linux_kernel/arch/mips/kernel/r4k_switch.S

/*
 * 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. */
	msa_save_all	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)

#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)