crt0.S

/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * Copyright (C) Paul Mackerras 1997.
 *
 * Adapted for 64 bit LE PowerPC by Andrew Tauferner
 */

#include "ppc_asm.h"

RELA = 7
RELASZ = 8
RELAENT = 9

	.data
	/* A procedure descriptor used when booting this as a COFF file.
	 * When making COFF, this comes first in the link and we're
	 * linked at 0x500000.
	 */
	.globl	_zimage_start_opd
_zimage_start_opd:
	.long	0x500000, 0, 0, 0
	.text
	b	_zimage_start

#ifdef __powerpc64__
.balign 8
p_start:	.8byte	_start
p_etext:	.8byte	_etext
p_bss_start:	.8byte	__bss_start
p_end:		.8byte	_end

p_toc:		.8byte	.TOC. - p_base
p_dyn:		.8byte	__dynamic_start - p_base
p_rela:		.8byte	__rela_dyn_start - p_base
p_prom:		.8byte	0
	.weak	_platform_stack_top
p_pstack:	.8byte	_platform_stack_top
#else
p_start:	.long	_start
p_etext:	.long	_etext
p_bss_start:	.long	__bss_start
p_end:		.long	_end

	.weak	_platform_stack_top
p_pstack:	.long	_platform_stack_top
#endif

	.weak	_zimage_start
_zimage_start:
	.globl	_zimage_start_lib
_zimage_start_lib:
	/* Work out the offset between the address we were linked at
	   and the address where we're running. */
	bcl	20,31,.+4
p_base:	mflr	r10		/* r10 now points to runtime addr of p_base */
#ifndef __powerpc64__
	/* grab the link address of the dynamic section in r11 */
	addis	r11,r10,(_GLOBAL_OFFSET_TABLE_-p_base)@ha
	lwz	r11,(_GLOBAL_OFFSET_TABLE_-p_base)@l(r11)
	cmpwi	r11,0
	beq	3f		/* if not linked -pie */
	/* get the runtime address of the dynamic section in r12 */
	.weak	__dynamic_start
	addis	r12,r10,(__dynamic_start-p_base)@ha
	addi	r12,r12,(__dynamic_start-p_base)@l
	subf	r11,r11,r12	/* runtime - linktime offset */

	/* The dynamic section contains a series of tagged entries.
	 * We need the RELA and RELACOUNT entries. */
	li	r9,0
	li	r0,0
9:	lwz	r8,0(r12)	/* get tag */
	cmpwi	r8,0
	beq	10f		/* end of list */
	cmpwi	r8,RELA
	bne	11f
	lwz	r9,4(r12)	/* get RELA pointer in r9 */
	b	12f
11:	cmpwi	r8,RELASZ
	bne	.Lcheck_for_relaent
	lwz	r0,4(r12)       /* get RELASZ value in r0 */
	b	12f
.Lcheck_for_relaent:
	cmpwi	r8,RELAENT
	bne	12f
	lwz     r14,4(r12)      /* get RELAENT value in r14 */
12:	addi	r12,r12,8
	b	9b

	/* The relocation section contains a list of relocations.
	 * We now do the R_PPC_RELATIVE ones, which point to words
	 * which need to be initialized with addend + offset */
10:	/* skip relocation if we don't have both */
	cmpwi	r0,0
	beq	3f
	cmpwi	r9,0
	beq	3f
	cmpwi	r14,0
	beq	3f

	add	r9,r9,r11	/* Relocate RELA pointer */
	divwu   r0,r0,r14       /* RELASZ / RELAENT */
	mtctr	r0
2:	lbz	r0,4+3(r9)	/* ELF32_R_INFO(reloc->r_info) */
	cmpwi	r0,22		/* R_PPC_RELATIVE */
	bne	.Lnext
	lwz	r12,0(r9)	/* reloc->r_offset */
	lwz	r0,8(r9)	/* reloc->r_addend */
	add	r0,r0,r11
	stwx	r0,r11,r12
.Lnext:	add	r9,r9,r14
	bdnz	2b

	/* Do a cache flush for our text, in case the loader didn't */
3:	lwz	r9,p_start-p_base(r10)	/* note: these are relocated now */
	lwz	r8,p_etext-p_base(r10)
4:	dcbf	r0,r9
	icbi	r0,r9
	addi	r9,r9,0x20
	cmplw	cr0,r9,r8
	blt	4b
	sync
	isync

	/* Clear the BSS */
	lwz	r9,p_bss_start-p_base(r10)
	lwz	r8,p_end-p_base(r10)
	li	r0,0
5:	stw	r0,0(r9)
	addi	r9,r9,4
	cmplw	cr0,r9,r8
	blt	5b

	/* Possibly set up a custom stack */
	lwz	r8,p_pstack-p_base(r10)
	cmpwi	r8,0
	beq	6f
	lwz	r1,0(r8)
	li	r0,0
	stwu	r0,-16(r1)	/* establish a stack frame */
6:
#else /* __powerpc64__ */
	/* Save the prom pointer at p_prom. */
	std	r5,(p_prom-p_base)(r10)

	/* Set r2 to the TOC. */
	ld	r2,(p_toc-p_base)(r10)
	add	r2,r2,r10

	/* Grab the link address of the dynamic section in r11. */
	ld	r11,-32768(r2)
	cmpwi	r11,0
	beq	3f              /* if not linked -pie then no dynamic section */

	ld	r11,(p_dyn-p_base)(r10)
	add	r11,r11,r10
	ld	r9,(p_rela-p_base)(r10)
	add	r9,r9,r10

	li	r13,0
	li	r8,0
9:	ld	r12,0(r11)       /* get tag */
	cmpdi	r12,0
	beq	12f              /* end of list */
	cmpdi	r12,RELA
	bne	10f
	ld	r13,8(r11)       /* get RELA pointer in r13 */
	b	11f
10:	cmpwi   r12,RELASZ
	bne	.Lcheck_for_relaent
	lwz	r8,8(r11)	/* get RELASZ pointer in r8 */
	b	11f
.Lcheck_for_relaent:
	cmpwi	r12,RELAENT
	bne     11f
	lwz     r14,8(r11)      /* get RELAENT pointer in r14 */
11:	addi	r11,r11,16
	b	9b
12:
	cmpdi	r13,0            /* check we have both RELA, RELASZ, RELAENT*/
	cmpdi	cr1,r8,0
	beq	3f
	beq	cr1,3f
	cmpdi	r14,0
	beq	3f

	/* Calcuate the runtime offset. */
	subf	r13,r13,r9

	/* Run through the list of relocations and process the
	 * R_PPC64_RELATIVE ones. */
	divdu   r8,r8,r14       /* RELASZ / RELAENT */
	mtctr	r8
13:	ld	r0,8(r9)        /* ELF64_R_TYPE(reloc->r_info) */
	cmpdi	r0,22           /* R_PPC64_RELATIVE */
	bne	.Lnext
	ld	r12,0(r9)        /* reloc->r_offset */
	ld	r0,16(r9)       /* reloc->r_addend */
	add	r0,r0,r13
	stdx	r0,r13,r12
.Lnext:	add	r9,r9,r14
	bdnz	13b

	/* Do a cache flush for our text, in case the loader didn't */
3:	ld	r9,p_start-p_base(r10)	/* note: these are relocated now */
	ld	r8,p_etext-p_base(r10)
4:	dcbf	r0,r9
	icbi	r0,r9
	addi	r9,r9,0x20
	cmpld	cr0,r9,r8
	blt	4b
	sync
	isync

	/* Clear the BSS */
	ld	r9,p_bss_start-p_base(r10)
	ld	r8,p_end-p_base(r10)
	li	r0,0
5:	std	r0,0(r9)
	addi	r9,r9,8
	cmpld	cr0,r9,r8
	blt	5b

	/* Possibly set up a custom stack */
	ld	r8,p_pstack-p_base(r10)
	cmpdi	r8,0
	beq	6f
	ld	r1,0(r8)
	li	r0,0
	stdu	r0,-112(r1)	/* establish a stack frame */
6:
#endif  /* __powerpc64__ */
	/* Call platform_init() */
	bl	platform_init

	/* Call start */
	b	start

#ifdef __powerpc64__

#define PROM_FRAME_SIZE 512

.macro OP_REGS op, width, start, end, base, offset
	.Lreg=\start
	.rept (\end - \start + 1)
	\op	.Lreg,\offset+\width*.Lreg(\base)
	.Lreg=.Lreg+1
	.endr
.endm

#define SAVE_GPRS(start, end, base)	OP_REGS std, 8, start, end, base, 0
#define REST_GPRS(start, end, base)	OP_REGS ld, 8, start, end, base, 0
#define SAVE_GPR(n, base)		SAVE_GPRS(n, n, base)
#define REST_GPR(n, base)		REST_GPRS(n, n, base)

/* prom handles the jump into and return from firmware.  The prom args pointer
   is loaded in r3. */
.globl prom
prom:
	mflr	r0
	std	r0,16(r1)
	stdu	r1,-PROM_FRAME_SIZE(r1) /* Save SP and create stack space */

	SAVE_GPR(2, r1)
	SAVE_GPRS(13, 31, r1)
	mfcr    r10
	std     r10,8*32(r1)
	mfmsr   r10
	std     r10,8*33(r1)

	/* remove MSR_LE from msr but keep MSR_SF */
	mfmsr	r10
	rldicr	r10,r10,0,62
	mtsrr1	r10

	/* Load FW address, set LR to label 1, and jump to FW */
	bcl	20,31,0f
0:	mflr	r10
	addi	r11,r10,(1f-0b)
	mtlr	r11

	ld	r10,(p_prom-0b)(r10)
	mtsrr0	r10

	rfid

1:	/* Return from OF */
	FIXUP_ENDIAN

	/* Restore registers and return. */
	rldicl  r1,r1,0,32

	/* Restore the MSR (back to 64 bits) */
	ld      r10,8*(33)(r1)
	mtmsr	r10
	isync

	/* Restore other registers */
	REST_GPR(2, r1)
	REST_GPRS(13, 31, r1)
	ld      r10,8*32(r1)
	mtcr	r10

	addi    r1,r1,PROM_FRAME_SIZE
	ld      r0,16(r1)
	mtlr    r0
	blr
#endif