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 static void do_wakeup(unsigned long);
  85 static DECLARE_TASKLET(kmemcheck_tasklet, &do_wakeup, 0);
  86
  87 /*
  88  * Save the context of an error report.
  89  */
  90 void kmemcheck_error_save(enum kmemcheck_shadow state,
  91         unsigned long address, unsigned int size, struct pt_regs *regs)
  92 {
  93         static unsigned long prev_ip;
  94
  95         struct kmemcheck_error *e;
  96         void *shadow_copy;
  97         void *memory_copy;
  98
  99         /* Don't report several adjacent errors from the same EIP. */
 100         if (regs->ip == prev_ip)
 101                 return;
 102         prev_ip = regs->ip;
 103
 104         e = error_next_wr();
 105         if (!e)
 106                 return;
 107
 108         e->type = KMEMCHECK_ERROR_INVALID_ACCESS;
 109
 110         e->state = state;
 111         e->address = address;
 112         e->size = size;
 113
 114         /* Save regs */
 115         memcpy(&e->regs, regs, sizeof(*regs));
 116
 117         /* Save stack trace */
 118         e->trace.nr_entries = 0;
 119         e->trace.entries = e->trace_entries;
 120         e->trace.max_entries = ARRAY_SIZE(e->trace_entries);
 121         e->trace.skip = 0;
 122         save_stack_trace_bp(&e->trace, regs->bp);
 123
 124         /* Round address down to nearest 16 bytes */
 125         shadow_copy = kmemcheck_shadow_lookup(address
 126                 & ~(SHADOW_COPY_SIZE - 1));
 127         BUG_ON(!shadow_copy);
 128
 129         memcpy(e->shadow_copy, shadow_copy, SHADOW_COPY_SIZE);
 130
 131         kmemcheck_show_addr(address);
 132         memory_copy = (void *) (address & ~(SHADOW_COPY_SIZE - 1));
 133         memcpy(e->memory_copy, memory_copy, SHADOW_COPY_SIZE);
 134         kmemcheck_hide_addr(address);
 135
 136         tasklet_hi_schedule_first(&kmemcheck_tasklet);
 137 }
 138
 139 /*
 140  * Save the context of a kmemcheck bug.
 141  */
 142 void kmemcheck_error_save_bug(struct pt_regs *regs)
 143 {
 144         struct kmemcheck_error *e;
 145
 146         e = error_next_wr();
 147         if (!e)
 148                 return;
 149
 150         e->type = KMEMCHECK_ERROR_BUG;
 151
 152         memcpy(&e->regs, regs, sizeof(*regs));
 153
 154         e->trace.nr_entries = 0;
 155         e->trace.entries = e->trace_entries;
 156         e->trace.max_entries = ARRAY_SIZE(e->trace_entries);
 157         e->trace.skip = 1;
 158         save_stack_trace(&e->trace);
 159
 160         tasklet_hi_schedule_first(&kmemcheck_tasklet);
 161 }
 162
 163 void kmemcheck_error_recall(void)
 164 {
 165         static const char *desc[] = {
 166                 [KMEMCHECK_SHADOW_UNALLOCATED]          = "unallocated",
 167                 [KMEMCHECK_SHADOW_UNINITIALIZED]        = "uninitialized",
 168                 [KMEMCHECK_SHADOW_INITIALIZED]          = "initialized",
 169                 [KMEMCHECK_SHADOW_FREED]                = "freed",
 170         };
 171
 172         static const char short_desc[] = {
 173                 [KMEMCHECK_SHADOW_UNALLOCATED]          = 'a',
 174                 [KMEMCHECK_SHADOW_UNINITIALIZED]        = 'u',
 175                 [KMEMCHECK_SHADOW_INITIALIZED]          = 'i',
 176                 [KMEMCHECK_SHADOW_FREED]                = 'f',
 177         };
 178
 179         struct kmemcheck_error *e;
 180         unsigned int i;
 181
 182         e = error_next_rd();
 183         if (!e)
 184                 return;
 185
 186         switch (e->type) {
 187         case KMEMCHECK_ERROR_INVALID_ACCESS:
 188                 printk(KERN_ERR  "WARNING: kmemcheck: Caught %d-bit read "
 189                         "from %s memory (%p)\n",
 190                         8 * e->size, e->state < ARRAY_SIZE(desc) ?
 191                                 desc[e->state] : "(invalid shadow state)",
 192                         (void *) e->address);
 193
 194                 printk(KERN_INFO);
 195                 for (i = 0; i < SHADOW_COPY_SIZE; ++i)
 196                         printk("%02x", e->memory_copy[i]);
 197                 printk("\n");
 198
 199                 printk(KERN_INFO);
 200                 for (i = 0; i < SHADOW_COPY_SIZE; ++i) {
 201                         if (e->shadow_copy[i] < ARRAY_SIZE(short_desc))
 202                                 printk(" %c", short_desc[e->shadow_copy[i]]);
 203                         else
 204                                 printk(" ?");
 205                 }
 206                 printk("\n");
 207                 printk(KERN_INFO "%*c\n", 2 + 2
 208                         * (int) (e->address & (SHADOW_COPY_SIZE - 1)), '^');
 209                 break;
 210         case KMEMCHECK_ERROR_BUG:
 211                 printk(KERN_EMERG "ERROR: kmemcheck: Fatal error\n");
 212                 break;
 213         }
 214
 215         __show_regs(&e->regs, 1);
 216         print_stack_trace(&e->trace, 0);
 217 }
 218
 219 static void do_wakeup(unsigned long data)
 220 {
 221         while (error_count > 0)
 222                 kmemcheck_error_recall();
 223
 224         if (error_missed_count > 0) {
 225                 printk(KERN_WARNING "kmemcheck: Lost %d error reports because "
 226                         "the queue was too small\n", error_missed_count);
 227                 error_missed_count = 0;
 228         }
 229 }