The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/ddb/db_main.c

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    1 /*-
    2  * Mach Operating System
    3  * Copyright (c) 1991,1990 Carnegie Mellon University
    4  * All Rights Reserved.
    5  *
    6  * Permission to use, copy, modify and distribute this software and its
    7  * documentation is hereby granted, provided that both the copyright
    8  * notice and this permission notice appear in all copies of the
    9  * software, derivative works or modified versions, and any portions
   10  * thereof, and that both notices appear in supporting documentation.
   11  *
   12  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS
   13  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
   14  * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
   15  *
   16  * Carnegie Mellon requests users of this software to return to
   17  *
   18  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
   19  *  School of Computer Science
   20  *  Carnegie Mellon University
   21  *  Pittsburgh PA 15213-3890
   22  *
   23  * any improvements or extensions that they make and grant Carnegie the
   24  * rights to redistribute these changes.
   25  */
   26 
   27 #include <sys/cdefs.h>
   28 __FBSDID("$FreeBSD: releng/11.0/sys/ddb/db_main.c 285774 2015-07-21 23:07:55Z markj $");
   29 
   30 #include <sys/param.h>
   31 #include <sys/systm.h>
   32 #include <sys/cons.h>
   33 #include <sys/linker.h>
   34 #include <sys/kdb.h>
   35 #include <sys/kernel.h>
   36 #include <sys/pcpu.h>
   37 #include <sys/proc.h>
   38 #include <sys/reboot.h>
   39 #include <sys/sysctl.h>
   40 
   41 #include <machine/kdb.h>
   42 #include <machine/pcb.h>
   43 #include <machine/setjmp.h>
   44 
   45 #include <ddb/ddb.h>
   46 #include <ddb/db_command.h>
   47 #include <ddb/db_sym.h>
   48 
   49 SYSCTL_NODE(_debug, OID_AUTO, ddb, CTLFLAG_RW, 0, "DDB settings");
   50 
   51 static dbbe_init_f db_init;
   52 static dbbe_trap_f db_trap;
   53 static dbbe_trace_f db_trace_self_wrapper;
   54 static dbbe_trace_thread_f db_trace_thread_wrapper;
   55 
   56 KDB_BACKEND(ddb, db_init, db_trace_self_wrapper, db_trace_thread_wrapper,
   57     db_trap);
   58 
   59 /*
   60  * Symbols can be loaded by specifying the exact addresses of
   61  * the symtab and strtab in memory. This is used when loaded from
   62  * boot loaders different than the native one (like Xen).
   63  */
   64 vm_offset_t ksymtab, kstrtab, ksymtab_size;
   65 
   66 bool
   67 X_db_line_at_pc(db_symtab_t *symtab, c_db_sym_t sym, char **file, int *line,
   68     db_expr_t off)
   69 {
   70         return (false);
   71 }
   72 
   73 c_db_sym_t
   74 X_db_lookup(db_symtab_t *symtab, const char *symbol)
   75 {
   76         c_linker_sym_t lsym;
   77         Elf_Sym *sym;
   78 
   79         if (symtab->private == NULL) {
   80                 return ((c_db_sym_t)((!linker_ddb_lookup(symbol, &lsym))
   81                         ? lsym : NULL));
   82         } else {
   83                 sym = (Elf_Sym *)symtab->start;
   84                 while ((char *)sym < symtab->end) {
   85                         if (sym->st_name != 0 &&
   86                             !strcmp(symtab->private + sym->st_name, symbol))
   87                                 return ((c_db_sym_t)sym);
   88                         sym++;
   89                 }
   90         }
   91         return (NULL);
   92 }
   93 
   94 c_db_sym_t
   95 X_db_search_symbol(db_symtab_t *symtab, db_addr_t off, db_strategy_t strat,
   96     db_expr_t *diffp)
   97 {
   98         c_linker_sym_t lsym;
   99         Elf_Sym *sym, *match;
  100         unsigned long diff;
  101 
  102         if (symtab->private == NULL) {
  103                 if (!linker_ddb_search_symbol((caddr_t)off, &lsym, &diff)) {
  104                         *diffp = (db_expr_t)diff;
  105                         return ((c_db_sym_t)lsym);
  106                 }
  107                 return (NULL);
  108         }
  109 
  110         diff = ~0UL;
  111         match = NULL;
  112         for (sym = (Elf_Sym*)symtab->start; (char*)sym < symtab->end; sym++) {
  113                 if (sym->st_name == 0 || sym->st_shndx == SHN_UNDEF)
  114                         continue;
  115                 if (off < sym->st_value)
  116                         continue;
  117                 if (ELF_ST_TYPE(sym->st_info) != STT_OBJECT &&
  118                     ELF_ST_TYPE(sym->st_info) != STT_FUNC &&
  119                     ELF_ST_TYPE(sym->st_info) != STT_NOTYPE)
  120                         continue;
  121                 if ((off - sym->st_value) > diff)
  122                         continue;
  123                 if ((off - sym->st_value) < diff) {
  124                         diff = off - sym->st_value;
  125                         match = sym;
  126                 } else {
  127                         if (match == NULL)
  128                                 match = sym;
  129                         else if (ELF_ST_BIND(match->st_info) == STB_LOCAL &&
  130                             ELF_ST_BIND(sym->st_info) != STB_LOCAL)
  131                                 match = sym;
  132                 }
  133                 if (diff == 0) {
  134                         if (strat == DB_STGY_PROC &&
  135                             ELF_ST_TYPE(sym->st_info) == STT_FUNC &&
  136                             ELF_ST_BIND(sym->st_info) != STB_LOCAL)
  137                                 break;
  138                         if (strat == DB_STGY_ANY &&
  139                             ELF_ST_BIND(sym->st_info) != STB_LOCAL)
  140                                 break;
  141                 }
  142         }
  143 
  144         *diffp = (match == NULL) ? off : diff;
  145         return ((c_db_sym_t)match);
  146 }
  147 
  148 bool
  149 X_db_sym_numargs(db_symtab_t *symtab, c_db_sym_t sym, int *nargp,
  150     char **argp)
  151 {
  152         return (false);
  153 }
  154 
  155 void
  156 X_db_symbol_values(db_symtab_t *symtab, c_db_sym_t sym, const char **namep,
  157     db_expr_t *valp)
  158 {
  159         linker_symval_t lval;
  160 
  161         if (symtab->private == NULL) {
  162                 linker_ddb_symbol_values((c_linker_sym_t)sym, &lval);
  163                 if (namep != NULL)
  164                         *namep = (const char*)lval.name;
  165                 if (valp != NULL)
  166                         *valp = (db_expr_t)lval.value;
  167         } else {
  168                 if (namep != NULL)
  169                         *namep = (const char *)symtab->private +
  170                             ((const Elf_Sym *)sym)->st_name;
  171                 if (valp != NULL)
  172                         *valp = (db_expr_t)((const Elf_Sym *)sym)->st_value;
  173         }
  174 }
  175 
  176 int
  177 db_fetch_ksymtab(vm_offset_t ksym_start, vm_offset_t ksym_end)
  178 {
  179         Elf_Size strsz;
  180 
  181         if (ksym_end > ksym_start && ksym_start != 0) {
  182                 ksymtab = ksym_start;
  183                 ksymtab_size = *(Elf_Size*)ksymtab;
  184                 ksymtab += sizeof(Elf_Size);
  185                 kstrtab = ksymtab + ksymtab_size;
  186                 strsz = *(Elf_Size*)kstrtab;
  187                 kstrtab += sizeof(Elf_Size);
  188                 if (kstrtab + strsz > ksym_end) {
  189                         /* Sizes doesn't match, unset everything. */
  190                         ksymtab = ksymtab_size = kstrtab = 0;
  191                 }
  192         }
  193 
  194         if (ksymtab == 0 || ksymtab_size == 0 || kstrtab == 0)
  195                 return (-1);
  196 
  197         return (0);
  198 }
  199 
  200 static int
  201 db_init(void)
  202 {
  203 
  204         db_command_init();
  205 
  206         if (ksymtab != 0 && kstrtab != 0 && ksymtab_size != 0) {
  207                 db_add_symbol_table((char *)ksymtab,
  208                     (char *)(ksymtab + ksymtab_size), "elf", (char *)kstrtab);
  209         }
  210         db_add_symbol_table(NULL, NULL, "kld", NULL);
  211         return (1);     /* We're the default debugger. */
  212 }
  213 
  214 static int
  215 db_trap(int type, int code)
  216 {
  217         jmp_buf jb;
  218         void *prev_jb;
  219         bool bkpt, watchpt;
  220         const char *why;
  221 
  222         /*
  223          * Don't handle the trap if the console is unavailable (i.e. it
  224          * is in graphics mode).
  225          */
  226         if (cnunavailable())
  227                 return (0);
  228 
  229         bkpt = IS_BREAKPOINT_TRAP(type, code);
  230         watchpt = IS_WATCHPOINT_TRAP(type, code);
  231 
  232         if (db_stop_at_pc(&bkpt)) {
  233                 if (db_inst_count) {
  234                         db_printf("After %d instructions (%d loads, %d stores),\n",
  235                             db_inst_count, db_load_count, db_store_count);
  236                 }
  237                 prev_jb = kdb_jmpbuf(jb);
  238                 if (setjmp(jb) == 0) {
  239                         db_dot = PC_REGS();
  240                         db_print_thread();
  241                         if (bkpt)
  242                                 db_printf("Breakpoint at\t");
  243                         else if (watchpt)
  244                                 db_printf("Watchpoint at\t");
  245                         else
  246                                 db_printf("Stopped at\t");
  247                         db_print_loc_and_inst(db_dot);
  248                 }
  249                 why = kdb_why;
  250                 db_script_kdbenter(why != KDB_WHY_UNSET ? why : "unknown");
  251                 db_command_loop();
  252                 (void)kdb_jmpbuf(prev_jb);
  253         }
  254 
  255         db_restart_at_pc(watchpt);
  256 
  257         return (1);
  258 }
  259 
  260 static void
  261 db_trace_self_wrapper(void)
  262 {
  263         jmp_buf jb;
  264         void *prev_jb;
  265 
  266         prev_jb = kdb_jmpbuf(jb);
  267         if (setjmp(jb) == 0)
  268                 db_trace_self();
  269         (void)kdb_jmpbuf(prev_jb);
  270 }
  271 
  272 static void
  273 db_trace_thread_wrapper(struct thread *td)
  274 {
  275         jmp_buf jb;
  276         void *prev_jb;
  277 
  278         prev_jb = kdb_jmpbuf(jb);
  279         if (setjmp(jb) == 0)
  280                 db_trace_thread(td, -1);
  281         (void)kdb_jmpbuf(prev_jb);
  282 }

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