1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Kernel module help for Alpha.
3 Copyright (C) 2002 Richard Henderson.
4
5 */
6 #include <linux/moduleloader.h>
7 #include <linux/elf.h>
8 #include <linux/vmalloc.h>
9 #include <linux/fs.h>
10 #include <linux/string.h>
11 #include <linux/kernel.h>
12 #include <linux/slab.h>
13
14 #if 0
15 #define DEBUGP printk
16 #else
17 #define DEBUGP(fmt...)
18 #endif
19
20 /* Allocate the GOT at the end of the core sections. */
21
22 struct got_entry {
23 struct got_entry *next;
24 Elf64_Sxword r_addend;
25 int got_offset;
26 };
27
28 static inline void
29 process_reloc_for_got(Elf64_Rela *rela,
30 struct got_entry *chains, Elf64_Xword *poffset)
31 {
32 unsigned long r_sym = ELF64_R_SYM (rela->r_info);
33 unsigned long r_type = ELF64_R_TYPE (rela->r_info);
34 Elf64_Sxword r_addend = rela->r_addend;
35 struct got_entry *g;
36
37 if (r_type != R_ALPHA_LITERAL)
38 return;
39
40 for (g = chains + r_sym; g ; g = g->next)
41 if (g->r_addend == r_addend) {
42 if (g->got_offset == 0) {
43 g->got_offset = *poffset;
44 *poffset += 8;
45 }
46 goto found_entry;
47 }
48
49 g = kmalloc (sizeof (*g), GFP_KERNEL);
50 g->next = chains[r_sym].next;
51 g->r_addend = r_addend;
52 g->got_offset = *poffset;
53 *poffset += 8;
54 chains[r_sym].next = g;
55
56 found_entry:
57 /* Trick: most of the ELF64_R_TYPE field is unused. There are
58 42 valid relocation types, and a 32-bit field. Co-opt the
59 bits above 256 to store the got offset for this reloc. */
60 rela->r_info |= g->got_offset << 8;
61 }
62
63 int
64 module_frob_arch_sections(Elf64_Ehdr *hdr, Elf64_Shdr *sechdrs,
65 char *secstrings, struct module *me)
66 {
67 struct got_entry *chains;
68 Elf64_Rela *rela;
69 Elf64_Shdr *esechdrs, *symtab, *s, *got;
70 unsigned long nsyms, nrela, i;
71
72 esechdrs = sechdrs + hdr->e_shnum;
73 symtab = got = NULL;
74
75 /* Find out how large the symbol table is. Allocate one got_entry
76 head per symbol. Normally this will be enough, but not always.
77 We'll chain different offsets for the symbol down each head. */
78 for (s = sechdrs; s < esechdrs; ++s)
79 if (s->sh_type == SHT_SYMTAB)
80 symtab = s;
81 else if (!strcmp(".got", secstrings + s->sh_name)) {
82 got = s;
83 me->arch.gotsecindex = s - sechdrs;
84 }
85
86 if (!symtab) {
87 printk(KERN_ERR "module %s: no symbol table\n", me->name);
88 return -ENOEXEC;
89 }
90 if (!got) {
91 printk(KERN_ERR "module %s: no got section\n", me->name);
92 return -ENOEXEC;
93 }
94
95 nsyms = symtab->sh_size / sizeof(Elf64_Sym);
96 chains = kcalloc(nsyms, sizeof(struct got_entry), GFP_KERNEL);
97 if (!chains) {
98 printk(KERN_ERR
99 "module %s: no memory for symbol chain buffer\n",
100 me->name);
101 return -ENOMEM;
102 }
103
104 got->sh_size = 0;
105 got->sh_addralign = 8;
106 got->sh_type = SHT_NOBITS;
107
108 /* Examine all LITERAL relocations to find out what GOT entries
109 are required. This sizes the GOT section as well. */
110 for (s = sechdrs; s < esechdrs; ++s)
111 if (s->sh_type == SHT_RELA) {
112 nrela = s->sh_size / sizeof(Elf64_Rela);
113 rela = (void *)hdr + s->sh_offset;
114 for (i = 0; i < nrela; ++i)
115 process_reloc_for_got(rela+i, chains,
116 &got->sh_size);
117 }
118
119 /* Free the memory we allocated. */
120 for (i = 0; i < nsyms; ++i) {
121 struct got_entry *g, *n;
122 for (g = chains[i].next; g ; g = n) {
123 n = g->next;
124 kfree(g);
125 }
126 }
127 kfree(chains);
128
129 return 0;
130 }
131
132 int
133 apply_relocate_add(Elf64_Shdr *sechdrs, const char *strtab,
134 unsigned int symindex, unsigned int relsec,
135 struct module *me)
136 {
137 Elf64_Rela *rela = (void *)sechdrs[relsec].sh_addr;
138 unsigned long i, n = sechdrs[relsec].sh_size / sizeof(*rela);
139 Elf64_Sym *symtab, *sym;
140 void *base, *location;
141 unsigned long got, gp;
142
143 DEBUGP("Applying relocate section %u to %u\n", relsec,
144 sechdrs[relsec].sh_info);
145
146 base = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr;
147 symtab = (Elf64_Sym *)sechdrs[symindex].sh_addr;
148
149 got = sechdrs[me->arch.gotsecindex].sh_addr;
150 gp = got + 0x8000;
151
152 for (i = 0; i < n; i++) {
153 unsigned long r_sym = ELF64_R_SYM (rela[i].r_info);
154 unsigned long r_type = ELF64_R_TYPE (rela[i].r_info);
155 unsigned long r_got_offset = r_type >> 8;
156 unsigned long value, hi, lo;
157 r_type &= 0xff;
158
159 /* This is where to make the change. */
160 location = base + rela[i].r_offset;
161
162 /* This is the symbol it is referring to. Note that all
163 unresolved symbols have been resolved. */
164 sym = symtab + r_sym;
165 value = sym->st_value + rela[i].r_addend;
166
167 switch (r_type) {
168 case R_ALPHA_NONE:
169 break;
170 case R_ALPHA_REFLONG:
171 *(u32 *)location = value;
172 break;
173 case R_ALPHA_REFQUAD:
174 /* BUG() can produce misaligned relocations. */
175 ((u32 *)location)[0] = value;
176 ((u32 *)location)[1] = value >> 32;
177 break;
178 case R_ALPHA_GPREL32:
179 value -= gp;
180 if ((int)value != value)
181 goto reloc_overflow;
182 *(u32 *)location = value;
183 break;
184 case R_ALPHA_LITERAL:
185 hi = got + r_got_offset;
186 lo = hi - gp;
187 if ((short)lo != lo)
188 goto reloc_overflow;
189 *(u16 *)location = lo;
190 *(u64 *)hi = value;
191 break;
192 case R_ALPHA_LITUSE:
193 break;
194 case R_ALPHA_GPDISP:
195 value = gp - (u64)location;
196 lo = (short)value;
197 hi = (int)(value - lo);
198 if (hi + lo != value)
199 goto reloc_overflow;
200 *(u16 *)location = hi >> 16;
201 *(u16 *)(location + rela[i].r_addend) = lo;
202 break;
203 case R_ALPHA_BRSGP:
204 /* BRSGP is only allowed to bind to local symbols.
205 If the section is undef, this means that the
206 value was resolved from somewhere else. */
207 if (sym->st_shndx == SHN_UNDEF)
208 goto reloc_overflow;
209 if ((sym->st_other & STO_ALPHA_STD_GPLOAD) ==
210 STO_ALPHA_STD_GPLOAD)
211 /* Omit the prologue. */
212 value += 8;
213 fallthrough;
214 case R_ALPHA_BRADDR:
215 value -= (u64)location + 4;
216 if (value & 3)
217 goto reloc_overflow;
218 value = (long)value >> 2;
219 if (value + (1<<21) >= 1<<22)
220 goto reloc_overflow;
221 value &= 0x1fffff;
222 value |= *(u32 *)location & ~0x1fffff;
223 *(u32 *)location = value;
224 break;
225 case R_ALPHA_HINT:
226 break;
227 case R_ALPHA_SREL32:
228 value -= (u64)location;
229 if ((int)value != value)
230 goto reloc_overflow;
231 *(u32 *)location = value;
232 break;
233 case R_ALPHA_SREL64:
234 value -= (u64)location;
235 *(u64 *)location = value;
236 break;
237 case R_ALPHA_GPRELHIGH:
238 value = (long)(value - gp + 0x8000) >> 16;
239 if ((short) value != value)
240 goto reloc_overflow;
241 *(u16 *)location = value;
242 break;
243 case R_ALPHA_GPRELLOW:
244 value -= gp;
245 *(u16 *)location = value;
246 break;
247 case R_ALPHA_GPREL16:
248 value -= gp;
249 if ((short) value != value)
250 goto reloc_overflow;
251 *(u16 *)location = value;
252 break;
253 default:
254 printk(KERN_ERR "module %s: Unknown relocation: %lu\n",
255 me->name, r_type);
256 return -ENOEXEC;
257 reloc_overflow:
258 if (ELF64_ST_TYPE (sym->st_info) == STT_SECTION)
259 printk(KERN_ERR
260 "module %s: Relocation (type %lu) overflow vs section %d\n",
261 me->name, r_type, sym->st_shndx);
262 else
263 printk(KERN_ERR
264 "module %s: Relocation (type %lu) overflow vs %s\n",
265 me->name, r_type, strtab + sym->st_name);
266 return -ENOEXEC;
267 }
268 }
269
270 return 0;
271 }
272
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