kgdb.c

Kernel code of linux kernel

	/* Wait till primary CPU is done with debugging */
	while (atomic_read(&passive_cpu_wait[cpu]))
		cpu_relax();

	kgdb_info[cpu].debuggerinfo = NULL;
	kgdb_info[cpu].task = NULL;

	/* fix up hardware debug registers on local cpu */
	if (arch_kgdb_ops.correct_hw_break)
		arch_kgdb_ops.correct_hw_break();

	/* Signal the primary CPU that we are done: */
	atomic_set(&cpu_in_kgdb[cpu], 0);
	touch_softlockup_watchdog();
	clocksource_touch_watchdog();
	local_irq_restore(flags);
}
#endif

/*
 * Some architectures need cache flushes when we set/clear a
 * breakpoint:
 */
static void kgdb_flush_swbreak_addr(unsigned long addr)
{
	if (!CACHE_FLUSH_IS_SAFE)
		return;

	if (current->mm && current->mm->mmap_cache) {
		flush_cache_range(current->mm->mmap_cache,
				  addr, addr + BREAK_INSTR_SIZE);
	}
	/* Force flush instruction cache if it was outside the mm */
	flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
}

/*
 * SW breakpoint management:
 */
static int kgdb_activate_sw_breakpoints(void)
{
	unsigned long addr;
	int error = 0;
	int i;

	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
		if (kgdb_break[i].state != BP_SET)
			continue;

		addr = kgdb_break[i].bpt_addr;
		error = kgdb_arch_set_breakpoint(addr,
				kgdb_break[i].saved_instr);
		if (error)
			return error;

		kgdb_flush_swbreak_addr(addr);
		kgdb_break[i].state = BP_ACTIVE;
	}
	return 0;
}

static int kgdb_set_sw_break(unsigned long addr)
{
	int err = kgdb_validate_break_address(addr);
	int breakno = -1;
	int i;

	if (err)
		return err;

	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
		if ((kgdb_break[i].state == BP_SET) &&
					(kgdb_break[i].bpt_addr == addr))
			return -EEXIST;
	}
	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
		if (kgdb_break[i].state == BP_REMOVED &&
					kgdb_break[i].bpt_addr == addr) {
			breakno = i;
			break;
		}
	}

	if (breakno == -1) {
		for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
			if (kgdb_break[i].state == BP_UNDEFINED) {
				breakno = i;
				break;
			}
		}
	}

	if (breakno == -1)
		return -E2BIG;

	kgdb_break[breakno].state = BP_SET;
	kgdb_break[breakno].type = BP_BREAKPOINT;
	kgdb_break[breakno].bpt_addr = addr;

	return 0;
}

static int kgdb_deactivate_sw_breakpoints(void)
{
	unsigned long addr;
	int error = 0;
	int i;

	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
		if (kgdb_break[i].state != BP_ACTIVE)
			continue;
		addr = kgdb_break[i].bpt_addr;
		error = kgdb_arch_remove_breakpoint(addr,
					kgdb_break[i].saved_instr);
		if (error)
			return error;

		kgdb_flush_swbreak_addr(addr);
		kgdb_break[i].state = BP_SET;
	}
	return 0;
}

static int kgdb_remove_sw_break(unsigned long addr)
{
	int i;

	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
		if ((kgdb_break[i].state == BP_SET) &&
				(kgdb_break[i].bpt_addr == addr)) {
			kgdb_break[i].state = BP_REMOVED;
			return 0;
		}
	}
	return -ENOENT;
}

int kgdb_isremovedbreak(unsigned long addr)
{
	int i;

	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
		if ((kgdb_break[i].state == BP_REMOVED) &&
					(kgdb_break[i].bpt_addr == addr))
			return 1;
	}
	return 0;
}

static int remove_all_break(void)
{
	unsigned long addr;
	int error;
	int i;

	/* Clear memory breakpoints. */
	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
		if (kgdb_break[i].state != BP_ACTIVE)
			goto setundefined;
		addr = kgdb_break[i].bpt_addr;
		error = kgdb_arch_remove_breakpoint(addr,
				kgdb_break[i].saved_instr);
		if (error)
			printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n",
			   addr);
setundefined:
		kgdb_break[i].state = BP_UNDEFINED;
	}

	/* Clear hardware breakpoints. */
	if (arch_kgdb_ops.remove_all_hw_break)
		arch_kgdb_ops.remove_all_hw_break();

	return 0;
}

/*
 * Remap normal tasks to their real PID,
 * CPU shadow threads are mapped to -CPU - 2
 */
static inline int shadow_pid(int realpid)
{
	if (realpid)
		return realpid;

	return -raw_smp_processor_id() - 2;
}

static char gdbmsgbuf[BUFMAX + 1];

static void kgdb_msg_write(const char *s, int len)
{
	char *bufptr;
	int wcount;
	int i;

	/* 'O'utput */
	gdbmsgbuf[0] = 'O';

	/* Fill and send buffers... */
	while (len > 0) {
		bufptr = gdbmsgbuf + 1;

		/* Calculate how many this time */
		if ((len << 1) > (BUFMAX - 2))
			wcount = (BUFMAX - 2) >> 1;
		else
			wcount = len;

		/* Pack in hex chars */
		for (i = 0; i < wcount; i++)
			bufptr = pack_hex_byte(bufptr, s[i]);
		*bufptr = '\0';

		/* Move up */
		s += wcount;
		len -= wcount;

		/* Write packet */
		put_packet(gdbmsgbuf);
	}
}

/*
 * Return true if there is a valid kgdb I/O module.  Also if no
 * debugger is attached a message can be printed to the console about
 * waiting for the debugger to attach.
 *
 * The print_wait argument is only to be true when called from inside
 * the core kgdb_handle_exception, because it will wait for the
 * debugger to attach.
 */
static int kgdb_io_ready(int print_wait)
{
	if (!kgdb_io_ops)
		return 0;
	if (kgdb_connected)
		return 1;
	if (atomic_read(&kgdb_setting_breakpoint))
		return 1;
	if (print_wait)
		printk(KERN_CRIT "KGDB: Waiting for remote debugger\n");
	return 1;
}

/*
 * All the functions that start with gdb_cmd are the various
 * operations to implement the handlers for the gdbserial protocol
 * where KGDB is communicating with an external debugger
 */

/* Handle the '?' status packets */
static void gdb_cmd_status(struct kgdb_state *ks)
{
	/*
	 * We know that this packet is only sent
	 * during initial connect.  So to be safe,
	 * we clear out our breakpoints now in case
	 * GDB is reconnecting.
	 */
	remove_all_break();

	remcom_out_buffer[0] = 'S';
	pack_hex_byte(&remcom_out_buffer[1], ks->signo);
}

/* Handle the 'g' get registers request */
static void gdb_cmd_getregs(struct kgdb_state *ks)
{
	struct task_struct *thread;
	void *local_debuggerinfo;
	int i;

	thread = kgdb_usethread;
	if (!thread) {
		thread = kgdb_info[ks->cpu].task;
		local_debuggerinfo = kgdb_info[ks->cpu].debuggerinfo;
	} else {
		local_debuggerinfo = NULL;
		for_each_online_cpu(i) {
			/*
			 * Try to find the task on some other
			 * or possibly this node if we do not
			 * find the matching task then we try
			 * to approximate the results.
			 */
			if (thread == kgdb_info[i].task)
				local_debuggerinfo = kgdb_info[i].debuggerinfo;
		}
	}

	/*
	 * All threads that don't have debuggerinfo should be
	 * in __schedule() sleeping, since all other CPUs
	 * are in kgdb_wait, and thus have debuggerinfo.
	 */
	if (local_debuggerinfo) {
		pt_regs_to_gdb_regs(gdb_regs, local_debuggerinfo);
	} else {
		/*
		 * Pull stuff saved during switch_to; nothing
		 * else is accessible (or even particularly
		 * relevant).
		 *
		 * This should be enough for a stack trace.
		 */
		sleeping_thread_to_gdb_regs(gdb_regs, thread);
	}
	kgdb_mem2hex((char *)gdb_regs, remcom_out_buffer, NUMREGBYTES);
}

/* Handle the 'G' set registers request */
static void gdb_cmd_setregs(struct kgdb_state *ks)
{
	kgdb_hex2mem(&remcom_in_buffer[1], (char *)gdb_regs, NUMREGBYTES);

	if (kgdb_usethread && kgdb_usethread != current) {
		error_packet(remcom_out_buffer, -EINVAL);
	} else {
		gdb_regs_to_pt_regs(gdb_regs, ks->linux_regs);
		strcpy(remcom_out_buffer, "OK");
	}
}

/* Handle the 'm' memory read bytes */
static void gdb_cmd_memread(struct kgdb_state *ks)
{
	char *ptr = &remcom_in_buffer[1];
	unsigned long length;
	unsigned long addr;
	int err;

	if (kgdb_hex2long(&ptr, &addr) > 0 && *ptr++ == ',' &&
					kgdb_hex2long(&ptr, &length) > 0) {
		err = kgdb_mem2hex((char *)addr, remcom_out_buffer, length);
		if (err)
			error_packet(remcom_out_buffer, err);
	} else {
		error_packet(remcom_out_buffer, -EINVAL);
	}
}

/* Handle the 'M' memory write bytes */
static void gdb_cmd_memwrite(struct kgdb_state *ks)
{
	int err = write_mem_msg(0);

	if (err)
		error_packet(remcom_out_buffer, err);
	else
		strcpy(remcom_out_buffer, "OK");
}

/* Handle the 'X' memory binary write bytes */
static void gdb_cmd_binwrite(struct kgdb_state *ks)
{
	int err = write_mem_msg(1);

	if (err)
		error_packet(remcom_out_buffer, err);
	else
		strcpy(remcom_out_buffer, "OK");
}

/* Handle the 'D' or 'k', detach or kill packets */
static void gdb_cmd_detachkill(struct kgdb_state *ks)
{
	int error;

	/* The detach case */
	if (remcom_in_buffer[0] == 'D') {
		error = remove_all_break();
		if (error < 0) {
			error_packet(remcom_out_buffer, error);
		} else {
			strcpy(remcom_out_buffer, "OK");
			kgdb_connected = 0;
		}
		put_packet(remcom_out_buffer);
	} else {
		/*
		 * Assume the kill case, with no exit code checking,
		 * trying to force detach the debugger:
		 */
		remove_all_break();
		kgdb_connected = 0;
	}
}

/* Handle the 'R' reboot packets */
static int gdb_cmd_reboot(struct kgdb_state *ks)
{
	/* For now, only honor R0 */
	if (strcmp(remcom_in_buffer, "R0") == 0) {
		printk(KERN_CRIT "Executing emergency reboot\n");
		strcpy(remcom_out_buffer, "OK");
		put_packet(remcom_out_buffer);

		/*
		 * Execution should not return from
		 * machine_emergency_restart()
		 */
		machine_emergency_restart();
		kgdb_connected = 0;

		return 1;
	}
	return 0;
}

/* Handle the 'q' query packets */
static void gdb_cmd_query(struct kgdb_state *ks)
{
	struct task_struct *g;
	struct task_struct *p;
	unsigned char thref[8];
	char *ptr;
	int i;
	int cpu;
	int finished = 0;

	switch (remcom_in_buffer[1]) {
	case 's':
	case 'f':
		if (memcmp(remcom_in_buffer + 2, "ThreadInfo", 10)) {
			error_packet(remcom_out_buffer, -EINVAL);
			break;
		}

		i = 0;
		remcom_out_buffer[0] = 'm';
		ptr = remcom_out_buffer + 1;
		if (remcom_in_buffer[1] == 'f') {
			/* Each cpu is a shadow thread */
			for_each_online_cpu(cpu) {
				ks->thr_query = 0;
				int_to_threadref(thref, -cpu - 2);
				pack_threadid(ptr, thref);
				ptr += BUF_THREAD_ID_SIZE;
				*(ptr++) = ',';
				i++;
			}
		}

		do_each_thread(g, p) {
			if (i >= ks->thr_query && !finished) {
				int_to_threadref(thref, p->pid);
				pack_threadid(ptr, thref);
				ptr += BUF_THREAD_ID_SIZE;
				*(ptr++) = ',';
				ks->thr_query++;
				if (ks->thr_query % KGDB_MAX_THREAD_QUERY == 0)
					finished = 1;
			}
			i++;
		} while_each_thread(g, p);

		*(--ptr) = '\0';
		break;

	case 'C':
		/* Current thread id */
		strcpy(remcom_out_buffer, "QC");
		ks->threadid = shadow_pid(current->pid);
		int_to_threadref(thref, ks->threadid);
		pack_threadid(remcom_out_buffer + 2, thref);
		break;
	case 'T':
		if (memcmp(remcom_in_buffer + 1, "ThreadExtraInfo,", 16)) {
			error_packet(remcom_out_buffer, -EINVAL);
			break;
		}
		ks->threadid = 0;
		ptr = remcom_in_buffer + 17;
		kgdb_hex2long(&ptr, &ks->threadid);
		if (!getthread(ks->linux_regs, ks->threadid)) {
			error_packet(remcom_out_buffer, -EINVAL);
			break;
		}
		if ((int)ks->threadid > 0) {
			kgdb_mem2hex(getthread(ks->linux_regs,
					ks->threadid)->comm,
					remcom_out_buffer, 16);
		} else {
			static char tmpstr[23 + BUF_THREAD_ID_SIZE];

			sprintf(tmpstr, "shadowCPU%d",
					(int)(-ks->threadid - 2));
			kgdb_mem2hex(tmpstr, remcom_out_buffer, strlen(tmpstr));
		}
		break;
	}
}

/* Handle the 'H' task query packets */
static void gdb_cmd_task(struct kgdb_state *ks)
{
	struct task_struct *thread;
	char *ptr;

	switch (remcom_in_buffer[1]) {
	case 'g':
		ptr = &remcom_in_buffer[2];
		kgdb_hex2long(&ptr, &ks->threadid);
		thread = getthread(ks->linux_regs, ks->threadid);
		if (!thread && ks->threadid > 0) {
			error_packet(remcom_out_buffer, -EINVAL);
			break;
		}
		kgdb_usethread = thread;
		ks->kgdb_usethreadid = ks->threadid;
		strcpy(remcom_out_buffer, "OK");
		break;
	case 'c':
		ptr = &remcom_in_buffer[2];
		kgdb_hex2long(&ptr, &ks->threadid);
		if (!ks->threadid) {
			kgdb_contthread = NULL;
		} else {
			thread = getthread(ks->linux_regs, ks->threadid);
			if (!thread && ks->threadid > 0) {
				error_packet(remcom_out_buffer, -EINVAL);
				break;
			}
			kgdb_contthread = thread;
		}
		strcpy(remcom_out_buffer, "OK");
		break;
	}
}

/* Handle the 'T' thread query packets */
static void gdb_cmd_thread(struct kgdb_state *ks)
{
	char *ptr = &remcom_in_buffer[1];
	struct task_struct *thread;

	kgdb_hex2long(&ptr, &ks->threadid);
	thread = getthread(ks->linux_regs, ks->threadid);
	if (thread)
		strcpy(remcom_out_buffer, "OK");
	else
		error_packet(remcom_out_buffer, -EINVAL);
}

/* Handle the 'z' or 'Z' breakpoint remove or set packets */
static void gdb_cmd_break(struct kgdb_state *ks)
{
	/*
	 * Since GDB-5.3, it's been drafted that '0' is a software
	 * breakpoint, '1' is a hardware breakpoint, so let's do that.
	 */
	char *bpt_type = &remcom_in_buffer[1];
	char *ptr = &remcom_in_buffer[2];
	unsigned long addr;
	unsigned long length;
	int error = 0;

	if (arch_kgdb_ops.set_hw_breakpoint && *bpt_type >= '1') {
		/* Unsupported */
		if (*bpt_type > '4')
			return;
	} else {
		if (*bpt_type != '0' && *bpt_type != '1')
			/* Unsupported. */
			return;
	}

	/*
	 * Test if this is a hardware breakpoint, and
	 * if we support it:
	 */
	if (*bpt_type == '1' && !(arch_kgdb_ops.flags & KGDB_HW_BREAKPOINT))
		/* Unsupported. */
		return;

	if (*(ptr++) != ',') {
		error_packet(remcom_out_buffer, -EINVAL);
		return;