xref: /openbmc/linux/arch/powerpc/boot/crt0.S (revision f1575595) 
1/*
2 * Copyright (C) Paul Mackerras 1997.
3 *
4 * Adapted for 64 bit LE PowerPC by Andrew Tauferner
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 *
11 */
12
13#include "ppc_asm.h"
14
15RELA = 7
16RELACOUNT = 0x6ffffff9
17
18	.text
19	/* A procedure descriptor used when booting this as a COFF file.
20	 * When making COFF, this comes first in the link and we're
21	 * linked at 0x500000.
22	 */
23	.globl	_zimage_start_opd
24_zimage_start_opd:
25	.long	0x500000, 0, 0, 0
26
27#ifdef __powerpc64__
28.balign 8
29p_start:	.8byte	_start
30p_etext:	.8byte	_etext
31p_bss_start:	.8byte	__bss_start
32p_end:		.8byte	_end
33
34p_toc:		.8byte	__toc_start + 0x8000 - p_base
35p_dyn:		.8byte	__dynamic_start - p_base
36p_rela:		.8byte	__rela_dyn_start - p_base
37p_prom:		.8byte	0
38	.weak	_platform_stack_top
39p_pstack:	.8byte	_platform_stack_top
40#else
41p_start:	.long	_start
42p_etext:	.long	_etext
43p_bss_start:	.long	__bss_start
44p_end:		.long	_end
45
46	.weak	_platform_stack_top
47p_pstack:	.long	_platform_stack_top
48#endif
49
50	.weak	_zimage_start
51	.globl	_zimage_start
52_zimage_start:
53	.globl	_zimage_start_lib
54_zimage_start_lib:
55	/* Work out the offset between the address we were linked at
56	   and the address where we're running. */
57	bl	.+4
58p_base:	mflr	r10		/* r10 now points to runtime addr of p_base */
59#ifndef __powerpc64__
60	/* grab the link address of the dynamic section in r11 */
61	addis	r11,r10,(_GLOBAL_OFFSET_TABLE_-p_base)@ha
62	lwz	r11,(_GLOBAL_OFFSET_TABLE_-p_base)@l(r11)
63	cmpwi	r11,0
64	beq	3f		/* if not linked -pie */
65	/* get the runtime address of the dynamic section in r12 */
66	.weak	__dynamic_start
67	addis	r12,r10,(__dynamic_start-p_base)@ha
68	addi	r12,r12,(__dynamic_start-p_base)@l
69	subf	r11,r11,r12	/* runtime - linktime offset */
70
71	/* The dynamic section contains a series of tagged entries.
72	 * We need the RELA and RELACOUNT entries. */
73	li	r9,0
74	li	r0,0
759:	lwz	r8,0(r12)	/* get tag */
76	cmpwi	r8,0
77	beq	10f		/* end of list */
78	cmpwi	r8,RELA
79	bne	11f
80	lwz	r9,4(r12)	/* get RELA pointer in r9 */
81	b	12f
8211:	addis	r8,r8,(-RELACOUNT)@ha
83	cmpwi	r8,RELACOUNT@l
84	bne	12f
85	lwz	r0,4(r12)	/* get RELACOUNT value in r0 */
8612:	addi	r12,r12,8
87	b	9b
88
89	/* The relocation section contains a list of relocations.
90	 * We now do the R_PPC_RELATIVE ones, which point to words
91	 * which need to be initialized with addend + offset.
92	 * The R_PPC_RELATIVE ones come first and there are RELACOUNT
93	 * of them. */
9410:	/* skip relocation if we don't have both */
95	cmpwi	r0,0
96	beq	3f
97	cmpwi	r9,0
98	beq	3f
99
100	add	r9,r9,r11	/* Relocate RELA pointer */
101	mtctr	r0
1022:	lbz	r0,4+3(r9)	/* ELF32_R_INFO(reloc->r_info) */
103	cmpwi	r0,22		/* R_PPC_RELATIVE */
104	bne	3f
105	lwz	r12,0(r9)	/* reloc->r_offset */
106	lwz	r0,8(r9)	/* reloc->r_addend */
107	add	r0,r0,r11
108	stwx	r0,r11,r12
109	addi	r9,r9,12
110	bdnz	2b
111
112	/* Do a cache flush for our text, in case the loader didn't */
1133:	lwz	r9,p_start-p_base(r10)	/* note: these are relocated now */
114	lwz	r8,p_etext-p_base(r10)
1154:	dcbf	r0,r9
116	icbi	r0,r9
117	addi	r9,r9,0x20
118	cmplw	cr0,r9,r8
119	blt	4b
120	sync
121	isync
122
123	/* Clear the BSS */
124	lwz	r9,p_bss_start-p_base(r10)
125	lwz	r8,p_end-p_base(r10)
126	li	r0,0
1275:	stw	r0,0(r9)
128	addi	r9,r9,4
129	cmplw	cr0,r9,r8
130	blt	5b
131
132	/* Possibly set up a custom stack */
133	lwz	r8,p_pstack-p_base(r10)
134	cmpwi	r8,0
135	beq	6f
136	lwz	r1,0(r8)
137	li	r0,0
138	stwu	r0,-16(r1)	/* establish a stack frame */
1396:
140#else /* __powerpc64__ */
141	/* Save the prom pointer at p_prom. */
142	std	r5,(p_prom-p_base)(r10)
143
144	/* Set r2 to the TOC. */
145	ld	r2,(p_toc-p_base)(r10)
146	add	r2,r2,r10
147
148	/* Grab the link address of the dynamic section in r11. */
149	ld	r11,-32768(r2)
150	cmpwi	r11,0
151	beq	3f              /* if not linked -pie then no dynamic section */
152
153	ld	r11,(p_dyn-p_base)(r10)
154	add	r11,r11,r10
155	ld	r9,(p_rela-p_base)(r10)
156	add	r9,r9,r10
157
158	li	r13,0
159	li	r8,0
1609:	ld	r12,0(r11)       /* get tag */
161	cmpdi	r12,0
162	beq	12f              /* end of list */
163	cmpdi	r12,RELA
164	bne	10f
165	ld	r13,8(r11)       /* get RELA pointer in r13 */
166	b	11f
16710:	addis	r12,r12,(-RELACOUNT)@ha
168	cmpdi	r12,RELACOUNT@l
169	bne	11f
170	ld	r8,8(r11)       /* get RELACOUNT value in r8 */
17111:	addi	r11,r11,16
172	b	9b
17312:
174	cmpdi	r13,0            /* check we have both RELA and RELACOUNT */
175	cmpdi	cr1,r8,0
176	beq	3f
177	beq	cr1,3f
178
179	/* Calcuate the runtime offset. */
180	subf	r13,r13,r9
181
182	/* Run through the list of relocations and process the
183	 * R_PPC64_RELATIVE ones. */
184	mtctr	r8
18513:	ld	r0,8(r9)        /* ELF64_R_TYPE(reloc->r_info) */
186	cmpdi	r0,22           /* R_PPC64_RELATIVE */
187	bne	3f
188	ld	r12,0(r9)        /* reloc->r_offset */
189	ld	r0,16(r9)       /* reloc->r_addend */
190	add	r0,r0,r13
191	stdx	r0,r13,r12
192	addi	r9,r9,24
193	bdnz	13b
194
195	/* Do a cache flush for our text, in case the loader didn't */
1963:	ld	r9,p_start-p_base(r10)	/* note: these are relocated now */
197	ld	r8,p_etext-p_base(r10)
1984:	dcbf	r0,r9
199	icbi	r0,r9
200	addi	r9,r9,0x20
201	cmpld	cr0,r9,r8
202	blt	4b
203	sync
204	isync
205
206	/* Clear the BSS */
207	ld	r9,p_bss_start-p_base(r10)
208	ld	r8,p_end-p_base(r10)
209	li	r0,0
2105:	std	r0,0(r9)
211	addi	r9,r9,8
212	cmpld	cr0,r9,r8
213	blt	5b
214
215	/* Possibly set up a custom stack */
216	ld	r8,p_pstack-p_base(r10)
217	cmpdi	r8,0
218	beq	6f
219	ld	r1,0(r8)
220	li	r0,0
221	stdu	r0,-112(r1)	/* establish a stack frame */
2226:
223#endif  /* __powerpc64__ */
224	/* Call platform_init() */
225	bl	platform_init
226
227	/* Call start */
228	b	start
229
230#ifdef __powerpc64__
231
232#define PROM_FRAME_SIZE 512
233#define SAVE_GPR(n, base)       std     n,8*(n)(base)
234#define REST_GPR(n, base)       ld      n,8*(n)(base)
235#define SAVE_2GPRS(n, base)     SAVE_GPR(n, base); SAVE_GPR(n+1, base)
236#define SAVE_4GPRS(n, base)     SAVE_2GPRS(n, base); SAVE_2GPRS(n+2, base)
237#define SAVE_8GPRS(n, base)     SAVE_4GPRS(n, base); SAVE_4GPRS(n+4, base)
238#define SAVE_10GPRS(n, base)    SAVE_8GPRS(n, base); SAVE_2GPRS(n+8, base)
239#define REST_2GPRS(n, base)     REST_GPR(n, base); REST_GPR(n+1, base)
240#define REST_4GPRS(n, base)     REST_2GPRS(n, base); REST_2GPRS(n+2, base)
241#define REST_8GPRS(n, base)     REST_4GPRS(n, base); REST_4GPRS(n+4, base)
242#define REST_10GPRS(n, base)    REST_8GPRS(n, base); REST_2GPRS(n+8, base)
243
244/* prom handles the jump into and return from firmware.  The prom args pointer
245   is loaded in r3. */
246.globl prom
247prom:
248	mflr	r0
249	std	r0,16(r1)
250	stdu	r1,-PROM_FRAME_SIZE(r1) /* Save SP and create stack space */
251
252	SAVE_GPR(2, r1)
253	SAVE_GPR(13, r1)
254	SAVE_8GPRS(14, r1)
255	SAVE_10GPRS(22, r1)
256	mfcr    r10
257	std     r10,8*32(r1)
258	mfmsr   r10
259	std     r10,8*33(r1)
260
261	/* remove MSR_LE from msr but keep MSR_SF */
262	mfmsr	r10
263	rldicr	r10,r10,0,62
264	mtsrr1	r10
265
266	/* Load FW address, set LR to label 1, and jump to FW */
267	bl	0f
2680:	mflr	r10
269	addi	r11,r10,(1f-0b)
270	mtlr	r11
271
272	ld	r10,(p_prom-0b)(r10)
273	mtsrr0	r10
274
275	rfid
276
2771:	/* Return from OF */
278	FIXUP_ENDIAN
279
280	/* Restore registers and return. */
281	rldicl  r1,r1,0,32
282
283	/* Restore the MSR (back to 64 bits) */
284	ld      r10,8*(33)(r1)
285	mtmsr	r10
286	isync
287
288	/* Restore other registers */
289	REST_GPR(2, r1)
290	REST_GPR(13, r1)
291	REST_8GPRS(14, r1)
292	REST_10GPRS(22, r1)
293	ld      r10,8*32(r1)
294	mtcr	r10
295
296	addi    r1,r1,PROM_FRAME_SIZE
297	ld      r0,16(r1)
298	mtlr    r0
299	blr
300#endif
301