xref: /openbmc/linux/arch/powerpc/boot/crt0.S (revision e3d786a3) 
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	.globl	_zimage_start
51	/* Clang appears to require the .weak directive to be after the symbol
52	 * is defined. See https://bugs.llvm.org/show_bug.cgi?id=38921  */
53	.weak	_zimage_start
54_zimage_start:
55	.globl	_zimage_start_lib
56_zimage_start_lib:
57	/* Work out the offset between the address we were linked at
58	   and the address where we're running. */
59	bl	.+4
60p_base:	mflr	r10		/* r10 now points to runtime addr of p_base */
61#ifndef __powerpc64__
62	/* grab the link address of the dynamic section in r11 */
63	addis	r11,r10,(_GLOBAL_OFFSET_TABLE_-p_base)@ha
64	lwz	r11,(_GLOBAL_OFFSET_TABLE_-p_base)@l(r11)
65	cmpwi	r11,0
66	beq	3f		/* if not linked -pie */
67	/* get the runtime address of the dynamic section in r12 */
68	.weak	__dynamic_start
69	addis	r12,r10,(__dynamic_start-p_base)@ha
70	addi	r12,r12,(__dynamic_start-p_base)@l
71	subf	r11,r11,r12	/* runtime - linktime offset */
72
73	/* The dynamic section contains a series of tagged entries.
74	 * We need the RELA and RELACOUNT entries. */
75	li	r9,0
76	li	r0,0
779:	lwz	r8,0(r12)	/* get tag */
78	cmpwi	r8,0
79	beq	10f		/* end of list */
80	cmpwi	r8,RELA
81	bne	11f
82	lwz	r9,4(r12)	/* get RELA pointer in r9 */
83	b	12f
8411:	addis	r8,r8,(-RELACOUNT)@ha
85	cmpwi	r8,RELACOUNT@l
86	bne	12f
87	lwz	r0,4(r12)	/* get RELACOUNT value in r0 */
8812:	addi	r12,r12,8
89	b	9b
90
91	/* The relocation section contains a list of relocations.
92	 * We now do the R_PPC_RELATIVE ones, which point to words
93	 * which need to be initialized with addend + offset.
94	 * The R_PPC_RELATIVE ones come first and there are RELACOUNT
95	 * of them. */
9610:	/* skip relocation if we don't have both */
97	cmpwi	r0,0
98	beq	3f
99	cmpwi	r9,0
100	beq	3f
101
102	add	r9,r9,r11	/* Relocate RELA pointer */
103	mtctr	r0
1042:	lbz	r0,4+3(r9)	/* ELF32_R_INFO(reloc->r_info) */
105	cmpwi	r0,22		/* R_PPC_RELATIVE */
106	bne	3f
107	lwz	r12,0(r9)	/* reloc->r_offset */
108	lwz	r0,8(r9)	/* reloc->r_addend */
109	add	r0,r0,r11
110	stwx	r0,r11,r12
111	addi	r9,r9,12
112	bdnz	2b
113
114	/* Do a cache flush for our text, in case the loader didn't */
1153:	lwz	r9,p_start-p_base(r10)	/* note: these are relocated now */
116	lwz	r8,p_etext-p_base(r10)
1174:	dcbf	r0,r9
118	icbi	r0,r9
119	addi	r9,r9,0x20
120	cmplw	cr0,r9,r8
121	blt	4b
122	sync
123	isync
124
125	/* Clear the BSS */
126	lwz	r9,p_bss_start-p_base(r10)
127	lwz	r8,p_end-p_base(r10)
128	li	r0,0
1295:	stw	r0,0(r9)
130	addi	r9,r9,4
131	cmplw	cr0,r9,r8
132	blt	5b
133
134	/* Possibly set up a custom stack */
135	lwz	r8,p_pstack-p_base(r10)
136	cmpwi	r8,0
137	beq	6f
138	lwz	r1,0(r8)
139	li	r0,0
140	stwu	r0,-16(r1)	/* establish a stack frame */
1416:
142#else /* __powerpc64__ */
143	/* Save the prom pointer at p_prom. */
144	std	r5,(p_prom-p_base)(r10)
145
146	/* Set r2 to the TOC. */
147	ld	r2,(p_toc-p_base)(r10)
148	add	r2,r2,r10
149
150	/* Grab the link address of the dynamic section in r11. */
151	ld	r11,-32768(r2)
152	cmpwi	r11,0
153	beq	3f              /* if not linked -pie then no dynamic section */
154
155	ld	r11,(p_dyn-p_base)(r10)
156	add	r11,r11,r10
157	ld	r9,(p_rela-p_base)(r10)
158	add	r9,r9,r10
159
160	li	r13,0
161	li	r8,0
1629:	ld	r12,0(r11)       /* get tag */
163	cmpdi	r12,0
164	beq	12f              /* end of list */
165	cmpdi	r12,RELA
166	bne	10f
167	ld	r13,8(r11)       /* get RELA pointer in r13 */
168	b	11f
16910:	addis	r12,r12,(-RELACOUNT)@ha
170	cmpdi	r12,RELACOUNT@l
171	bne	11f
172	ld	r8,8(r11)       /* get RELACOUNT value in r8 */
17311:	addi	r11,r11,16
174	b	9b
17512:
176	cmpdi	r13,0            /* check we have both RELA and RELACOUNT */
177	cmpdi	cr1,r8,0
178	beq	3f
179	beq	cr1,3f
180
181	/* Calcuate the runtime offset. */
182	subf	r13,r13,r9
183
184	/* Run through the list of relocations and process the
185	 * R_PPC64_RELATIVE ones. */
186	mtctr	r8
18713:	ld	r0,8(r9)        /* ELF64_R_TYPE(reloc->r_info) */
188	cmpdi	r0,22           /* R_PPC64_RELATIVE */
189	bne	3f
190	ld	r12,0(r9)        /* reloc->r_offset */
191	ld	r0,16(r9)       /* reloc->r_addend */
192	add	r0,r0,r13
193	stdx	r0,r13,r12
194	addi	r9,r9,24
195	bdnz	13b
196
197	/* Do a cache flush for our text, in case the loader didn't */
1983:	ld	r9,p_start-p_base(r10)	/* note: these are relocated now */
199	ld	r8,p_etext-p_base(r10)
2004:	dcbf	r0,r9
201	icbi	r0,r9
202	addi	r9,r9,0x20
203	cmpld	cr0,r9,r8
204	blt	4b
205	sync
206	isync
207
208	/* Clear the BSS */
209	ld	r9,p_bss_start-p_base(r10)
210	ld	r8,p_end-p_base(r10)
211	li	r0,0
2125:	std	r0,0(r9)
213	addi	r9,r9,8
214	cmpld	cr0,r9,r8
215	blt	5b
216
217	/* Possibly set up a custom stack */
218	ld	r8,p_pstack-p_base(r10)
219	cmpdi	r8,0
220	beq	6f
221	ld	r1,0(r8)
222	li	r0,0
223	stdu	r0,-112(r1)	/* establish a stack frame */
2246:
225#endif  /* __powerpc64__ */
226	/* Call platform_init() */
227	bl	platform_init
228
229	/* Call start */
230	b	start
231
232#ifdef __powerpc64__
233
234#define PROM_FRAME_SIZE 512
235#define SAVE_GPR(n, base)       std     n,8*(n)(base)
236#define REST_GPR(n, base)       ld      n,8*(n)(base)
237#define SAVE_2GPRS(n, base)     SAVE_GPR(n, base); SAVE_GPR(n+1, base)
238#define SAVE_4GPRS(n, base)     SAVE_2GPRS(n, base); SAVE_2GPRS(n+2, base)
239#define SAVE_8GPRS(n, base)     SAVE_4GPRS(n, base); SAVE_4GPRS(n+4, base)
240#define SAVE_10GPRS(n, base)    SAVE_8GPRS(n, base); SAVE_2GPRS(n+8, base)
241#define REST_2GPRS(n, base)     REST_GPR(n, base); REST_GPR(n+1, base)
242#define REST_4GPRS(n, base)     REST_2GPRS(n, base); REST_2GPRS(n+2, base)
243#define REST_8GPRS(n, base)     REST_4GPRS(n, base); REST_4GPRS(n+4, base)
244#define REST_10GPRS(n, base)    REST_8GPRS(n, base); REST_2GPRS(n+8, base)
245
246/* prom handles the jump into and return from firmware.  The prom args pointer
247   is loaded in r3. */
248.globl prom
249prom:
250	mflr	r0
251	std	r0,16(r1)
252	stdu	r1,-PROM_FRAME_SIZE(r1) /* Save SP and create stack space */
253
254	SAVE_GPR(2, r1)
255	SAVE_GPR(13, r1)
256	SAVE_8GPRS(14, r1)
257	SAVE_10GPRS(22, r1)
258	mfcr    r10
259	std     r10,8*32(r1)
260	mfmsr   r10
261	std     r10,8*33(r1)
262
263	/* remove MSR_LE from msr but keep MSR_SF */
264	mfmsr	r10
265	rldicr	r10,r10,0,62
266	mtsrr1	r10
267
268	/* Load FW address, set LR to label 1, and jump to FW */
269	bl	0f
2700:	mflr	r10
271	addi	r11,r10,(1f-0b)
272	mtlr	r11
273
274	ld	r10,(p_prom-0b)(r10)
275	mtsrr0	r10
276
277	rfid
278
2791:	/* Return from OF */
280	FIXUP_ENDIAN
281
282	/* Restore registers and return. */
283	rldicl  r1,r1,0,32
284
285	/* Restore the MSR (back to 64 bits) */
286	ld      r10,8*(33)(r1)
287	mtmsr	r10
288	isync
289
290	/* Restore other registers */
291	REST_GPR(2, r1)
292	REST_GPR(13, r1)
293	REST_8GPRS(14, r1)
294	REST_10GPRS(22, r1)
295	ld      r10,8*32(r1)
296	mtcr	r10
297
298	addi    r1,r1,PROM_FRAME_SIZE
299	ld      r0,16(r1)
300	mtlr    r0
301	blr
302#endif
303