arch/s390/lib/test_unwind.c

   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(&regs, 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) ? &regs : 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");