xref: /openbmc/linux/arch/powerpc/kernel/rtas_entry.S (revision 07940b4b61cf0cbcfb9e4226c07318f737157c42)

/* SPDX-License-Identifier: GPL-2.0-or-later */

#include <asm/asm-offsets.h>
#include <asm/bug.h>
#include <asm/page.h>
#include <asm/ppc_asm.h>

/*
 * RTAS is called with MSR IR, DR, EE disabled, and LR in the return address.
 *
 * Note: r3 is an input parameter to rtas, so don't trash it...
 */

#ifdef CONFIG_PPC32
_GLOBAL(enter_rtas)
	stwu	r1,-INT_FRAME_SIZE(r1)
	mflr	r0
	stw	r0,INT_FRAME_SIZE+4(r1)
	LOAD_REG_ADDR(r4, rtas)
	lis	r6,1f@ha	/* physical return address for rtas */
	addi	r6,r6,1f@l
	tophys(r6,r6)
	lwz	r8,RTASENTRY(r4)
	lwz	r4,RTASBASE(r4)
	mfmsr	r9
	stw	r9,8(r1)
	LOAD_REG_IMMEDIATE(r0,MSR_KERNEL)
	mtmsr	r0	/* disable interrupts so SRR0/1 don't get trashed */
	li	r9,MSR_KERNEL & ~(MSR_IR|MSR_DR)
	mtlr	r6
	stw	r1, THREAD + RTAS_SP(r2)
	mtspr	SPRN_SRR0,r8
	mtspr	SPRN_SRR1,r9
	rfi
1:
	lis	r8, 1f@h
	ori	r8, r8, 1f@l
	LOAD_REG_IMMEDIATE(r9,MSR_KERNEL)
	mtspr	SPRN_SRR0,r8
	mtspr	SPRN_SRR1,r9
	rfi			/* Reactivate MMU translation */
1:
	lwz	r8,INT_FRAME_SIZE+4(r1)	/* get return address */
	lwz	r9,8(r1)	/* original msr value */
	addi	r1,r1,INT_FRAME_SIZE
	li	r0,0
	stw	r0, THREAD + RTAS_SP(r2)
	mtlr	r8
	mtmsr	r9
	blr			/* return to caller */
_ASM_NOKPROBE_SYMBOL(enter_rtas)

#else /* CONFIG_PPC32 */
#include <asm/exception-64s.h>

/*
 * 32-bit rtas on 64-bit machines has the additional problem that RTAS may
 * not preserve the upper parts of registers it uses.
 */
_GLOBAL(enter_rtas)
	mflr	r0
	std	r0,16(r1)
        stdu	r1,-SWITCH_FRAME_SIZE(r1) /* Save SP and create stack space. */

	/* Because RTAS is running in 32b mode, it clobbers the high order half
	 * of all registers that it saves.  We therefore save those registers
	 * RTAS might touch to the stack.  (r0, r3-r13 are caller saved)
   	 */
	SAVE_GPR(2, r1)			/* Save the TOC */
	SAVE_GPR(13, r1)		/* Save paca */
	SAVE_NVGPRS(r1)			/* Save the non-volatiles */

	mfcr	r4
	std	r4,_CCR(r1)
	mfctr	r5
	std	r5,_CTR(r1)
	mfspr	r6,SPRN_XER
	std	r6,_XER(r1)
	mfdar	r7
	std	r7,_DAR(r1)
	mfdsisr	r8
	std	r8,_DSISR(r1)

	/* Temporary workaround to clear CR until RTAS can be modified to
	 * ignore all bits.
	 */
	li	r0,0
	mtcr	r0

#ifdef CONFIG_BUG
	/* There is no way it is acceptable to get here with interrupts enabled,
	 * check it with the asm equivalent of WARN_ON
	 */
	lbz	r0,PACAIRQSOFTMASK(r13)
1:	tdeqi	r0,IRQS_ENABLED
	EMIT_WARN_ENTRY 1b,__FILE__,__LINE__,BUGFLAG_WARNING
#endif

	/* Hard-disable interrupts */
	mfmsr	r6
	rldicl	r7,r6,48,1
	rotldi	r7,r7,16
	mtmsrd	r7,1

	/* Unfortunately, the stack pointer and the MSR are also clobbered,
	 * so they are saved in the PACA which allows us to restore
	 * our original state after RTAS returns.
         */
	std	r1,PACAR1(r13)
        std	r6,PACASAVEDMSR(r13)

	/* Setup our real return addr */
	LOAD_REG_ADDR(r4,rtas_return_loc)
	clrldi	r4,r4,2			/* convert to realmode address */
       	mtlr	r4

__enter_rtas:
	LOAD_REG_ADDR(r4, rtas)
	ld	r5,RTASENTRY(r4)	/* get the rtas->entry value */
	ld	r4,RTASBASE(r4)		/* get the rtas->base value */

	/*
	 * RTAS runs in 32-bit big endian real mode, but leave MSR[RI] on as we
	 * may hit NMI (SRESET or MCE) while in RTAS. RTAS should disable RI in
	 * its critical regions (as specified in PAPR+ section 7.2.1). MSR[S]
	 * is not impacted by RFI_TO_KERNEL (only urfid can unset it). So if
	 * MSR[S] is set, it will remain when entering RTAS.
	 */
	LOAD_REG_IMMEDIATE(r6, MSR_ME | MSR_RI)

	li      r0,0
	mtmsrd  r0,1                    /* disable RI before using SRR0/1 */

	mtspr	SPRN_SRR0,r5
	mtspr	SPRN_SRR1,r6
	RFI_TO_KERNEL
	b	.	/* prevent speculative execution */
rtas_return_loc:
	FIXUP_ENDIAN

	/*
	 * Clear RI and set SF before anything.
	 */
	mfmsr   r6
	li	r0,MSR_RI
	andc	r6,r6,r0
	sldi	r0,r0,(MSR_SF_LG - MSR_RI_LG)
	or	r6,r6,r0
	sync
	mtmsrd  r6

	/* relocation is off at this point */
	GET_PACA(r4)
	clrldi	r4,r4,2			/* convert to realmode address */

	bcl	20,31,$+4
0:	mflr	r3
	ld	r3,(1f-0b)(r3)		/* get &rtas_restore_regs */

        ld	r1,PACAR1(r4)           /* Restore our SP */
        ld	r4,PACASAVEDMSR(r4)     /* Restore our MSR */

	mtspr	SPRN_SRR0,r3
	mtspr	SPRN_SRR1,r4
	RFI_TO_KERNEL
	b	.	/* prevent speculative execution */
_ASM_NOKPROBE_SYMBOL(enter_rtas)
_ASM_NOKPROBE_SYMBOL(__enter_rtas)
_ASM_NOKPROBE_SYMBOL(rtas_return_loc)

	.align	3
1:	.8byte	rtas_restore_regs

rtas_restore_regs:
	/* relocation is on at this point */
	REST_GPR(2, r1)			/* Restore the TOC */
	REST_GPR(13, r1)		/* Restore paca */
	REST_NVGPRS(r1)			/* Restore the non-volatiles */

	GET_PACA(r13)

	ld	r4,_CCR(r1)
	mtcr	r4
	ld	r5,_CTR(r1)
	mtctr	r5
	ld	r6,_XER(r1)
	mtspr	SPRN_XER,r6
	ld	r7,_DAR(r1)
	mtdar	r7
	ld	r8,_DSISR(r1)
	mtdsisr	r8

        addi	r1,r1,SWITCH_FRAME_SIZE	/* Unstack our frame */
	ld	r0,16(r1)		/* get return address */

	mtlr    r0
        blr				/* return to caller */

#endif /* CONFIG_PPC32 */