tm.S

/*
 * Transactional memory support routines to reclaim and recheckpoint
 * transactional process state.
 *
 * Copyright 2012 Matt Evans & Michael Neuling, IBM Corporation.
 */

#include <asm/asm-offsets.h>
#include <asm/ppc_asm.h>
#include <asm/ppc-opcode.h>
#include <asm/ptrace.h>
#include <asm/reg.h>

#ifdef CONFIG_VSX
/* See fpu.S, this is very similar but to save/restore checkpointed FPRs/VSRs */
#define __SAVE_32FPRS_VSRS_TRANSACT(n,c,base)	\
BEGIN_FTR_SECTION				\
	b	2f;				\
END_FTR_SECTION_IFSET(CPU_FTR_VSX);		\
	SAVE_32FPRS_TRANSACT(n,base);		\
	b	3f;				\
2:	SAVE_32VSRS_TRANSACT(n,c,base);		\
3:
/* ...and this is just plain borrowed from there. */
#define __REST_32FPRS_VSRS(n,c,base)		\
BEGIN_FTR_SECTION				\
	b	2f;				\
END_FTR_SECTION_IFSET(CPU_FTR_VSX);		\
	REST_32FPRS(n,base);			\
	b	3f;				\
2:	REST_32VSRS(n,c,base);			\
3:
#else
#define __SAVE_32FPRS_VSRS_TRANSACT(n,c,base) SAVE_32FPRS_TRANSACT(n, base)
#define __REST_32FPRS_VSRS(n,c,base)	      REST_32FPRS(n, base)
#endif
#define SAVE_32FPRS_VSRS_TRANSACT(n,c,base) \
	__SAVE_32FPRS_VSRS_TRANSACT(n,__REG_##c,__REG_##base)
#define REST_32FPRS_VSRS(n,c,base) \
	__REST_32FPRS_VSRS(n,__REG_##c,__REG_##base)

/* Stack frame offsets for local variables. */
#define TM_FRAME_L0	TM_FRAME_SIZE-16
#define TM_FRAME_L1	TM_FRAME_SIZE-8
#define STACK_PARAM(x)	(48+((x)*8))


/* In order to access the TM SPRs, TM must be enabled.  So, do so: */
_GLOBAL(tm_enable)
	mfmsr	r4
	li	r3, MSR_TM >> 32
	sldi	r3, r3, 32
	and.	r0, r4, r3
	bne	1f
	or	r4, r4, r3
	mtmsrd	r4
1:	blr

_GLOBAL(tm_save_sprs)
	mfspr	r0, SPRN_TFHAR
	std	r0, THREAD_TM_TFHAR(r3)
	mfspr	r0, SPRN_TEXASR
	std	r0, THREAD_TM_TEXASR(r3)
	mfspr	r0, SPRN_TFIAR
	std	r0, THREAD_TM_TFIAR(r3)
	blr

_GLOBAL(tm_restore_sprs)
	ld	r0, THREAD_TM_TFHAR(r3)
	mtspr	SPRN_TFHAR, r0
	ld	r0, THREAD_TM_TEXASR(r3)
	mtspr	SPRN_TEXASR, r0
	ld	r0, THREAD_TM_TFIAR(r3)
	mtspr	SPRN_TFIAR, r0
	blr

	/* Passed an 8-bit failure cause as first argument. */
_GLOBAL(tm_abort)
	TABORT(R3)
	blr


/* void tm_reclaim(struct thread_struct *thread,
 *                 unsigned long orig_msr,
 *		   uint8_t cause)
 *
 *	- Performs a full reclaim.  This destroys outstanding
 *	  transactions and updates thread->regs.tm_ckpt_* with the
 *	  original checkpointed state.  Note that thread->regs is
 *	  unchanged.
 *	- FP regs are written back to thread->transact_fpr before
 *	  reclaiming.  These are the transactional (current) versions.
 *
 * Purpose is to both abort transactions of, and preserve the state of,
 * a transactions at a context switch. We preserve/restore both sets of process
 * state to restore them when the thread's scheduled again.  We continue in
 * userland as though nothing happened, but when the transaction is resumed
 * they will abort back to the checkpointed state we save out here.
 *
 * Call with IRQs off, stacks get all out of sync for some periods in here!
 */
_GLOBAL(tm_reclaim)
	mfcr	r6
	mflr	r0
	std	r6, 8(r1)
	std	r0, 16(r1)
	std	r2, 40(r1)
	stdu	r1, -TM_FRAME_SIZE(r1)

	/* We've a struct pt_regs at [r1+STACK_FRAME_OVERHEAD]. */

	std	r3, STACK_PARAM(0)(r1)
	SAVE_NVGPRS(r1)

	/* We need to setup MSR for VSX register save instructions.  Here we
	 * also clear the MSR RI since when we do the treclaim, we won't have a
	 * valid kernel pointer for a while.  We clear RI here as it avoids
	 * adding another mtmsr closer to the treclaim.  This makes the region
	 * maked as non-recoverable wider than it needs to be but it saves on
	 * inserting another mtmsrd later.
	 */
	mfmsr	r14
	mr	r15, r14
	ori	r15, r15, MSR_FP
	li	r16, MSR_RI
	andc	r15, r15, r16
	oris	r15, r15, MSR_VEC@h
#ifdef CONFIG_VSX
	BEGIN_FTR_SECTION
	oris	r15,r15, MSR_VSX@h
	END_FTR_SECTION_IFSET(CPU_FTR_VSX)
#endif
	mtmsrd	r15
	std	r14, TM_FRAME_L0(r1)

	/* Stash the stack pointer away for use after reclaim */
	std	r1, PACAR1(r13)

	/* ******************** FPR/VR/VSRs ************
	 * Before reclaiming, capture the current/transactional FPR/VR
	* versions /if used/.
	 *
	 * (If VSX used, FP and VMX are implied.  Or, we don't need to look
	 * at MSR.VSX as copying FP regs if .FP, vector regs if .VMX covers it.)
	 *
	 * We're passed the thread's MSR as parameter 2.
	 *
	 * We enabled VEC/FP/VSX in the msr above, so we can execute these
	 * instructions!
	 */
	andis.		r0, r4, MSR_VEC@h
	beq	dont_backup_vec

	SAVE_32VRS_TRANSACT(0, r6, r3)	/* r6 scratch, r3 thread */
	mfvscr	vr0
	li	r6, THREAD_TRANSACT_VSCR
	stvx	vr0, r3, r6
dont_backup_vec:
	mfspr	r0, SPRN_VRSAVE
	std	r0, THREAD_TRANSACT_VRSAVE(r3)

	andi.	r0, r4, MSR_FP
	beq	dont_backup_fp

	SAVE_32FPRS_VSRS_TRANSACT(0, R6, R3)	/* r6 scratch, r3 thread */

	mffs    fr0
	stfd    fr0,THREAD_TRANSACT_FPSCR(r3)

dont_backup_fp:
	/* The moment we treclaim, ALL of our GPRs will switch
	 * to user register state.  (FPRs, CCR etc. also!)
	 * Use an sprg and a tm_scratch in the PACA to shuffle.
	 */
	TRECLAIM(R5)				/* Cause in r5 */

	/* ******************** GPRs ******************** */
	/* Stash the checkpointed r13 away in the scratch SPR and get the real
	 *  paca
	 */
	SET_SCRATCH0(r13)
	GET_PACA(r13)

	/* Stash the checkpointed r1 away in paca tm_scratch and get the real
	 * stack pointer back
	 */
	std	r1, PACATMSCRATCH(r13)
	ld	r1, PACAR1(r13)

	/* Now get some more GPRS free */
	std	r7, GPR7(r1)			/* Temporary stash */
	std	r12, GPR12(r1)			/* ''   ''    ''   */
	ld	r12, STACK_PARAM(0)(r1)		/* Param 0, thread_struct * */

	addi	r7, r12, PT_CKPT_REGS		/* Thread's ckpt_regs */

	/* Make r7 look like an exception frame so that we
	 * can use the neat GPRx(n) macros.  r7 is NOT a pt_regs ptr!
	 */
	subi	r7, r7, STACK_FRAME_OVERHEAD

	/* Sync the userland GPRs 2-12, 14-31 to thread->regs: */
	SAVE_GPR(0, r7)				/* user r0 */
	SAVE_GPR(2, r7)			/* user r2 */
	SAVE_4GPRS(3, r7)			/* user r3-r6 */
	SAVE_4GPRS(8, r7)			/* user r8-r11 */
	ld	r3, PACATMSCRATCH(r13)		/* user r1 */
	ld	r4, GPR7(r1)			/* user r7 */
	ld	r5, GPR12(r1)			/* user r12 */
	GET_SCRATCH0(6)				/* user r13 */
	std	r3, GPR1(r7)
	std	r4, GPR7(r7)
	std	r5, GPR12(r7)
	std	r6, GPR13(r7)

	SAVE_NVGPRS(r7)				/* user r14-r31 */

	/* ******************** NIP ******************** */
	mfspr	r3, SPRN_TFHAR
	std	r3, _NIP(r7)			/* Returns to failhandler */
	/* The checkpointed NIP is ignored when rescheduling/rechkpting,
	 * but is used in signal return to 'wind back' to the abort handler.
	 */

	/* ******************** CR,LR,CCR,MSR ********** */
	mfctr	r3
	mflr	r4
	mfcr	r5
	mfxer	r6

	std	r3, _CTR(r7)
	std	r4, _LINK(r7)
	std	r5, _CCR(r7)
	std	r6, _XER(r7)


	/* ******************** TAR, PPR, DSCR ********** */
	mfspr	r3, SPRN_TAR
	mfspr	r4, SPRN_PPR
	mfspr	r5, SPRN_DSCR

	std	r3, THREAD_TM_TAR(r12)
	std	r4, THREAD_TM_PPR(r12)
	std	r5, THREAD_TM_DSCR(r12)

	/* MSR and flags:  We don't change CRs, and we don't need to alter
	 * MSR.
	 */

	/* TM regs, incl TEXASR -- these live in thread_struct.  Note they've
	 * been updated by the treclaim, to explain to userland the failure
	 * cause (aborted).
	 */
	mfspr	r0, SPRN_TEXASR
	mfspr	r3, SPRN_TFHAR
	mfspr	r4, SPRN_TFIAR
	std	r0, THREAD_TM_TEXASR(r12)
	std	r3, THREAD_TM_TFHAR(r12)
	std	r4, THREAD_TM_TFIAR(r12)

	/* AMR and PPR are checkpointed too, but are unsupported by Linux. */

	/* Restore original MSR/IRQ state & clear TM mode */
	ld	r14, TM_FRAME_L0(r1)		/* Orig MSR */
	li	r15, 0
	rldimi  r14, r15, MSR_TS_LG, (63-MSR_TS_LG)-1
	mtmsrd  r14

	REST_NVGPRS(r1)

	addi    r1, r1, TM_FRAME_SIZE
	ld	r4, 8(r1)
	ld	r0, 16(r1)
	mtcr	r4
	mtlr	r0
	ld	r2, 40(r1)
	blr


	/* void tm_recheckpoint(struct thread_struct *thread,
	 *			unsigned long orig_msr)
	 *	- Restore the checkpointed register state saved by tm_reclaim
	 *	  when we switch_to a process.
	 *
	 *	Call with IRQs off, stacks get all out of sync for
	 *	some periods in here!
	 */
_GLOBAL(tm_recheckpoint)
	mfcr	r5
	mflr	r0
	std	r5, 8(r1)
	std	r0, 16(r1)
	std	r2, 40(r1)
	stdu	r1, -TM_FRAME_SIZE(r1)

	/* We've a struct pt_regs at [r1+STACK_FRAME_OVERHEAD].
	 * This is used for backing up the NVGPRs:
	 */
	SAVE_NVGPRS(r1)

	std	r1, PACAR1(r13)

	/* Load complete register state from ts_ckpt* registers */

	addi	r7, r3, PT_CKPT_REGS		/* Thread's ckpt_regs */

	/* Make r7 look like an exception frame so that we
	 * can use the neat GPRx(n) macros.  r7 is now NOT a pt_regs ptr!
	 */
	subi	r7, r7, STACK_FRAME_OVERHEAD

	SET_SCRATCH0(r1)

	mfmsr	r6
	/* R4 = original MSR to indicate whether thread used FP/Vector etc. */

	/* Enable FP/vec in MSR if necessary! */
	lis	r5, MSR_VEC@h
	ori	r5, r5, MSR_FP
	and.	r5, r4, r5
	beq	restore_gprs			/* if neither, skip both */

#ifdef CONFIG_VSX
	BEGIN_FTR_SECTION
	oris	r5, r5, MSR_VSX@h
	END_FTR_SECTION_IFSET(CPU_FTR_VSX)
#endif
	or	r5, r6, r5			/* Set MSR.FP+.VSX/.VEC */
	mtmsr	r5

#ifdef CONFIG_ALTIVEC
	/* FP and VEC registers:  These are recheckpointed from thread.fpr[]
	 * and thread.vr[] respectively.  The thread.transact_fpr[] version
	 * is more modern, and will be loaded subsequently by any FPUnavailable
	 * trap.
	 */
	andis.	r0, r4, MSR_VEC@h
	beq	dont_restore_vec

	li	r5, THREAD_VSCR
	lvx	vr0, r3, r5
	mtvscr	vr0
	REST_32VRS(0, r5, r3)			/* r5 scratch, r3 THREAD ptr */
dont_restore_vec:
	ld	r5, THREAD_VRSAVE(r3)
	mtspr	SPRN_VRSAVE, r5
#endif

	andi.	r0, r4, MSR_FP
	beq	dont_restore_fp

	lfd	fr0, THREAD_FPSCR(r3)
	MTFSF_L(fr0)
	REST_32FPRS_VSRS(0, R4, R3)

dont_restore_fp:
	mtmsr	r6				/* FP/Vec off again! */

restore_gprs:

	/* ******************** TAR, PPR, DSCR ********** */
	ld	r4, THREAD_TM_TAR(r3)
	ld	r5, THREAD_TM_PPR(r3)
	ld	r6, THREAD_TM_DSCR(r3)

	mtspr	SPRN_TAR,	r4
	mtspr	SPRN_PPR,	r5
	mtspr	SPRN_DSCR,	r6

	/* ******************** CR,LR,CCR,MSR ********** */
	ld	r3, _CTR(r7)
	ld	r4, _LINK(r7)
	ld	r5, _CCR(r7)
	ld	r6, _XER(r7)

	mtctr	r3
	mtlr	r4
	mtcr	r5
	mtxer	r6

	/* Clear the MSR RI since we are about to change R1.  EE is already off
	 */
	li	r4, 0
	mtmsrd	r4, 1

	REST_4GPRS(0, r7)			/* GPR0-3 */
	REST_GPR(4, r7)				/* GPR4-6 */
	REST_GPR(5, r7)
	REST_GPR(6, r7)
	REST_4GPRS(8, r7)			/* GPR8-11 */
	REST_2GPRS(12, r7)			/* GPR12-13 */

	REST_NVGPRS(r7)				/* GPR14-31 */

	ld	r7, GPR7(r7)			/* GPR7 */

	/* Commit register state as checkpointed state: */
	TRECHKPT

	/* Our transactional state has now changed.
	 *
	 * Now just get out of here.  Transactional (current) state will be
	 * updated once restore is called on the return path in the _switch-ed
	 * -to process.
	 */

	GET_PACA(r13)
	GET_SCRATCH0(r1)

	/* R1 is restored, so we are recoverable again.  EE is still off */
	li	r4, MSR_RI
	mtmsrd	r4, 1

	REST_NVGPRS(r1)

	addi    r1, r1, TM_FRAME_SIZE
	ld	r4, 8(r1)
	ld	r0, 16(r1)
	mtcr	r4
	mtlr	r0
	ld	r2, 40(r1)
	blr

	/* ****************************************************************** */