arch/x86/kernel/ds_selftest.c

   1 /*
   2  * Debug Store support - selftest
   3  *
   4  *
   5  * Copyright (C) 2009 Intel Corporation.
   6  * Markus Metzger <markus.t.metzger@intel.com>, 2009
   7  */
   8
   9 #include "ds_selftest.h"
  10
  11 #include <linux/kernel.h>
  12 #include <linux/string.h>
  13 #include <linux/smp.h>
  14 #include <linux/cpu.h>
  15
  16 #include <asm/ds.h>
  17
  18
  19 #define BUFFER_SIZE     521 /* Intentionally chose an odd size. */
  20
  21
  22 struct ds_selftest_bts_conf {
  23         struct bts_tracer *tracer;
  24         int error;
  25         int (*suspend)(struct bts_tracer *);
  26         int (*resume)(struct bts_tracer *);
  27 };
  28
  29 static int ds_selftest_bts_consistency(const struct bts_trace *trace)
  30 {
  31         int error = 0;
  32
  33         if (!trace) {
  34                 printk(KERN_CONT "failed to access trace...");
  35                 /* Bail out. Other tests are pointless. */
  36                 return -1;
  37         }
  38
  39         if (!trace->read) {
  40                 printk(KERN_CONT "bts read not available...");
  41                 error = -1;
  42         }
  43
  44         /* Do some sanity checks on the trace configuration. */
  45         if (!trace->ds.n) {
  46                 printk(KERN_CONT "empty bts buffer...");
  47                 error = -1;
  48         }
  49         if (!trace->ds.size) {
  50                 printk(KERN_CONT "bad bts trace setup...");
  51                 error = -1;
  52         }
  53         if (trace->ds.end !=
  54             (char *)trace->ds.begin + (trace->ds.n * trace->ds.size)) {
  55                 printk(KERN_CONT "bad bts buffer setup...");
  56                 error = -1;
  57         }
  58         /*
  59          * We allow top in [begin; end], since its not clear when the
  60          * overflow adjustment happens: after the increment or before the
  61          * write.
  62          */
  63         if ((trace->ds.top < trace->ds.begin) ||
  64             (trace->ds.end < trace->ds.top)) {
  65                 printk(KERN_CONT "bts top out of bounds...");
  66                 error = -1;
  67         }
  68
  69         return error;
  70 }
  71
  72 static int ds_selftest_bts_read(struct bts_tracer *tracer,
  73                                 const struct bts_trace *trace,
  74                                 const void *from, const void *to)
  75 {
  76         const unsigned char *at;
  77
  78         /*
  79          * Check a few things which do not belong to this test.
  80          * They should be covered by other tests.
  81          */
  82         if (!trace)
  83                 return -1;
  84
  85         if (!trace->read)
  86                 return -1;
  87
  88         if (to < from)
  89                 return -1;
  90
  91         if (from < trace->ds.begin)
  92                 return -1;
  93
  94         if (trace->ds.end < to)
  95                 return -1;
  96
  97         if (!trace->ds.size)
  98                 return -1;
  99
 100         /* Now to the test itself. */
 101         for (at = from; (void *)at < to; at += trace->ds.size) {
 102                 struct bts_struct bts;
 103                 unsigned long index;
 104                 int error;
 105
 106                 if (((void *)at - trace->ds.begin) % trace->ds.size) {
 107                         printk(KERN_CONT
 108                                "read from non-integer index...");
 109                         return -1;
 110                 }
 111                 index = ((void *)at - trace->ds.begin) / trace->ds.size;
 112
 113                 memset(&bts, 0, sizeof(bts));
 114                 error = trace->read(tracer, at, &bts);
 115                 if (error < 0) {
 116                         printk(KERN_CONT
 117                                "error reading bts trace at [%lu] (0x%p)...",
 118                                index, at);
 119                         return error;
 120                 }
 121
 122                 switch (bts.qualifier) {
 123                 case BTS_BRANCH:
 124                         break;
 125                 default:
 126                         printk(KERN_CONT
 127                                "unexpected bts entry %llu at [%lu] (0x%p)...",
 128                                bts.qualifier, index, at);
 129                         return -1;
 130                 }
 131         }
 132
 133         return 0;
 134 }
 135
 136 static void ds_selftest_bts_cpu(void *arg)
 137 {
 138         struct ds_selftest_bts_conf *conf = arg;
 139         const struct bts_trace *trace;
 140         void *top;
 141
 142         if (IS_ERR(conf->tracer)) {
 143                 conf->error = PTR_ERR(conf->tracer);
 144                 conf->tracer = NULL;
 145
 146                 printk(KERN_CONT
 147                        "initialization failed (err: %d)...", conf->error);
 148                 return;
 149         }
 150
 151         /* We should meanwhile have enough trace. */
 152         conf->error = conf->suspend(conf->tracer);
 153         if (conf->error < 0)
 154                 return;
 155
 156         /* Let's see if we can access the trace. */
 157         trace = ds_read_bts(conf->tracer);
 158
 159         conf->error = ds_selftest_bts_consistency(trace);
 160         if (conf->error < 0)
 161                 return;
 162
 163         /* If everything went well, we should have a few trace entries. */
 164         if (trace->ds.top == trace->ds.begin) {
 165                 /*
 166                  * It is possible but highly unlikely that we got a
 167                  * buffer overflow and end up at exactly the same
 168                  * position we started from.
 169                  * Let's issue a warning, but continue.
 170                  */
 171                 printk(KERN_CONT "no trace/overflow...");
 172         }
 173
 174         /* Let's try to read the trace we collected. */
 175         conf->error =
 176                 ds_selftest_bts_read(conf->tracer, trace,
 177                                      trace->ds.begin, trace->ds.top);
 178         if (conf->error < 0)
 179                 return;
 180
 181         /*
 182          * Let's read the trace again.
 183          * Since we suspended tracing, we should get the same result.
 184          */
 185         top = trace->ds.top;
 186
 187         trace = ds_read_bts(conf->tracer);
 188         conf->error = ds_selftest_bts_consistency(trace);
 189         if (conf->error < 0)
 190                 return;
 191
 192         if (top != trace->ds.top) {
 193                 printk(KERN_CONT "suspend not working...");
 194                 conf->error = -1;
 195                 return;
 196         }
 197
 198         /* Let's collect some more trace - see if resume is working. */
 199         conf->error = conf->resume(conf->tracer);
 200         if (conf->error < 0)
 201                 return;
 202
 203         conf->error = conf->suspend(conf->tracer);
 204         if (conf->error < 0)
 205                 return;
 206
 207         trace = ds_read_bts(conf->tracer);
 208
 209         conf->error = ds_selftest_bts_consistency(trace);
 210         if (conf->error < 0)
 211                 return;
 212
 213         if (trace->ds.top == top) {
 214                 /*
 215                  * It is possible but highly unlikely that we got a
 216                  * buffer overflow and end up at exactly the same
 217                  * position we started from.
 218                  * Let's issue a warning and check the full trace.
 219                  */
 220                 printk(KERN_CONT
 221                        "no resume progress/overflow...");
 222
 223                 conf->error =
 224                         ds_selftest_bts_read(conf->tracer, trace,
 225                                              trace->ds.begin, trace->ds.end);
 226         } else if (trace->ds.top < top) {
 227                 /*
 228                  * We had a buffer overflow - the entire buffer should
 229                  * contain trace records.
 230                  */
 231                 conf->error =
 232                         ds_selftest_bts_read(conf->tracer, trace,
 233                                              trace->ds.begin, trace->ds.end);
 234         } else {
 235                 /*
 236                  * It is quite likely that the buffer did not overflow.
 237                  * Let's just check the delta trace.
 238                  */
 239                 conf->error =
 240                         ds_selftest_bts_read(conf->tracer, trace, top,
 241                                              trace->ds.top);
 242         }
 243         if (conf->error < 0)
 244                 return;
 245
 246         conf->error = 0;
 247 }
 248
 249 static int ds_suspend_bts_wrap(struct bts_tracer *tracer)
 250 {
 251         ds_suspend_bts(tracer);
 252         return 0;
 253 }
 254
 255 static int ds_resume_bts_wrap(struct bts_tracer *tracer)
 256 {
 257         ds_resume_bts(tracer);
 258         return 0;
 259 }
 260
 261 static void ds_release_bts_noirq_wrap(void *tracer)
 262 {
 263         (void)ds_release_bts_noirq(tracer);
 264 }
 265
 266 static int ds_selftest_bts_bad_release_noirq(int cpu,
 267                                              struct bts_tracer *tracer)
 268 {
 269         int error = -EPERM;
 270
 271         /* Try to release the tracer on the wrong cpu. */
 272         get_cpu();
 273         if (cpu != smp_processor_id()) {
 274                 error = ds_release_bts_noirq(tracer);
 275                 if (error != -EPERM)
 276                         printk(KERN_CONT "release on wrong cpu...");
 277         }
 278         put_cpu();
 279
 280         return error ? 0 : -1;
 281 }
 282
 283 int ds_selftest_bts(void)
 284 {
 285         struct ds_selftest_bts_conf conf;
 286         unsigned char buffer[BUFFER_SIZE];
 287         int cpu;
 288
 289         printk(KERN_INFO "[ds] bts selftest...");
 290         conf.error = 0;
 291
 292         get_online_cpus();
 293         for_each_online_cpu(cpu) {
 294                 conf.suspend = ds_suspend_bts_wrap;
 295                 conf.resume = ds_resume_bts_wrap;
 296                 conf.tracer =
 297                         ds_request_bts_cpu(cpu, buffer, BUFFER_SIZE,
 298                                            NULL, (size_t)-1, BTS_KERNEL);
 299                 ds_selftest_bts_cpu(&conf);
 300                 ds_release_bts(conf.tracer);
 301                 if (conf.error < 0)
 302                         goto out;
 303
 304                 conf.suspend = ds_suspend_bts_noirq;
 305                 conf.resume = ds_resume_bts_noirq;
 306                 conf.tracer =
 307                         ds_request_bts_cpu(cpu, buffer, BUFFER_SIZE,
 308                                            NULL, (size_t)-1, BTS_KERNEL);
 309                 smp_call_function_single(cpu, ds_selftest_bts_cpu, &conf, 1);
 310                 if (conf.error >= 0) {
 311                         conf.error =
 312                                 ds_selftest_bts_bad_release_noirq(cpu,
 313                                                                   conf.tracer);
 314                         /* We must not release the tracer twice. */
 315                         if (conf.error < 0)
 316                                 conf.tracer = NULL;
 317                 }
 318                 smp_call_function_single(cpu, ds_release_bts_noirq_wrap,
 319                                          conf.tracer, 1);
 320                 if (conf.error < 0)
 321                         goto out;
 322         }
 323
 324         conf.error = 0;
 325  out:
 326         put_online_cpus();
 327         printk(KERN_CONT "%s.\n", (conf.error ? "failed" : "passed"));
 328
 329         return conf.error;
 330 }
 331
 332 int ds_selftest_pebs(void)
 333 {
 334         return 0;
 335 }