1/*
2 * Code to process dynamic relocations for PPC32.
3 *
4 * Copyrights (C) IBM Corporation, 2011.
5 *	Author: Suzuki Poulose <suzuki@in.ibm.com>
6 *
7 *  - Based on ppc64 code - reloc_64.S
8 *
9 *  This program is free software; you can redistribute it and/or
10 *  modify it under the terms of the GNU General Public License
11 *  as published by the Free Software Foundation; either version
12 *  2 of the License, or (at your option) any later version.
13 */
14
15#include <asm/ppc_asm.h>
16
17/* Dynamic section table entry tags */
18DT_RELA = 7			/* Tag for Elf32_Rela section */
19DT_RELASZ = 8			/* Size of the Rela relocs */
20DT_RELAENT = 9			/* Size of one Rela reloc entry */
21
22STN_UNDEF = 0			/* Undefined symbol index */
23STB_LOCAL = 0			/* Local binding for the symbol */
24
25R_PPC_ADDR16_LO = 4		/* Lower half of (S+A) */
26R_PPC_ADDR16_HI = 5		/* Upper half of (S+A) */
27R_PPC_ADDR16_HA = 6		/* High Adjusted (S+A) */
28R_PPC_RELATIVE = 22
29
30/*
31 * r3 = desired final address
32 */
33
34_GLOBAL(relocate)
35
36	mflr	r0		/* Save our LR */
37	bl	0f		/* Find our current runtime address */
380:	mflr	r12		/* Make it accessible */
39	mtlr	r0
40
41	lwz	r11, (p_dyn - 0b)(r12)
42	add	r11, r11, r12	/* runtime address of .dynamic section */
43	lwz	r9, (p_rela - 0b)(r12)
44	add	r9, r9, r12	/* runtime address of .rela.dyn section */
45	lwz	r10, (p_st - 0b)(r12)
46	add	r10, r10, r12	/* runtime address of _stext section */
47	lwz	r13, (p_sym - 0b)(r12)
48	add	r13, r13, r12	/* runtime address of .dynsym section */
49
50	/*
51	 * Scan the dynamic section for RELA, RELASZ entries
52	 */
53	li	r6, 0
54	li	r7, 0
55	li	r8, 0
561:	lwz	r5, 0(r11)	/* ELF_Dyn.d_tag */
57	cmpwi	r5, 0		/* End of ELF_Dyn[] */
58	beq	eodyn
59	cmpwi	r5, DT_RELA
60	bne	relasz
61	lwz	r7, 4(r11)	/* r7 = rela.link */
62	b	skip
63relasz:
64	cmpwi	r5, DT_RELASZ
65	bne	relaent
66	lwz	r8, 4(r11)	/* r8 = Total Rela relocs size */
67	b	skip
68relaent:
69	cmpwi	r5, DT_RELAENT
70	bne	skip
71	lwz	r6, 4(r11)	/* r6 = Size of one Rela reloc */
72skip:
73	addi	r11, r11, 8
74	b	1b
75eodyn:				/* End of Dyn Table scan */
76
77	/* Check if we have found all the entries */
78	cmpwi	r7, 0
79	beq	done
80	cmpwi	r8, 0
81	beq	done
82	cmpwi	r6, 0
83	beq	done
84
85
86	/*
87	 * Work out the current offset from the link time address of .rela
88	 * section.
89	 *  cur_offset[r7] = rela.run[r9] - rela.link [r7]
90	 *  _stext.link[r12] = _stext.run[r10] - cur_offset[r7]
91	 *  final_offset[r3] = _stext.final[r3] - _stext.link[r12]
92	 */
93	subf	r7, r7, r9	/* cur_offset */
94	subf	r12, r7, r10
95	subf	r3, r12, r3	/* final_offset */
96
97	subf	r8, r6, r8	/* relaz -= relaent */
98	/*
99	 * Scan through the .rela table and process each entry
100	 * r9	- points to the current .rela table entry
101	 * r13	- points to the symbol table
102	 */
103
104	/*
105	 * Check if we have a relocation based on symbol
106	 * r5 will hold the value of the symbol.
107	 */
108applyrela:
109	lwz	r4, 4(r9)		/* r4 = rela.r_info */
110	srwi	r5, r4, 8		/* ELF32_R_SYM(r_info) */
111	cmpwi	r5, STN_UNDEF	/* sym == STN_UNDEF ? */
112	beq	get_type	/* value = 0 */
113	/* Find the value of the symbol at index(r5) */
114	slwi	r5, r5, 4		/* r5 = r5 * sizeof(Elf32_Sym) */
115	add	r12, r13, r5	/* r12 = &__dyn_sym[Index] */
116
117	/*
118	 * GNU ld has a bug, where dynamic relocs based on
119	 * STB_LOCAL symbols, the value should be assumed
120	 * to be zero. - Alan Modra
121	 */
122	/* XXX: Do we need to check if we are using GNU ld ? */
123	lbz	r5, 12(r12)	/* r5 = dyn_sym[Index].st_info */
124	extrwi	r5, r5, 4, 24	/* r5 = ELF32_ST_BIND(r5) */
125	cmpwi	r5, STB_LOCAL	/* st_value = 0, ld bug */
126	beq	get_type	/* We have r5 = 0 */
127	lwz	r5, 4(r12)	/* r5 = __dyn_sym[Index].st_value */
128
129get_type:
130	/* Load the relocation type to r4 */
131	extrwi	r4, r4, 8, 24	/* r4 = ELF32_R_TYPE(r_info) = ((char*)r4)[3] */
132
133	/* R_PPC_RELATIVE */
134	cmpwi	r4, R_PPC_RELATIVE
135	bne	hi16
136	lwz	r4, 0(r9)	/* r_offset */
137	lwz	r0, 8(r9)	/* r_addend */
138	add	r0, r0, r3	/* final addend */
139	stwx	r0, r4, r7	/* memory[r4+r7]) = (u32)r0 */
140	b	nxtrela		/* continue */
141
142	/* R_PPC_ADDR16_HI */
143hi16:
144	cmpwi	r4, R_PPC_ADDR16_HI
145	bne	ha16
146	lwz	r4, 0(r9)	/* r_offset */
147	lwz	r0, 8(r9)	/* r_addend */
148	add	r0, r0, r3
149	add	r0, r0, r5	/* r0 = (S+A+Offset) */
150	extrwi	r0, r0, 16, 0	/* r0 = (r0 >> 16) */
151	b	store_half
152
153	/* R_PPC_ADDR16_HA */
154ha16:
155	cmpwi	r4, R_PPC_ADDR16_HA
156	bne	lo16
157	lwz	r4, 0(r9)	/* r_offset */
158	lwz	r0, 8(r9)	/* r_addend */
159	add	r0, r0, r3
160	add	r0, r0, r5	/* r0 = (S+A+Offset) */
161	extrwi	r5, r0, 1, 16	/* Extract bit 16 */
162	extrwi	r0, r0, 16, 0	/* r0 = (r0 >> 16) */
163	add	r0, r0, r5	/* Add it to r0 */
164	b	store_half
165
166	/* R_PPC_ADDR16_LO */
167lo16:
168	cmpwi	r4, R_PPC_ADDR16_LO
169	bne	unknown_type
170	lwz	r4, 0(r9)	/* r_offset */
171	lwz	r0, 8(r9)	/* r_addend */
172	add	r0, r0, r3
173	add	r0, r0, r5	/* r0 = (S+A+Offset) */
174	extrwi	r0, r0, 16, 16	/* r0 &= 0xffff */
175	/* Fall through to */
176
177	/* Store half word */
178store_half:
179	sthx	r0, r4, r7	/* memory[r4+r7] = (u16)r0 */
180
181nxtrela:
182	/*
183	 * We have to flush the modified instructions to the
184	 * main storage from the d-cache. And also, invalidate the
185	 * cached instructions in i-cache which has been modified.
186	 *
187	 * We delay the sync / isync operation till the end, since
188	 * we won't be executing the modified instructions until
189	 * we return from here.
190	 */
191	dcbst	r4,r7
192	sync			/* Ensure the data is flushed before icbi */
193	icbi	r4,r7
194unknown_type:
195	cmpwi	r8, 0		/* relasz = 0 ? */
196	ble	done
197	add	r9, r9, r6	/* move to next entry in the .rela table */
198	subf	r8, r6, r8	/* relasz -= relaent */
199	b	applyrela
200
201done:
202	sync			/* Wait for the flush to finish */
203	isync			/* Discard prefetched instructions */
204	blr
205
206p_dyn:		.long	__dynamic_start - 0b
207p_rela:		.long	__rela_dyn_start - 0b
208p_sym:		.long	__dynamic_symtab - 0b
209p_st:		.long	_stext - 0b
210