db_main.c

/*-
 * SPDX-License-Identifier: MIT-CMU
 *
 * Mach Operating System
 * Copyright (c) 1991,1990 Carnegie Mellon University
 * All Rights Reserved.
 *
 * Permission to use, copy, modify and distribute this software and its
 * documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 *
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 *
 * Carnegie Mellon requests users of this software to return to
 *
 *  Software Distribution Coordinator  or  [email protected]
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 *
 * any improvements or extensions that they make and grant Carnegie the
 * rights to redistribute these changes.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/cons.h>
#include <sys/linker.h>
#include <sys/kdb.h>
#include <sys/kernel.h>
#include <sys/pcpu.h>
#include <sys/proc.h>
#include <sys/reboot.h>
#include <sys/sysctl.h>

#include <machine/kdb.h>
#include <machine/pcb.h>
#include <machine/setjmp.h>

#include <ddb/ddb.h>
#include <ddb/db_command.h>
#include <ddb/db_sym.h>

struct db_private {
	char*		strtab;
	vm_offset_t	relbase;
};
typedef struct db_private *db_private_t;

#define DB_PRIVATE(x) ((db_private_t)(x->private))

SYSCTL_NODE(_debug, OID_AUTO, ddb, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "DDB settings");

static dbbe_init_f db_init;
static dbbe_trap_f db_trap;
static dbbe_trace_f db_trace_self_wrapper;
static dbbe_trace_thread_f db_trace_thread_wrapper;

KDB_BACKEND(ddb, db_init, db_trace_self_wrapper, db_trace_thread_wrapper,
    db_trap);

/*
 * Symbols can be loaded by specifying the exact addresses of
 * the symtab and strtab in memory. This is used when loaded from
 * boot loaders different than the native one (like Xen).
 */
vm_offset_t ksymtab, kstrtab, ksymtab_size, ksymtab_relbase;
static struct db_private ksymtab_private;

bool
X_db_line_at_pc(db_symtab_t *symtab, c_db_sym_t sym, char **file, int *line,
    db_expr_t off)
{
	return (false);
}

c_db_sym_t
X_db_lookup(db_symtab_t *symtab, const char *symbol)
{
	c_linker_sym_t lsym;
	Elf_Sym *sym;

	if (symtab->private == NULL) {
		return ((c_db_sym_t)((!linker_ddb_lookup(symbol, &lsym))
			? lsym : NULL));
	} else {
		sym = (Elf_Sym *)symtab->start;
		while ((char *)sym < symtab->end) {
			if (sym->st_name != 0 &&
			    !strcmp(DB_PRIVATE(symtab)->strtab +
			    sym->st_name, symbol))
				return ((c_db_sym_t)sym);
			sym++;
		}
	}
	return (NULL);
}

c_db_sym_t
X_db_search_symbol(db_symtab_t *symtab, db_addr_t off, db_strategy_t strat,
    db_expr_t *diffp)
{
	c_linker_sym_t lsym;
	Elf_Sym *sym, *match;
	unsigned long diff;
	db_addr_t stoffs = off;

	if (symtab->private == NULL) {
		if (!linker_ddb_search_symbol((caddr_t)off, &lsym, &diff)) {
			*diffp = (db_expr_t)diff;
			return ((c_db_sym_t)lsym);
		}
		return (NULL);
	}
	else
		stoffs -= DB_PRIVATE(symtab)->relbase;

	diff = ~0UL;
	match = NULL;
	for (sym = (Elf_Sym*)symtab->start; (char*)sym < symtab->end; sym++) {
		if (sym->st_name == 0 || sym->st_shndx == SHN_UNDEF)
			continue;
		if (stoffs < sym->st_value)
			continue;
		if (ELF_ST_TYPE(sym->st_info) != STT_OBJECT &&
		    ELF_ST_TYPE(sym->st_info) != STT_FUNC &&
		    ELF_ST_TYPE(sym->st_info) != STT_NOTYPE)
			continue;
		if ((stoffs - sym->st_value) > diff)
			continue;
		if ((stoffs - sym->st_value) < diff) {
			diff = stoffs - sym->st_value;
			match = sym;
		} else {
			if (match == NULL)
				match = sym;
			else if (ELF_ST_BIND(match->st_info) == STB_LOCAL &&
			    ELF_ST_BIND(sym->st_info) != STB_LOCAL)
				match = sym;
		}
		if (diff == 0) {
			if (strat == DB_STGY_PROC &&
			    ELF_ST_TYPE(sym->st_info) == STT_FUNC &&
			    ELF_ST_BIND(sym->st_info) != STB_LOCAL)
				break;
			if (strat == DB_STGY_ANY &&
			    ELF_ST_BIND(sym->st_info) != STB_LOCAL)
				break;
		}
	}

	*diffp = (match == NULL) ? off : diff;
	return ((c_db_sym_t)match);
}

bool
X_db_sym_numargs(db_symtab_t *symtab, c_db_sym_t sym, int *nargp,
    char **argp)
{
	return (false);
}

void
X_db_symbol_values(db_symtab_t *symtab, c_db_sym_t sym, const char **namep,
    db_expr_t *valp)
{
	linker_symval_t lval;

	if (symtab->private == NULL) {
		linker_ddb_symbol_values((c_linker_sym_t)sym, &lval);
		if (namep != NULL)
			*namep = (const char*)lval.name;
		if (valp != NULL)
			*valp = (db_expr_t)lval.value;
	} else {
		if (namep != NULL)
			*namep = (const char *)DB_PRIVATE(symtab)->strtab +
			    ((const Elf_Sym *)sym)->st_name;
		if (valp != NULL)
			*valp = (db_expr_t)((const Elf_Sym *)sym)->st_value +
			    DB_PRIVATE(symtab)->relbase;
	}
}

int
db_fetch_ksymtab(vm_offset_t ksym_start, vm_offset_t ksym_end,
    vm_offset_t relbase)
{
	Elf_Size strsz;

	if (ksym_end > ksym_start && ksym_start != 0) {
		ksymtab = ksym_start;
		ksymtab_size = *(Elf_Size*)ksymtab;
		ksymtab += sizeof(Elf_Size);
		kstrtab = ksymtab + ksymtab_size;
		strsz = *(Elf_Size*)kstrtab;
		kstrtab += sizeof(Elf_Size);
		ksymtab_relbase = relbase;
		if (kstrtab + strsz > ksym_end) {
			/* Sizes doesn't match, unset everything. */
			ksymtab = ksymtab_size = kstrtab = ksymtab_relbase
			    = 0;
		}
	}

	if (ksymtab == 0 || ksymtab_size == 0 || kstrtab == 0)
		return (-1);

	return (0);
}

static int
db_init(void)
{

	db_command_init();

	if (ksymtab != 0 && kstrtab != 0 && ksymtab_size != 0) {
		ksymtab_private.strtab = (char *)kstrtab;
		ksymtab_private.relbase = ksymtab_relbase;
		db_add_symbol_table((char *)ksymtab,
		    (char *)(ksymtab + ksymtab_size), "elf", (char *)&ksymtab_private);
	}
	db_add_symbol_table(NULL, NULL, "kld", NULL);
	return (1);	/* We're the default debugger. */
}

static int
db_trap(int type, int code)
{
	jmp_buf jb;
	void *prev_jb;
	bool bkpt, watchpt;
	const char *why;

	/*
	 * Don't handle the trap if the console is unavailable (i.e. it
	 * is in graphics mode).
	 */
	if (cnunavailable())
		return (0);

	if (db_stop_at_pc(type, code, &bkpt, &watchpt)) {
		if (db_inst_count) {
			db_printf("After %d instructions (%d loads, %d stores),\n",
			    db_inst_count, db_load_count, db_store_count);
		}
		prev_jb = kdb_jmpbuf(jb);
		if (setjmp(jb) == 0) {
			db_dot = PC_REGS();
			db_print_thread();
			if (bkpt)
				db_printf("Breakpoint at\t");
			else if (watchpt)
				db_printf("Watchpoint at\t");
			else
				db_printf("Stopped at\t");
			db_print_loc_and_inst(db_dot);
		}
		why = kdb_why;
		db_script_kdbenter(why != KDB_WHY_UNSET ? why : "unknown");
		db_command_loop();
		(void)kdb_jmpbuf(prev_jb);
	}

	db_restart_at_pc(watchpt);

	return (1);
}

static void
db_trace_self_wrapper(void)
{
	jmp_buf jb;
	void *prev_jb;

	prev_jb = kdb_jmpbuf(jb);
	if (setjmp(jb) == 0)
		db_trace_self();
	(void)kdb_jmpbuf(prev_jb);
}

static void
db_trace_thread_wrapper(struct thread *td)
{
	jmp_buf jb;
	void *prev_jb;

	prev_jb = kdb_jmpbuf(jb);
	if (setjmp(jb) == 0)
		db_trace_thread(td, -1);
	(void)kdb_jmpbuf(prev_jb);
}