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Linux/kernel/debug/kdb/kdb_support.c

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  1 /*
  2  * Kernel Debugger Architecture Independent Support Functions
  3  *
  4  * This file is subject to the terms and conditions of the GNU General Public
  5  * License.  See the file "COPYING" in the main directory of this archive
  6  * for more details.
  7  *
  8  * Copyright (c) 1999-2004 Silicon Graphics, Inc.  All Rights Reserved.
  9  * Copyright (c) 2009 Wind River Systems, Inc.  All Rights Reserved.
 10  * 03/02/13    added new 2.5 kallsyms <xavier.bru@bull.net>
 11  */
 12 
 13 #include <stdarg.h>
 14 #include <linux/types.h>
 15 #include <linux/sched.h>
 16 #include <linux/mm.h>
 17 #include <linux/kallsyms.h>
 18 #include <linux/stddef.h>
 19 #include <linux/vmalloc.h>
 20 #include <linux/ptrace.h>
 21 #include <linux/module.h>
 22 #include <linux/highmem.h>
 23 #include <linux/hardirq.h>
 24 #include <linux/delay.h>
 25 #include <linux/uaccess.h>
 26 #include <linux/kdb.h>
 27 #include <linux/slab.h>
 28 #include "kdb_private.h"
 29 
 30 /*
 31  * kdbgetsymval - Return the address of the given symbol.
 32  *
 33  * Parameters:
 34  *      symname Character string containing symbol name
 35  *      symtab  Structure to receive results
 36  * Returns:
 37  *      0       Symbol not found, symtab zero filled
 38  *      1       Symbol mapped to module/symbol/section, data in symtab
 39  */
 40 int kdbgetsymval(const char *symname, kdb_symtab_t *symtab)
 41 {
 42         if (KDB_DEBUG(AR))
 43                 kdb_printf("kdbgetsymval: symname=%s, symtab=%p\n", symname,
 44                            symtab);
 45         memset(symtab, 0, sizeof(*symtab));
 46         symtab->sym_start = kallsyms_lookup_name(symname);
 47         if (symtab->sym_start) {
 48                 if (KDB_DEBUG(AR))
 49                         kdb_printf("kdbgetsymval: returns 1, "
 50                                    "symtab->sym_start=0x%lx\n",
 51                                    symtab->sym_start);
 52                 return 1;
 53         }
 54         if (KDB_DEBUG(AR))
 55                 kdb_printf("kdbgetsymval: returns 0\n");
 56         return 0;
 57 }
 58 EXPORT_SYMBOL(kdbgetsymval);
 59 
 60 static char *kdb_name_table[100];       /* arbitrary size */
 61 
 62 /*
 63  * kdbnearsym - Return the name of the symbol with the nearest address
 64  *      less than 'addr'.
 65  *
 66  * Parameters:
 67  *      addr    Address to check for symbol near
 68  *      symtab  Structure to receive results
 69  * Returns:
 70  *      0       No sections contain this address, symtab zero filled
 71  *      1       Address mapped to module/symbol/section, data in symtab
 72  * Remarks:
 73  *      2.6 kallsyms has a "feature" where it unpacks the name into a
 74  *      string.  If that string is reused before the caller expects it
 75  *      then the caller sees its string change without warning.  To
 76  *      avoid cluttering up the main kdb code with lots of kdb_strdup,
 77  *      tests and kfree calls, kdbnearsym maintains an LRU list of the
 78  *      last few unique strings.  The list is sized large enough to
 79  *      hold active strings, no kdb caller of kdbnearsym makes more
 80  *      than ~20 later calls before using a saved value.
 81  */
 82 int kdbnearsym(unsigned long addr, kdb_symtab_t *symtab)
 83 {
 84         int ret = 0;
 85         unsigned long symbolsize = 0;
 86         unsigned long offset = 0;
 87 #define knt1_size 128           /* must be >= kallsyms table size */
 88         char *knt1 = NULL;
 89 
 90         if (KDB_DEBUG(AR))
 91                 kdb_printf("kdbnearsym: addr=0x%lx, symtab=%p\n", addr, symtab);
 92         memset(symtab, 0, sizeof(*symtab));
 93 
 94         if (addr < 4096)
 95                 goto out;
 96         knt1 = debug_kmalloc(knt1_size, GFP_ATOMIC);
 97         if (!knt1) {
 98                 kdb_printf("kdbnearsym: addr=0x%lx cannot kmalloc knt1\n",
 99                            addr);
100                 goto out;
101         }
102         symtab->sym_name = kallsyms_lookup(addr, &symbolsize , &offset,
103                                 (char **)(&symtab->mod_name), knt1);
104         if (offset > 8*1024*1024) {
105                 symtab->sym_name = NULL;
106                 addr = offset = symbolsize = 0;
107         }
108         symtab->sym_start = addr - offset;
109         symtab->sym_end = symtab->sym_start + symbolsize;
110         ret = symtab->sym_name != NULL && *(symtab->sym_name) != '\0';
111 
112         if (ret) {
113                 int i;
114                 /* Another 2.6 kallsyms "feature".  Sometimes the sym_name is
115                  * set but the buffer passed into kallsyms_lookup is not used,
116                  * so it contains garbage.  The caller has to work out which
117                  * buffer needs to be saved.
118                  *
119                  * What was Rusty smoking when he wrote that code?
120                  */
121                 if (symtab->sym_name != knt1) {
122                         strncpy(knt1, symtab->sym_name, knt1_size);
123                         knt1[knt1_size-1] = '\0';
124                 }
125                 for (i = 0; i < ARRAY_SIZE(kdb_name_table); ++i) {
126                         if (kdb_name_table[i] &&
127                             strcmp(kdb_name_table[i], knt1) == 0)
128                                 break;
129                 }
130                 if (i >= ARRAY_SIZE(kdb_name_table)) {
131                         debug_kfree(kdb_name_table[0]);
132                         memcpy(kdb_name_table, kdb_name_table+1,
133                                sizeof(kdb_name_table[0]) *
134                                (ARRAY_SIZE(kdb_name_table)-1));
135                 } else {
136                         debug_kfree(knt1);
137                         knt1 = kdb_name_table[i];
138                         memcpy(kdb_name_table+i, kdb_name_table+i+1,
139                                sizeof(kdb_name_table[0]) *
140                                (ARRAY_SIZE(kdb_name_table)-i-1));
141                 }
142                 i = ARRAY_SIZE(kdb_name_table) - 1;
143                 kdb_name_table[i] = knt1;
144                 symtab->sym_name = kdb_name_table[i];
145                 knt1 = NULL;
146         }
147 
148         if (symtab->mod_name == NULL)
149                 symtab->mod_name = "kernel";
150         if (KDB_DEBUG(AR))
151                 kdb_printf("kdbnearsym: returns %d symtab->sym_start=0x%lx, "
152                    "symtab->mod_name=%p, symtab->sym_name=%p (%s)\n", ret,
153                    symtab->sym_start, symtab->mod_name, symtab->sym_name,
154                    symtab->sym_name);
155 
156 out:
157         debug_kfree(knt1);
158         return ret;
159 }
160 
161 void kdbnearsym_cleanup(void)
162 {
163         int i;
164         for (i = 0; i < ARRAY_SIZE(kdb_name_table); ++i) {
165                 if (kdb_name_table[i]) {
166                         debug_kfree(kdb_name_table[i]);
167                         kdb_name_table[i] = NULL;
168                 }
169         }
170 }
171 
172 static char ks_namebuf[KSYM_NAME_LEN+1], ks_namebuf_prev[KSYM_NAME_LEN+1];
173 
174 /*
175  * kallsyms_symbol_complete
176  *
177  * Parameters:
178  *      prefix_name     prefix of a symbol name to lookup
179  *      max_len         maximum length that can be returned
180  * Returns:
181  *      Number of symbols which match the given prefix.
182  * Notes:
183  *      prefix_name is changed to contain the longest unique prefix that
184  *      starts with this prefix (tab completion).
185  */
186 int kallsyms_symbol_complete(char *prefix_name, int max_len)
187 {
188         loff_t pos = 0;
189         int prefix_len = strlen(prefix_name), prev_len = 0;
190         int i, number = 0;
191         const char *name;
192 
193         while ((name = kdb_walk_kallsyms(&pos))) {
194                 if (strncmp(name, prefix_name, prefix_len) == 0) {
195                         strcpy(ks_namebuf, name);
196                         /* Work out the longest name that matches the prefix */
197                         if (++number == 1) {
198                                 prev_len = min_t(int, max_len-1,
199                                                  strlen(ks_namebuf));
200                                 memcpy(ks_namebuf_prev, ks_namebuf, prev_len);
201                                 ks_namebuf_prev[prev_len] = '\0';
202                                 continue;
203                         }
204                         for (i = 0; i < prev_len; i++) {
205                                 if (ks_namebuf[i] != ks_namebuf_prev[i]) {
206                                         prev_len = i;
207                                         ks_namebuf_prev[i] = '\0';
208                                         break;
209                                 }
210                         }
211                 }
212         }
213         if (prev_len > prefix_len)
214                 memcpy(prefix_name, ks_namebuf_prev, prev_len+1);
215         return number;
216 }
217 
218 /*
219  * kallsyms_symbol_next
220  *
221  * Parameters:
222  *      prefix_name     prefix of a symbol name to lookup
223  *      flag    0 means search from the head, 1 means continue search.
224  * Returns:
225  *      1 if a symbol matches the given prefix.
226  *      0 if no string found
227  */
228 int kallsyms_symbol_next(char *prefix_name, int flag)
229 {
230         int prefix_len = strlen(prefix_name);
231         static loff_t pos;
232         const char *name;
233 
234         if (!flag)
235                 pos = 0;
236 
237         while ((name = kdb_walk_kallsyms(&pos))) {
238                 if (strncmp(name, prefix_name, prefix_len) == 0) {
239                         strncpy(prefix_name, name, strlen(name)+1);
240                         return 1;
241                 }
242         }
243         return 0;
244 }
245 
246 /*
247  * kdb_symbol_print - Standard method for printing a symbol name and offset.
248  * Inputs:
249  *      addr    Address to be printed.
250  *      symtab  Address of symbol data, if NULL this routine does its
251  *              own lookup.
252  *      punc    Punctuation for string, bit field.
253  * Remarks:
254  *      The string and its punctuation is only printed if the address
255  *      is inside the kernel, except that the value is always printed
256  *      when requested.
257  */
258 void kdb_symbol_print(unsigned long addr, const kdb_symtab_t *symtab_p,
259                       unsigned int punc)
260 {
261         kdb_symtab_t symtab, *symtab_p2;
262         if (symtab_p) {
263                 symtab_p2 = (kdb_symtab_t *)symtab_p;
264         } else {
265                 symtab_p2 = &symtab;
266                 kdbnearsym(addr, symtab_p2);
267         }
268         if (!(symtab_p2->sym_name || (punc & KDB_SP_VALUE)))
269                 return;
270         if (punc & KDB_SP_SPACEB)
271                 kdb_printf(" ");
272         if (punc & KDB_SP_VALUE)
273                 kdb_printf(kdb_machreg_fmt0, addr);
274         if (symtab_p2->sym_name) {
275                 if (punc & KDB_SP_VALUE)
276                         kdb_printf(" ");
277                 if (punc & KDB_SP_PAREN)
278                         kdb_printf("(");
279                 if (strcmp(symtab_p2->mod_name, "kernel"))
280                         kdb_printf("[%s]", symtab_p2->mod_name);
281                 kdb_printf("%s", symtab_p2->sym_name);
282                 if (addr != symtab_p2->sym_start)
283                         kdb_printf("+0x%lx", addr - symtab_p2->sym_start);
284                 if (punc & KDB_SP_SYMSIZE)
285                         kdb_printf("/0x%lx",
286                                    symtab_p2->sym_end - symtab_p2->sym_start);
287                 if (punc & KDB_SP_PAREN)
288                         kdb_printf(")");
289         }
290         if (punc & KDB_SP_SPACEA)
291                 kdb_printf(" ");
292         if (punc & KDB_SP_NEWLINE)
293                 kdb_printf("\n");
294 }
295 
296 /*
297  * kdb_strdup - kdb equivalent of strdup, for disasm code.
298  * Inputs:
299  *      str     The string to duplicate.
300  *      type    Flags to kmalloc for the new string.
301  * Returns:
302  *      Address of the new string, NULL if storage could not be allocated.
303  * Remarks:
304  *      This is not in lib/string.c because it uses kmalloc which is not
305  *      available when string.o is used in boot loaders.
306  */
307 char *kdb_strdup(const char *str, gfp_t type)
308 {
309         int n = strlen(str)+1;
310         char *s = kmalloc(n, type);
311         if (!s)
312                 return NULL;
313         return strcpy(s, str);
314 }
315 
316 /*
317  * kdb_getarea_size - Read an area of data.  The kdb equivalent of
318  *      copy_from_user, with kdb messages for invalid addresses.
319  * Inputs:
320  *      res     Pointer to the area to receive the result.
321  *      addr    Address of the area to copy.
322  *      size    Size of the area.
323  * Returns:
324  *      0 for success, < 0 for error.
325  */
326 int kdb_getarea_size(void *res, unsigned long addr, size_t size)
327 {
328         int ret = probe_kernel_read((char *)res, (char *)addr, size);
329         if (ret) {
330                 if (!KDB_STATE(SUPPRESS)) {
331                         kdb_printf("kdb_getarea: Bad address 0x%lx\n", addr);
332                         KDB_STATE_SET(SUPPRESS);
333                 }
334                 ret = KDB_BADADDR;
335         } else {
336                 KDB_STATE_CLEAR(SUPPRESS);
337         }
338         return ret;
339 }
340 
341 /*
342  * kdb_putarea_size - Write an area of data.  The kdb equivalent of
343  *      copy_to_user, with kdb messages for invalid addresses.
344  * Inputs:
345  *      addr    Address of the area to write to.
346  *      res     Pointer to the area holding the data.
347  *      size    Size of the area.
348  * Returns:
349  *      0 for success, < 0 for error.
350  */
351 int kdb_putarea_size(unsigned long addr, void *res, size_t size)
352 {
353         int ret = probe_kernel_read((char *)addr, (char *)res, size);
354         if (ret) {
355                 if (!KDB_STATE(SUPPRESS)) {
356                         kdb_printf("kdb_putarea: Bad address 0x%lx\n", addr);
357                         KDB_STATE_SET(SUPPRESS);
358                 }
359                 ret = KDB_BADADDR;
360         } else {
361                 KDB_STATE_CLEAR(SUPPRESS);
362         }
363         return ret;
364 }
365 
366 /*
367  * kdb_getphys - Read data from a physical address. Validate the
368  *      address is in range, use kmap_atomic() to get data
369  *      similar to kdb_getarea() - but for phys addresses
370  * Inputs:
371  *      res     Pointer to the word to receive the result
372  *      addr    Physical address of the area to copy
373  *      size    Size of the area
374  * Returns:
375  *      0 for success, < 0 for error.
376  */
377 static int kdb_getphys(void *res, unsigned long addr, size_t size)
378 {
379         unsigned long pfn;
380         void *vaddr;
381         struct page *page;
382 
383         pfn = (addr >> PAGE_SHIFT);
384         if (!pfn_valid(pfn))
385                 return 1;
386         page = pfn_to_page(pfn);
387         vaddr = kmap_atomic(page);
388         memcpy(res, vaddr + (addr & (PAGE_SIZE - 1)), size);
389         kunmap_atomic(vaddr);
390 
391         return 0;
392 }
393 
394 /*
395  * kdb_getphysword
396  * Inputs:
397  *      word    Pointer to the word to receive the result.
398  *      addr    Address of the area to copy.
399  *      size    Size of the area.
400  * Returns:
401  *      0 for success, < 0 for error.
402  */
403 int kdb_getphysword(unsigned long *word, unsigned long addr, size_t size)
404 {
405         int diag;
406         __u8  w1;
407         __u16 w2;
408         __u32 w4;
409         __u64 w8;
410         *word = 0;      /* Default value if addr or size is invalid */
411 
412         switch (size) {
413         case 1:
414                 diag = kdb_getphys(&w1, addr, sizeof(w1));
415                 if (!diag)
416                         *word = w1;
417                 break;
418         case 2:
419                 diag = kdb_getphys(&w2, addr, sizeof(w2));
420                 if (!diag)
421                         *word = w2;
422                 break;
423         case 4:
424                 diag = kdb_getphys(&w4, addr, sizeof(w4));
425                 if (!diag)
426                         *word = w4;
427                 break;
428         case 8:
429                 if (size <= sizeof(*word)) {
430                         diag = kdb_getphys(&w8, addr, sizeof(w8));
431                         if (!diag)
432                                 *word = w8;
433                         break;
434                 }
435                 /* drop through */
436         default:
437                 diag = KDB_BADWIDTH;
438                 kdb_printf("kdb_getphysword: bad width %ld\n", (long) size);
439         }
440         return diag;
441 }
442 
443 /*
444  * kdb_getword - Read a binary value.  Unlike kdb_getarea, this treats
445  *      data as numbers.
446  * Inputs:
447  *      word    Pointer to the word to receive the result.
448  *      addr    Address of the area to copy.
449  *      size    Size of the area.
450  * Returns:
451  *      0 for success, < 0 for error.
452  */
453 int kdb_getword(unsigned long *word, unsigned long addr, size_t size)
454 {
455         int diag;
456         __u8  w1;
457         __u16 w2;
458         __u32 w4;
459         __u64 w8;
460         *word = 0;      /* Default value if addr or size is invalid */
461         switch (size) {
462         case 1:
463                 diag = kdb_getarea(w1, addr);
464                 if (!diag)
465                         *word = w1;
466                 break;
467         case 2:
468                 diag = kdb_getarea(w2, addr);
469                 if (!diag)
470                         *word = w2;
471                 break;
472         case 4:
473                 diag = kdb_getarea(w4, addr);
474                 if (!diag)
475                         *word = w4;
476                 break;
477         case 8:
478                 if (size <= sizeof(*word)) {
479                         diag = kdb_getarea(w8, addr);
480                         if (!diag)
481                                 *word = w8;
482                         break;
483                 }
484                 /* drop through */
485         default:
486                 diag = KDB_BADWIDTH;
487                 kdb_printf("kdb_getword: bad width %ld\n", (long) size);
488         }
489         return diag;
490 }
491 
492 /*
493  * kdb_putword - Write a binary value.  Unlike kdb_putarea, this
494  *      treats data as numbers.
495  * Inputs:
496  *      addr    Address of the area to write to..
497  *      word    The value to set.
498  *      size    Size of the area.
499  * Returns:
500  *      0 for success, < 0 for error.
501  */
502 int kdb_putword(unsigned long addr, unsigned long word, size_t size)
503 {
504         int diag;
505         __u8  w1;
506         __u16 w2;
507         __u32 w4;
508         __u64 w8;
509         switch (size) {
510         case 1:
511                 w1 = word;
512                 diag = kdb_putarea(addr, w1);
513                 break;
514         case 2:
515                 w2 = word;
516                 diag = kdb_putarea(addr, w2);
517                 break;
518         case 4:
519                 w4 = word;
520                 diag = kdb_putarea(addr, w4);
521                 break;
522         case 8:
523                 if (size <= sizeof(word)) {
524                         w8 = word;
525                         diag = kdb_putarea(addr, w8);
526                         break;
527                 }
528                 /* drop through */
529         default:
530                 diag = KDB_BADWIDTH;
531                 kdb_printf("kdb_putword: bad width %ld\n", (long) size);
532         }
533         return diag;
534 }
535 
536 /*
537  * kdb_task_state_string - Convert a string containing any of the
538  *      letters DRSTCZEUIMA to a mask for the process state field and
539  *      return the value.  If no argument is supplied, return the mask
540  *      that corresponds to environment variable PS, DRSTCZEU by
541  *      default.
542  * Inputs:
543  *      s       String to convert
544  * Returns:
545  *      Mask for process state.
546  * Notes:
547  *      The mask folds data from several sources into a single long value, so
548  *      be careful not to overlap the bits.  TASK_* bits are in the LSB,
549  *      special cases like UNRUNNABLE are in the MSB.  As of 2.6.10-rc1 there
550  *      is no overlap between TASK_* and EXIT_* but that may not always be
551  *      true, so EXIT_* bits are shifted left 16 bits before being stored in
552  *      the mask.
553  */
554 
555 /* unrunnable is < 0 */
556 #define UNRUNNABLE      (1UL << (8*sizeof(unsigned long) - 1))
557 #define RUNNING         (1UL << (8*sizeof(unsigned long) - 2))
558 #define IDLE            (1UL << (8*sizeof(unsigned long) - 3))
559 #define DAEMON          (1UL << (8*sizeof(unsigned long) - 4))
560 
561 unsigned long kdb_task_state_string(const char *s)
562 {
563         long res = 0;
564         if (!s) {
565                 s = kdbgetenv("PS");
566                 if (!s)
567                         s = "DRSTCZEU"; /* default value for ps */
568         }
569         while (*s) {
570                 switch (*s) {
571                 case 'D':
572                         res |= TASK_UNINTERRUPTIBLE;
573                         break;
574                 case 'R':
575                         res |= RUNNING;
576                         break;
577                 case 'S':
578                         res |= TASK_INTERRUPTIBLE;
579                         break;
580                 case 'T':
581                         res |= TASK_STOPPED;
582                         break;
583                 case 'C':
584                         res |= TASK_TRACED;
585                         break;
586                 case 'Z':
587                         res |= EXIT_ZOMBIE << 16;
588                         break;
589                 case 'E':
590                         res |= EXIT_DEAD << 16;
591                         break;
592                 case 'U':
593                         res |= UNRUNNABLE;
594                         break;
595                 case 'I':
596                         res |= IDLE;
597                         break;
598                 case 'M':
599                         res |= DAEMON;
600                         break;
601                 case 'A':
602                         res = ~0UL;
603                         break;
604                 default:
605                           kdb_printf("%s: unknown flag '%c' ignored\n",
606                                      __func__, *s);
607                           break;
608                 }
609                 ++s;
610         }
611         return res;
612 }
613 
614 /*
615  * kdb_task_state_char - Return the character that represents the task state.
616  * Inputs:
617  *      p       struct task for the process
618  * Returns:
619  *      One character to represent the task state.
620  */
621 char kdb_task_state_char (const struct task_struct *p)
622 {
623         int cpu;
624         char state;
625         unsigned long tmp;
626 
627         if (!p || probe_kernel_read(&tmp, (char *)p, sizeof(unsigned long)))
628                 return 'E';
629 
630         cpu = kdb_process_cpu(p);
631         state = (p->state == 0) ? 'R' :
632                 (p->state < 0) ? 'U' :
633                 (p->state & TASK_UNINTERRUPTIBLE) ? 'D' :
634                 (p->state & TASK_STOPPED) ? 'T' :
635                 (p->state & TASK_TRACED) ? 'C' :
636                 (p->exit_state & EXIT_ZOMBIE) ? 'Z' :
637                 (p->exit_state & EXIT_DEAD) ? 'E' :
638                 (p->state & TASK_INTERRUPTIBLE) ? 'S' : '?';
639         if (is_idle_task(p)) {
640                 /* Idle task.  Is it really idle, apart from the kdb
641                  * interrupt? */
642                 if (!kdb_task_has_cpu(p) || kgdb_info[cpu].irq_depth == 1) {
643                         if (cpu != kdb_initial_cpu)
644                                 state = 'I';    /* idle task */
645                 }
646         } else if (!p->mm && state == 'S') {
647                 state = 'M';    /* sleeping system daemon */
648         }
649         return state;
650 }
651 
652 /*
653  * kdb_task_state - Return true if a process has the desired state
654  *      given by the mask.
655  * Inputs:
656  *      p       struct task for the process
657  *      mask    mask from kdb_task_state_string to select processes
658  * Returns:
659  *      True if the process matches at least one criteria defined by the mask.
660  */
661 unsigned long kdb_task_state(const struct task_struct *p, unsigned long mask)
662 {
663         char state[] = { kdb_task_state_char(p), '\0' };
664         return (mask & kdb_task_state_string(state)) != 0;
665 }
666 
667 /*
668  * kdb_print_nameval - Print a name and its value, converting the
669  *      value to a symbol lookup if possible.
670  * Inputs:
671  *      name    field name to print
672  *      val     value of field
673  */
674 void kdb_print_nameval(const char *name, unsigned long val)
675 {
676         kdb_symtab_t symtab;
677         kdb_printf("  %-11.11s ", name);
678         if (kdbnearsym(val, &symtab))
679                 kdb_symbol_print(val, &symtab,
680                                  KDB_SP_VALUE|KDB_SP_SYMSIZE|KDB_SP_NEWLINE);
681         else
682                 kdb_printf("0x%lx\n", val);
683 }
684 
685 /* Last ditch allocator for debugging, so we can still debug even when
686  * the GFP_ATOMIC pool has been exhausted.  The algorithms are tuned
687  * for space usage, not for speed.  One smallish memory pool, the free
688  * chain is always in ascending address order to allow coalescing,
689  * allocations are done in brute force best fit.
690  */
691 
692 struct debug_alloc_header {
693         u32 next;       /* offset of next header from start of pool */
694         u32 size;
695         void *caller;
696 };
697 
698 /* The memory returned by this allocator must be aligned, which means
699  * so must the header size.  Do not assume that sizeof(struct
700  * debug_alloc_header) is a multiple of the alignment, explicitly
701  * calculate the overhead of this header, including the alignment.
702  * The rest of this code must not use sizeof() on any header or
703  * pointer to a header.
704  */
705 #define dah_align 8
706 #define dah_overhead ALIGN(sizeof(struct debug_alloc_header), dah_align)
707 
708 static u64 debug_alloc_pool_aligned[256*1024/dah_align];        /* 256K pool */
709 static char *debug_alloc_pool = (char *)debug_alloc_pool_aligned;
710 static u32 dah_first, dah_first_call = 1, dah_used, dah_used_max;
711 
712 /* Locking is awkward.  The debug code is called from all contexts,
713  * including non maskable interrupts.  A normal spinlock is not safe
714  * in NMI context.  Try to get the debug allocator lock, if it cannot
715  * be obtained after a second then give up.  If the lock could not be
716  * previously obtained on this cpu then only try once.
717  *
718  * sparse has no annotation for "this function _sometimes_ acquires a
719  * lock", so fudge the acquire/release notation.
720  */
721 static DEFINE_SPINLOCK(dap_lock);
722 static int get_dap_lock(void)
723         __acquires(dap_lock)
724 {
725         static int dap_locked = -1;
726         int count;
727         if (dap_locked == smp_processor_id())
728                 count = 1;
729         else
730                 count = 1000;
731         while (1) {
732                 if (spin_trylock(&dap_lock)) {
733                         dap_locked = -1;
734                         return 1;
735                 }
736                 if (!count--)
737                         break;
738                 udelay(1000);
739         }
740         dap_locked = smp_processor_id();
741         __acquire(dap_lock);
742         return 0;
743 }
744 
745 void *debug_kmalloc(size_t size, gfp_t flags)
746 {
747         unsigned int rem, h_offset;
748         struct debug_alloc_header *best, *bestprev, *prev, *h;
749         void *p = NULL;
750         if (!get_dap_lock()) {
751                 __release(dap_lock);    /* we never actually got it */
752                 return NULL;
753         }
754         h = (struct debug_alloc_header *)(debug_alloc_pool + dah_first);
755         if (dah_first_call) {
756                 h->size = sizeof(debug_alloc_pool_aligned) - dah_overhead;
757                 dah_first_call = 0;
758         }
759         size = ALIGN(size, dah_align);
760         prev = best = bestprev = NULL;
761         while (1) {
762                 if (h->size >= size && (!best || h->size < best->size)) {
763                         best = h;
764                         bestprev = prev;
765                         if (h->size == size)
766                                 break;
767                 }
768                 if (!h->next)
769                         break;
770                 prev = h;
771                 h = (struct debug_alloc_header *)(debug_alloc_pool + h->next);
772         }
773         if (!best)
774                 goto out;
775         rem = best->size - size;
776         /* The pool must always contain at least one header */
777         if (best->next == 0 && bestprev == NULL && rem < dah_overhead)
778                 goto out;
779         if (rem >= dah_overhead) {
780                 best->size = size;
781                 h_offset = ((char *)best - debug_alloc_pool) +
782                            dah_overhead + best->size;
783                 h = (struct debug_alloc_header *)(debug_alloc_pool + h_offset);
784                 h->size = rem - dah_overhead;
785                 h->next = best->next;
786         } else
787                 h_offset = best->next;
788         best->caller = __builtin_return_address(0);
789         dah_used += best->size;
790         dah_used_max = max(dah_used, dah_used_max);
791         if (bestprev)
792                 bestprev->next = h_offset;
793         else
794                 dah_first = h_offset;
795         p = (char *)best + dah_overhead;
796         memset(p, POISON_INUSE, best->size - 1);
797         *((char *)p + best->size - 1) = POISON_END;
798 out:
799         spin_unlock(&dap_lock);
800         return p;
801 }
802 
803 void debug_kfree(void *p)
804 {
805         struct debug_alloc_header *h;
806         unsigned int h_offset;
807         if (!p)
808                 return;
809         if ((char *)p < debug_alloc_pool ||
810             (char *)p >= debug_alloc_pool + sizeof(debug_alloc_pool_aligned)) {
811                 kfree(p);
812                 return;
813         }
814         if (!get_dap_lock()) {
815                 __release(dap_lock);    /* we never actually got it */
816                 return;         /* memory leak, cannot be helped */
817         }
818         h = (struct debug_alloc_header *)((char *)p - dah_overhead);
819         memset(p, POISON_FREE, h->size - 1);
820         *((char *)p + h->size - 1) = POISON_END;
821         h->caller = NULL;
822         dah_used -= h->size;
823         h_offset = (char *)h - debug_alloc_pool;
824         if (h_offset < dah_first) {
825                 h->next = dah_first;
826                 dah_first = h_offset;
827         } else {
828                 struct debug_alloc_header *prev;
829                 unsigned int prev_offset;
830                 prev = (struct debug_alloc_header *)(debug_alloc_pool +
831                                                      dah_first);
832                 while (1) {
833                         if (!prev->next || prev->next > h_offset)
834                                 break;
835                         prev = (struct debug_alloc_header *)
836                                 (debug_alloc_pool + prev->next);
837                 }
838                 prev_offset = (char *)prev - debug_alloc_pool;
839                 if (prev_offset + dah_overhead + prev->size == h_offset) {
840                         prev->size += dah_overhead + h->size;
841                         memset(h, POISON_FREE, dah_overhead - 1);
842                         *((char *)h + dah_overhead - 1) = POISON_END;
843                         h = prev;
844                         h_offset = prev_offset;
845                 } else {
846                         h->next = prev->next;
847                         prev->next = h_offset;
848                 }
849         }
850         if (h_offset + dah_overhead + h->size == h->next) {
851                 struct debug_alloc_header *next;
852                 next = (struct debug_alloc_header *)
853                         (debug_alloc_pool + h->next);
854                 h->size += dah_overhead + next->size;
855                 h->next = next->next;
856                 memset(next, POISON_FREE, dah_overhead - 1);
857                 *((char *)next + dah_overhead - 1) = POISON_END;
858         }
859         spin_unlock(&dap_lock);
860 }
861 
862 void debug_kusage(void)
863 {
864         struct debug_alloc_header *h_free, *h_used;
865 #ifdef  CONFIG_IA64
866         /* FIXME: using dah for ia64 unwind always results in a memory leak.
867          * Fix that memory leak first, then set debug_kusage_one_time = 1 for
868          * all architectures.
869          */
870         static int debug_kusage_one_time;
871 #else
872         static int debug_kusage_one_time = 1;
873 #endif
874         if (!get_dap_lock()) {
875                 __release(dap_lock);    /* we never actually got it */
876                 return;
877         }
878         h_free = (struct debug_alloc_header *)(debug_alloc_pool + dah_first);
879         if (dah_first == 0 &&
880             (h_free->size == sizeof(debug_alloc_pool_aligned) - dah_overhead ||
881              dah_first_call))
882                 goto out;
883         if (!debug_kusage_one_time)
884                 goto out;
885         debug_kusage_one_time = 0;
886         kdb_printf("%s: debug_kmalloc memory leak dah_first %d\n",
887                    __func__, dah_first);
888         if (dah_first) {
889                 h_used = (struct debug_alloc_header *)debug_alloc_pool;
890                 kdb_printf("%s: h_used %p size %d\n", __func__, h_used,
891                            h_used->size);
892         }
893         do {
894                 h_used = (struct debug_alloc_header *)
895                           ((char *)h_free + dah_overhead + h_free->size);
896                 kdb_printf("%s: h_used %p size %d caller %p\n",
897                            __func__, h_used, h_used->size, h_used->caller);
898                 h_free = (struct debug_alloc_header *)
899                           (debug_alloc_pool + h_free->next);
900         } while (h_free->next);
901         h_used = (struct debug_alloc_header *)
902                   ((char *)h_free + dah_overhead + h_free->size);
903         if ((char *)h_used - debug_alloc_pool !=
904             sizeof(debug_alloc_pool_aligned))
905                 kdb_printf("%s: h_used %p size %d caller %p\n",
906                            __func__, h_used, h_used->size, h_used->caller);
907 out:
908         spin_unlock(&dap_lock);
909 }
910 
911 /* Maintain a small stack of kdb_flags to allow recursion without disturbing
912  * the global kdb state.
913  */
914 
915 static int kdb_flags_stack[4], kdb_flags_index;
916 
917 void kdb_save_flags(void)
918 {
919         BUG_ON(kdb_flags_index >= ARRAY_SIZE(kdb_flags_stack));
920         kdb_flags_stack[kdb_flags_index++] = kdb_flags;
921 }
922 
923 void kdb_restore_flags(void)
924 {
925         BUG_ON(kdb_flags_index <= 0);
926         kdb_flags = kdb_flags_stack[--kdb_flags_index];
927 }
928 

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