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/text-patching.h>
22
23/* Count how many different relocations (different symbol, different
24 addend) */
25static 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
48static 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 */
73static 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(base: (void *)hdr + sechdrs[i].sh_offset,
106 num: sechdrs[i].sh_size / sizeof(Elf32_Rela),
107 size: sizeof(Elf32_Rela), cmp_func: 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
120int 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, is_init: 0);
142 sechdrs[me->arch.init_plt_section].sh_size
143 = get_plt_size(hdr, sechdrs, secstrings, is_init: 1);
144 return 0;
145}
146
147static 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 */
157static 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 (within_module_core(addr: (unsigned long)location, mod))
167 entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr;
168 else
169 entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr;
170
171 /* Find this entry, or if that fails, the next avail. entry */
172 while (entry->jump[0]) {
173 if (entry_matches(entry, val)) return (uint32_t)entry;
174 entry++;
175 }
176
177 if (patch_instruction(&entry->jump[0], ppc_inst(PPC_RAW_LIS(_R12, PPC_HA(val)))))
178 return 0;
179 if (patch_instruction(&entry->jump[1], ppc_inst(PPC_RAW_ADDI(_R12, _R12, PPC_LO(val)))))
180 return 0;
181 if (patch_instruction(&entry->jump[2], ppc_inst(PPC_RAW_MTCTR(_R12))))
182 return 0;
183 if (patch_instruction(&entry->jump[3], ppc_inst(PPC_RAW_BCTR())))
184 return 0;
185
186 pr_debug("Initialized plt for 0x%x at %p\n", val, entry);
187 return (uint32_t)entry;
188}
189
190static int patch_location_16(uint32_t *loc, u16 value)
191{
192 loc = PTR_ALIGN_DOWN(loc, sizeof(u32));
193 return patch_instruction(loc, ppc_inst((*loc & 0xffff0000) | value));
194}
195
196int apply_relocate_add(Elf32_Shdr *sechdrs,
197 const char *strtab,
198 unsigned int symindex,
199 unsigned int relsec,
200 struct module *module)
201{
202 unsigned int i;
203 Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr;
204 Elf32_Sym *sym;
205 uint32_t *location;
206 uint32_t value;
207
208 pr_debug("Applying ADD relocate section %u to %u\n", relsec,
209 sechdrs[relsec].sh_info);
210 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) {
211 /* This is where to make the change */
212 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
213 + rela[i].r_offset;
214 /* This is the symbol it is referring to. Note that all
215 undefined symbols have been resolved. */
216 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
217 + ELF32_R_SYM(rela[i].r_info);
218 /* `Everything is relative'. */
219 value = sym->st_value + rela[i].r_addend;
220
221 switch (ELF32_R_TYPE(rela[i].r_info)) {
222 case R_PPC_ADDR32:
223 /* Simply set it */
224 *(uint32_t *)location = value;
225 break;
226
227 case R_PPC_ADDR16_LO:
228 /* Low half of the symbol */
229 if (patch_location_16(loc: location, value: PPC_LO(value)))
230 return -EFAULT;
231 break;
232
233 case R_PPC_ADDR16_HI:
234 /* Higher half of the symbol */
235 if (patch_location_16(loc: location, value: PPC_HI(value)))
236 return -EFAULT;
237 break;
238
239 case R_PPC_ADDR16_HA:
240 if (patch_location_16(loc: location, value: PPC_HA(value)))
241 return -EFAULT;
242 break;
243
244 case R_PPC_REL24:
245 if ((int)(value - (uint32_t)location) < -0x02000000
246 || (int)(value - (uint32_t)location) >= 0x02000000) {
247 value = do_plt_call(location, val: value,
248 sechdrs, mod: module);
249 if (!value)
250 return -EFAULT;
251 }
252
253 /* Only replace bits 2 through 26 */
254 pr_debug("REL24 value = %08X. location = %08X\n",
255 value, (uint32_t)location);
256 pr_debug("Location before: %08X.\n",
257 *(uint32_t *)location);
258 value = (*(uint32_t *)location & ~PPC_LI_MASK) |
259 PPC_LI(value - (uint32_t)location);
260
261 if (patch_instruction(location, ppc_inst(value)))
262 return -EFAULT;
263
264 pr_debug("Location after: %08X.\n",
265 *(uint32_t *)location);
266 pr_debug("ie. jump to %08X+%08X = %08X\n",
267 *(uint32_t *)PPC_LI((uint32_t)location), (uint32_t)location,
268 (*(uint32_t *)PPC_LI((uint32_t)location)) + (uint32_t)location);
269 break;
270
271 case R_PPC_REL32:
272 /* 32-bit relative jump. */
273 *(uint32_t *)location = value - (uint32_t)location;
274 break;
275
276 default:
277 pr_err("%s: unknown ADD relocation: %u\n",
278 module->name,
279 ELF32_R_TYPE(rela[i].r_info));
280 return -ENOEXEC;
281 }
282 }
283
284 return 0;
285}
286
287#ifdef CONFIG_DYNAMIC_FTRACE
288notrace int module_trampoline_target(struct module *mod, unsigned long addr,
289 unsigned long *target)
290{
291 ppc_inst_t jmp[4];
292
293 /* Find where the trampoline jumps to */
294 if (copy_inst_from_kernel_nofault(jmp, (void *)addr))
295 return -EFAULT;
296 if (__copy_inst_from_kernel_nofault(jmp + 1, (void *)addr + 4))
297 return -EFAULT;
298 if (__copy_inst_from_kernel_nofault(jmp + 2, (void *)addr + 8))
299 return -EFAULT;
300 if (__copy_inst_from_kernel_nofault(jmp + 3, (void *)addr + 12))
301 return -EFAULT;
302
303 /* verify that this is what we expect it to be */
304 if ((ppc_inst_val(jmp[0]) & 0xffff0000) != PPC_RAW_LIS(_R12, 0))
305 return -EINVAL;
306 if ((ppc_inst_val(jmp[1]) & 0xffff0000) != PPC_RAW_ADDI(_R12, _R12, 0))
307 return -EINVAL;
308 if (ppc_inst_val(jmp[2]) != PPC_RAW_MTCTR(_R12))
309 return -EINVAL;
310 if (ppc_inst_val(jmp[3]) != PPC_RAW_BCTR())
311 return -EINVAL;
312
313 addr = (ppc_inst_val(jmp[1]) & 0xffff) | ((ppc_inst_val(jmp[0]) & 0xffff) << 16);
314 if (addr & 0x8000)
315 addr -= 0x10000;
316
317 *target = addr;
318
319 return 0;
320}
321
322int module_finalize_ftrace(struct module *module, const Elf_Shdr *sechdrs)
323{
324 module->arch.tramp = do_plt_call(location: module->mem[MOD_TEXT].base,
325 val: (unsigned long)ftrace_caller,
326 sechdrs, mod: module);
327 if (!module->arch.tramp)
328 return -ENOENT;
329
330#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
331 module->arch.tramp_regs = do_plt_call(location: module->mem[MOD_TEXT].base,
332 val: (unsigned long)ftrace_regs_caller,
333 sechdrs, mod: module);
334 if (!module->arch.tramp_regs)
335 return -ENOENT;
336#endif
337
338 return 0;
339}
340#endif
341

source code of linux/arch/powerpc/kernel/module_32.c