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e1e554a382
off single-stepping). Only do this on arches (only x86 so far) which classify single-step traps unambiguously. This allows other parts of the kernel to be intentionally and unintentionally sloppy about generating single-step traps. On x86, at least the following places were unintentionally sloppy: - all operations that context-switched [er]flags. Especially spinlock_enter()/exit() and cpu_switch(). When single-stepped, saving the flags leaves PSL_T set in the saved flags, so restoring gives a trap that is spurious if it occurs after single-step mode has been left. Switching contexts away from a low priority thread gives especially long-lived saved copies. - the vm86 emulation allows user mode to set PSL_T. This was correct until vm86 bios call mode was unintentionally given access to kdb handling its single-step traps. Now these places are intentionally sloppy, but unexpected debugger traps still cause panics if no debugger that handles the trap is attached when the trap is delivered.
413 lines
9.7 KiB
C
413 lines
9.7 KiB
C
/*-
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* Mach Operating System
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* Copyright (c) 1991,1990 Carnegie Mellon University
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* All Rights Reserved.
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*
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* Permission to use, copy, modify and distribute this software and its
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* documentation is hereby granted, provided that both the copyright
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* notice and this permission notice appear in all copies of the
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* software, derivative works or modified versions, and any portions
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* thereof, and that both notices appear in supporting documentation.
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*
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* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS
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* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
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* ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
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*
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* Carnegie Mellon requests users of this software to return to
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*
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* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
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* School of Computer Science
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* Carnegie Mellon University
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* Pittsburgh PA 15213-3890
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*
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* any improvements or extensions that they make and grant Carnegie the
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* rights to redistribute these changes.
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*/
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/*
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* Author: David B. Golub, Carnegie Mellon University
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* Date: 7/90
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*/
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/*
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* Commands to run process.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/kdb.h>
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#include <sys/proc.h>
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#include <machine/kdb.h>
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#include <machine/pcb.h>
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#include <vm/vm.h>
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#include <ddb/ddb.h>
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#include <ddb/db_break.h>
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#include <ddb/db_access.h>
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#define STEP_ONCE 1
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#define STEP_RETURN 2
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#define STEP_CALLT 3
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#define STEP_CONTINUE 4
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#define STEP_INVISIBLE 5
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#define STEP_COUNT 6
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static int db_run_mode = STEP_CONTINUE;
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static bool db_sstep_multiple;
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static bool db_sstep_print;
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static int db_loop_count;
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static int db_call_depth;
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int db_inst_count;
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int db_load_count;
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int db_store_count;
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#ifdef SOFTWARE_SSTEP
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db_breakpoint_t db_not_taken_bkpt = 0;
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db_breakpoint_t db_taken_bkpt = 0;
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#endif
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#ifndef db_set_single_step
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void db_set_single_step(void);
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#endif
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#ifndef db_clear_single_step
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void db_clear_single_step(void);
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#endif
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#ifndef db_pc_is_singlestep
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static bool
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db_pc_is_singlestep(db_addr_t pc)
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{
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#ifdef SOFTWARE_SSTEP
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if ((db_not_taken_bkpt != 0 && pc == db_not_taken_bkpt->address)
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|| (db_taken_bkpt != 0 && pc == db_taken_bkpt->address))
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return (true);
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#endif
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return (false);
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}
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#endif
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bool
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db_stop_at_pc(int type, int code, bool *is_breakpoint, bool *is_watchpoint)
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{
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db_addr_t pc;
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db_breakpoint_t bkpt;
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*is_breakpoint = IS_BREAKPOINT_TRAP(type, code);
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*is_watchpoint = IS_WATCHPOINT_TRAP(type, code);
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pc = PC_REGS();
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if (db_pc_is_singlestep(pc))
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*is_breakpoint = false;
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db_clear_single_step();
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db_clear_breakpoints();
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db_clear_watchpoints();
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#ifdef FIXUP_PC_AFTER_BREAK
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if (*is_breakpoint) {
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/*
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* Breakpoint trap. Fix up the PC if the
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* machine requires it.
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*/
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FIXUP_PC_AFTER_BREAK
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pc = PC_REGS();
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}
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#endif
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/*
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* Now check for a breakpoint at this address.
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*/
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bkpt = db_find_breakpoint_here(pc);
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if (bkpt) {
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if (--bkpt->count == 0) {
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bkpt->count = bkpt->init_count;
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*is_breakpoint = true;
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return (true); /* stop here */
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}
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return (false); /* continue the countdown */
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} else if (*is_breakpoint) {
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#ifdef BKPT_SKIP
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BKPT_SKIP;
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#endif
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}
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*is_breakpoint = false; /* might be a breakpoint, but not ours */
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/*
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* If not stepping, then silently ignore single-step traps
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* (except for clearing the single-step-flag above).
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*
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* If stepping, then abort if the trap type is unexpected.
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* Breakpoints owned by us are expected and were handled above.
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* Single-steps are expected and are handled below. All others
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* are unexpected.
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*
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* Only do either of these if the MD layer claims to classify
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* single-step traps unambiguously (by defining IS_SSTEP_TRAP).
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* Otherwise, fall through to the bad historical behaviour
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* given by turning unexpected traps into expected traps: if not
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* stepping, then expect only breakpoints and stop, and if
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* stepping, then expect only single-steps and step.
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*/
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#ifdef IS_SSTEP_TRAP
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if (db_run_mode == STEP_CONTINUE && IS_SSTEP_TRAP(type, code))
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return (false);
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if (db_run_mode != STEP_CONTINUE && !IS_SSTEP_TRAP(type, code)) {
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printf("Stepping aborted\n");
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return (true);
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}
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#endif
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if (db_run_mode == STEP_INVISIBLE) {
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db_run_mode = STEP_CONTINUE;
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return (false); /* continue */
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}
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if (db_run_mode == STEP_COUNT) {
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return (false); /* continue */
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}
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if (db_run_mode == STEP_ONCE) {
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if (--db_loop_count > 0) {
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if (db_sstep_print) {
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db_printf("\t\t");
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db_print_loc_and_inst(pc);
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}
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return (false); /* continue */
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}
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}
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if (db_run_mode == STEP_RETURN) {
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/* continue until matching return */
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db_expr_t ins;
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ins = db_get_value(pc, sizeof(int), false);
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if (!inst_trap_return(ins) &&
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(!inst_return(ins) || --db_call_depth != 0)) {
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if (db_sstep_print) {
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if (inst_call(ins) || inst_return(ins)) {
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int i;
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db_printf("[after %6d] ", db_inst_count);
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for (i = db_call_depth; --i > 0; )
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db_printf(" ");
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db_print_loc_and_inst(pc);
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}
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}
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if (inst_call(ins))
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db_call_depth++;
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return (false); /* continue */
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}
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}
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if (db_run_mode == STEP_CALLT) {
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/* continue until call or return */
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db_expr_t ins;
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ins = db_get_value(pc, sizeof(int), false);
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if (!inst_call(ins) &&
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!inst_return(ins) &&
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!inst_trap_return(ins)) {
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return (false); /* continue */
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}
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}
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return (true);
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}
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void
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db_restart_at_pc(bool watchpt)
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{
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db_addr_t pc = PC_REGS();
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if ((db_run_mode == STEP_COUNT) ||
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((db_run_mode == STEP_ONCE) && db_sstep_multiple) ||
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(db_run_mode == STEP_RETURN) ||
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(db_run_mode == STEP_CALLT)) {
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/*
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* We are about to execute this instruction,
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* so count it now.
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*/
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#ifdef SOFTWARE_SSTEP
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db_expr_t ins =
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#endif
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db_get_value(pc, sizeof(int), false);
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db_inst_count++;
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db_load_count += inst_load(ins);
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db_store_count += inst_store(ins);
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#ifdef SOFTWARE_SSTEP
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/* XXX works on mips, but... */
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if (inst_branch(ins) || inst_call(ins)) {
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ins = db_get_value(next_instr_address(pc,1),
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sizeof(int), false);
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db_inst_count++;
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db_load_count += inst_load(ins);
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db_store_count += inst_store(ins);
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}
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#endif /* SOFTWARE_SSTEP */
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}
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if (db_run_mode == STEP_CONTINUE) {
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if (watchpt || db_find_breakpoint_here(pc)) {
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/*
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* Step over breakpoint/watchpoint.
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*/
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db_run_mode = STEP_INVISIBLE;
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db_set_single_step();
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} else {
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db_set_breakpoints();
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db_set_watchpoints();
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}
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} else {
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db_set_single_step();
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}
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}
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#ifdef SOFTWARE_SSTEP
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/*
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* Software implementation of single-stepping.
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* If your machine does not have a trace mode
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* similar to the vax or sun ones you can use
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* this implementation, done for the mips.
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* Just define the above conditional and provide
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* the functions/macros defined below.
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*
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* extern bool
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* inst_branch(), returns true if the instruction might branch
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* extern unsigned
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* branch_taken(), return the address the instruction might
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* branch to
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* db_getreg_val(); return the value of a user register,
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* as indicated in the hardware instruction
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* encoding, e.g. 8 for r8
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*
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* next_instr_address(pc,bd) returns the address of the first
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* instruction following the one at "pc",
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* which is either in the taken path of
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* the branch (bd==1) or not. This is
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* for machines (mips) with branch delays.
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*
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* A single-step may involve at most 2 breakpoints -
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* one for branch-not-taken and one for branch taken.
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* If one of these addresses does not already have a breakpoint,
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* we allocate a breakpoint and save it here.
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* These breakpoints are deleted on return.
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*/
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void
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db_set_single_step(void)
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{
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db_addr_t pc = PC_REGS(), brpc;
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unsigned inst;
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/*
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* User was stopped at pc, e.g. the instruction
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* at pc was not executed.
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*/
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inst = db_get_value(pc, sizeof(int), false);
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if (inst_branch(inst) || inst_call(inst) || inst_return(inst)) {
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brpc = branch_taken(inst, pc);
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if (brpc != pc) { /* self-branches are hopeless */
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db_taken_bkpt = db_set_temp_breakpoint(brpc);
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}
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pc = next_instr_address(pc, 1);
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}
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pc = next_instr_address(pc, 0);
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db_not_taken_bkpt = db_set_temp_breakpoint(pc);
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}
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void
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db_clear_single_step(void)
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{
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if (db_not_taken_bkpt != 0) {
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db_delete_temp_breakpoint(db_not_taken_bkpt);
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db_not_taken_bkpt = 0;
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}
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if (db_taken_bkpt != 0) {
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db_delete_temp_breakpoint(db_taken_bkpt);
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db_taken_bkpt = 0;
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}
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}
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#endif /* SOFTWARE_SSTEP */
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extern int db_cmd_loop_done;
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/* single-step */
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/*ARGSUSED*/
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void
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db_single_step_cmd(db_expr_t addr, bool have_addr, db_expr_t count, char *modif)
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{
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bool print = false;
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if (count == -1)
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count = 1;
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if (modif[0] == 'p')
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print = true;
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db_run_mode = STEP_ONCE;
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db_loop_count = count;
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db_sstep_multiple = (count != 1);
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db_sstep_print = print;
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db_inst_count = 0;
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db_load_count = 0;
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db_store_count = 0;
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db_cmd_loop_done = 1;
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}
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/* trace and print until call/return */
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/*ARGSUSED*/
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void
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db_trace_until_call_cmd(db_expr_t addr, bool have_addr, db_expr_t count,
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char *modif)
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{
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bool print = false;
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if (modif[0] == 'p')
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print = true;
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db_run_mode = STEP_CALLT;
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db_sstep_print = print;
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db_inst_count = 0;
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db_load_count = 0;
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db_store_count = 0;
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db_cmd_loop_done = 1;
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}
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/*ARGSUSED*/
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void
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db_trace_until_matching_cmd(db_expr_t addr, bool have_addr, db_expr_t count,
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char *modif)
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{
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bool print = false;
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if (modif[0] == 'p')
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print = true;
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db_run_mode = STEP_RETURN;
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db_call_depth = 1;
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db_sstep_print = print;
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db_inst_count = 0;
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db_load_count = 0;
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db_store_count = 0;
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db_cmd_loop_done = 1;
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}
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/* continue */
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/*ARGSUSED*/
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void
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db_continue_cmd(db_expr_t addr, bool have_addr, db_expr_t count, char *modif)
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{
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if (modif[0] == 'c')
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db_run_mode = STEP_COUNT;
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else
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db_run_mode = STEP_CONTINUE;
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db_inst_count = 0;
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db_load_count = 0;
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db_store_count = 0;
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db_cmd_loop_done = 1;
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}
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