aboutsummaryrefslogtreecommitdiff
path: root/arch/powerpc/kernel/reloc_32.S
blob: f366fedb08723036187657446bb1ac15d570d920 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
/*
 * Code to process dynamic relocations for PPC32.
 *
 * Copyrights (C) IBM Corporation, 2011.
 *	Author: Suzuki Poulose <suzuki@in.ibm.com>
 *
 *  - Based on ppc64 code - reloc_64.S
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version
 *  2 of the License, or (at your option) any later version.
 */

#include <asm/ppc_asm.h>

/* Dynamic section table entry tags */
DT_RELA = 7			/* Tag for Elf32_Rela section */
DT_RELASZ = 8			/* Size of the Rela relocs */
DT_RELAENT = 9			/* Size of one Rela reloc entry */

STN_UNDEF = 0			/* Undefined symbol index */
STB_LOCAL = 0			/* Local binding for the symbol */

R_PPC_ADDR16_LO = 4		/* Lower half of (S+A) */
R_PPC_ADDR16_HI = 5		/* Upper half of (S+A) */
R_PPC_ADDR16_HA = 6		/* High Adjusted (S+A) */
R_PPC_RELATIVE = 22

/*
 * r3 = desired final address
 */

_GLOBAL(relocate)

	mflr	r0		/* Save our LR */
	bl	0f		/* Find our current runtime address */
0:	mflr	r12		/* Make it accessible */
	mtlr	r0

	lwz	r11, (p_dyn - 0b)(r12)
	add	r11, r11, r12	/* runtime address of .dynamic section */
	lwz	r9, (p_rela - 0b)(r12)
	add	r9, r9, r12	/* runtime address of .rela.dyn section */
	lwz	r10, (p_st - 0b)(r12)
	add	r10, r10, r12	/* runtime address of _stext section */
	lwz	r13, (p_sym - 0b)(r12)
	add	r13, r13, r12	/* runtime address of .dynsym section */

	/*
	 * Scan the dynamic section for RELA, RELASZ entries
	 */
	li	r6, 0
	li	r7, 0
	li	r8, 0
1:	lwz	r5, 0(r11)	/* ELF_Dyn.d_tag */
	cmpwi	r5, 0		/* End of ELF_Dyn[] */
	beq	eodyn
	cmpwi	r5, DT_RELA
	bne	relasz
	lwz	r7, 4(r11)	/* r7 = rela.link */
	b	skip
relasz:
	cmpwi	r5, DT_RELASZ
	bne	relaent
	lwz	r8, 4(r11)	/* r8 = Total Rela relocs size */
	b	skip
relaent:
	cmpwi	r5, DT_RELAENT
	bne	skip
	lwz	r6, 4(r11)	/* r6 = Size of one Rela reloc */
skip:
	addi	r11, r11, 8
	b	1b
eodyn:				/* End of Dyn Table scan */

	/* Check if we have found all the entries */
	cmpwi	r7, 0
	beq	done
	cmpwi	r8, 0
	beq	done
	cmpwi	r6, 0
	beq	done


	/*
	 * Work out the current offset from the link time address of .rela
	 * section.
	 *  cur_offset[r7] = rela.run[r9] - rela.link [r7]
	 *  _stext.link[r12] = _stext.run[r10] - cur_offset[r7]
	 *  final_offset[r3] = _stext.final[r3] - _stext.link[r12]
	 */
	subf	r7, r7, r9	/* cur_offset */
	subf	r12, r7, r10
	subf	r3, r12, r3	/* final_offset */

	subf	r8, r6, r8	/* relaz -= relaent */
	/*
	 * Scan through the .rela table and process each entry
	 * r9	- points to the current .rela table entry
	 * r13	- points to the symbol table
	 */

	/*
	 * Check if we have a relocation based on symbol
	 * r5 will hold the value of the symbol.
	 */
applyrela:
	lwz	r4, 4(r9)		/* r4 = rela.r_info */
	srwi	r5, r4, 8		/* ELF32_R_SYM(r_info) */
	cmpwi	r5, STN_UNDEF	/* sym == STN_UNDEF ? */
	beq	get_type	/* value = 0 */
	/* Find the value of the symbol at index(r5) */
	slwi	r5, r5, 4		/* r5 = r5 * sizeof(Elf32_Sym) */
	add	r12, r13, r5	/* r12 = &__dyn_sym[Index] */

	/*
	 * GNU ld has a bug, where dynamic relocs based on
	 * STB_LOCAL symbols, the value should be assumed
	 * to be zero. - Alan Modra
	 */
	/* XXX: Do we need to check if we are using GNU ld ? */
	lbz	r5, 12(r12)	/* r5 = dyn_sym[Index].st_info */
	extrwi	r5, r5, 4, 24	/* r5 = ELF32_ST_BIND(r5) */
	cmpwi	r5, STB_LOCAL	/* st_value = 0, ld bug */
	beq	get_type	/* We have r5 = 0 */
	lwz	r5, 4(r12)	/* r5 = __dyn_sym[Index].st_value */

get_type:
	/* Load the relocation type to r4 */
	extrwi	r4, r4, 8, 24	/* r4 = ELF32_R_TYPE(r_info) = ((char*)r4)[3] */

	/* R_PPC_RELATIVE */
	cmpwi	r4, R_PPC_RELATIVE
	bne	hi16
	lwz	r4, 0(r9)	/* r_offset */
	lwz	r0, 8(r9)	/* r_addend */
	add	r0, r0, r3	/* final addend */
	stwx	r0, r4, r7	/* memory[r4+r7]) = (u32)r0 */
	b	nxtrela		/* continue */

	/* R_PPC_ADDR16_HI */
hi16:
	cmpwi	r4, R_PPC_ADDR16_HI
	bne	ha16
	lwz	r4, 0(r9)	/* r_offset */
	lwz	r0, 8(r9)	/* r_addend */
	add	r0, r0, r3
	add	r0, r0, r5	/* r0 = (S+A+Offset) */
	extrwi	r0, r0, 16, 0	/* r0 = (r0 >> 16) */
	b	store_half

	/* R_PPC_ADDR16_HA */
ha16:
	cmpwi	r4, R_PPC_ADDR16_HA
	bne	lo16
	lwz	r4, 0(r9)	/* r_offset */
	lwz	r0, 8(r9)	/* r_addend */
	add	r0, r0, r3
	add	r0, r0, r5	/* r0 = (S+A+Offset) */
	extrwi	r5, r0, 1, 16	/* Extract bit 16 */
	extrwi	r0, r0, 16, 0	/* r0 = (r0 >> 16) */
	add	r0, r0, r5	/* Add it to r0 */
	b	store_half

	/* R_PPC_ADDR16_LO */
lo16:
	cmpwi	r4, R_PPC_ADDR16_LO
	bne	unknown_type
	lwz	r4, 0(r9)	/* r_offset */
	lwz	r0, 8(r9)	/* r_addend */
	add	r0, r0, r3
	add	r0, r0, r5	/* r0 = (S+A+Offset) */
	extrwi	r0, r0, 16, 16	/* r0 &= 0xffff */
	/* Fall through to */

	/* Store half word */
store_half:
	sthx	r0, r4, r7	/* memory[r4+r7] = (u16)r0 */

nxtrela:
	/*
	 * We have to flush the modified instructions to the
	 * main storage from the d-cache. And also, invalidate the
	 * cached instructions in i-cache which has been modified.
	 *
	 * We delay the sync / isync operation till the end, since
	 * we won't be executing the modified instructions until
	 * we return from here.
	 */
	dcbst	r4,r7
	sync			/* Ensure the data is flushed before icbi */
	icbi	r4,r7
unknown_type:
	cmpwi	r8, 0		/* relasz = 0 ? */
	ble	done
	add	r9, r9, r6	/* move to next entry in the .rela table */
	subf	r8, r6, r8	/* relasz -= relaent */
	b	applyrela

done:
	sync			/* Wait for the flush to finish */
	isync			/* Discard prefetched instructions */
	blr

p_dyn:		.long	__dynamic_start - 0b
p_rela:		.long	__rela_dyn_start - 0b
p_sym:		.long	__dynamic_symtab - 0b
p_st:		.long	_stext - 0b