xref: /openbmc/linux/arch/powerpc/kernel/reloc_32.S (revision 762f99f4f3cb41a775b5157dd761217beba65873)
1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /*
3  * Code to process dynamic relocations for PPC32.
4  *
5  * Copyrights (C) IBM Corporation, 2011.
6  *	Author: Suzuki Poulose <suzuki@in.ibm.com>
7  *
8  *  - Based on ppc64 code - reloc_64.S
9  */
10 
11 #include <asm/ppc_asm.h>
12 
13 /* Dynamic section table entry tags */
14 DT_RELA = 7			/* Tag for Elf32_Rela section */
15 DT_RELASZ = 8			/* Size of the Rela relocs */
16 DT_RELAENT = 9			/* Size of one Rela reloc entry */
17 
18 STN_UNDEF = 0			/* Undefined symbol index */
19 STB_LOCAL = 0			/* Local binding for the symbol */
20 
21 R_PPC_ADDR16_LO = 4		/* Lower half of (S+A) */
22 R_PPC_ADDR16_HI = 5		/* Upper half of (S+A) */
23 R_PPC_ADDR16_HA = 6		/* High Adjusted (S+A) */
24 R_PPC_RELATIVE = 22
25 
26 /*
27  * r3 = desired final address
28  */
29 
30 _GLOBAL(relocate)
31 
32 	mflr	r0		/* Save our LR */
33 	bcl	20,31,$+4	/* Find our current runtime address */
34 0:	mflr	r12		/* Make it accessible */
35 	mtlr	r0
36 
37 	lwz	r11, (p_dyn - 0b)(r12)
38 	add	r11, r11, r12	/* runtime address of .dynamic section */
39 	lwz	r9, (p_rela - 0b)(r12)
40 	add	r9, r9, r12	/* runtime address of .rela.dyn section */
41 	lwz	r10, (p_st - 0b)(r12)
42 	add	r10, r10, r12	/* runtime address of _stext section */
43 	lwz	r13, (p_sym - 0b)(r12)
44 	add	r13, r13, r12	/* runtime address of .dynsym section */
45 
46 	/*
47 	 * Scan the dynamic section for RELA, RELASZ entries
48 	 */
49 	li	r6, 0
50 	li	r7, 0
51 	li	r8, 0
52 1:	lwz	r5, 0(r11)	/* ELF_Dyn.d_tag */
53 	cmpwi	r5, 0		/* End of ELF_Dyn[] */
54 	beq	eodyn
55 	cmpwi	r5, DT_RELA
56 	bne	relasz
57 	lwz	r7, 4(r11)	/* r7 = rela.link */
58 	b	skip
59 relasz:
60 	cmpwi	r5, DT_RELASZ
61 	bne	relaent
62 	lwz	r8, 4(r11)	/* r8 = Total Rela relocs size */
63 	b	skip
64 relaent:
65 	cmpwi	r5, DT_RELAENT
66 	bne	skip
67 	lwz	r6, 4(r11)	/* r6 = Size of one Rela reloc */
68 skip:
69 	addi	r11, r11, 8
70 	b	1b
71 eodyn:				/* End of Dyn Table scan */
72 
73 	/* Check if we have found all the entries */
74 	cmpwi	r7, 0
75 	beq	done
76 	cmpwi	r8, 0
77 	beq	done
78 	cmpwi	r6, 0
79 	beq	done
80 
81 
82 	/*
83 	 * Work out the current offset from the link time address of .rela
84 	 * section.
85 	 *  cur_offset[r7] = rela.run[r9] - rela.link [r7]
86 	 *  _stext.link[r12] = _stext.run[r10] - cur_offset[r7]
87 	 *  final_offset[r3] = _stext.final[r3] - _stext.link[r12]
88 	 */
89 	subf	r7, r7, r9	/* cur_offset */
90 	subf	r12, r7, r10
91 	subf	r3, r12, r3	/* final_offset */
92 
93 	subf	r8, r6, r8	/* relaz -= relaent */
94 	/*
95 	 * Scan through the .rela table and process each entry
96 	 * r9	- points to the current .rela table entry
97 	 * r13	- points to the symbol table
98 	 */
99 
100 	/*
101 	 * Check if we have a relocation based on symbol
102 	 * r5 will hold the value of the symbol.
103 	 */
104 applyrela:
105 	lwz	r4, 4(r9)		/* r4 = rela.r_info */
106 	srwi	r5, r4, 8		/* ELF32_R_SYM(r_info) */
107 	cmpwi	r5, STN_UNDEF	/* sym == STN_UNDEF ? */
108 	beq	get_type	/* value = 0 */
109 	/* Find the value of the symbol at index(r5) */
110 	slwi	r5, r5, 4		/* r5 = r5 * sizeof(Elf32_Sym) */
111 	add	r12, r13, r5	/* r12 = &__dyn_sym[Index] */
112 
113 	/*
114 	 * GNU ld has a bug, where dynamic relocs based on
115 	 * STB_LOCAL symbols, the value should be assumed
116 	 * to be zero. - Alan Modra
117 	 */
118 	/* XXX: Do we need to check if we are using GNU ld ? */
119 	lbz	r5, 12(r12)	/* r5 = dyn_sym[Index].st_info */
120 	extrwi	r5, r5, 4, 24	/* r5 = ELF32_ST_BIND(r5) */
121 	cmpwi	r5, STB_LOCAL	/* st_value = 0, ld bug */
122 	beq	get_type	/* We have r5 = 0 */
123 	lwz	r5, 4(r12)	/* r5 = __dyn_sym[Index].st_value */
124 
125 get_type:
126 	/* Load the relocation type to r4 */
127 	extrwi	r4, r4, 8, 24	/* r4 = ELF32_R_TYPE(r_info) = ((char*)r4)[3] */
128 
129 	/* R_PPC_RELATIVE */
130 	cmpwi	r4, R_PPC_RELATIVE
131 	bne	hi16
132 	lwz	r4, 0(r9)	/* r_offset */
133 	lwz	r0, 8(r9)	/* r_addend */
134 	add	r0, r0, r3	/* final addend */
135 	stwx	r0, r4, r7	/* memory[r4+r7]) = (u32)r0 */
136 	b	nxtrela		/* continue */
137 
138 	/* R_PPC_ADDR16_HI */
139 hi16:
140 	cmpwi	r4, R_PPC_ADDR16_HI
141 	bne	ha16
142 	lwz	r4, 0(r9)	/* r_offset */
143 	lwz	r0, 8(r9)	/* r_addend */
144 	add	r0, r0, r3
145 	add	r0, r0, r5	/* r0 = (S+A+Offset) */
146 	extrwi	r0, r0, 16, 0	/* r0 = (r0 >> 16) */
147 	b	store_half
148 
149 	/* R_PPC_ADDR16_HA */
150 ha16:
151 	cmpwi	r4, R_PPC_ADDR16_HA
152 	bne	lo16
153 	lwz	r4, 0(r9)	/* r_offset */
154 	lwz	r0, 8(r9)	/* r_addend */
155 	add	r0, r0, r3
156 	add	r0, r0, r5	/* r0 = (S+A+Offset) */
157 	extrwi	r5, r0, 1, 16	/* Extract bit 16 */
158 	extrwi	r0, r0, 16, 0	/* r0 = (r0 >> 16) */
159 	add	r0, r0, r5	/* Add it to r0 */
160 	b	store_half
161 
162 	/* R_PPC_ADDR16_LO */
163 lo16:
164 	cmpwi	r4, R_PPC_ADDR16_LO
165 	bne	unknown_type
166 	lwz	r4, 0(r9)	/* r_offset */
167 	lwz	r0, 8(r9)	/* r_addend */
168 	add	r0, r0, r3
169 	add	r0, r0, r5	/* r0 = (S+A+Offset) */
170 	extrwi	r0, r0, 16, 16	/* r0 &= 0xffff */
171 	/* Fall through to */
172 
173 	/* Store half word */
174 store_half:
175 	sthx	r0, r4, r7	/* memory[r4+r7] = (u16)r0 */
176 
177 nxtrela:
178 	/*
179 	 * We have to flush the modified instructions to the
180 	 * main storage from the d-cache. And also, invalidate the
181 	 * cached instructions in i-cache which has been modified.
182 	 *
183 	 * We delay the sync / isync operation till the end, since
184 	 * we won't be executing the modified instructions until
185 	 * we return from here.
186 	 */
187 	dcbst	r4,r7
188 	sync			/* Ensure the data is flushed before icbi */
189 	icbi	r4,r7
190 unknown_type:
191 	cmpwi	r8, 0		/* relasz = 0 ? */
192 	ble	done
193 	add	r9, r9, r6	/* move to next entry in the .rela table */
194 	subf	r8, r6, r8	/* relasz -= relaent */
195 	b	applyrela
196 
197 done:
198 	sync			/* Wait for the flush to finish */
199 	isync			/* Discard prefetched instructions */
200 	blr
201 
202 p_dyn:		.long	__dynamic_start - 0b
203 p_rela:		.long	__rela_dyn_start - 0b
204 p_sym:		.long	__dynamic_symtab - 0b
205 p_st:		.long	_stext - 0b
206