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_run.c

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    1 /*-
    2  * SPDX-License-Identifier: MIT-CMU
    3  *
    4  * Mach Operating System
    5  * Copyright (c) 1991,1990 Carnegie Mellon University
    6  * All Rights Reserved.
    7  *
    8  * Permission to use, copy, modify and distribute this software and its
    9  * documentation is hereby granted, provided that both the copyright
   10  * notice and this permission notice appear in all copies of the
   11  * software, derivative works or modified versions, and any portions
   12  * thereof, and that both notices appear in supporting documentation.
   13  *
   14  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS
   15  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
   16  * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
   17  *
   18  * Carnegie Mellon requests users of this software to return to
   19  *
   20  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
   21  *  School of Computer Science
   22  *  Carnegie Mellon University
   23  *  Pittsburgh PA 15213-3890
   24  *
   25  * any improvements or extensions that they make and grant Carnegie the
   26  * rights to redistribute these changes.
   27  */
   28 /*
   29  *      Author: David B. Golub, Carnegie Mellon University
   30  *      Date:   7/90
   31  */
   32 
   33 /*
   34  * Commands to run process.
   35  */
   36 
   37 #include <sys/cdefs.h>
   38 __FBSDID("$FreeBSD$");
   39 
   40 #include <sys/param.h>
   41 #include <sys/kdb.h>
   42 #include <sys/proc.h>
   43 #include <sys/systm.h>
   44 
   45 #include <machine/kdb.h>
   46 #include <machine/pcb.h>
   47 
   48 #include <vm/vm.h>
   49 
   50 #include <ddb/ddb.h>
   51 #include <ddb/db_break.h>
   52 #include <ddb/db_access.h>
   53 
   54 #define STEP_ONCE       1
   55 #define STEP_RETURN     2
   56 #define STEP_CALLT      3
   57 #define STEP_CONTINUE   4
   58 #define STEP_INVISIBLE  5
   59 #define STEP_COUNT      6
   60 static int      db_run_mode = STEP_CONTINUE;
   61 
   62 static bool             db_sstep_multiple;
   63 static bool             db_sstep_print;
   64 static int              db_loop_count;
   65 static int              db_call_depth;
   66 
   67 int             db_inst_count;
   68 int             db_load_count;
   69 int             db_store_count;
   70 
   71 #ifdef SOFTWARE_SSTEP
   72 db_breakpoint_t db_not_taken_bkpt = 0;
   73 db_breakpoint_t db_taken_bkpt = 0;
   74 #endif
   75 
   76 #ifndef db_set_single_step
   77 void db_set_single_step(void);
   78 #endif
   79 #ifndef db_clear_single_step
   80 void db_clear_single_step(void);
   81 #endif
   82 #ifndef db_pc_is_singlestep
   83 static bool
   84 db_pc_is_singlestep(db_addr_t pc)
   85 {
   86 #ifdef SOFTWARE_SSTEP
   87         if ((db_not_taken_bkpt != 0 && pc == db_not_taken_bkpt->address)
   88             || (db_taken_bkpt != 0 && pc == db_taken_bkpt->address))
   89                 return (true);
   90 #endif
   91         return (false);
   92 }
   93 #endif
   94 
   95 bool
   96 db_stop_at_pc(int type, int code, bool *is_breakpoint, bool *is_watchpoint)
   97 {
   98         db_addr_t       pc;
   99         db_breakpoint_t bkpt;
  100 
  101         *is_breakpoint = IS_BREAKPOINT_TRAP(type, code);
  102         *is_watchpoint = IS_WATCHPOINT_TRAP(type, code);
  103         pc = PC_REGS();
  104         if (db_pc_is_singlestep(pc))
  105                 *is_breakpoint = false;
  106 
  107         db_clear_single_step();
  108         db_clear_breakpoints();
  109         db_clear_watchpoints();
  110 
  111 #ifdef  FIXUP_PC_AFTER_BREAK
  112         if (*is_breakpoint) {
  113             /*
  114              * Breakpoint trap.  Fix up the PC if the
  115              * machine requires it.
  116              */
  117             FIXUP_PC_AFTER_BREAK
  118             pc = PC_REGS();
  119         }
  120 #endif
  121 
  122         /*
  123          * Now check for a breakpoint at this address.
  124          */
  125         bkpt = db_find_breakpoint_here(pc);
  126         if (bkpt) {
  127             if (--bkpt->count == 0) {
  128                 bkpt->count = bkpt->init_count;
  129                 *is_breakpoint = true;
  130                 return (true);  /* stop here */
  131             }
  132             return (false);     /* continue the countdown */
  133         } else if (*is_breakpoint) {
  134 #ifdef BKPT_SKIP
  135                 BKPT_SKIP;
  136 #endif
  137         }
  138 
  139         *is_breakpoint = false; /* might be a breakpoint, but not ours */
  140 
  141         /*
  142          * If not stepping, then silently ignore single-step traps
  143          * (except for clearing the single-step-flag above).
  144          *
  145          * If stepping, then abort if the trap type is unexpected.
  146          * Breakpoints owned by us are expected and were handled above.
  147          * Single-steps are expected and are handled below.  All others
  148          * are unexpected.
  149          *
  150          * Only do either of these if the MD layer claims to classify
  151          * single-step traps unambiguously (by defining IS_SSTEP_TRAP).
  152          * Otherwise, fall through to the bad historical behaviour
  153          * given by turning unexpected traps into expected traps: if not
  154          * stepping, then expect only breakpoints and stop, and if
  155          * stepping, then expect only single-steps and step.
  156          */
  157 #ifdef IS_SSTEP_TRAP
  158         if (db_run_mode == STEP_CONTINUE && IS_SSTEP_TRAP(type, code))
  159             return (false);
  160         if (db_run_mode != STEP_CONTINUE && !IS_SSTEP_TRAP(type, code)) {
  161             printf("Stepping aborted\n");
  162             return (true);
  163         }
  164 #endif
  165 
  166         if (db_run_mode == STEP_INVISIBLE) {
  167             db_run_mode = STEP_CONTINUE;
  168             return (false);     /* continue */
  169         }
  170         if (db_run_mode == STEP_COUNT) {
  171             return (false); /* continue */
  172         }
  173         if (db_run_mode == STEP_ONCE) {
  174             if (--db_loop_count > 0) {
  175                 if (db_sstep_print) {
  176                     db_printf("\t\t");
  177                     db_print_loc_and_inst(pc);
  178                 }
  179                 return (false); /* continue */
  180             }
  181         }
  182         if (db_run_mode == STEP_RETURN) {
  183             /* continue until matching return */
  184             db_expr_t ins;
  185 
  186             ins = db_get_value(pc, sizeof(int), false);
  187             if (!inst_trap_return(ins) &&
  188                 (!inst_return(ins) || --db_call_depth != 0)) {
  189                 if (db_sstep_print) {
  190                     if (inst_call(ins) || inst_return(ins)) {
  191                         int i;
  192 
  193                         db_printf("[after %6d]     ", db_inst_count);
  194                         for (i = db_call_depth; --i > 0; )
  195                             db_printf("  ");
  196                         db_print_loc_and_inst(pc);
  197                     }
  198                 }
  199                 if (inst_call(ins))
  200                     db_call_depth++;
  201                 return (false); /* continue */
  202             }
  203         }
  204         if (db_run_mode == STEP_CALLT) {
  205             /* continue until call or return */
  206             db_expr_t ins;
  207 
  208             ins = db_get_value(pc, sizeof(int), false);
  209             if (!inst_call(ins) &&
  210                 !inst_return(ins) &&
  211                 !inst_trap_return(ins)) {
  212                 return (false); /* continue */
  213             }
  214         }
  215         return (true);
  216 }
  217 
  218 void
  219 db_restart_at_pc(bool watchpt)
  220 {
  221         db_addr_t       pc = PC_REGS();
  222 
  223         if ((db_run_mode == STEP_COUNT) ||
  224             ((db_run_mode == STEP_ONCE) && db_sstep_multiple) ||
  225             (db_run_mode == STEP_RETURN) ||
  226             (db_run_mode == STEP_CALLT)) {
  227             /*
  228              * We are about to execute this instruction,
  229              * so count it now.
  230              */
  231 #ifdef  SOFTWARE_SSTEP
  232             db_expr_t           ins =
  233 #endif
  234             db_get_value(pc, sizeof(int), false);
  235             db_inst_count++;
  236             db_load_count += inst_load(ins);
  237             db_store_count += inst_store(ins);
  238 #ifdef  SOFTWARE_SSTEP
  239             /* XXX works on mips, but... */
  240             if (inst_branch(ins) || inst_call(ins)) {
  241                 ins = db_get_value(next_instr_address(pc,1),
  242                                    sizeof(int), false);
  243                 db_inst_count++;
  244                 db_load_count += inst_load(ins);
  245                 db_store_count += inst_store(ins);
  246             }
  247 #endif  /* SOFTWARE_SSTEP */
  248         }
  249 
  250         if (db_run_mode == STEP_CONTINUE) {
  251             if (watchpt || db_find_breakpoint_here(pc)) {
  252                 /*
  253                  * Step over breakpoint/watchpoint.
  254                  */
  255                 db_run_mode = STEP_INVISIBLE;
  256                 db_set_single_step();
  257             } else {
  258                 db_set_breakpoints();
  259                 db_set_watchpoints();
  260             }
  261         } else {
  262             db_set_single_step();
  263         }
  264 }
  265 
  266 #ifdef  SOFTWARE_SSTEP
  267 /*
  268  *      Software implementation of single-stepping.
  269  *      If your machine does not have a trace mode
  270  *      similar to the vax or sun ones you can use
  271  *      this implementation, done for the mips.
  272  *      Just define the above conditional and provide
  273  *      the functions/macros defined below.
  274  *
  275  * extern bool
  276  *      inst_branch(),          returns true if the instruction might branch
  277  * extern unsigned
  278  *      branch_taken(),         return the address the instruction might
  279  *                              branch to
  280  *      db_getreg_val();        return the value of a user register,
  281  *                              as indicated in the hardware instruction
  282  *                              encoding, e.g. 8 for r8
  283  *
  284  * next_instr_address(pc,bd)    returns the address of the first
  285  *                              instruction following the one at "pc",
  286  *                              which is either in the taken path of
  287  *                              the branch (bd==1) or not.  This is
  288  *                              for machines (mips) with branch delays.
  289  *
  290  *      A single-step may involve at most 2 breakpoints -
  291  *      one for branch-not-taken and one for branch taken.
  292  *      If one of these addresses does not already have a breakpoint,
  293  *      we allocate a breakpoint and save it here.
  294  *      These breakpoints are deleted on return.
  295  */
  296 
  297 void
  298 db_set_single_step(void)
  299 {
  300         db_addr_t pc = PC_REGS(), brpc;
  301         unsigned inst;
  302 
  303         /*
  304          *      User was stopped at pc, e.g. the instruction
  305          *      at pc was not executed.
  306          */
  307         inst = db_get_value(pc, sizeof(int), false);
  308         if (inst_branch(inst) || inst_call(inst) || inst_return(inst)) {
  309                 brpc = branch_taken(inst, pc);
  310                 if (brpc != pc) {       /* self-branches are hopeless */
  311                         db_taken_bkpt = db_set_temp_breakpoint(brpc);
  312                 }
  313                 pc = next_instr_address(pc, 1);
  314         }
  315         pc = next_instr_address(pc, 0);
  316         db_not_taken_bkpt = db_set_temp_breakpoint(pc);
  317 }
  318 
  319 void
  320 db_clear_single_step(void)
  321 {
  322 
  323         if (db_not_taken_bkpt != 0) {
  324                 db_delete_temp_breakpoint(db_not_taken_bkpt);
  325                 db_not_taken_bkpt = 0;
  326         }
  327         if (db_taken_bkpt != 0) {
  328                 db_delete_temp_breakpoint(db_taken_bkpt);
  329                 db_taken_bkpt = 0;
  330         }
  331 }
  332 
  333 #endif  /* SOFTWARE_SSTEP */
  334 
  335 extern int      db_cmd_loop_done;
  336 
  337 /* single-step */
  338 /*ARGSUSED*/
  339 void
  340 db_single_step_cmd(db_expr_t addr, bool have_addr, db_expr_t count, char *modif)
  341 {
  342         bool            print = false;
  343 
  344         if (count == -1)
  345             count = 1;
  346 
  347         if (modif[0] == 'p')
  348             print = true;
  349 
  350         db_run_mode = STEP_ONCE;
  351         db_loop_count = count;
  352         db_sstep_multiple = (count != 1);
  353         db_sstep_print = print;
  354         db_inst_count = 0;
  355         db_load_count = 0;
  356         db_store_count = 0;
  357 
  358         db_cmd_loop_done = 1;
  359 }
  360 
  361 /* trace and print until call/return */
  362 /*ARGSUSED*/
  363 void
  364 db_trace_until_call_cmd(db_expr_t addr, bool have_addr, db_expr_t count,
  365     char *modif)
  366 {
  367         bool    print = false;
  368 
  369         if (modif[0] == 'p')
  370             print = true;
  371 
  372         db_run_mode = STEP_CALLT;
  373         db_sstep_print = print;
  374         db_inst_count = 0;
  375         db_load_count = 0;
  376         db_store_count = 0;
  377 
  378         db_cmd_loop_done = 1;
  379 }
  380 
  381 /*ARGSUSED*/
  382 void
  383 db_trace_until_matching_cmd(db_expr_t addr, bool have_addr, db_expr_t count,
  384     char *modif)
  385 {
  386         bool    print = false;
  387 
  388         if (modif[0] == 'p')
  389             print = true;
  390 
  391         db_run_mode = STEP_RETURN;
  392         db_call_depth = 1;
  393         db_sstep_print = print;
  394         db_inst_count = 0;
  395         db_load_count = 0;
  396         db_store_count = 0;
  397 
  398         db_cmd_loop_done = 1;
  399 }
  400 
  401 /* continue */
  402 /*ARGSUSED*/
  403 void
  404 db_continue_cmd(db_expr_t addr, bool have_addr, db_expr_t count, char *modif)
  405 {
  406         if (modif[0] == 'c')
  407             db_run_mode = STEP_COUNT;
  408         else
  409             db_run_mode = STEP_CONTINUE;
  410         db_inst_count = 0;
  411         db_load_count = 0;
  412         db_store_count = 0;
  413 
  414         db_cmd_loop_done = 1;
  415 }

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