arch/x86/mm/kmemcheck/error.c

   1 #include <linux/interrupt.h>
   2 #include <linux/kdebug.h>
   3 #include <linux/kmemcheck.h>
   4 #include <linux/kernel.h>
   5 #include <linux/types.h>
   6 #include <linux/ptrace.h>
   7 #include <linux/stacktrace.h>
   8 #include <linux/string.h>
   9
  10 #include "error.h"
  11 #include "shadow.h"
  12
  13 enum kmemcheck_error_type {
  14         KMEMCHECK_ERROR_INVALID_ACCESS,
  15         KMEMCHECK_ERROR_BUG,
  16 };
  17
  18 #define SHADOW_COPY_SIZE (1 << CONFIG_KMEMCHECK_SHADOW_COPY_SHIFT)
  19
  20 struct kmemcheck_error {
  21         enum kmemcheck_error_type type;
  22
  23         union {
  24                 /* KMEMCHECK_ERROR_INVALID_ACCESS */
  25                 struct {
  26                         /* Kind of access that caused the error */
  27                         enum kmemcheck_shadow state;
  28                         /* Address and size of the erroneous read */
  29                         unsigned long   address;
  30                         unsigned int    size;
  31                 };
  32         };
  33
  34         struct pt_regs          regs;
  35         struct stack_trace      trace;
  36         unsigned long           trace_entries[32];
  37
  38         /* We compress it to a char. */
  39         unsigned char           shadow_copy[SHADOW_COPY_SIZE];
  40         unsigned char           memory_copy[SHADOW_COPY_SIZE];
  41 };
  42
  43 /*
  44  * Create a ring queue of errors to output. We can't call printk() directly
  45  * from the kmemcheck traps, since this may call the console drivers and
  46  * result in a recursive fault.
  47  */
  48 static struct kmemcheck_error error_fifo[CONFIG_KMEMCHECK_QUEUE_SIZE];
  49 static unsigned int error_count;
  50 static unsigned int error_rd;
  51 static unsigned int error_wr;
  52 static unsigned int error_missed_count;
  53
  54 static struct kmemcheck_error *error_next_wr(void)
  55 {
  56         struct kmemcheck_error *e;
  57
  58         if (error_count == ARRAY_SIZE(error_fifo)) {
  59                 ++error_missed_count;
  60                 return NULL;
  61         }
  62
  63         e = &error_fifo[error_wr];
  64         if (++error_wr == ARRAY_SIZE(error_fifo))
  65                 error_wr = 0;
  66         ++error_count;
  67         return e;
  68 }
  69
  70 static struct kmemcheck_error *error_next_rd(void)
  71 {
  72         struct kmemcheck_error *e;
  73
  74         if (error_count == 0)
  75                 return NULL;
  76
  77         e = &error_fifo[error_rd];
  78         if (++error_rd == ARRAY_SIZE(error_fifo))
  79                 error_rd = 0;
  80         --error_count;
  81         return e;
  82 }
  83
  84 void kmemcheck_error_recall(void)
  85 {
  86         static const char *desc[] = {
  87                 [KMEMCHECK_SHADOW_UNALLOCATED]          = "unallocated",
  88                 [KMEMCHECK_SHADOW_UNINITIALIZED]        = "uninitialized",
  89                 [KMEMCHECK_SHADOW_INITIALIZED]          = "initialized",
  90                 [KMEMCHECK_SHADOW_FREED]                = "freed",
  91         };
  92
  93         static const char short_desc[] = {
  94                 [KMEMCHECK_SHADOW_UNALLOCATED]          = 'a',
  95                 [KMEMCHECK_SHADOW_UNINITIALIZED]        = 'u',
  96                 [KMEMCHECK_SHADOW_INITIALIZED]          = 'i',
  97                 [KMEMCHECK_SHADOW_FREED]                = 'f',
  98         };
  99
 100         struct kmemcheck_error *e;
 101         unsigned int i;
 102
 103         e = error_next_rd();
 104         if (!e)
 105                 return;
 106
 107         switch (e->type) {
 108         case KMEMCHECK_ERROR_INVALID_ACCESS:
 109                 printk(KERN_WARNING "WARNING: kmemcheck: Caught %d-bit read from %s memory (%p)\n",
 110                         8 * e->size, e->state < ARRAY_SIZE(desc) ?
 111                                 desc[e->state] : "(invalid shadow state)",
 112                         (void *) e->address);
 113
 114                 printk(KERN_WARNING);
 115                 for (i = 0; i < SHADOW_COPY_SIZE; ++i)
 116                         printk(KERN_CONT "%02x", e->memory_copy[i]);
 117                 printk(KERN_CONT "\n");
 118
 119                 printk(KERN_WARNING);
 120                 for (i = 0; i < SHADOW_COPY_SIZE; ++i) {
 121                         if (e->shadow_copy[i] < ARRAY_SIZE(short_desc))
 122                                 printk(KERN_CONT " %c", short_desc[e->shadow_copy[i]]);
 123                         else
 124                                 printk(KERN_CONT " ?");
 125                 }
 126                 printk(KERN_CONT "\n");
 127                 printk(KERN_WARNING "%*c\n", 2 + 2
 128                         * (int) (e->address & (SHADOW_COPY_SIZE - 1)), '^');
 129                 break;
 130         case KMEMCHECK_ERROR_BUG:
 131                 printk(KERN_EMERG "ERROR: kmemcheck: Fatal error\n");
 132                 break;
 133         }
 134
 135         __show_regs(&e->regs, 1);
 136         print_stack_trace(&e->trace, 0);
 137 }
 138
 139 static void do_wakeup(unsigned long data)
 140 {
 141         while (error_count > 0)
 142                 kmemcheck_error_recall();
 143
 144         if (error_missed_count > 0) {
 145                 printk(KERN_WARNING "kmemcheck: Lost %d error reports because "
 146                         "the queue was too small\n", error_missed_count);
 147                 error_missed_count = 0;
 148         }
 149 }
 150
 151 static DECLARE_TASKLET(kmemcheck_tasklet, &do_wakeup, 0);
 152
 153 /*
 154  * Save the context of an error report.
 155  */
 156 void kmemcheck_error_save(enum kmemcheck_shadow state,
 157         unsigned long address, unsigned int size, struct pt_regs *regs)
 158 {
 159         static unsigned long prev_ip;
 160
 161         struct kmemcheck_error *e;
 162         void *shadow_copy;
 163         void *memory_copy;
 164
 165         /* Don't report several adjacent errors from the same EIP. */
 166         if (regs->ip == prev_ip)
 167                 return;
 168         prev_ip = regs->ip;
 169
 170         e = error_next_wr();
 171         if (!e)
 172                 return;
 173
 174         e->type = KMEMCHECK_ERROR_INVALID_ACCESS;
 175
 176         e->state = state;
 177         e->address = address;
 178         e->size = size;
 179
 180         /* Save regs */
 181         memcpy(&e->regs, regs, sizeof(*regs));
 182
 183         /* Save stack trace */
 184         e->trace.nr_entries = 0;
 185         e->trace.entries = e->trace_entries;
 186         e->trace.max_entries = ARRAY_SIZE(e->trace_entries);
 187         e->trace.skip = 0;
 188         save_stack_trace_bp(&e->trace, regs->bp);
 189
 190         /* Round address down to nearest 16 bytes */
 191         shadow_copy = kmemcheck_shadow_lookup(address
 192                 & ~(SHADOW_COPY_SIZE - 1));
 193         BUG_ON(!shadow_copy);
 194
 195         memcpy(e->shadow_copy, shadow_copy, SHADOW_COPY_SIZE);
 196
 197         kmemcheck_show_addr(address);
 198         memory_copy = (void *) (address & ~(SHADOW_COPY_SIZE - 1));
 199         memcpy(e->memory_copy, memory_copy, SHADOW_COPY_SIZE);
 200         kmemcheck_hide_addr(address);
 201
 202         tasklet_hi_schedule_first(&kmemcheck_tasklet);
 203 }
 204
 205 /*
 206  * Save the context of a kmemcheck bug.
 207  */
 208 void kmemcheck_error_save_bug(struct pt_regs *regs)
 209 {
 210         struct kmemcheck_error *e;
 211
 212         e = error_next_wr();
 213         if (!e)
 214                 return;
 215
 216         e->type = KMEMCHECK_ERROR_BUG;
 217
 218         memcpy(&e->regs, regs, sizeof(*regs));
 219
 220         e->trace.nr_entries = 0;
 221         e->trace.entries = e->trace_entries;
 222         e->trace.max_entries = ARRAY_SIZE(e->trace_entries);
 223         e->trace.skip = 1;
 224         save_stack_trace(&e->trace);
 225
 226         tasklet_hi_schedule_first(&kmemcheck_tasklet);
 227 }