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 size_t len; 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 offset_in_page(addr)); 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 bool across_pages = (offset_in_page(addr) + len) > PAGE_SIZE; 69 void *waddr = addr; 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 patch_unmap(FIX_TEXT_POKE0); 93 94 if (across_pages) 95 patch_unmap(FIX_TEXT_POKE1); 96 97 preempt_enable(); 98 99 return 0; 100 } 101 NOKPROBE_SYMBOL(__patch_insn_set); 102 103 static int __patch_insn_write(void *addr, const void *insn, size_t len) 104 { 105 bool across_pages = (offset_in_page(addr) + len) > PAGE_SIZE; 106 void *waddr = addr; 107 int ret; 108 109 /* 110 * Only two pages can be mapped at a time for writing. 111 */ 112 if (len + offset_in_page(addr) > 2 * PAGE_SIZE) 113 return -EINVAL; 114 115 /* 116 * Before reaching here, it was expected to lock the text_mutex 117 * already, so we don't need to give another lock here and could 118 * ensure that it was safe between each cores. 119 * 120 * We're currently using stop_machine() for ftrace & kprobes, and while 121 * that ensures text_mutex is held before installing the mappings it 122 * does not ensure text_mutex is held by the calling thread. That's 123 * safe but triggers a lockdep failure, so just elide it for that 124 * specific case. 125 */ 126 if (!riscv_patch_in_stop_machine) 127 lockdep_assert_held(&text_mutex); 128 129 preempt_disable(); 130 131 if (across_pages) 132 patch_map(addr + PAGE_SIZE, FIX_TEXT_POKE1); 133 134 waddr = patch_map(addr, FIX_TEXT_POKE0); 135 136 ret = copy_to_kernel_nofault(waddr, insn, len); 137 138 patch_unmap(FIX_TEXT_POKE0); 139 140 if (across_pages) 141 patch_unmap(FIX_TEXT_POKE1); 142 143 preempt_enable(); 144 145 return ret; 146 } 147 NOKPROBE_SYMBOL(__patch_insn_write); 148 #else 149 static int __patch_insn_set(void *addr, u8 c, size_t len) 150 { 151 memset(addr, c, len); 152 153 return 0; 154 } 155 NOKPROBE_SYMBOL(__patch_insn_set); 156 157 static int __patch_insn_write(void *addr, const void *insn, size_t len) 158 { 159 return copy_to_kernel_nofault(addr, insn, len); 160 } 161 NOKPROBE_SYMBOL(__patch_insn_write); 162 #endif /* CONFIG_MMU */ 163 164 static int patch_insn_set(void *addr, u8 c, size_t len) 165 { 166 size_t size; 167 int ret; 168 169 /* 170 * __patch_insn_set() can only work on 2 pages at a time so call it in a 171 * loop with len <= 2 * PAGE_SIZE. 172 */ 173 while (len) { 174 size = min(len, PAGE_SIZE * 2 - offset_in_page(addr)); 175 ret = __patch_insn_set(addr, c, size); 176 if (ret) 177 return ret; 178 179 addr += size; 180 len -= size; 181 } 182 183 return 0; 184 } 185 NOKPROBE_SYMBOL(patch_insn_set); 186 187 int patch_text_set_nosync(void *addr, u8 c, size_t len) 188 { 189 u32 *tp = addr; 190 int ret; 191 192 ret = patch_insn_set(tp, c, len); 193 194 if (!ret) 195 flush_icache_range((uintptr_t)tp, (uintptr_t)tp + len); 196 197 return ret; 198 } 199 NOKPROBE_SYMBOL(patch_text_set_nosync); 200 201 int patch_insn_write(void *addr, const void *insn, size_t len) 202 { 203 size_t size; 204 int ret; 205 206 /* 207 * Copy the instructions to the destination address, two pages at a time 208 * because __patch_insn_write() can only handle len <= 2 * PAGE_SIZE. 209 */ 210 while (len) { 211 size = min(len, PAGE_SIZE * 2 - offset_in_page(addr)); 212 ret = __patch_insn_write(addr, insn, size); 213 if (ret) 214 return ret; 215 216 addr += size; 217 insn += size; 218 len -= size; 219 } 220 221 return 0; 222 } 223 NOKPROBE_SYMBOL(patch_insn_write); 224 225 int patch_text_nosync(void *addr, const void *insns, size_t len) 226 { 227 u32 *tp = addr; 228 int ret; 229 230 ret = patch_insn_write(tp, insns, len); 231 232 if (!ret) 233 flush_icache_range((uintptr_t) tp, (uintptr_t) tp + len); 234 235 return ret; 236 } 237 NOKPROBE_SYMBOL(patch_text_nosync); 238 239 static int patch_text_cb(void *data) 240 { 241 struct patch_insn *patch = data; 242 int ret = 0; 243 244 if (atomic_inc_return(&patch->cpu_count) == num_online_cpus()) { 245 ret = patch_insn_write(patch->addr, patch->insns, patch->len); 246 /* 247 * Make sure the patching store is effective *before* we 248 * increment the counter which releases all waiting CPUs 249 * by using the release variant of atomic increment. The 250 * release pairs with the call to local_flush_icache_all() 251 * on the waiting CPU. 252 */ 253 atomic_inc_return_release(&patch->cpu_count); 254 } else { 255 while (atomic_read(&patch->cpu_count) <= num_online_cpus()) 256 cpu_relax(); 257 } 258 259 local_flush_icache_all(); 260 261 return ret; 262 } 263 NOKPROBE_SYMBOL(patch_text_cb); 264 265 int patch_text(void *addr, u32 *insns, size_t len) 266 { 267 int ret; 268 struct patch_insn patch = { 269 .addr = addr, 270 .insns = insns, 271 .len = len, 272 .cpu_count = ATOMIC_INIT(0), 273 }; 274 275 /* 276 * kprobes takes text_mutex, before calling patch_text(), but as we call 277 * calls stop_machine(), the lockdep assertion in patch_insn_write() 278 * gets confused by the context in which the lock is taken. 279 * Instead, ensure the lock is held before calling stop_machine(), and 280 * set riscv_patch_in_stop_machine to skip the check in 281 * patch_insn_write(). 282 */ 283 lockdep_assert_held(&text_mutex); 284 riscv_patch_in_stop_machine = true; 285 ret = stop_machine_cpuslocked(patch_text_cb, &patch, cpu_online_mask); 286 riscv_patch_in_stop_machine = false; 287 return ret; 288 } 289 NOKPROBE_SYMBOL(patch_text); 290