1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Test module for unwind_for_each_frame 4 */ 5 6 #define pr_fmt(fmt) "test_unwind: " fmt 7 #include <asm/unwind.h> 8 #include <linux/completion.h> 9 #include <linux/kallsyms.h> 10 #include <linux/kthread.h> 11 #include <linux/module.h> 12 #include <linux/timer.h> 13 #include <linux/slab.h> 14 #include <linux/string.h> 15 #include <linux/kprobes.h> 16 #include <linux/wait.h> 17 #include <asm/irq.h> 18 19 #define BT_BUF_SIZE (PAGE_SIZE * 4) 20 21 /* 22 * To avoid printk line limit split backtrace by lines 23 */ 24 static void print_backtrace(char *bt) 25 { 26 char *p; 27 28 while (true) { 29 p = strsep(&bt, "\n"); 30 if (!p) 31 break; 32 pr_err("%s\n", p); 33 } 34 } 35 36 /* 37 * Calls unwind_for_each_frame(task, regs, sp) and verifies that the result 38 * contains unwindme_func2 followed by unwindme_func1. 39 */ 40 static noinline int test_unwind(struct task_struct *task, struct pt_regs *regs, 41 unsigned long sp) 42 { 43 int frame_count, prev_is_func2, seen_func2_func1; 44 const int max_frames = 128; 45 struct unwind_state state; 46 size_t bt_pos = 0; 47 int ret = 0; 48 char *bt; 49 50 bt = kmalloc(BT_BUF_SIZE, GFP_ATOMIC); 51 if (!bt) { 52 pr_err("failed to allocate backtrace buffer\n"); 53 return -ENOMEM; 54 } 55 /* Unwind. */ 56 frame_count = 0; 57 prev_is_func2 = 0; 58 seen_func2_func1 = 0; 59 unwind_for_each_frame(&state, task, regs, sp) { 60 unsigned long addr = unwind_get_return_address(&state); 61 char sym[KSYM_SYMBOL_LEN]; 62 63 if (frame_count++ == max_frames) 64 break; 65 if (state.reliable && !addr) { 66 pr_err("unwind state reliable but addr is 0\n"); 67 kfree(bt); 68 return -EINVAL; 69 } 70 sprint_symbol(sym, addr); 71 if (bt_pos < BT_BUF_SIZE) { 72 bt_pos += snprintf(bt + bt_pos, BT_BUF_SIZE - bt_pos, 73 state.reliable ? " [%-7s%px] %pSR\n" : 74 "([%-7s%px] %pSR)\n", 75 stack_type_name(state.stack_info.type), 76 (void *)state.sp, (void *)state.ip); 77 if (bt_pos >= BT_BUF_SIZE) 78 pr_err("backtrace buffer is too small\n"); 79 } 80 frame_count += 1; 81 if (prev_is_func2 && str_has_prefix(sym, "unwindme_func1")) 82 seen_func2_func1 = 1; 83 prev_is_func2 = str_has_prefix(sym, "unwindme_func2"); 84 } 85 86 /* Check the results. */ 87 if (unwind_error(&state)) { 88 pr_err("unwind error\n"); 89 ret = -EINVAL; 90 } 91 if (!seen_func2_func1) { 92 pr_err("unwindme_func2 and unwindme_func1 not found\n"); 93 ret = -EINVAL; 94 } 95 if (frame_count == max_frames) { 96 pr_err("Maximum number of frames exceeded\n"); 97 ret = -EINVAL; 98 } 99 if (ret) 100 print_backtrace(bt); 101 kfree(bt); 102 return ret; 103 } 104 105 /* State of the task being unwound. */ 106 struct unwindme { 107 int flags; 108 int ret; 109 struct task_struct *task; 110 struct completion task_ready; 111 wait_queue_head_t task_wq; 112 unsigned long sp; 113 }; 114 115 static struct unwindme *unwindme; 116 117 /* Values of unwindme.flags. */ 118 #define UWM_DEFAULT 0x0 119 #define UWM_THREAD 0x1 /* Unwind a separate task. */ 120 #define UWM_REGS 0x2 /* Pass regs to test_unwind(). */ 121 #define UWM_SP 0x4 /* Pass sp to test_unwind(). */ 122 #define UWM_CALLER 0x8 /* Unwind starting from caller. */ 123 #define UWM_SWITCH_STACK 0x10 /* Use CALL_ON_STACK. */ 124 #define UWM_IRQ 0x20 /* Unwind from irq context. */ 125 #define UWM_PGM 0x40 /* Unwind from program check handler. */ 126 127 static __always_inline unsigned long get_psw_addr(void) 128 { 129 unsigned long psw_addr; 130 131 asm volatile( 132 "basr %[psw_addr],0\n" 133 : [psw_addr] "=d" (psw_addr)); 134 return psw_addr; 135 } 136 137 #ifdef CONFIG_KPROBES 138 static int pgm_pre_handler(struct kprobe *p, struct pt_regs *regs) 139 { 140 struct unwindme *u = unwindme; 141 142 u->ret = test_unwind(NULL, (u->flags & UWM_REGS) ? regs : NULL, 143 (u->flags & UWM_SP) ? u->sp : 0); 144 return 0; 145 } 146 #endif 147 148 /* This function may or may not appear in the backtrace. */ 149 static noinline int unwindme_func4(struct unwindme *u) 150 { 151 if (!(u->flags & UWM_CALLER)) 152 u->sp = current_frame_address(); 153 if (u->flags & UWM_THREAD) { 154 complete(&u->task_ready); 155 wait_event(u->task_wq, kthread_should_park()); 156 kthread_parkme(); 157 return 0; 158 #ifdef CONFIG_KPROBES 159 } else if (u->flags & UWM_PGM) { 160 struct kprobe kp; 161 int ret; 162 163 unwindme = u; 164 memset(&kp, 0, sizeof(kp)); 165 kp.symbol_name = "do_report_trap"; 166 kp.pre_handler = pgm_pre_handler; 167 ret = register_kprobe(&kp); 168 if (ret < 0) { 169 pr_err("register_kprobe failed %d\n", ret); 170 return -EINVAL; 171 } 172 173 /* 174 * trigger specification exception 175 */ 176 asm volatile( 177 " mvcl %%r1,%%r1\n" 178 "0: nopr %%r7\n" 179 EX_TABLE(0b, 0b) 180 :); 181 182 unregister_kprobe(&kp); 183 unwindme = NULL; 184 return u->ret; 185 #endif 186 } else { 187 struct pt_regs regs; 188 189 memset(®s, 0, sizeof(regs)); 190 regs.psw.addr = get_psw_addr(); 191 regs.gprs[15] = current_stack_pointer(); 192 return test_unwind(NULL, 193 (u->flags & UWM_REGS) ? ®s : NULL, 194 (u->flags & UWM_SP) ? u->sp : 0); 195 } 196 } 197 198 /* This function may or may not appear in the backtrace. */ 199 static noinline int unwindme_func3(struct unwindme *u) 200 { 201 u->sp = current_frame_address(); 202 return unwindme_func4(u); 203 } 204 205 /* This function must appear in the backtrace. */ 206 static noinline int unwindme_func2(struct unwindme *u) 207 { 208 unsigned long flags; 209 int rc; 210 211 if (u->flags & UWM_SWITCH_STACK) { 212 local_irq_save(flags); 213 local_mcck_disable(); 214 rc = CALL_ON_STACK(unwindme_func3, S390_lowcore.nodat_stack, 1, u); 215 local_mcck_enable(); 216 local_irq_restore(flags); 217 return rc; 218 } else { 219 return unwindme_func3(u); 220 } 221 } 222 223 /* This function must follow unwindme_func2 in the backtrace. */ 224 static noinline int unwindme_func1(void *u) 225 { 226 return unwindme_func2((struct unwindme *)u); 227 } 228 229 static void unwindme_timer_fn(struct timer_list *unused) 230 { 231 struct unwindme *u = READ_ONCE(unwindme); 232 233 if (u) { 234 unwindme = NULL; 235 u->task = NULL; 236 u->ret = unwindme_func1(u); 237 complete(&u->task_ready); 238 } 239 } 240 241 static struct timer_list unwind_timer; 242 243 static int test_unwind_irq(struct unwindme *u) 244 { 245 unwindme = u; 246 init_completion(&u->task_ready); 247 timer_setup(&unwind_timer, unwindme_timer_fn, 0); 248 mod_timer(&unwind_timer, jiffies + 1); 249 wait_for_completion(&u->task_ready); 250 return u->ret; 251 } 252 253 /* Spawns a task and passes it to test_unwind(). */ 254 static int test_unwind_task(struct unwindme *u) 255 { 256 struct task_struct *task; 257 int ret; 258 259 /* Initialize thread-related fields. */ 260 init_completion(&u->task_ready); 261 init_waitqueue_head(&u->task_wq); 262 263 /* 264 * Start the task and wait until it reaches unwindme_func4() and sleeps 265 * in (task_ready, unwind_done] range. 266 */ 267 task = kthread_run(unwindme_func1, u, "%s", __func__); 268 if (IS_ERR(task)) { 269 pr_err("kthread_run() failed\n"); 270 return PTR_ERR(task); 271 } 272 /* 273 * Make sure task reaches unwindme_func4 before parking it, 274 * we might park it before kthread function has been executed otherwise 275 */ 276 wait_for_completion(&u->task_ready); 277 kthread_park(task); 278 /* Unwind. */ 279 ret = test_unwind(task, NULL, (u->flags & UWM_SP) ? u->sp : 0); 280 kthread_stop(task); 281 return ret; 282 } 283 284 static int test_unwind_flags(int flags) 285 { 286 struct unwindme u; 287 288 u.flags = flags; 289 if (u.flags & UWM_THREAD) 290 return test_unwind_task(&u); 291 else if (u.flags & UWM_IRQ) 292 return test_unwind_irq(&u); 293 else 294 return unwindme_func1(&u); 295 } 296 297 static int test_unwind_init(void) 298 { 299 int ret = 0; 300 301 #define TEST(flags) \ 302 do { \ 303 pr_info("[ RUN ] " #flags "\n"); \ 304 if (!test_unwind_flags((flags))) { \ 305 pr_info("[ OK ] " #flags "\n"); \ 306 } else { \ 307 pr_err("[ FAILED ] " #flags "\n"); \ 308 ret = -EINVAL; \ 309 } \ 310 } while (0) 311 312 TEST(UWM_DEFAULT); 313 TEST(UWM_SP); 314 TEST(UWM_REGS); 315 TEST(UWM_SWITCH_STACK); 316 TEST(UWM_SP | UWM_REGS); 317 TEST(UWM_CALLER | UWM_SP); 318 TEST(UWM_CALLER | UWM_SP | UWM_REGS); 319 TEST(UWM_CALLER | UWM_SP | UWM_REGS | UWM_SWITCH_STACK); 320 TEST(UWM_THREAD); 321 TEST(UWM_THREAD | UWM_SP); 322 TEST(UWM_THREAD | UWM_CALLER | UWM_SP); 323 TEST(UWM_IRQ); 324 TEST(UWM_IRQ | UWM_SWITCH_STACK); 325 TEST(UWM_IRQ | UWM_SP); 326 TEST(UWM_IRQ | UWM_REGS); 327 TEST(UWM_IRQ | UWM_SP | UWM_REGS); 328 TEST(UWM_IRQ | UWM_CALLER | UWM_SP); 329 TEST(UWM_IRQ | UWM_CALLER | UWM_SP | UWM_REGS); 330 TEST(UWM_IRQ | UWM_CALLER | UWM_SP | UWM_REGS | UWM_SWITCH_STACK); 331 #ifdef CONFIG_KPROBES 332 TEST(UWM_PGM); 333 TEST(UWM_PGM | UWM_SP); 334 TEST(UWM_PGM | UWM_REGS); 335 TEST(UWM_PGM | UWM_SP | UWM_REGS); 336 #endif 337 #undef TEST 338 339 return ret; 340 } 341 342 static void test_unwind_exit(void) 343 { 344 } 345 346 module_init(test_unwind_init); 347 module_exit(test_unwind_exit); 348 MODULE_LICENSE("GPL"); 349