1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Kernel module help for PPC.
3 Copyright (C) 2001 Rusty Russell.
7 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9 #include <linux/module.h>
10 #include <linux/moduleloader.h>
11 #include <linux/elf.h>
12 #include <linux/vmalloc.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>
22 /* Count how many different relocations (different symbol, different
24 static unsigned int count_relocs(const Elf32_Rela *rela, unsigned int num)
26 unsigned int i, r_info, r_addend, _count_relocs;
31 for (i = 0; i < num; i++)
32 /* Only count 24-bit relocs, others don't need stubs */
33 if (ELF32_R_TYPE(rela[i].r_info) == R_PPC_REL24 &&
34 (r_info != ELF32_R_SYM(rela[i].r_info) ||
35 r_addend != rela[i].r_addend)) {
37 r_info = ELF32_R_SYM(rela[i].r_info);
38 r_addend = rela[i].r_addend;
41 #ifdef CONFIG_DYNAMIC_FTRACE
42 _count_relocs++; /* add one for ftrace_caller */
47 static int relacmp(const void *_x, const void *_y)
49 const Elf32_Rela *x, *y;
54 /* Compare the entire r_info (as opposed to ELF32_R_SYM(r_info) only) to
55 * make the comparison cheaper/faster. It won't affect the sorting or
56 * the counting algorithms' performance
58 if (x->r_info < y->r_info)
60 else if (x->r_info > y->r_info)
62 else if (x->r_addend < y->r_addend)
64 else if (x->r_addend > y->r_addend)
70 static void relaswap(void *_x, void *_y, int size)
78 for (i = 0; i < sizeof(Elf32_Rela) / sizeof(uint32_t); i++) {
85 /* Get the potential trampolines size required of the init and
87 static unsigned long get_plt_size(const Elf32_Ehdr *hdr,
88 const Elf32_Shdr *sechdrs,
89 const char *secstrings,
92 unsigned long ret = 0;
95 /* Everything marked ALLOC (this includes the exported
97 for (i = 1; i < hdr->e_shnum; i++) {
98 /* If it's called *.init*, and we're not init, we're
100 if ((strstr(secstrings + sechdrs[i].sh_name, ".init") != NULL)
104 /* We don't want to look at debug sections. */
105 if (strstr(secstrings + sechdrs[i].sh_name, ".debug"))
108 if (sechdrs[i].sh_type == SHT_RELA) {
109 pr_debug("Found relocations in section %u\n", i);
110 pr_debug("Ptr: %p. Number: %u\n",
111 (void *)hdr + sechdrs[i].sh_offset,
112 sechdrs[i].sh_size / sizeof(Elf32_Rela));
114 /* Sort the relocation information based on a symbol and
115 * addend key. This is a stable O(n*log n) complexity
116 * alogrithm but it will reduce the complexity of
117 * count_relocs() to linear complexity O(n)
119 sort((void *)hdr + sechdrs[i].sh_offset,
120 sechdrs[i].sh_size / sizeof(Elf32_Rela),
121 sizeof(Elf32_Rela), relacmp, relaswap);
123 ret += count_relocs((void *)hdr
124 + sechdrs[i].sh_offset,
126 / sizeof(Elf32_Rela))
127 * sizeof(struct ppc_plt_entry);
134 int module_frob_arch_sections(Elf32_Ehdr *hdr,
141 /* Find .plt and .init.plt sections */
142 for (i = 0; i < hdr->e_shnum; i++) {
143 if (strcmp(secstrings + sechdrs[i].sh_name, ".init.plt") == 0)
144 me->arch.init_plt_section = i;
145 else if (strcmp(secstrings + sechdrs[i].sh_name, ".plt") == 0)
146 me->arch.core_plt_section = i;
148 if (!me->arch.core_plt_section || !me->arch.init_plt_section) {
149 pr_err("Module doesn't contain .plt or .init.plt sections.\n");
153 /* Override their sizes */
154 sechdrs[me->arch.core_plt_section].sh_size
155 = get_plt_size(hdr, sechdrs, secstrings, 0);
156 sechdrs[me->arch.init_plt_section].sh_size
157 = get_plt_size(hdr, sechdrs, secstrings, 1);
161 static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val)
163 if (entry->jump[0] != (PPC_INST_ADDIS | __PPC_RT(R12) | PPC_HA(val)))
165 if (entry->jump[1] != (PPC_INST_ADDI | __PPC_RT(R12) | __PPC_RA(R12) |
171 /* Set up a trampoline in the PLT to bounce us to the distant function */
172 static uint32_t do_plt_call(void *location,
174 const Elf32_Shdr *sechdrs,
177 struct ppc_plt_entry *entry;
179 pr_debug("Doing plt for call to 0x%x at 0x%x\n", val, (unsigned int)location);
180 /* Init, or core PLT? */
181 if (location >= mod->core_layout.base
182 && location < mod->core_layout.base + mod->core_layout.size)
183 entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr;
185 entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr;
187 /* Find this entry, or if that fails, the next avail. entry */
188 while (entry->jump[0]) {
189 if (entry_matches(entry, val)) return (uint32_t)entry;
195 * addi r12, r12, sym@l
199 entry->jump[0] = PPC_INST_ADDIS | __PPC_RT(R12) | PPC_HA(val);
200 entry->jump[1] = PPC_INST_ADDI | __PPC_RT(R12) | __PPC_RA(R12) | PPC_LO(val);
201 entry->jump[2] = PPC_INST_MTCTR | __PPC_RS(R12);
202 entry->jump[3] = PPC_INST_BCTR;
204 pr_debug("Initialized plt for 0x%x at %p\n", val, entry);
205 return (uint32_t)entry;
208 int apply_relocate_add(Elf32_Shdr *sechdrs,
210 unsigned int symindex,
212 struct module *module)
215 Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr;
220 pr_debug("Applying ADD relocate section %u to %u\n", relsec,
221 sechdrs[relsec].sh_info);
222 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) {
223 /* This is where to make the change */
224 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
226 /* This is the symbol it is referring to. Note that all
227 undefined symbols have been resolved. */
228 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
229 + ELF32_R_SYM(rela[i].r_info);
230 /* `Everything is relative'. */
231 value = sym->st_value + rela[i].r_addend;
233 switch (ELF32_R_TYPE(rela[i].r_info)) {
236 *(uint32_t *)location = value;
239 case R_PPC_ADDR16_LO:
240 /* Low half of the symbol */
241 *(uint16_t *)location = value;
244 case R_PPC_ADDR16_HI:
245 /* Higher half of the symbol */
246 *(uint16_t *)location = (value >> 16);
249 case R_PPC_ADDR16_HA:
250 /* Sign-adjusted lower 16 bits: PPC ELF ABI says:
251 (((x >> 16) + ((x & 0x8000) ? 1 : 0))) & 0xFFFF.
252 This is the same, only sane.
254 *(uint16_t *)location = (value + 0x8000) >> 16;
258 if ((int)(value - (uint32_t)location) < -0x02000000
259 || (int)(value - (uint32_t)location) >= 0x02000000)
260 value = do_plt_call(location, value,
263 /* Only replace bits 2 through 26 */
264 pr_debug("REL24 value = %08X. location = %08X\n",
265 value, (uint32_t)location);
266 pr_debug("Location before: %08X.\n",
267 *(uint32_t *)location);
268 *(uint32_t *)location
269 = (*(uint32_t *)location & ~0x03fffffc)
270 | ((value - (uint32_t)location)
272 pr_debug("Location after: %08X.\n",
273 *(uint32_t *)location);
274 pr_debug("ie. jump to %08X+%08X = %08X\n",
275 *(uint32_t *)location & 0x03fffffc,
277 (*(uint32_t *)location & 0x03fffffc)
278 + (uint32_t)location);
282 /* 32-bit relative jump. */
283 *(uint32_t *)location = value - (uint32_t)location;
287 pr_err("%s: unknown ADD relocation: %u\n",
289 ELF32_R_TYPE(rela[i].r_info));
297 #ifdef CONFIG_DYNAMIC_FTRACE
298 int module_finalize_ftrace(struct module *module, const Elf_Shdr *sechdrs)
300 module->arch.tramp = do_plt_call(module->core_layout.base,
301 (unsigned long)ftrace_caller,
303 if (!module->arch.tramp)