $f8
dmtc1 t1, $f10
dmtc1 t1, $f12
dmtc1 t1, $f14
dmtc1 t1, $f16
dmtc1 t1, $f18
dmtc1 t1, $f20
dmtc1 t1, $f22
dmtc1 t1, $f24
dmtc1 t1, $f26
dmtc1 t1, $f28
dmtc1 t1, $f30
#endif
jr ra
END(_init_fpu)
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