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 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 void *waddr = addr; 106 bool across_pages = (((uintptr_t) addr & ~PAGE_MASK) + len) > PAGE_SIZE; 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 patched = 0; 167 size_t size; 168 int ret = 0; 169 170 /* 171 * __patch_insn_set() can only work on 2 pages at a time so call it in a 172 * loop with len <= 2 * PAGE_SIZE. 173 */ 174 while (patched < len && !ret) { 175 size = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(addr + patched), len - patched); 176 ret = __patch_insn_set(addr + patched, c, size); 177 178 patched += size; 179 } 180 181 return ret; 182 } 183 NOKPROBE_SYMBOL(patch_insn_set); 184 185 int patch_text_set_nosync(void *addr, u8 c, size_t len) 186 { 187 u32 *tp = addr; 188 int ret; 189 190 ret = patch_insn_set(tp, c, len); 191 192 if (!ret) 193 flush_icache_range((uintptr_t)tp, (uintptr_t)tp + len); 194 195 return ret; 196 } 197 NOKPROBE_SYMBOL(patch_text_set_nosync); 198 199 static int patch_insn_write(void *addr, const void *insn, size_t len) 200 { 201 size_t patched = 0; 202 size_t size; 203 int ret = 0; 204 205 /* 206 * Copy the instructions to the destination address, two pages at a time 207 * because __patch_insn_write() can only handle len <= 2 * PAGE_SIZE. 208 */ 209 while (patched < len && !ret) { 210 size = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(addr + patched), len - patched); 211 ret = __patch_insn_write(addr + patched, insn + patched, size); 212 213 patched += size; 214 } 215 216 return ret; 217 } 218 NOKPROBE_SYMBOL(patch_insn_write); 219 220 int patch_text_nosync(void *addr, const void *insns, size_t len) 221 { 222 u32 *tp = addr; 223 int ret; 224 225 ret = patch_insn_write(tp, insns, len); 226 227 if (!ret) 228 flush_icache_range((uintptr_t) tp, (uintptr_t) tp + len); 229 230 return ret; 231 } 232 NOKPROBE_SYMBOL(patch_text_nosync); 233 234 static int patch_text_cb(void *data) 235 { 236 struct patch_insn *patch = data; 237 unsigned long len; 238 int i, ret = 0; 239 240 if (atomic_inc_return(&patch->cpu_count) == num_online_cpus()) { 241 for (i = 0; ret == 0 && i < patch->ninsns; i++) { 242 len = GET_INSN_LENGTH(patch->insns[i]); 243 ret = patch_text_nosync(patch->addr + i * len, 244 &patch->insns[i], len); 245 } 246 atomic_inc(&patch->cpu_count); 247 } else { 248 while (atomic_read(&patch->cpu_count) <= num_online_cpus()) 249 cpu_relax(); 250 smp_mb(); 251 } 252 253 return ret; 254 } 255 NOKPROBE_SYMBOL(patch_text_cb); 256 257 int patch_text(void *addr, u32 *insns, int ninsns) 258 { 259 int ret; 260 struct patch_insn patch = { 261 .addr = addr, 262 .insns = insns, 263 .ninsns = ninsns, 264 .cpu_count = ATOMIC_INIT(0), 265 }; 266 267 /* 268 * kprobes takes text_mutex, before calling patch_text(), but as we call 269 * calls stop_machine(), the lockdep assertion in patch_insn_write() 270 * gets confused by the context in which the lock is taken. 271 * Instead, ensure the lock is held before calling stop_machine(), and 272 * set riscv_patch_in_stop_machine to skip the check in 273 * patch_insn_write(). 274 */ 275 lockdep_assert_held(&text_mutex); 276 riscv_patch_in_stop_machine = true; 277 ret = stop_machine_cpuslocked(patch_text_cb, &patch, cpu_online_mask); 278 riscv_patch_in_stop_machine = false; 279 return ret; 280 } 281 NOKPROBE_SYMBOL(patch_text); 282