1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) 2020 SiFive 4 */ 5 6 #include <linux/spinlock.h> 7 #include <linux/mm.h> 8 #include <linux/memory.h> 9 #include <linux/string.h> 10 #include <linux/uaccess.h> 11 #include <linux/stop_machine.h> 12 #include <asm/kprobes.h> 13 #include <asm/cacheflush.h> 14 #include <asm/fixmap.h> 15 #include <asm/ftrace.h> 16 #include <asm/patch.h> 17 #include <asm/sections.h> 18 19 struct patch_insn { 20 void *addr; 21 u32 *insns; 22 int ninsns; 23 atomic_t cpu_count; 24 }; 25 26 int riscv_patch_in_stop_machine = false; 27 28 #ifdef CONFIG_MMU 29 30 static inline bool is_kernel_exittext(uintptr_t addr) 31 { 32 return system_state < SYSTEM_RUNNING && 33 addr >= (uintptr_t)__exittext_begin && 34 addr < (uintptr_t)__exittext_end; 35 } 36 37 /* 38 * The fix_to_virt(, idx) needs a const value (not a dynamic variable of 39 * reg-a0) or BUILD_BUG_ON failed with "idx >= __end_of_fixed_addresses". 40 * So use '__always_inline' and 'const unsigned int fixmap' here. 41 */ 42 static __always_inline void *patch_map(void *addr, const unsigned int fixmap) 43 { 44 uintptr_t uintaddr = (uintptr_t) addr; 45 struct page *page; 46 47 if (core_kernel_text(uintaddr) || is_kernel_exittext(uintaddr)) 48 page = phys_to_page(__pa_symbol(addr)); 49 else if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX)) 50 page = vmalloc_to_page(addr); 51 else 52 return addr; 53 54 BUG_ON(!page); 55 56 return (void *)set_fixmap_offset(fixmap, page_to_phys(page) + 57 (uintaddr & ~PAGE_MASK)); 58 } 59 60 static void patch_unmap(int fixmap) 61 { 62 clear_fixmap(fixmap); 63 } 64 NOKPROBE_SYMBOL(patch_unmap); 65 66 static int __patch_insn_set(void *addr, u8 c, size_t len) 67 { 68 void *waddr = addr; 69 bool across_pages = (((uintptr_t)addr & ~PAGE_MASK) + len) > PAGE_SIZE; 70 71 /* 72 * Only two pages can be mapped at a time for writing. 73 */ 74 if (len + offset_in_page(addr) > 2 * PAGE_SIZE) 75 return -EINVAL; 76 /* 77 * Before reaching here, it was expected to lock the text_mutex 78 * already, so we don't need to give another lock here and could 79 * ensure that it was safe between each cores. 80 */ 81 lockdep_assert_held(&text_mutex); 82 83 preempt_disable(); 84 85 if (across_pages) 86 patch_map(addr + PAGE_SIZE, FIX_TEXT_POKE1); 87 88 waddr = patch_map(addr, FIX_TEXT_POKE0); 89 90 memset(waddr, c, len); 91 92 /* 93 * We could have just patched a function that is about to be 94 * called so make sure we don't execute partially patched 95 * instructions by flushing the icache as soon as possible. 96 */ 97 local_flush_icache_range((unsigned long)waddr, 98 (unsigned long)waddr + len); 99 100 patch_unmap(FIX_TEXT_POKE0); 101 102 if (across_pages) 103 patch_unmap(FIX_TEXT_POKE1); 104 105 preempt_enable(); 106 107 return 0; 108 } 109 NOKPROBE_SYMBOL(__patch_insn_set); 110 111 static int __patch_insn_write(void *addr, const void *insn, size_t len) 112 { 113 void *waddr = addr; 114 bool across_pages = (((uintptr_t) addr & ~PAGE_MASK) + len) > PAGE_SIZE; 115 int ret; 116 117 /* 118 * Only two pages can be mapped at a time for writing. 119 */ 120 if (len + offset_in_page(addr) > 2 * PAGE_SIZE) 121 return -EINVAL; 122 123 /* 124 * Before reaching here, it was expected to lock the text_mutex 125 * already, so we don't need to give another lock here and could 126 * ensure that it was safe between each cores. 127 * 128 * We're currently using stop_machine() for ftrace & kprobes, and while 129 * that ensures text_mutex is held before installing the mappings it 130 * does not ensure text_mutex is held by the calling thread. That's 131 * safe but triggers a lockdep failure, so just elide it for that 132 * specific case. 133 */ 134 if (!riscv_patch_in_stop_machine) 135 lockdep_assert_held(&text_mutex); 136 137 preempt_disable(); 138 139 if (across_pages) 140 patch_map(addr + PAGE_SIZE, FIX_TEXT_POKE1); 141 142 waddr = patch_map(addr, FIX_TEXT_POKE0); 143 144 ret = copy_to_kernel_nofault(waddr, insn, len); 145 146 /* 147 * We could have just patched a function that is about to be 148 * called so make sure we don't execute partially patched 149 * instructions by flushing the icache as soon as possible. 150 */ 151 local_flush_icache_range((unsigned long)waddr, 152 (unsigned long)waddr + len); 153 154 patch_unmap(FIX_TEXT_POKE0); 155 156 if (across_pages) 157 patch_unmap(FIX_TEXT_POKE1); 158 159 preempt_enable(); 160 161 return ret; 162 } 163 NOKPROBE_SYMBOL(__patch_insn_write); 164 #else 165 static int __patch_insn_set(void *addr, u8 c, size_t len) 166 { 167 memset(addr, c, len); 168 169 return 0; 170 } 171 NOKPROBE_SYMBOL(__patch_insn_set); 172 173 static int __patch_insn_write(void *addr, const void *insn, size_t len) 174 { 175 return copy_to_kernel_nofault(addr, insn, len); 176 } 177 NOKPROBE_SYMBOL(__patch_insn_write); 178 #endif /* CONFIG_MMU */ 179 180 static int patch_insn_set(void *addr, u8 c, size_t len) 181 { 182 size_t patched = 0; 183 size_t size; 184 int ret = 0; 185 186 /* 187 * __patch_insn_set() can only work on 2 pages at a time so call it in a 188 * loop with len <= 2 * PAGE_SIZE. 189 */ 190 while (patched < len && !ret) { 191 size = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(addr + patched), len - patched); 192 ret = __patch_insn_set(addr + patched, c, size); 193 194 patched += size; 195 } 196 197 return ret; 198 } 199 NOKPROBE_SYMBOL(patch_insn_set); 200 201 int patch_text_set_nosync(void *addr, u8 c, size_t len) 202 { 203 u32 *tp = addr; 204 int ret; 205 206 ret = patch_insn_set(tp, c, len); 207 208 return ret; 209 } 210 NOKPROBE_SYMBOL(patch_text_set_nosync); 211 212 int patch_insn_write(void *addr, const void *insn, size_t len) 213 { 214 size_t patched = 0; 215 size_t size; 216 int ret = 0; 217 218 /* 219 * Copy the instructions to the destination address, two pages at a time 220 * because __patch_insn_write() can only handle len <= 2 * PAGE_SIZE. 221 */ 222 while (patched < len && !ret) { 223 size = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(addr + patched), len - patched); 224 ret = __patch_insn_write(addr + patched, insn + patched, size); 225 226 patched += size; 227 } 228 229 return ret; 230 } 231 NOKPROBE_SYMBOL(patch_insn_write); 232 233 int patch_text_nosync(void *addr, const void *insns, size_t len) 234 { 235 u32 *tp = addr; 236 int ret; 237 238 ret = patch_insn_write(tp, insns, len); 239 240 return ret; 241 } 242 NOKPROBE_SYMBOL(patch_text_nosync); 243 244 static int patch_text_cb(void *data) 245 { 246 struct patch_insn *patch = data; 247 unsigned long len; 248 int i, ret = 0; 249 250 if (atomic_inc_return(&patch->cpu_count) == num_online_cpus()) { 251 for (i = 0; ret == 0 && i < patch->ninsns; i++) { 252 len = GET_INSN_LENGTH(patch->insns[i]); 253 ret = patch_insn_write(patch->addr + i * len, &patch->insns[i], len); 254 } 255 /* 256 * Make sure the patching store is effective *before* we 257 * increment the counter which releases all waiting CPUs 258 * by using the release variant of atomic increment. The 259 * release pairs with the call to local_flush_icache_all() 260 * on the waiting CPU. 261 */ 262 atomic_inc_return_release(&patch->cpu_count); 263 } else { 264 while (atomic_read(&patch->cpu_count) <= num_online_cpus()) 265 cpu_relax(); 266 267 local_flush_icache_all(); 268 } 269 270 return ret; 271 } 272 NOKPROBE_SYMBOL(patch_text_cb); 273 274 int patch_text(void *addr, u32 *insns, int ninsns) 275 { 276 int ret; 277 struct patch_insn patch = { 278 .addr = addr, 279 .insns = insns, 280 .ninsns = ninsns, 281 .cpu_count = ATOMIC_INIT(0), 282 }; 283 284 /* 285 * kprobes takes text_mutex, before calling patch_text(), but as we call 286 * calls stop_machine(), the lockdep assertion in patch_insn_write() 287 * gets confused by the context in which the lock is taken. 288 * Instead, ensure the lock is held before calling stop_machine(), and 289 * set riscv_patch_in_stop_machine to skip the check in 290 * patch_insn_write(). 291 */ 292 lockdep_assert_held(&text_mutex); 293 riscv_patch_in_stop_machine = true; 294 ret = stop_machine_cpuslocked(patch_text_cb, &patch, cpu_online_mask); 295 riscv_patch_in_stop_machine = false; 296 return ret; 297 } 298 NOKPROBE_SYMBOL(patch_text); 299