Merge tag 'kgdb-5.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/danielt/linux

Pull kgdb updates from Daniel Thompson:
 "By far the biggest change in this cycle are the changes that allow
  much earlier debug of systems that are hooked up via UART by taking
  advantage of the earlycon framework to implement the kgdb I/O hooks
  before handing over to the regular polling I/O drivers once they are
  available. When discussing Doug's work we also found and fixed an
  broken raw_smp_processor_id() sequence in in_dbg_master().

  Also included are a collection of much smaller fixes and tweaks: a
  couple of tweaks to ged rid of doc gen or coccicheck warnings, future
  proof some internal calculations that made implicit power-of-2
  assumptions and eliminate some rather weird handling of magic
  environment variables in kdb"

* tag 'kgdb-5.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/danielt/linux:
  kdb: Remove the misfeature 'KDBFLAGS'
  kdb: Cleanup math with KDB_CMD_HISTORY_COUNT
  serial: amba-pl011: Support kgdboc_earlycon
  serial: 8250_early: Support kgdboc_earlycon
  serial: qcom_geni_serial: Support kgdboc_earlycon
  serial: kgdboc: Allow earlycon initialization to be deferred
  Documentation: kgdboc: Document new kgdboc_earlycon parameter
  kgdb: Don't call the deinit under spinlock
  kgdboc: Disable all the early code when kgdboc is a module
  kgdboc: Add kgdboc_earlycon to support early kgdb using boot consoles
  kgdboc: Remove useless #ifdef CONFIG_KGDB_SERIAL_CONSOLE in kgdboc
  kgdb: Prevent infinite recursive entries to the debugger
  kgdb: Delay "kgdbwait" to dbg_late_init() by default
  kgdboc: Use a platform device to handle tty drivers showing up late
  Revert "kgdboc: disable the console lock when in kgdb"
  kgdb: Disable WARN_CONSOLE_UNLOCKED for all kgdb
  kgdb: Return true in kgdb_nmi_poll_knock()
  kgdb: Drop malformed kernel doc comment
  kgdb: Fix spurious true from in_dbg_master()

2 files changed, 46 insertions, 22 deletions

diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index 2b7c9b67931d..ef94e906f05a 100644
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -67,9 +67,7 @@ static int kgdb_break_asap;
 
 struct debuggerinfo_struct kgdb_info[NR_CPUS];
 
-/**
- * kgdb_connected - Is a host GDB connected to us?
- */
+/* kgdb_connected - Is a host GDB connected to us? */
 int				kgdb_connected;
 EXPORT_SYMBOL_GPL(kgdb_connected);
 
@@ -532,6 +530,7 @@ static int kgdb_reenter_check(struct kgdb_state *ks)
 
 	if (exception_level > 1) {
 		dump_stack();
+		kgdb_io_module_registered = false;
 		panic("Recursive entry to debugger");
 	}
 
@@ -668,6 +667,8 @@ return_normal:
 	if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
 		goto kgdb_restore;
 
+	atomic_inc(&ignore_console_lock_warning);
+
 	/* Call the I/O driver's pre_exception routine */
 	if (dbg_io_ops->pre_exception)
 		dbg_io_ops->pre_exception();
@@ -740,6 +741,8 @@ cpu_master_loop:
 	if (dbg_io_ops->post_exception)
 		dbg_io_ops->post_exception();
 
+	atomic_dec(&ignore_console_lock_warning);
+
 	if (!kgdb_single_step) {
 		raw_spin_unlock(&dbg_slave_lock);
 		/* Wait till all the CPUs have quit from the debugger. */
@@ -946,6 +949,14 @@ void kgdb_panic(const char *msg)
 	kgdb_breakpoint();
 }
 
+static void kgdb_initial_breakpoint(void)
+{
+	kgdb_break_asap = 0;
+
+	pr_crit("Waiting for connection from remote gdb...\n");
+	kgdb_breakpoint();
+}
+
 void __weak kgdb_arch_late(void)
 {
 }
@@ -956,6 +967,9 @@ void __init dbg_late_init(void)
 	if (kgdb_io_module_registered)
 		kgdb_arch_late();
 	kdb_init(KDB_INIT_FULL);
+
+	if (kgdb_io_module_registered && kgdb_break_asap)
+		kgdb_initial_breakpoint();
 }
 
 static int
@@ -1051,14 +1065,6 @@ void kgdb_schedule_breakpoint(void)
 }
 EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
 
-static void kgdb_initial_breakpoint(void)
-{
-	kgdb_break_asap = 0;
-
-	pr_crit("Waiting for connection from remote gdb...\n");
-	kgdb_breakpoint();
-}
-
 /**
  *	kgdb_register_io_module - register KGDB IO module
  *	@new_dbg_io_ops: the io ops vector
@@ -1067,15 +1073,22 @@ static void kgdb_initial_breakpoint(void)
  */
 int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
 {
+	struct kgdb_io *old_dbg_io_ops;
 	int err;
 
 	spin_lock(&kgdb_registration_lock);
 
-	if (dbg_io_ops) {
-		spin_unlock(&kgdb_registration_lock);
+	old_dbg_io_ops = dbg_io_ops;
+	if (old_dbg_io_ops) {
+		if (!old_dbg_io_ops->deinit) {
+			spin_unlock(&kgdb_registration_lock);
 
-		pr_err("Another I/O driver is already registered with KGDB\n");
-		return -EBUSY;
+			pr_err("KGDB I/O driver %s can't replace %s.\n",
+				new_dbg_io_ops->name, old_dbg_io_ops->name);
+			return -EBUSY;
+		}
+		pr_info("Replacing I/O driver %s with %s\n",
+			old_dbg_io_ops->name, new_dbg_io_ops->name);
 	}
 
 	if (new_dbg_io_ops->init) {
@@ -1090,12 +1103,18 @@ int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
 
 	spin_unlock(&kgdb_registration_lock);
 
+	if (old_dbg_io_ops) {
+		old_dbg_io_ops->deinit();
+		return 0;
+	}
+
 	pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name);
 
 	/* Arm KGDB now. */
 	kgdb_register_callbacks();
 
-	if (kgdb_break_asap)
+	if (kgdb_break_asap &&
+	    (!dbg_is_early || IS_ENABLED(CONFIG_ARCH_HAS_EARLY_DEBUG)))
 		kgdb_initial_breakpoint();
 
 	return 0;
@@ -1125,6 +1144,9 @@ void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
 
 	spin_unlock(&kgdb_registration_lock);
 
+	if (old_dbg_io_ops->deinit)
+		old_dbg_io_ops->deinit();
+
 	pr_info("Unregistered I/O driver %s, debugger disabled\n",
 		old_dbg_io_ops->name);
 }
@@ -1165,7 +1187,8 @@ static int __init opt_kgdb_wait(char *str)
 	kgdb_break_asap = 1;
 
 	kdb_init(KDB_INIT_EARLY);
-	if (kgdb_io_module_registered)
+	if (kgdb_io_module_registered &&
+	    IS_ENABLED(CONFIG_ARCH_HAS_EARLY_DEBUG))
 		kgdb_initial_breakpoint();
 
 	return 0;
diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index 515379cbf209..ec190569f690 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -62,7 +62,7 @@ int kdb_grep_trailing;
 /*
  * Kernel debugger state flags
  */
-int kdb_flags;
+unsigned int kdb_flags;
 
 /*
  * kdb_lock protects updates to kdb_initial_cpu.  Used to
@@ -418,8 +418,7 @@ int kdb_set(int argc, const char **argv)
 				    argv[2]);
 			return 0;
 		}
-		kdb_flags = (kdb_flags &
-			     ~(KDB_DEBUG_FLAG_MASK << KDB_DEBUG_FLAG_SHIFT))
+		kdb_flags = (kdb_flags & ~KDB_DEBUG(MASK))
 			| (debugflags << KDB_DEBUG_FLAG_SHIFT);
 
 		return 0;
@@ -1108,7 +1107,8 @@ static int handle_ctrl_cmd(char *cmd)
 	switch (*cmd) {
 	case CTRL_P:
 		if (cmdptr != cmd_tail)
-			cmdptr = (cmdptr-1) % KDB_CMD_HISTORY_COUNT;
+			cmdptr = (cmdptr + KDB_CMD_HISTORY_COUNT - 1) %
+				 KDB_CMD_HISTORY_COUNT;
 		strscpy(cmd_cur, cmd_hist[cmdptr], CMD_BUFLEN);
 		return 1;
 	case CTRL_N:
@@ -2081,7 +2081,8 @@ static int kdb_env(int argc, const char **argv)
 	}
 
 	if (KDB_DEBUG(MASK))
-		kdb_printf("KDBFLAGS=0x%x\n", kdb_flags);
+		kdb_printf("KDBDEBUG=0x%x\n",
+			(kdb_flags & KDB_DEBUG(MASK)) >> KDB_DEBUG_FLAG_SHIFT);
 
 	return 0;
 }