1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Kernel module help for PPC.
3 Copyright (C) 2001 Rusty Russell.
4
5 */
6
7 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
8
9 #include <linux/module.h>
10 #include <linux/moduleloader.h>
11 #include <linux/elf.h>
12 #include <linux/vmalloc.h>
13 #include <linux/fs.h>
14 #include <linux/string.h>
15 #include <linux/kernel.h>
16 #include <linux/ftrace.h>
17 #include <linux/cache.h>
18 #include <linux/bug.h>
19 #include <linux/sort.h>
20 #include <asm/setup.h>
21 #include <asm/code-patching.h>
22
23 /* Count how many different relocations (different symbol, different
24 addend) */
count_relocs(const Elf32_Rela * rela,unsigned int num)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 24-bit relocs, others don't need stubs */
34 if (ELF32_R_TYPE(rela[i].r_info) == R_PPC_REL24 &&
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 #ifdef CONFIG_DYNAMIC_FTRACE
43 _count_relocs++; /* add one for ftrace_caller */
44 #endif
45 return _count_relocs;
46 }
47
relacmp(const void * _x,const void * _y)48 static int relacmp(const void *_x, const void *_y)
49 {
50 const Elf32_Rela *x, *y;
51
52 y = (Elf32_Rela *)_x;
53 x = (Elf32_Rela *)_y;
54
55 /* Compare the entire r_info (as opposed to ELF32_R_SYM(r_info) only) to
56 * make the comparison cheaper/faster. It won't affect the sorting or
57 * the counting algorithms' performance
58 */
59 if (x->r_info < y->r_info)
60 return -1;
61 else if (x->r_info > y->r_info)
62 return 1;
63 else if (x->r_addend < y->r_addend)
64 return -1;
65 else if (x->r_addend > y->r_addend)
66 return 1;
67 else
68 return 0;
69 }
70
71 /* Get the potential trampolines size required of the init and
72 non-init sections */
get_plt_size(const Elf32_Ehdr * hdr,const Elf32_Shdr * sechdrs,const char * secstrings,int is_init)73 static unsigned long get_plt_size(const Elf32_Ehdr *hdr,
74 const Elf32_Shdr *sechdrs,
75 const char *secstrings,
76 int is_init)
77 {
78 unsigned long ret = 0;
79 unsigned i;
80
81 /* Everything marked ALLOC (this includes the exported
82 symbols) */
83 for (i = 1; i < hdr->e_shnum; i++) {
84 /* If it's called *.init*, and we're not init, we're
85 not interested */
86 if ((strstr(secstrings + sechdrs[i].sh_name, ".init") != NULL)
87 != is_init)
88 continue;
89
90 /* We don't want to look at debug sections. */
91 if (strstr(secstrings + sechdrs[i].sh_name, ".debug"))
92 continue;
93
94 if (sechdrs[i].sh_type == SHT_RELA) {
95 pr_debug("Found relocations in section %u\n", i);
96 pr_debug("Ptr: %p. Number: %u\n",
97 (void *)hdr + sechdrs[i].sh_offset,
98 sechdrs[i].sh_size / sizeof(Elf32_Rela));
99
100 /* Sort the relocation information based on a symbol and
101 * addend key. This is a stable O(n*log n) complexity
102 * algorithm but it will reduce the complexity of
103 * count_relocs() to linear complexity O(n)
104 */
105 sort((void *)hdr + sechdrs[i].sh_offset,
106 sechdrs[i].sh_size / sizeof(Elf32_Rela),
107 sizeof(Elf32_Rela), relacmp, NULL);
108
109 ret += count_relocs((void *)hdr
110 + sechdrs[i].sh_offset,
111 sechdrs[i].sh_size
112 / sizeof(Elf32_Rela))
113 * sizeof(struct ppc_plt_entry);
114 }
115 }
116
117 return ret;
118 }
119
module_frob_arch_sections(Elf32_Ehdr * hdr,Elf32_Shdr * sechdrs,char * secstrings,struct module * me)120 int module_frob_arch_sections(Elf32_Ehdr *hdr,
121 Elf32_Shdr *sechdrs,
122 char *secstrings,
123 struct module *me)
124 {
125 unsigned int i;
126
127 /* Find .plt and .init.plt sections */
128 for (i = 0; i < hdr->e_shnum; i++) {
129 if (strcmp(secstrings + sechdrs[i].sh_name, ".init.plt") == 0)
130 me->arch.init_plt_section = i;
131 else if (strcmp(secstrings + sechdrs[i].sh_name, ".plt") == 0)
132 me->arch.core_plt_section = i;
133 }
134 if (!me->arch.core_plt_section || !me->arch.init_plt_section) {
135 pr_err("Module doesn't contain .plt or .init.plt sections.\n");
136 return -ENOEXEC;
137 }
138
139 /* Override their sizes */
140 sechdrs[me->arch.core_plt_section].sh_size
141 = get_plt_size(hdr, sechdrs, secstrings, 0);
142 sechdrs[me->arch.init_plt_section].sh_size
143 = get_plt_size(hdr, sechdrs, secstrings, 1);
144 return 0;
145 }
146
entry_matches(struct ppc_plt_entry * entry,Elf32_Addr val)147 static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val)
148 {
149 if (entry->jump[0] != PPC_RAW_LIS(_R12, PPC_HA(val)))
150 return 0;
151 if (entry->jump[1] != PPC_RAW_ADDI(_R12, _R12, PPC_LO(val)))
152 return 0;
153 return 1;
154 }
155
156 /* Set up a trampoline in the PLT to bounce us to the distant function */
do_plt_call(void * location,Elf32_Addr val,const Elf32_Shdr * sechdrs,struct module * mod)157 static uint32_t do_plt_call(void *location,
158 Elf32_Addr val,
159 const Elf32_Shdr *sechdrs,
160 struct module *mod)
161 {
162 struct ppc_plt_entry *entry;
163
164 pr_debug("Doing plt for call to 0x%x at 0x%x\n", val, (unsigned int)location);
165 /* Init, or core PLT? */
166 if (location >= mod->core_layout.base
167 && location < mod->core_layout.base + mod->core_layout.size)
168 entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr;
169 else
170 entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr;
171
172 /* Find this entry, or if that fails, the next avail. entry */
173 while (entry->jump[0]) {
174 if (entry_matches(entry, val)) return (uint32_t)entry;
175 entry++;
176 }
177
178 if (patch_instruction(&entry->jump[0], ppc_inst(PPC_RAW_LIS(_R12, PPC_HA(val)))))
179 return 0;
180 if (patch_instruction(&entry->jump[1], ppc_inst(PPC_RAW_ADDI(_R12, _R12, PPC_LO(val)))))
181 return 0;
182 if (patch_instruction(&entry->jump[2], ppc_inst(PPC_RAW_MTCTR(_R12))))
183 return 0;
184 if (patch_instruction(&entry->jump[3], ppc_inst(PPC_RAW_BCTR())))
185 return 0;
186
187 pr_debug("Initialized plt for 0x%x at %p\n", val, entry);
188 return (uint32_t)entry;
189 }
190
patch_location_16(uint32_t * loc,u16 value)191 static int patch_location_16(uint32_t *loc, u16 value)
192 {
193 loc = PTR_ALIGN_DOWN(loc, sizeof(u32));
194 return patch_instruction(loc, ppc_inst((*loc & 0xffff0000) | value));
195 }
196
apply_relocate_add(Elf32_Shdr * sechdrs,const char * strtab,unsigned int symindex,unsigned int relsec,struct module * module)197 int apply_relocate_add(Elf32_Shdr *sechdrs,
198 const char *strtab,
199 unsigned int symindex,
200 unsigned int relsec,
201 struct module *module)
202 {
203 unsigned int i;
204 Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr;
205 Elf32_Sym *sym;
206 uint32_t *location;
207 uint32_t value;
208
209 pr_debug("Applying ADD relocate section %u to %u\n", relsec,
210 sechdrs[relsec].sh_info);
211 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) {
212 /* This is where to make the change */
213 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
214 + rela[i].r_offset;
215 /* This is the symbol it is referring to. Note that all
216 undefined symbols have been resolved. */
217 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
218 + ELF32_R_SYM(rela[i].r_info);
219 /* `Everything is relative'. */
220 value = sym->st_value + rela[i].r_addend;
221
222 switch (ELF32_R_TYPE(rela[i].r_info)) {
223 case R_PPC_ADDR32:
224 /* Simply set it */
225 *(uint32_t *)location = value;
226 break;
227
228 case R_PPC_ADDR16_LO:
229 /* Low half of the symbol */
230 if (patch_location_16(location, PPC_LO(value)))
231 return -EFAULT;
232 break;
233
234 case R_PPC_ADDR16_HI:
235 /* Higher half of the symbol */
236 if (patch_location_16(location, PPC_HI(value)))
237 return -EFAULT;
238 break;
239
240 case R_PPC_ADDR16_HA:
241 if (patch_location_16(location, PPC_HA(value)))
242 return -EFAULT;
243 break;
244
245 case R_PPC_REL24:
246 if ((int)(value - (uint32_t)location) < -0x02000000
247 || (int)(value - (uint32_t)location) >= 0x02000000) {
248 value = do_plt_call(location, value,
249 sechdrs, module);
250 if (!value)
251 return -EFAULT;
252 }
253
254 /* Only replace bits 2 through 26 */
255 pr_debug("REL24 value = %08X. location = %08X\n",
256 value, (uint32_t)location);
257 pr_debug("Location before: %08X.\n",
258 *(uint32_t *)location);
259 value = (*(uint32_t *)location & ~PPC_LI_MASK) |
260 PPC_LI(value - (uint32_t)location);
261
262 if (patch_instruction(location, ppc_inst(value)))
263 return -EFAULT;
264
265 pr_debug("Location after: %08X.\n",
266 *(uint32_t *)location);
267 pr_debug("ie. jump to %08X+%08X = %08X\n",
268 *(uint32_t *)PPC_LI((uint32_t)location), (uint32_t)location,
269 (*(uint32_t *)PPC_LI((uint32_t)location)) + (uint32_t)location);
270 break;
271
272 case R_PPC_REL32:
273 /* 32-bit relative jump. */
274 *(uint32_t *)location = value - (uint32_t)location;
275 break;
276
277 default:
278 pr_err("%s: unknown ADD relocation: %u\n",
279 module->name,
280 ELF32_R_TYPE(rela[i].r_info));
281 return -ENOEXEC;
282 }
283 }
284
285 return 0;
286 }
287
288 #ifdef CONFIG_DYNAMIC_FTRACE
module_trampoline_target(struct module * mod,unsigned long addr,unsigned long * target)289 notrace int module_trampoline_target(struct module *mod, unsigned long addr,
290 unsigned long *target)
291 {
292 ppc_inst_t jmp[4];
293
294 /* Find where the trampoline jumps to */
295 if (copy_inst_from_kernel_nofault(jmp, (void *)addr))
296 return -EFAULT;
297 if (__copy_inst_from_kernel_nofault(jmp + 1, (void *)addr + 4))
298 return -EFAULT;
299 if (__copy_inst_from_kernel_nofault(jmp + 2, (void *)addr + 8))
300 return -EFAULT;
301 if (__copy_inst_from_kernel_nofault(jmp + 3, (void *)addr + 12))
302 return -EFAULT;
303
304 /* verify that this is what we expect it to be */
305 if ((ppc_inst_val(jmp[0]) & 0xffff0000) != PPC_RAW_LIS(_R12, 0))
306 return -EINVAL;
307 if ((ppc_inst_val(jmp[1]) & 0xffff0000) != PPC_RAW_ADDI(_R12, _R12, 0))
308 return -EINVAL;
309 if (ppc_inst_val(jmp[2]) != PPC_RAW_MTCTR(_R12))
310 return -EINVAL;
311 if (ppc_inst_val(jmp[3]) != PPC_RAW_BCTR())
312 return -EINVAL;
313
314 addr = (ppc_inst_val(jmp[1]) & 0xffff) | ((ppc_inst_val(jmp[0]) & 0xffff) << 16);
315 if (addr & 0x8000)
316 addr -= 0x10000;
317
318 *target = addr;
319
320 return 0;
321 }
322
module_finalize_ftrace(struct module * module,const Elf_Shdr * sechdrs)323 int module_finalize_ftrace(struct module *module, const Elf_Shdr *sechdrs)
324 {
325 module->arch.tramp = do_plt_call(module->core_layout.base,
326 (unsigned long)ftrace_caller,
327 sechdrs, module);
328 if (!module->arch.tramp)
329 return -ENOENT;
330
331 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
332 module->arch.tramp_regs = do_plt_call(module->core_layout.base,
333 (unsigned long)ftrace_regs_caller,
334 sechdrs, module);
335 if (!module->arch.tramp_regs)
336 return -ENOENT;
337 #endif
338
339 return 0;
340 }
341 #endif
342