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Linux/arch/powerpc/kernel/module_32.c

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  1 /*  Kernel module help for PPC.
  2     Copyright (C) 2001 Rusty Russell.
  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/module.h>
 19 #include <linux/moduleloader.h>
 20 #include <linux/elf.h>
 21 #include <linux/vmalloc.h>
 22 #include <linux/fs.h>
 23 #include <linux/string.h>
 24 #include <linux/kernel.h>
 25 #include <linux/ftrace.h>
 26 #include <linux/cache.h>
 27 #include <linux/bug.h>
 28 #include <linux/sort.h>
 29 
 30 #include "setup.h"
 31 
 32 #if 0
 33 #define DEBUGP printk
 34 #else
 35 #define DEBUGP(fmt , ...)
 36 #endif
 37 
 38 /* Count how many different relocations (different symbol, different
 39    addend) */
 40 static unsigned int count_relocs(const Elf32_Rela *rela, unsigned int num)
 41 {
 42         unsigned int i, r_info, r_addend, _count_relocs;
 43 
 44         _count_relocs = 0;
 45         r_info = 0;
 46         r_addend = 0;
 47         for (i = 0; i < num; i++)
 48                 /* Only count 24-bit relocs, others don't need stubs */
 49                 if (ELF32_R_TYPE(rela[i].r_info) == R_PPC_REL24 &&
 50                     (r_info != ELF32_R_SYM(rela[i].r_info) ||
 51                      r_addend != rela[i].r_addend)) {
 52                         _count_relocs++;
 53                         r_info = ELF32_R_SYM(rela[i].r_info);
 54                         r_addend = rela[i].r_addend;
 55                 }
 56 
 57 #ifdef CONFIG_DYNAMIC_FTRACE
 58         _count_relocs++;        /* add one for ftrace_caller */
 59 #endif
 60         return _count_relocs;
 61 }
 62 
 63 static int relacmp(const void *_x, const void *_y)
 64 {
 65         const Elf32_Rela *x, *y;
 66 
 67         y = (Elf32_Rela *)_x;
 68         x = (Elf32_Rela *)_y;
 69 
 70         /* Compare the entire r_info (as opposed to ELF32_R_SYM(r_info) only) to
 71          * make the comparison cheaper/faster. It won't affect the sorting or
 72          * the counting algorithms' performance
 73          */
 74         if (x->r_info < y->r_info)
 75                 return -1;
 76         else if (x->r_info > y->r_info)
 77                 return 1;
 78         else if (x->r_addend < y->r_addend)
 79                 return -1;
 80         else if (x->r_addend > y->r_addend)
 81                 return 1;
 82         else
 83                 return 0;
 84 }
 85 
 86 static void relaswap(void *_x, void *_y, int size)
 87 {
 88         uint32_t *x, *y, tmp;
 89         int i;
 90 
 91         y = (uint32_t *)_x;
 92         x = (uint32_t *)_y;
 93 
 94         for (i = 0; i < sizeof(Elf32_Rela) / sizeof(uint32_t); i++) {
 95                 tmp = x[i];
 96                 x[i] = y[i];
 97                 y[i] = tmp;
 98         }
 99 }
100 
101 /* Get the potential trampolines size required of the init and
102    non-init sections */
103 static unsigned long get_plt_size(const Elf32_Ehdr *hdr,
104                                   const Elf32_Shdr *sechdrs,
105                                   const char *secstrings,
106                                   int is_init)
107 {
108         unsigned long ret = 0;
109         unsigned i;
110 
111         /* Everything marked ALLOC (this includes the exported
112            symbols) */
113         for (i = 1; i < hdr->e_shnum; i++) {
114                 /* If it's called *.init*, and we're not init, we're
115                    not interested */
116                 if ((strstr(secstrings + sechdrs[i].sh_name, ".init") != 0)
117                     != is_init)
118                         continue;
119 
120                 /* We don't want to look at debug sections. */
121                 if (strstr(secstrings + sechdrs[i].sh_name, ".debug") != 0)
122                         continue;
123 
124                 if (sechdrs[i].sh_type == SHT_RELA) {
125                         DEBUGP("Found relocations in section %u\n", i);
126                         DEBUGP("Ptr: %p.  Number: %u\n",
127                                (void *)hdr + sechdrs[i].sh_offset,
128                                sechdrs[i].sh_size / sizeof(Elf32_Rela));
129 
130                         /* Sort the relocation information based on a symbol and
131                          * addend key. This is a stable O(n*log n) complexity
132                          * alogrithm but it will reduce the complexity of
133                          * count_relocs() to linear complexity O(n)
134                          */
135                         sort((void *)hdr + sechdrs[i].sh_offset,
136                              sechdrs[i].sh_size / sizeof(Elf32_Rela),
137                              sizeof(Elf32_Rela), relacmp, relaswap);
138 
139                         ret += count_relocs((void *)hdr
140                                              + sechdrs[i].sh_offset,
141                                              sechdrs[i].sh_size
142                                              / sizeof(Elf32_Rela))
143                                 * sizeof(struct ppc_plt_entry);
144                 }
145         }
146 
147         return ret;
148 }
149 
150 int module_frob_arch_sections(Elf32_Ehdr *hdr,
151                               Elf32_Shdr *sechdrs,
152                               char *secstrings,
153                               struct module *me)
154 {
155         unsigned int i;
156 
157         /* Find .plt and .init.plt sections */
158         for (i = 0; i < hdr->e_shnum; i++) {
159                 if (strcmp(secstrings + sechdrs[i].sh_name, ".init.plt") == 0)
160                         me->arch.init_plt_section = i;
161                 else if (strcmp(secstrings + sechdrs[i].sh_name, ".plt") == 0)
162                         me->arch.core_plt_section = i;
163         }
164         if (!me->arch.core_plt_section || !me->arch.init_plt_section) {
165                 printk("Module doesn't contain .plt or .init.plt sections.\n");
166                 return -ENOEXEC;
167         }
168 
169         /* Override their sizes */
170         sechdrs[me->arch.core_plt_section].sh_size
171                 = get_plt_size(hdr, sechdrs, secstrings, 0);
172         sechdrs[me->arch.init_plt_section].sh_size
173                 = get_plt_size(hdr, sechdrs, secstrings, 1);
174         return 0;
175 }
176 
177 int apply_relocate(Elf32_Shdr *sechdrs,
178                    const char *strtab,
179                    unsigned int symindex,
180                    unsigned int relsec,
181                    struct module *module)
182 {
183         printk(KERN_ERR "%s: Non-ADD RELOCATION unsupported\n",
184                module->name);
185         return -ENOEXEC;
186 }
187 
188 static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val)
189 {
190         if (entry->jump[0] == 0x3d800000 + ((val + 0x8000) >> 16)
191             && entry->jump[1] == 0x398c0000 + (val & 0xffff))
192                 return 1;
193         return 0;
194 }
195 
196 /* Set up a trampoline in the PLT to bounce us to the distant function */
197 static uint32_t do_plt_call(void *location,
198                             Elf32_Addr val,
199                             Elf32_Shdr *sechdrs,
200                             struct module *mod)
201 {
202         struct ppc_plt_entry *entry;
203 
204         DEBUGP("Doing plt for call to 0x%x at 0x%x\n", val, (unsigned int)location);
205         /* Init, or core PLT? */
206         if (location >= mod->module_core
207             && location < mod->module_core + mod->core_size)
208                 entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr;
209         else
210                 entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr;
211 
212         /* Find this entry, or if that fails, the next avail. entry */
213         while (entry->jump[0]) {
214                 if (entry_matches(entry, val)) return (uint32_t)entry;
215                 entry++;
216         }
217 
218         entry->jump[0] = 0x3d800000+((val+0x8000)>>16); /* lis r12,sym@ha */
219         entry->jump[1] = 0x398c0000 + (val&0xffff);     /* addi r12,r12,sym@l*/
220         entry->jump[2] = 0x7d8903a6;                    /* mtctr r12 */
221         entry->jump[3] = 0x4e800420;                    /* bctr */
222 
223         DEBUGP("Initialized plt for 0x%x at %p\n", val, entry);
224         return (uint32_t)entry;
225 }
226 
227 int apply_relocate_add(Elf32_Shdr *sechdrs,
228                        const char *strtab,
229                        unsigned int symindex,
230                        unsigned int relsec,
231                        struct module *module)
232 {
233         unsigned int i;
234         Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr;
235         Elf32_Sym *sym;
236         uint32_t *location;
237         uint32_t value;
238 
239         DEBUGP("Applying ADD relocate section %u to %u\n", relsec,
240                sechdrs[relsec].sh_info);
241         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) {
242                 /* This is where to make the change */
243                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
244                         + rela[i].r_offset;
245                 /* This is the symbol it is referring to.  Note that all
246                    undefined symbols have been resolved.  */
247                 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
248                         + ELF32_R_SYM(rela[i].r_info);
249                 /* `Everything is relative'. */
250                 value = sym->st_value + rela[i].r_addend;
251 
252                 switch (ELF32_R_TYPE(rela[i].r_info)) {
253                 case R_PPC_ADDR32:
254                         /* Simply set it */
255                         *(uint32_t *)location = value;
256                         break;
257 
258                 case R_PPC_ADDR16_LO:
259                         /* Low half of the symbol */
260                         *(uint16_t *)location = value;
261                         break;
262 
263                 case R_PPC_ADDR16_HI:
264                         /* Higher half of the symbol */
265                         *(uint16_t *)location = (value >> 16);
266                         break;
267 
268                 case R_PPC_ADDR16_HA:
269                         /* Sign-adjusted lower 16 bits: PPC ELF ABI says:
270                            (((x >> 16) + ((x & 0x8000) ? 1 : 0))) & 0xFFFF.
271                            This is the same, only sane.
272                          */
273                         *(uint16_t *)location = (value + 0x8000) >> 16;
274                         break;
275 
276                 case R_PPC_REL24:
277                         if ((int)(value - (uint32_t)location) < -0x02000000
278                             || (int)(value - (uint32_t)location) >= 0x02000000)
279                                 value = do_plt_call(location, value,
280                                                     sechdrs, module);
281 
282                         /* Only replace bits 2 through 26 */
283                         DEBUGP("REL24 value = %08X. location = %08X\n",
284                                value, (uint32_t)location);
285                         DEBUGP("Location before: %08X.\n",
286                                *(uint32_t *)location);
287                         *(uint32_t *)location
288                                 = (*(uint32_t *)location & ~0x03fffffc)
289                                 | ((value - (uint32_t)location)
290                                    & 0x03fffffc);
291                         DEBUGP("Location after: %08X.\n",
292                                *(uint32_t *)location);
293                         DEBUGP("ie. jump to %08X+%08X = %08X\n",
294                                *(uint32_t *)location & 0x03fffffc,
295                                (uint32_t)location,
296                                (*(uint32_t *)location & 0x03fffffc)
297                                + (uint32_t)location);
298                         break;
299 
300                 case R_PPC_REL32:
301                         /* 32-bit relative jump. */
302                         *(uint32_t *)location = value - (uint32_t)location;
303                         break;
304 
305                 default:
306                         printk("%s: unknown ADD relocation: %u\n",
307                                module->name,
308                                ELF32_R_TYPE(rela[i].r_info));
309                         return -ENOEXEC;
310                 }
311         }
312 #ifdef CONFIG_DYNAMIC_FTRACE
313         module->arch.tramp =
314                 do_plt_call(module->module_core,
315                             (unsigned long)ftrace_caller,
316                             sechdrs, module);
317 #endif
318         return 0;
319 }
320 

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