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Linux/arch/alpha/kernel/module.c

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  1 /*  Kernel module help for Alpha.
  2     Copyright (C) 2002 Richard Henderson.
  3 
  4     This program is free software; you can redistribute it and/or modify
  5     it under the terms of the GNU General Public License as published by
  6     the Free Software Foundation; either version 2 of the License, or
  7     (at your option) any later version.
  8 
  9     This program is distributed in the hope that it will be useful,
 10     but WITHOUT ANY WARRANTY; without even the implied warranty of
 11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 12     GNU General Public License for more details.
 13 
 14     You should have received a copy of the GNU General Public License
 15     along with this program; if not, write to the Free Software
 16     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 17 */
 18 #include <linux/moduleloader.h>
 19 #include <linux/elf.h>
 20 #include <linux/vmalloc.h>
 21 #include <linux/fs.h>
 22 #include <linux/string.h>
 23 #include <linux/kernel.h>
 24 #include <linux/slab.h>
 25 
 26 #if 0
 27 #define DEBUGP printk
 28 #else
 29 #define DEBUGP(fmt...)
 30 #endif
 31 
 32 /* Allocate the GOT at the end of the core sections.  */
 33 
 34 struct got_entry {
 35         struct got_entry *next;
 36         Elf64_Sxword r_addend;
 37         int got_offset;
 38 };
 39 
 40 static inline void
 41 process_reloc_for_got(Elf64_Rela *rela,
 42                       struct got_entry *chains, Elf64_Xword *poffset)
 43 {
 44         unsigned long r_sym = ELF64_R_SYM (rela->r_info);
 45         unsigned long r_type = ELF64_R_TYPE (rela->r_info);
 46         Elf64_Sxword r_addend = rela->r_addend;
 47         struct got_entry *g;
 48 
 49         if (r_type != R_ALPHA_LITERAL)
 50                 return;
 51 
 52         for (g = chains + r_sym; g ; g = g->next)
 53                 if (g->r_addend == r_addend) {
 54                         if (g->got_offset == 0) {
 55                                 g->got_offset = *poffset;
 56                                 *poffset += 8;
 57                         }
 58                         goto found_entry;
 59                 }
 60 
 61         g = kmalloc (sizeof (*g), GFP_KERNEL);
 62         g->next = chains[r_sym].next;
 63         g->r_addend = r_addend;
 64         g->got_offset = *poffset;
 65         *poffset += 8;
 66         chains[r_sym].next = g;
 67 
 68  found_entry:
 69         /* Trick: most of the ELF64_R_TYPE field is unused.  There are
 70            42 valid relocation types, and a 32-bit field.  Co-opt the
 71            bits above 256 to store the got offset for this reloc.  */
 72         rela->r_info |= g->got_offset << 8;
 73 }
 74 
 75 int
 76 module_frob_arch_sections(Elf64_Ehdr *hdr, Elf64_Shdr *sechdrs,
 77                           char *secstrings, struct module *me)
 78 {
 79         struct got_entry *chains;
 80         Elf64_Rela *rela;
 81         Elf64_Shdr *esechdrs, *symtab, *s, *got;
 82         unsigned long nsyms, nrela, i;
 83 
 84         esechdrs = sechdrs + hdr->e_shnum;
 85         symtab = got = NULL;
 86 
 87         /* Find out how large the symbol table is.  Allocate one got_entry
 88            head per symbol.  Normally this will be enough, but not always.
 89            We'll chain different offsets for the symbol down each head.  */
 90         for (s = sechdrs; s < esechdrs; ++s)
 91                 if (s->sh_type == SHT_SYMTAB)
 92                         symtab = s;
 93                 else if (!strcmp(".got", secstrings + s->sh_name)) {
 94                         got = s;
 95                         me->arch.gotsecindex = s - sechdrs;
 96                 }
 97 
 98         if (!symtab) {
 99                 printk(KERN_ERR "module %s: no symbol table\n", me->name);
100                 return -ENOEXEC;
101         }
102         if (!got) {
103                 printk(KERN_ERR "module %s: no got section\n", me->name);
104                 return -ENOEXEC;
105         }
106 
107         nsyms = symtab->sh_size / sizeof(Elf64_Sym);
108         chains = kcalloc(nsyms, sizeof(struct got_entry), GFP_KERNEL);
109         if (!chains) {
110                 printk(KERN_ERR
111                        "module %s: no memory for symbol chain buffer\n",
112                        me->name);
113                 return -ENOMEM;
114         }
115 
116         got->sh_size = 0;
117         got->sh_addralign = 8;
118         got->sh_type = SHT_NOBITS;
119 
120         /* Examine all LITERAL relocations to find out what GOT entries
121            are required.  This sizes the GOT section as well.  */
122         for (s = sechdrs; s < esechdrs; ++s)
123                 if (s->sh_type == SHT_RELA) {
124                         nrela = s->sh_size / sizeof(Elf64_Rela);
125                         rela = (void *)hdr + s->sh_offset;
126                         for (i = 0; i < nrela; ++i)
127                                 process_reloc_for_got(rela+i, chains,
128                                                       &got->sh_size);
129                 }
130 
131         /* Free the memory we allocated.  */
132         for (i = 0; i < nsyms; ++i) {
133                 struct got_entry *g, *n;
134                 for (g = chains[i].next; g ; g = n) {
135                         n = g->next;
136                         kfree(g);
137                 }
138         }
139         kfree(chains);
140 
141         return 0;
142 }
143 
144 int
145 apply_relocate_add(Elf64_Shdr *sechdrs, const char *strtab,
146                    unsigned int symindex, unsigned int relsec,
147                    struct module *me)
148 {
149         Elf64_Rela *rela = (void *)sechdrs[relsec].sh_addr;
150         unsigned long i, n = sechdrs[relsec].sh_size / sizeof(*rela);
151         Elf64_Sym *symtab, *sym;
152         void *base, *location;
153         unsigned long got, gp;
154 
155         DEBUGP("Applying relocate section %u to %u\n", relsec,
156                sechdrs[relsec].sh_info);
157 
158         base = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr;
159         symtab = (Elf64_Sym *)sechdrs[symindex].sh_addr;
160 
161         /* The small sections were sorted to the end of the segment.
162            The following should definitely cover them.  */
163         gp = (u64)me->core_layout.base + me->core_layout.size - 0x8000;
164         got = sechdrs[me->arch.gotsecindex].sh_addr;
165 
166         for (i = 0; i < n; i++) {
167                 unsigned long r_sym = ELF64_R_SYM (rela[i].r_info);
168                 unsigned long r_type = ELF64_R_TYPE (rela[i].r_info);
169                 unsigned long r_got_offset = r_type >> 8;
170                 unsigned long value, hi, lo;
171                 r_type &= 0xff;
172 
173                 /* This is where to make the change.  */
174                 location = base + rela[i].r_offset;
175 
176                 /* This is the symbol it is referring to.  Note that all
177                    unresolved symbols have been resolved.  */
178                 sym = symtab + r_sym;
179                 value = sym->st_value + rela[i].r_addend;
180 
181                 switch (r_type) {
182                 case R_ALPHA_NONE:
183                         break;
184                 case R_ALPHA_REFQUAD:
185                         /* BUG() can produce misaligned relocations. */
186                         ((u32 *)location)[0] = value;
187                         ((u32 *)location)[1] = value >> 32;
188                         break;
189                 case R_ALPHA_GPREL32:
190                         value -= gp;
191                         if ((int)value != value)
192                                 goto reloc_overflow;
193                         *(u32 *)location = value;
194                         break;
195                 case R_ALPHA_LITERAL:
196                         hi = got + r_got_offset;
197                         lo = hi - gp;
198                         if ((short)lo != lo)
199                                 goto reloc_overflow;
200                         *(u16 *)location = lo;
201                         *(u64 *)hi = value;
202                         break;
203                 case R_ALPHA_LITUSE:
204                         break;
205                 case R_ALPHA_GPDISP:
206                         value = gp - (u64)location;
207                         lo = (short)value;
208                         hi = (int)(value - lo);
209                         if (hi + lo != value)
210                                 goto reloc_overflow;
211                         *(u16 *)location = hi >> 16;
212                         *(u16 *)(location + rela[i].r_addend) = lo;
213                         break;
214                 case R_ALPHA_BRSGP:
215                         /* BRSGP is only allowed to bind to local symbols.
216                            If the section is undef, this means that the
217                            value was resolved from somewhere else.  */
218                         if (sym->st_shndx == SHN_UNDEF)
219                                 goto reloc_overflow;
220                         if ((sym->st_other & STO_ALPHA_STD_GPLOAD) ==
221                             STO_ALPHA_STD_GPLOAD)
222                                 /* Omit the prologue. */
223                                 value += 8;
224                         /* FALLTHRU */
225                 case R_ALPHA_BRADDR:
226                         value -= (u64)location + 4;
227                         if (value & 3)
228                                 goto reloc_overflow;
229                         value = (long)value >> 2;
230                         if (value + (1<<21) >= 1<<22)
231                                 goto reloc_overflow;
232                         value &= 0x1fffff;
233                         value |= *(u32 *)location & ~0x1fffff;
234                         *(u32 *)location = value;
235                         break;
236                 case R_ALPHA_HINT:
237                         break;
238                 case R_ALPHA_SREL32:
239                         value -= (u64)location;
240                         if ((int)value != value)
241                                 goto reloc_overflow;
242                         *(u32 *)location = value;
243                         break;
244                 case R_ALPHA_SREL64:
245                         value -= (u64)location;
246                         *(u64 *)location = value;
247                         break;
248                 case R_ALPHA_GPRELHIGH:
249                         value = (long)(value - gp + 0x8000) >> 16;
250                         if ((short) value != value)
251                                 goto reloc_overflow;
252                         *(u16 *)location = value;
253                         break;
254                 case R_ALPHA_GPRELLOW:
255                         value -= gp;
256                         *(u16 *)location = value;
257                         break;
258                 case R_ALPHA_GPREL16:
259                         value -= gp;
260                         if ((short) value != value)
261                                 goto reloc_overflow;
262                         *(u16 *)location = value;
263                         break;
264                 default:
265                         printk(KERN_ERR "module %s: Unknown relocation: %lu\n",
266                                me->name, r_type);
267                         return -ENOEXEC;
268                 reloc_overflow:
269                         if (ELF64_ST_TYPE (sym->st_info) == STT_SECTION)
270                           printk(KERN_ERR
271                                  "module %s: Relocation (type %lu) overflow vs section %d\n",
272                                  me->name, r_type, sym->st_shndx);
273                         else
274                           printk(KERN_ERR
275                                  "module %s: Relocation (type %lu) overflow vs %s\n",
276                                  me->name, r_type, strtab + sym->st_name);
277                         return -ENOEXEC;
278                 }
279         }
280 
281         return 0;
282 }
283 

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