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Linux/arch/metag/kernel/module.c

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  1 /*  Kernel module help for Meta.
  2 
  3     This program is free software; you can redistribute it and/or modify
  4     it under the terms of the GNU General Public License as published by
  5     the Free Software Foundation; either version 2 of the License, or
  6     (at your option) any later version.
  7 
  8     This program is distributed in the hope that it will be useful,
  9     but WITHOUT ANY WARRANTY; without even the implied warranty of
 10     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 11     GNU General Public License for more details.
 12 */
 13 #include <linux/moduleloader.h>
 14 #include <linux/elf.h>
 15 #include <linux/vmalloc.h>
 16 #include <linux/fs.h>
 17 #include <linux/string.h>
 18 #include <linux/kernel.h>
 19 #include <linux/sort.h>
 20 
 21 #include <asm/unaligned.h>
 22 
 23 /* Count how many different relocations (different symbol, different
 24    addend) */
 25 static unsigned int count_relocs(const Elf32_Rela *rela, unsigned int num)
 26 {
 27         unsigned int i, r_info, r_addend, _count_relocs;
 28 
 29         _count_relocs = 0;
 30         r_info = 0;
 31         r_addend = 0;
 32         for (i = 0; i < num; i++)
 33                 /* Only count relbranch relocs, others don't need stubs */
 34                 if (ELF32_R_TYPE(rela[i].r_info) == R_METAG_RELBRANCH &&
 35                     (r_info != ELF32_R_SYM(rela[i].r_info) ||
 36                      r_addend != rela[i].r_addend)) {
 37                         _count_relocs++;
 38                         r_info = ELF32_R_SYM(rela[i].r_info);
 39                         r_addend = rela[i].r_addend;
 40                 }
 41 
 42         return _count_relocs;
 43 }
 44 
 45 static int relacmp(const void *_x, const void *_y)
 46 {
 47         const Elf32_Rela *x, *y;
 48 
 49         y = (Elf32_Rela *)_x;
 50         x = (Elf32_Rela *)_y;
 51 
 52         /* Compare the entire r_info (as opposed to ELF32_R_SYM(r_info) only) to
 53          * make the comparison cheaper/faster. It won't affect the sorting or
 54          * the counting algorithms' performance
 55          */
 56         if (x->r_info < y->r_info)
 57                 return -1;
 58         else if (x->r_info > y->r_info)
 59                 return 1;
 60         else if (x->r_addend < y->r_addend)
 61                 return -1;
 62         else if (x->r_addend > y->r_addend)
 63                 return 1;
 64         else
 65                 return 0;
 66 }
 67 
 68 static void relaswap(void *_x, void *_y, int size)
 69 {
 70         uint32_t *x, *y, tmp;
 71         int i;
 72 
 73         y = (uint32_t *)_x;
 74         x = (uint32_t *)_y;
 75 
 76         for (i = 0; i < sizeof(Elf32_Rela) / sizeof(uint32_t); i++) {
 77                 tmp = x[i];
 78                 x[i] = y[i];
 79                 y[i] = tmp;
 80         }
 81 }
 82 
 83 /* Get the potential trampolines size required of the init and
 84    non-init sections */
 85 static unsigned long get_plt_size(const Elf32_Ehdr *hdr,
 86                                   const Elf32_Shdr *sechdrs,
 87                                   const char *secstrings,
 88                                   int is_init)
 89 {
 90         unsigned long ret = 0;
 91         unsigned i;
 92 
 93         /* Everything marked ALLOC (this includes the exported
 94            symbols) */
 95         for (i = 1; i < hdr->e_shnum; i++) {
 96                 /* If it's called *.init*, and we're not init, we're
 97                    not interested */
 98                 if ((strstr(secstrings + sechdrs[i].sh_name, ".init") != NULL)
 99                     != is_init)
100                         continue;
101 
102                 /* We don't want to look at debug sections. */
103                 if (strstr(secstrings + sechdrs[i].sh_name, ".debug") != NULL)
104                         continue;
105 
106                 if (sechdrs[i].sh_type == SHT_RELA) {
107                         pr_debug("Found relocations in section %u\n", i);
108                         pr_debug("Ptr: %p.  Number: %u\n",
109                                  (void *)hdr + sechdrs[i].sh_offset,
110                                  sechdrs[i].sh_size / sizeof(Elf32_Rela));
111 
112                         /* Sort the relocation information based on a symbol and
113                          * addend key. This is a stable O(n*log n) complexity
114                          * alogrithm but it will reduce the complexity of
115                          * count_relocs() to linear complexity O(n)
116                          */
117                         sort((void *)hdr + sechdrs[i].sh_offset,
118                              sechdrs[i].sh_size / sizeof(Elf32_Rela),
119                              sizeof(Elf32_Rela), relacmp, relaswap);
120 
121                         ret += count_relocs((void *)hdr
122                                              + sechdrs[i].sh_offset,
123                                              sechdrs[i].sh_size
124                                              / sizeof(Elf32_Rela))
125                                 * sizeof(struct metag_plt_entry);
126                 }
127         }
128 
129         return ret;
130 }
131 
132 int module_frob_arch_sections(Elf32_Ehdr *hdr,
133                               Elf32_Shdr *sechdrs,
134                               char *secstrings,
135                               struct module *me)
136 {
137         unsigned int i;
138 
139         /* Find .plt and .init.plt sections */
140         for (i = 0; i < hdr->e_shnum; i++) {
141                 if (strcmp(secstrings + sechdrs[i].sh_name, ".init.plt") == 0)
142                         me->arch.init_plt_section = i;
143                 else if (strcmp(secstrings + sechdrs[i].sh_name, ".plt") == 0)
144                         me->arch.core_plt_section = i;
145         }
146         if (!me->arch.core_plt_section || !me->arch.init_plt_section) {
147                 pr_err("Module doesn't contain .plt or .init.plt sections.\n");
148                 return -ENOEXEC;
149         }
150 
151         /* Override their sizes */
152         sechdrs[me->arch.core_plt_section].sh_size
153                 = get_plt_size(hdr, sechdrs, secstrings, 0);
154         sechdrs[me->arch.core_plt_section].sh_type = SHT_NOBITS;
155         sechdrs[me->arch.init_plt_section].sh_size
156                 = get_plt_size(hdr, sechdrs, secstrings, 1);
157         sechdrs[me->arch.init_plt_section].sh_type = SHT_NOBITS;
158         return 0;
159 }
160 
161 /* Set up a trampoline in the PLT to bounce us to the distant function */
162 static uint32_t do_plt_call(void *location, Elf32_Addr val,
163                             Elf32_Shdr *sechdrs, struct module *mod)
164 {
165         struct metag_plt_entry *entry;
166         /* Instructions used to do the indirect jump.  */
167         uint32_t tramp[2];
168 
169         /* We have to trash a register, so we assume that any control
170            transfer more than 21-bits away must be a function call
171            (so we can use a call-clobbered register).  */
172 
173         /* MOVT D0Re0,#HI(v) */
174         tramp[0] = 0x02000005 | (((val & 0xffff0000) >> 16) << 3);
175         /* JUMP D0Re0,#LO(v) */
176         tramp[1] = 0xac000001 | ((val & 0x0000ffff) << 3);
177 
178         /* Init, or core PLT? */
179         if (location >= mod->module_core
180             && location < mod->module_core + mod->core_size)
181                 entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr;
182         else
183                 entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr;
184 
185         /* Find this entry, or if that fails, the next avail. entry */
186         while (entry->tramp[0])
187                 if (entry->tramp[0] == tramp[0] && entry->tramp[1] == tramp[1])
188                         return (uint32_t)entry;
189                 else
190                         entry++;
191 
192         entry->tramp[0] = tramp[0];
193         entry->tramp[1] = tramp[1];
194 
195         return (uint32_t)entry;
196 }
197 
198 int apply_relocate_add(Elf32_Shdr *sechdrs,
199                    const char *strtab,
200                    unsigned int symindex,
201                    unsigned int relsec,
202                    struct module *me)
203 {
204         unsigned int i;
205         Elf32_Rela *rel = (void *)sechdrs[relsec].sh_addr;
206         Elf32_Sym *sym;
207         Elf32_Addr relocation;
208         uint32_t *location;
209         int32_t value;
210 
211         pr_debug("Applying relocate section %u to %u\n", relsec,
212                  sechdrs[relsec].sh_info);
213         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
214                 /* This is where to make the change */
215                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
216                         + rel[i].r_offset;
217                 /* This is the symbol it is referring to.  Note that all
218                    undefined symbols have been resolved.  */
219                 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
220                         + ELF32_R_SYM(rel[i].r_info);
221                 relocation = sym->st_value + rel[i].r_addend;
222 
223                 switch (ELF32_R_TYPE(rel[i].r_info)) {
224                 case R_METAG_NONE:
225                         break;
226                 case R_METAG_HIADDR16:
227                         relocation >>= 16;
228                 case R_METAG_LOADDR16:
229                         *location = (*location & 0xfff80007) |
230                                 ((relocation & 0xffff) << 3);
231                         break;
232                 case R_METAG_ADDR32:
233                         /*
234                          * Packed data structures may cause a misaligned
235                          * R_METAG_ADDR32 to be emitted.
236                          */
237                         put_unaligned(relocation, location);
238                         break;
239                 case R_METAG_GETSETOFF:
240                         *location += ((relocation & 0xfff) << 7);
241                         break;
242                 case R_METAG_RELBRANCH:
243                         if (*location & (0x7ffff << 5)) {
244                                 pr_err("bad relbranch relocation\n");
245                                 break;
246                         }
247 
248                         /* This jump is too big for the offset slot. Build
249                          * a PLT to jump through to get to where we want to go.
250                          * NB: 21bit check - not scaled to 19bit yet
251                          */
252                         if (((int32_t)(relocation -
253                                        (uint32_t)location) > 0xfffff) ||
254                             ((int32_t)(relocation -
255                                        (uint32_t)location) < -0xfffff)) {
256                                 relocation = do_plt_call(location, relocation,
257                                                          sechdrs, me);
258                         }
259 
260                         value = relocation - (uint32_t)location;
261 
262                         /* branch instruction aligned */
263                         value /= 4;
264 
265                         if ((value > 0x7ffff) || (value < -0x7ffff)) {
266                                 /*
267                                  * this should have been caught by the code
268                                  * above!
269                                  */
270                                 pr_err("overflow of relbranch reloc\n");
271                         }
272 
273                         *location = (*location & (~(0x7ffff << 5))) |
274                                 ((value & 0x7ffff) << 5);
275                         break;
276 
277                 default:
278                         pr_err("module %s: Unknown relocation: %u\n",
279                                me->name, ELF32_R_TYPE(rel[i].r_info));
280                         return -ENOEXEC;
281                 }
282         }
283         return 0;
284 }
285 

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