1 // SPDX-License-Identifier: GPL-2.0-only 2 3 #define pr_fmt(fmt) "callthunks: " fmt 4 5 #include <linux/debugfs.h> 6 #include <linux/kallsyms.h> 7 #include <linux/memory.h> 8 #include <linux/moduleloader.h> 9 #include <linux/static_call.h> 10 11 #include <asm/alternative.h> 12 #include <asm/asm-offsets.h> 13 #include <asm/cpu.h> 14 #include <asm/ftrace.h> 15 #include <asm/insn.h> 16 #include <asm/kexec.h> 17 #include <asm/nospec-branch.h> 18 #include <asm/paravirt.h> 19 #include <asm/sections.h> 20 #include <asm/switch_to.h> 21 #include <asm/sync_core.h> 22 #include <asm/text-patching.h> 23 #include <asm/xen/hypercall.h> 24 25 static int __initdata_or_module debug_callthunks; 26 27 #define prdbg(fmt, args...) \ 28 do { \ 29 if (debug_callthunks) \ 30 printk(KERN_DEBUG pr_fmt(fmt), ##args); \ 31 } while(0) 32 33 static int __init debug_thunks(char *str) 34 { 35 debug_callthunks = 1; 36 return 1; 37 } 38 __setup("debug-callthunks", debug_thunks); 39 40 #ifdef CONFIG_CALL_THUNKS_DEBUG 41 DEFINE_PER_CPU(u64, __x86_call_count); 42 DEFINE_PER_CPU(u64, __x86_ret_count); 43 DEFINE_PER_CPU(u64, __x86_stuffs_count); 44 DEFINE_PER_CPU(u64, __x86_ctxsw_count); 45 EXPORT_SYMBOL_GPL(__x86_ctxsw_count); 46 EXPORT_SYMBOL_GPL(__x86_call_count); 47 #endif 48 49 extern s32 __call_sites[], __call_sites_end[]; 50 51 struct thunk_desc { 52 void *template; 53 unsigned int template_size; 54 }; 55 56 struct core_text { 57 unsigned long base; 58 unsigned long end; 59 const char *name; 60 }; 61 62 static bool thunks_initialized __ro_after_init; 63 64 static const struct core_text builtin_coretext = { 65 .base = (unsigned long)_text, 66 .end = (unsigned long)_etext, 67 .name = "builtin", 68 }; 69 70 asm ( 71 ".pushsection .rodata \n" 72 ".global skl_call_thunk_template \n" 73 "skl_call_thunk_template: \n" 74 __stringify(INCREMENT_CALL_DEPTH)" \n" 75 ".global skl_call_thunk_tail \n" 76 "skl_call_thunk_tail: \n" 77 ".popsection \n" 78 ); 79 80 extern u8 skl_call_thunk_template[]; 81 extern u8 skl_call_thunk_tail[]; 82 83 #define SKL_TMPL_SIZE \ 84 ((unsigned int)(skl_call_thunk_tail - skl_call_thunk_template)) 85 86 extern void error_entry(void); 87 extern void xen_error_entry(void); 88 extern void paranoid_entry(void); 89 90 static inline bool within_coretext(const struct core_text *ct, void *addr) 91 { 92 unsigned long p = (unsigned long)addr; 93 94 return ct->base <= p && p < ct->end; 95 } 96 97 static inline bool within_module_coretext(void *addr) 98 { 99 bool ret = false; 100 101 #ifdef CONFIG_MODULES 102 struct module *mod; 103 104 preempt_disable(); 105 mod = __module_address((unsigned long)addr); 106 if (mod && within_module_core((unsigned long)addr, mod)) 107 ret = true; 108 preempt_enable(); 109 #endif 110 return ret; 111 } 112 113 static bool is_coretext(const struct core_text *ct, void *addr) 114 { 115 if (ct && within_coretext(ct, addr)) 116 return true; 117 if (within_coretext(&builtin_coretext, addr)) 118 return true; 119 return within_module_coretext(addr); 120 } 121 122 static bool skip_addr(void *dest) 123 { 124 if (dest == error_entry) 125 return true; 126 if (dest == paranoid_entry) 127 return true; 128 if (dest == xen_error_entry) 129 return true; 130 /* Does FILL_RSB... */ 131 if (dest == __switch_to_asm) 132 return true; 133 /* Accounts directly */ 134 if (dest == ret_from_fork) 135 return true; 136 #ifdef CONFIG_HOTPLUG_CPU 137 if (dest == start_cpu0) 138 return true; 139 #endif 140 #ifdef CONFIG_FUNCTION_TRACER 141 if (dest == __fentry__) 142 return true; 143 #endif 144 #ifdef CONFIG_KEXEC_CORE 145 if (dest >= (void *)relocate_kernel && 146 dest < (void*)relocate_kernel + KEXEC_CONTROL_CODE_MAX_SIZE) 147 return true; 148 #endif 149 #ifdef CONFIG_XEN 150 if (dest >= (void *)hypercall_page && 151 dest < (void*)hypercall_page + PAGE_SIZE) 152 return true; 153 #endif 154 return false; 155 } 156 157 static __init_or_module void *call_get_dest(void *addr) 158 { 159 struct insn insn; 160 void *dest; 161 int ret; 162 163 ret = insn_decode_kernel(&insn, addr); 164 if (ret) 165 return ERR_PTR(ret); 166 167 /* Patched out call? */ 168 if (insn.opcode.bytes[0] != CALL_INSN_OPCODE) 169 return NULL; 170 171 dest = addr + insn.length + insn.immediate.value; 172 if (skip_addr(dest)) 173 return NULL; 174 return dest; 175 } 176 177 static const u8 nops[] = { 178 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 179 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 180 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 181 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 182 }; 183 184 static void *patch_dest(void *dest, bool direct) 185 { 186 unsigned int tsize = SKL_TMPL_SIZE; 187 u8 *pad = dest - tsize; 188 189 /* Already patched? */ 190 if (!bcmp(pad, skl_call_thunk_template, tsize)) 191 return pad; 192 193 /* Ensure there are nops */ 194 if (bcmp(pad, nops, tsize)) { 195 pr_warn_once("Invalid padding area for %pS\n", dest); 196 return NULL; 197 } 198 199 if (direct) 200 memcpy(pad, skl_call_thunk_template, tsize); 201 else 202 text_poke_copy_locked(pad, skl_call_thunk_template, tsize, true); 203 return pad; 204 } 205 206 static __init_or_module void patch_call(void *addr, const struct core_text *ct) 207 { 208 void *pad, *dest; 209 u8 bytes[8]; 210 211 if (!within_coretext(ct, addr)) 212 return; 213 214 dest = call_get_dest(addr); 215 if (!dest || WARN_ON_ONCE(IS_ERR(dest))) 216 return; 217 218 if (!is_coretext(ct, dest)) 219 return; 220 221 pad = patch_dest(dest, within_coretext(ct, dest)); 222 if (!pad) 223 return; 224 225 prdbg("Patch call at: %pS %px to %pS %px -> %px \n", addr, addr, 226 dest, dest, pad); 227 __text_gen_insn(bytes, CALL_INSN_OPCODE, addr, pad, CALL_INSN_SIZE); 228 text_poke_early(addr, bytes, CALL_INSN_SIZE); 229 } 230 231 static __init_or_module void 232 patch_call_sites(s32 *start, s32 *end, const struct core_text *ct) 233 { 234 s32 *s; 235 236 for (s = start; s < end; s++) 237 patch_call((void *)s + *s, ct); 238 } 239 240 static __init_or_module void 241 patch_paravirt_call_sites(struct paravirt_patch_site *start, 242 struct paravirt_patch_site *end, 243 const struct core_text *ct) 244 { 245 struct paravirt_patch_site *p; 246 247 for (p = start; p < end; p++) 248 patch_call(p->instr, ct); 249 } 250 251 static __init_or_module void 252 callthunks_setup(struct callthunk_sites *cs, const struct core_text *ct) 253 { 254 prdbg("Patching call sites %s\n", ct->name); 255 patch_call_sites(cs->call_start, cs->call_end, ct); 256 patch_paravirt_call_sites(cs->pv_start, cs->pv_end, ct); 257 prdbg("Patching call sites done%s\n", ct->name); 258 } 259 260 void __init callthunks_patch_builtin_calls(void) 261 { 262 struct callthunk_sites cs = { 263 .call_start = __call_sites, 264 .call_end = __call_sites_end, 265 .pv_start = __parainstructions, 266 .pv_end = __parainstructions_end 267 }; 268 269 if (!cpu_feature_enabled(X86_FEATURE_CALL_DEPTH)) 270 return; 271 272 pr_info("Setting up call depth tracking\n"); 273 mutex_lock(&text_mutex); 274 callthunks_setup(&cs, &builtin_coretext); 275 static_call_force_reinit(); 276 thunks_initialized = true; 277 mutex_unlock(&text_mutex); 278 } 279 280 void *callthunks_translate_call_dest(void *dest) 281 { 282 void *target; 283 284 lockdep_assert_held(&text_mutex); 285 286 if (!thunks_initialized || skip_addr(dest)) 287 return dest; 288 289 if (!is_coretext(NULL, dest)) 290 return dest; 291 292 target = patch_dest(dest, false); 293 return target ? : dest; 294 } 295 296 bool is_callthunk(void *addr) 297 { 298 unsigned int tmpl_size = SKL_TMPL_SIZE; 299 void *tmpl = skl_call_thunk_template; 300 unsigned long dest; 301 302 dest = roundup((unsigned long)addr, CONFIG_FUNCTION_ALIGNMENT); 303 if (!thunks_initialized || skip_addr((void *)dest)) 304 return false; 305 306 return !bcmp((void *)(dest - tmpl_size), tmpl, tmpl_size); 307 } 308 309 #ifdef CONFIG_BPF_JIT 310 int x86_call_depth_emit_accounting(u8 **pprog, void *func) 311 { 312 unsigned int tmpl_size = SKL_TMPL_SIZE; 313 void *tmpl = skl_call_thunk_template; 314 315 if (!thunks_initialized) 316 return 0; 317 318 /* Is function call target a thunk? */ 319 if (func && is_callthunk(func)) 320 return 0; 321 322 memcpy(*pprog, tmpl, tmpl_size); 323 *pprog += tmpl_size; 324 return tmpl_size; 325 } 326 #endif 327 328 #ifdef CONFIG_MODULES 329 void noinline callthunks_patch_module_calls(struct callthunk_sites *cs, 330 struct module *mod) 331 { 332 struct core_text ct = { 333 .base = (unsigned long)mod->mem[MOD_TEXT].base, 334 .end = (unsigned long)mod->mem[MOD_TEXT].base + mod->mem[MOD_TEXT].size, 335 .name = mod->name, 336 }; 337 338 if (!thunks_initialized) 339 return; 340 341 mutex_lock(&text_mutex); 342 callthunks_setup(cs, &ct); 343 mutex_unlock(&text_mutex); 344 } 345 #endif /* CONFIG_MODULES */ 346 347 #if defined(CONFIG_CALL_THUNKS_DEBUG) && defined(CONFIG_DEBUG_FS) 348 static int callthunks_debug_show(struct seq_file *m, void *p) 349 { 350 unsigned long cpu = (unsigned long)m->private; 351 352 seq_printf(m, "C: %16llu R: %16llu S: %16llu X: %16llu\n,", 353 per_cpu(__x86_call_count, cpu), 354 per_cpu(__x86_ret_count, cpu), 355 per_cpu(__x86_stuffs_count, cpu), 356 per_cpu(__x86_ctxsw_count, cpu)); 357 return 0; 358 } 359 360 static int callthunks_debug_open(struct inode *inode, struct file *file) 361 { 362 return single_open(file, callthunks_debug_show, inode->i_private); 363 } 364 365 static const struct file_operations dfs_ops = { 366 .open = callthunks_debug_open, 367 .read = seq_read, 368 .llseek = seq_lseek, 369 .release = single_release, 370 }; 371 372 static int __init callthunks_debugfs_init(void) 373 { 374 struct dentry *dir; 375 unsigned long cpu; 376 377 dir = debugfs_create_dir("callthunks", NULL); 378 for_each_possible_cpu(cpu) { 379 void *arg = (void *)cpu; 380 char name [10]; 381 382 sprintf(name, "cpu%lu", cpu); 383 debugfs_create_file(name, 0644, dir, arg, &dfs_ops); 384 } 385 return 0; 386 } 387 __initcall(callthunks_debugfs_init); 388 #endif 389