[PATCH 0/7] kgdb: Support late serial drivers; enable early debug w/ boot consoles

[PATCH 0/7] kgdb: Support late serial drivers; enable early debug w/ boot consoles

[Douglas Anderson]

This whole pile of patches was motivated by me trying to get kgdb to
work properly on a platform where my serial driver ended up being hit
by the -EPROBE_DEFER virus (it wasn't practicing social distancing
from other drivers).  Specifically my serial driver's parent device
depended on a resource that wasn't available when its probe was first
called.  It returned -EPROBE_DEFER which meant that when "kgdboc"
tried to run its setup the serial driver wasn't there.  Unfortunately
"kgdboc" never tried again, so that meant that kgdb was disabled until
I manually enalbed it via sysfs.

While I could try to figure out how to get around the -EPROBE_DEFER
somehow, the above problems could happen to anyone and -EPROBE_DEFER
is generally considered something you just have to live with.  In any
case the current "kgdboc" setup is a bit of a race waiting to happen.
I _think_ I saw during early testing that even adding a msleep() in
the typical serial driver's probe() is enough to trigger similar
issues.

I decided that for the above race the best attitude to get kgdb to
register at boot was probably "if you can't beat 'em, join 'em".
Thus, "kgdboc" now jumps on the -EPROBE_DEFER bandwagon (now that my
driver uses it it's no longer a virus).  It does so a little awkwardly
because "kgdboc" hasn't normally had a "struct device" associated with
it, but it's really not _that_ ugly to make a platform device and
seems less ugly than alternatives.

Unfortunately now on my system the debugger is one of the last things
to register at boot.  That's OK for debugging problems that show up
significantly after boot, but isn't so hot for all the boot problems
that I end up debugging.  This motivated me to try to get something
working a little earlier.

My first attempt was to try to get the existing "ekgdboc" to work
earlier.  I tried that for a bit until I realized that it needed to
work at the tty layer and I couldn't find any serial drivers that
managed to register themselves to the tty layer super early at boot.
The only documented use of "ekgdboc" is "ekgdboc=kbd" and that's a bit
of a special snowflake.  Trying to get my serial driver and all its
dependencies to probe normally and register the tty driver super early
at boot seemed like a bad way to go.  In fact, all the complexity
needed to do something like this is why the system already has a
special concept of a "boot console" that lives only long enough to
transition to the normal console.

Leveraging the boot console seemed like a good way to go and that's
what this series does.  I found that consoles could have a read()
function, though I couldn't find anyone who implemented it.  I
implemented it for two serial drivers for the devices I had easy
access to, making the assumption that for boot consoles that we could
assume read() and write() were polling-compatible (seems sane I
think).

Now anyone who makes a small change to their serial driver can easily
enable early kgdb debugging!

The devices I had for testing were:
- arm32: rk3288-veyron-jerry
- arm64: rk3399-gru-kevin
- arm64: qcom-sc7180-trogdor (not mainline yet)

These are the devices I tested this series on.  I tried to test
various combinations of enabling/disabling various options and I
hopefully caught the corner cases, but I'd appreciate any extra
testing people can do.  Notably I didn't test on x86, but (I think) I
didn't touch much there so I shouldn't have broken anything.

When testing I found a few problems with actually dropping into the
debugger super early on arm and arm64 devices.  Patches in this series
should help with this.  For arm I just avoid dropping into the
debugger until a little later and for arm64 I actually enable
debugging super early.

I realize that bits of this series might feel a little hacky, though
I've tried to do things in the cleanest way I could without overly
interferring with the rest of the kernel.  If you hate the way I
solved a problem I would love it if you could provide guidance on how
you think I could solve the problem better.

This series (and my comments / documentation / commit messages) are
now long enough that my eyes glaze over when I try to read it all over
to double-check.  I've nontheless tried to double-check it, but I'm
pretty sure I did something stupid.  Thank you ahead of time for
pointing it out to me so I can fix it in v2.  If somehow I managed to
not do anything stupid (really?) then thank you for double-checking me
anyway.


Douglas Anderson (7):
  kgdboc: Use a platform device to handle tty drivers showing up late
  kgdb: Delay "kgdbwait" to dbg_late_init() by default
  arm64: Add call_break_hook() to early_brk64() for early kgdb
  kgdboc: Add earlycon_kgdboc to support early kgdb using boot consoles
  Documentation: kgdboc: Document new earlycon_kgdboc parameter
  serial: qcom_geni_serial: Support earlycon_kgdboc
  serial: 8250_early: Support earlycon_kgdboc

 .../admin-guide/kernel-parameters.txt         |  20 ++
 Documentation/dev-tools/kgdb.rst              |  14 +
 arch/arm64/include/asm/debug-monitors.h       |   2 +
 arch/arm64/kernel/debug-monitors.c            |   2 +-
 arch/arm64/kernel/kgdb.c                      |   5 +
 arch/arm64/kernel/traps.c                     |   3 +
 arch/x86/kernel/kgdb.c                        |   5 +
 drivers/tty/serial/8250/8250_early.c          |  23 ++
 drivers/tty/serial/kgdboc.c                   | 266 ++++++++++++++++--
 drivers/tty/serial/qcom_geni_serial.c         |  32 +++
 include/linux/kgdb.h                          |  25 +-
 kernel/debug/debug_core.c                     |  44 ++-
 12 files changed, 401 insertions(+), 40 deletions(-)

-- 
2.26.0.110.g2183baf09c-goog

[PATCH 1/7] kgdboc: Use a platform device to handle tty drivers showing up late

[Douglas Anderson]

If you build CONFIG_KGDB_SERIAL_CONSOLE into the kernel then you
should be able to have KGDB init itself at bootup by specifying the
"kgdboc=..." kernel command line parameter.  This has worked OK for me
for many years, but on a new device I switched to it stopped working.

The problem is that on this new device the serial driver gets its
probe deferred.  Now when kgdb initializes it can't find the tty
driver and when it gives up it never tries again.

We could try to find ways to move up the initialization of the serial
driver and such a thing might be worthwhile, but it's nice to be
robust against serial drivers that load late.  We could move kgdb to
init itself later but that penalizes our ability to debug early boot
code on systems where the driver inits early.  We could roll our own
system of detecting when new tty drivers get loaded and then use that
to figure out when kgdb can init, but that's ugly.

Instead, let's jump on the -EPROBE_DEFER bandwagon.  We'll create a
singleton instance of a "kgdboc" platform device.  If we can't find
our tty device when the singleton "kgdboc" probes we'll return
-EPROBE_DEFER which means that the system will call us back later to
try again when the tty device might be there.

We won't fully transition all of the kgdboc to a platform device
because early kgdb initialization (via the "ekgdboc" kernel command
line parameter) still runs before the platform device has been
created.  The kgdb platform device is merely used as a convenient way
to hook into the system's normal probe deferral mechanisms.

As part of this, we'll ever-so-slightly change how the "kgdboc=..."
kernel command line parameter works.  Previously if you booted up and
kgdb couldn't find the tty driver then later reading
'/sys/module/kgdboc/parameters/kgdboc' would return a blank string.
Now kgdb will keep track of the string that came as part of the
command line and give it back to you.  It's expected that this should
be an OK change.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

 drivers/tty/serial/kgdboc.c | 126 +++++++++++++++++++++++++++++-------
 1 file changed, 101 insertions(+), 25 deletions(-)

diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c
index c7d51b51898f..9ace39fc4f95 100644
--- a/drivers/tty/serial/kgdboc.c
+++ b/drivers/tty/serial/kgdboc.c
@@ -20,6 +20,7 @@
 #include <linux/vt_kern.h>
 #include <linux/input.h>
 #include <linux/module.h>
+#include <linux/platform_device.h>
 
 #define MAX_CONFIG_LEN		40
 
@@ -27,6 +28,7 @@ static struct kgdb_io		kgdboc_io_ops;
 
 /* -1 = init not run yet, 0 = unconfigured, 1 = configured. */
 static int configured		= -1;
+DEFINE_MUTEX(config_mutex);
 
 static char config[MAX_CONFIG_LEN];
 static struct kparam_string kps = {
@@ -38,6 +40,8 @@ static int kgdboc_use_kms;  /* 1 if we use kernel mode switching */
 static struct tty_driver	*kgdb_tty_driver;
 static int			kgdb_tty_line;
 
+static struct platform_device *kgdboc_pdev;
+
 #ifdef CONFIG_KDB_KEYBOARD
 static int kgdboc_reset_connect(struct input_handler *handler,
 				struct input_dev *dev,
@@ -133,11 +137,13 @@ static void kgdboc_unregister_kbd(void)
 
 static void cleanup_kgdboc(void)
 {
+	if (configured != 1)
+		return;
+
 	if (kgdb_unregister_nmi_console())
 		return;
 	kgdboc_unregister_kbd();
-	if (configured == 1)
-		kgdb_unregister_io_module(&kgdboc_io_ops);
+	kgdb_unregister_io_module(&kgdboc_io_ops);
 }
 
 static int configure_kgdboc(void)
@@ -200,20 +206,79 @@ static int configure_kgdboc(void)
 	kgdb_unregister_io_module(&kgdboc_io_ops);
 noconfig:
 	kgdboc_unregister_kbd();
-	config[0] = 0;
 	configured = 0;
-	cleanup_kgdboc();
 
 	return err;
 }
 
+static int kgdboc_probe(struct platform_device *pdev)
+{
+	int ret = 0;
+
+	mutex_lock(&config_mutex);
+	if (configured != 1) {
+		ret = configure_kgdboc();
+
+		/* Convert "no device" to "defer" so we'll keep trying */
+		if (ret == -ENODEV)
+			ret = -EPROBE_DEFER;
+	}
+	mutex_unlock(&config_mutex);
+
+	return ret;
+}
+
+static struct platform_driver kgdboc_platform_driver = {
+	.probe = kgdboc_probe,
+	.driver = {
+		.name = "kgdboc",
+		.suppress_bind_attrs = true,
+	},
+};
+
 static int __init init_kgdboc(void)
 {
-	/* Already configured? */
-	if (configured == 1)
+	int ret;
+
+	/*
+	 * kgdboc is a little bit of an odd "platform_driver".  It can be
+	 * up and running long before the platform_driver object is
+	 * created and thus doesn't actually store anything in it.  There's
+	 * only one instance of kgdb so anything is stored as global state.
+	 * The platform_driver is only created so that we can leverage the
+	 * kernel's mechanisms (like -EPROBE_DEFER) to call us when our
+	 * underlying tty is ready.  Here we init our platform driver and
+	 * then create the single kgdboc instance.
+	 */
+	ret = platform_driver_register(&kgdboc_platform_driver);
+	if (ret)
+		return ret;
+
+	kgdboc_pdev = platform_device_alloc("kgdboc", PLATFORM_DEVID_NONE);
+	if (!kgdboc_pdev) {
+		ret = -ENOMEM;
+		goto err_did_register;
+	}
+
+	ret = platform_device_add(kgdboc_pdev);
+	if (!ret)
 		return 0;
 
-	return configure_kgdboc();
+	platform_device_put(kgdboc_pdev);
+
+err_did_register:
+	platform_driver_unregister(&kgdboc_platform_driver);
+	return ret;
+}
+
+static void exit_kgdboc(void)
+{
+	mutex_lock(&config_mutex);
+	cleanup_kgdboc();
+	mutex_unlock(&config_mutex);
+
+	platform_device_unregister(kgdboc_pdev);
+	platform_driver_unregister(&kgdboc_platform_driver);
 }
 
 static int kgdboc_get_char(void)
@@ -236,24 +301,20 @@ static int param_set_kgdboc_var(const char *kmessage,
 				const struct kernel_param *kp)
 {
 	size_t len = strlen(kmessage);
+	int ret = 0;
 
 	if (len >= MAX_CONFIG_LEN) {
 		pr_err("config string too long\n");
 		return -ENOSPC;
 	}
 
-	/* Only copy in the string if the init function has not run yet */
-	if (configured < 0) {
-		strcpy(config, kmessage);
-		return 0;
-	}
-
 	if (kgdb_connected) {
 		pr_err("Cannot reconfigure while KGDB is connected.\n");
-
 		return -EBUSY;
 	}
 
+	mutex_lock(&config_mutex);
+
 	strcpy(config, kmessage);
 	/* Chop out \n char as a result of echo */
 	if (len && config[len - 1] == '\n')
@@ -262,8 +323,30 @@ static int param_set_kgdboc_var(const char *kmessage,
 	if (configured == 1)
 		cleanup_kgdboc();
 
-	/* Go and configure with the new params. */
-	return configure_kgdboc();
+	/*
+	 * Configure with the new params as long as init already ran.
+	 * Note that we can get called before init if someone loads us
+	 * with "modprobe kgdboc kgdboc=..." or if they happen to use the
+	 * the odd syntax of "kgdboc.kgdboc=..." on the kernel command.
+	 */
+	if (configured >= 0)
+		ret = configure_kgdboc();
+
+	/*
+	 * If we couldn't configure then clear out the config.  Note that
+	 * specifying an invalid config on the kernel command line vs.
+	 * through sysfs have slightly different behaviors.  If we fail
+	 * to configure what was specified on the kernel command line
+	 * we'll leave it in the 'config' and return -EPROBE_DEFER from
+	 * our probe.  When specified through sysfs userspace is
+	 * responsible for loading the tty driver before setting up.
+	 */
+	if (ret)
+		config[0] = '\0';
+
+	mutex_unlock(&config_mutex);
+
+	return ret;
 }
 
 static int dbg_restore_graphics;
@@ -326,15 +409,8 @@ __setup("kgdboc=", kgdboc_option_setup);
 /* This is only available if kgdboc is a built in for early debugging */
 static int __init kgdboc_early_init(char *opt)
 {
-	/* save the first character of the config string because the
-	 * init routine can destroy it.
-	 */
-	char save_ch;
-
 	kgdboc_option_setup(opt);
-	save_ch = config[0];
-	init_kgdboc();
-	config[0] = save_ch;
+	configure_kgdboc();
 	return 0;
 }
 
@@ -342,7 +418,7 @@ early_param("ekgdboc", kgdboc_early_init);
 #endif /* CONFIG_KGDB_SERIAL_CONSOLE */
 
 module_init(init_kgdboc);
-module_exit(cleanup_kgdboc);
+module_exit(exit_kgdboc);
 module_param_call(kgdboc, param_set_kgdboc_var, param_get_string, &kps, 0644);
 MODULE_PARM_DESC(kgdboc, "<serial_device>[,baud]");
 MODULE_DESCRIPTION("KGDB Console TTY Driver");
-- 
2.26.0.110.g2183baf09c-goog

[PATCH 2/7] kgdb: Delay "kgdbwait" to dbg_late_init() by default

[Douglas Anderson]

Using kgdb requires at least some level of architecture-level
initialization.  If nothing else, it relies on the architecture to
pass breakpoints / crashes onto kgdb.

On some architectures this all works super early, specifically it
starts working at some point in time before Linux parses
early_params's.  On other architectures it doesn't.  A survey of a few
platforms:

a) x86: Presumably it all works early since "ekgdboc" is documented to
   work here.
b) arm64: Catching crashes works; with a simple patch breakpoints can
   also be made to work.
c) arm: Nothing in kgdb works until
   paging_init() -> devicemaps_init() -> early_trap_init()

Let's be conservative and, by default, process "kgdbwait" (which tells
the kernel to drop into the debugger ASAP at boot) a bit later at
dbg_late_init() time.  If an architecture has tested it and wants to
re-enable super early debugging, they can implement the weak function
kgdb_arch_can_debug_early() to return true.  We'll do this for x86 to
start.  It should be noted that dbg_late_init() is still called quite
early in the system.

Note that this patch doesn't affect when kgdb runs its init.  If kgdb
is set to initialize early it will still initialize when parsing
early_params's.  This patch _only_ inhibits the initial breakpoint
from "kgdbwait".  This means:

* Without any extra patches arm64 platforms will at least catch
  crashes after kgdb inits.
* arm platforms will catch crashes (and could handle a hardcoded
  kgdb_breakpoint()) any time after early_trap_init() runs, even
  before dbg_late_init().

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
---

 arch/x86/kernel/kgdb.c    |  5 +++++
 include/linux/kgdb.h      | 22 ++++++++++++++++++++++
 kernel/debug/debug_core.c | 29 +++++++++++++++++++----------
 3 files changed, 46 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c
index c44fe7d8d9a4..60c47787c588 100644
--- a/arch/x86/kernel/kgdb.c
+++ b/arch/x86/kernel/kgdb.c
@@ -673,6 +673,11 @@ void kgdb_arch_late(void)
 	}
 }
 
+bool kgdb_arch_can_debug_early(void)
+{
+	return true;
+}
+
 /**
  *	kgdb_arch_exit - Perform any architecture specific uninitalization.
  *
diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h
index b072aeb1fd78..7371517aeacc 100644
--- a/include/linux/kgdb.h
+++ b/include/linux/kgdb.h
@@ -226,6 +226,28 @@ extern int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt);
  */
 extern void kgdb_arch_late(void);
 
+/**
+ *	kgdb_arch_can_debug_early - Check if OK to break before dbg_late_init()
+ *
+ *	If an architecture can definitely handle entering the debugger when
+ *	early_param's are parsed then it can override this function to return
+ *	true.  Otherwise if "kgdbwait" is passed on the kernel command line it
+ *	won't actually be processed until dbg_late_init() just after the call
+ *	to kgdb_arch_late() is made.
+ *
+ *	NOTE: Even if this returns false we will still try to register kgdb to
+ *	handle breakpoints and crashes when early_params's are parsed, we just
+ *	won't act on the "kgdbwait" parameter until dbg_late_init().  If you
+ *	get a crash and try to drop into kgdb somewhere between these two
+ *	places you might or might not end up being able to use kgdb depending
+ *	on exactly how far along the architecture has initted.
+ *
+ *	ALSO: dbg_late_init() is actually still fairly early in the system
+ *	boot process.
+ *
+ *	Return: true if platform can handle kgdb early.
+ */
+extern bool kgdb_arch_can_debug_early(void);
 
 /**
  * struct kgdb_arch - Describe architecture specific values.
diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index 2b7c9b67931d..9a4551a0fb4b 100644
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -946,16 +946,32 @@ 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)
 {
 }
 
+bool __weak kgdb_arch_can_debug_early(void)
+{
+	return false;
+}
+
 void __init dbg_late_init(void)
 {
 	dbg_is_early = false;
 	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 +1067,6 @@ 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
@@ -1095,7 +1103,8 @@ int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
 	/* Arm KGDB now. */
 	kgdb_register_callbacks();
 
-	if (kgdb_break_asap)
+	if (kgdb_break_asap &&
+	    (!dbg_is_early || kgdb_arch_can_debug_early()))
 		kgdb_initial_breakpoint();
 
 	return 0;
@@ -1165,7 +1174,7 @@ 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 && kgdb_arch_can_debug_early())
 		kgdb_initial_breakpoint();
 
 	return 0;
-- 
2.26.0.110.g2183baf09c-goog

[PATCH 3/7] arm64: Add call_break_hook() to early_brk64() for early kgdb

[Douglas Anderson]

In order to make early kgdb work properly we need early_brk64() to be
able to call into it.  This is as easy as adding a call into
call_break_hook() just like we do later in the normal brk_handler().

Once we do this we can let kgdb know that it can break into the
debugger a little earlier (specifically when parsing early_param's).

NOTE: without this patch it turns out that arm64 can't do breakpoints
even at dbg_late_init(), so if we decide something about this patch is
wrong we might need to move dbg_late_init() a little later.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
---

 arch/arm64/include/asm/debug-monitors.h | 2 ++
 arch/arm64/kernel/debug-monitors.c      | 2 +-
 arch/arm64/kernel/kgdb.c                | 5 +++++
 arch/arm64/kernel/traps.c               | 3 +++
 4 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/debug-monitors.h b/arch/arm64/include/asm/debug-monitors.h
index 7619f473155f..2d82a0314d29 100644
--- a/arch/arm64/include/asm/debug-monitors.h
+++ b/arch/arm64/include/asm/debug-monitors.h
@@ -97,6 +97,8 @@ void unregister_user_break_hook(struct break_hook *hook);
 void register_kernel_break_hook(struct break_hook *hook);
 void unregister_kernel_break_hook(struct break_hook *hook);
 
+int call_break_hook(struct pt_regs *regs, unsigned int esr);
+
 u8 debug_monitors_arch(void);
 
 enum dbg_active_el {
diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
index 48222a4760c2..59c353dfc8e9 100644
--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -297,7 +297,7 @@ void unregister_kernel_break_hook(struct break_hook *hook)
 	unregister_debug_hook(&hook->node);
 }
 
-static int call_break_hook(struct pt_regs *regs, unsigned int esr)
+int call_break_hook(struct pt_regs *regs, unsigned int esr)
 {
 	struct break_hook *hook;
 	struct list_head *list;
diff --git a/arch/arm64/kernel/kgdb.c b/arch/arm64/kernel/kgdb.c
index 43119922341f..96a47af870bc 100644
--- a/arch/arm64/kernel/kgdb.c
+++ b/arch/arm64/kernel/kgdb.c
@@ -301,6 +301,11 @@ static struct notifier_block kgdb_notifier = {
 	.priority	= -INT_MAX,
 };
 
+extern bool kgdb_arch_can_debug_early(void)
+{
+	return true;
+}
+
 /*
  * kgdb_arch_init - Perform any architecture specific initialization.
  * This function will handle the initialization of any architecture
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index cf402be5c573..a8173f0c1774 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -1044,6 +1044,9 @@ int __init early_brk64(unsigned long addr, unsigned int esr,
 	if ((comment & ~KASAN_BRK_MASK) == KASAN_BRK_IMM)
 		return kasan_handler(regs, esr) != DBG_HOOK_HANDLED;
 #endif
+	if (call_break_hook(regs, esr) == DBG_HOOK_HANDLED)
+		return 0;
+
 	return bug_handler(regs, esr) != DBG_HOOK_HANDLED;
 }
 
-- 
2.26.0.110.g2183baf09c-goog

[PATCH 4/7] kgdboc: Add earlycon_kgdboc to support early kgdb using boot consoles

[Douglas Anderson]

We want to enable kgdb to debug the early parts of the kernel.
Unfortunately kgdb normally is a client of the tty API in the kernel
and serial drivers don't register to the tty layer until fairly late
in the boot process.

Serial drivers do, however, commonly register a boot console.  Let's
enable the kgdboc driver to work with boot consoles to provide early
debugging.

This change co-opts the existing read() function pointer that's part
of "struct console".  It's assumed that if a boot console (with the
flag CON_BOOT) has implemented read() that both the read() and write()
function are polling functions.  That means they work without
interrupts and read() will return immediately (with 0 bytes read) if
there's nothing to read.  This should be a safe assumption since it
appears that no current boot consoles implement read() right now and
there seems no reason to do so unless they wanted to support
"earlycon_kgdboc".

The console API isn't really intended to have clients work with it
like we're doing.  Specifically there doesn't appear to be any way for
clients to be notified about a boot console being unregistered.  We'll
work around this by checking that our console is still valid before
using it.  We'll also try to transition off of the boot console and
onto the "tty" API as quickly as possible.

The normal/expected way to make all this work is to use
"earlycon_kgdboc" and "kgdboc" together.  You should point them both
to the same physical serial connection.  At boot time, as the system
transitions from the boot console to the normal console, kgdb will
switch over.  If you don't use things in the normal/expected way it's
a bit of a buyer-beware situation.  Things thought about:

- If you specify only "earlycon_kgdboc" but not "kgdboc" you still
  might end up dropping into kgdb upon a crash/sysrq but you may not
  be able to type.
- If you use "keep_bootcon" (which is already a bit of a buyer-beware
  option) and specify "earlycon_kgdboc" but not "kgdboc" we'll keep
  trying to use your boot console for kgdb.
- If your "earlycon_kgdboc" and "kgdboc" devices are not the same
  device things should work OK, but it'll be your job to switch over
  which device you're monitoring (including figuring out how to switch
  over gdb in-flight if you're using it).

When trying to enable "earlycon_kgdboc" it should be noted that the
names that are registered through the boot console layer and the tty
layer are not the same for the same port.  For example when debugging
on one board I'd need to pass "earlycon_kgdboc=qcom_geni
kgdboc=ttyMSM0" to enable things properly.  Since digging up the boot
console name is a pain and there will rarely be more than one boot
console enabled, you can provide the "earlycon_kgdboc" parameter
without specifying the name of the boot console.  In this case we'll
just pick the first boot that implements read() that we find.

This new "earlycon_kgdboc" parameter should be contrasted to the
existing "ekgdboc" parameter.  While both provide a way to debug very
early, the usage and mechanisms are quite different.  Specifically
"earlycon_kgdboc" is meant to be used in tandem with "kgdboc" and
there is a transition from one to the other.  The "ekgdboc" parameter,
on the other hand, replaces the "kgdboc" parameter.  It runs the same
logic as the "kgdboc" parameter but just relies on your TTY driver
being present super early.  The only known usage of the old "ekgdboc"
parameter is documented as "ekgdboc=kbd earlyprintk=vga".  It should
be noted that "kbd" has special treatment allowing it to init early as
a tty device.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

 drivers/tty/serial/kgdboc.c | 140 +++++++++++++++++++++++++++++++++++-
 include/linux/kgdb.h        |   3 +-
 kernel/debug/debug_core.c   |  15 +++-
 3 files changed, 154 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c
index 9ace39fc4f95..47cd0c28a0f6 100644
--- a/drivers/tty/serial/kgdboc.c
+++ b/drivers/tty/serial/kgdboc.c
@@ -21,6 +21,7 @@
 #include <linux/input.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
+#include <linux/serial_core.h>
 
 #define MAX_CONFIG_LEN		40
 
@@ -42,6 +43,14 @@ static int			kgdb_tty_line;
 
 static struct platform_device *kgdboc_pdev;
 
+#ifdef CONFIG_KGDB_SERIAL_CONSOLE
+static struct kgdb_io		earlycon_kgdboc_io_ops;
+struct console			*earlycon;
+bool				earlycon_neutered;
+#else /* ! CONFIG_KGDB_SERIAL_CONSOLE */
+#define earlycon NULL
+#endif /* ! CONFIG_KGDB_SERIAL_CONSOLE */
+
 #ifdef CONFIG_KDB_KEYBOARD
 static int kgdboc_reset_connect(struct input_handler *handler,
 				struct input_dev *dev,
@@ -135,8 +144,46 @@ static void kgdboc_unregister_kbd(void)
 #define kgdboc_restore_input()
 #endif /* ! CONFIG_KDB_KEYBOARD */
 
+#ifdef CONFIG_KGDB_SERIAL_CONSOLE
+
+static void cleanup_earlycon(bool unregister)
+{
+	if (earlycon && unregister)
+		kgdb_unregister_io_module(&earlycon_kgdboc_io_ops);
+	earlycon = NULL;
+}
+
+static bool is_earlycon_still_valid(void)
+{
+	struct console *con;
+
+	for_each_console(con)
+		if (con == earlycon)
+			return true;
+	return false;
+}
+
+static void cleanup_earlycon_if_invalid(void)
+{
+	console_lock();
+	if (earlycon && (earlycon_neutered || !is_earlycon_still_valid())) {
+		pr_warn("earlycon vanished; unregistering\n");
+		cleanup_earlycon(true);
+	}
+	console_unlock();
+}
+
+#else /* ! CONFIG_KGDB_SERIAL_CONSOLE */
+
+static inline void cleanup_earlycon(bool unregister) { ; }
+static inline void cleanup_earlycon_if_invalid(void) { ; }
+
+#endif /* ! CONFIG_KGDB_SERIAL_CONSOLE */
+
 static void cleanup_kgdboc(void)
 {
+	cleanup_earlycon(true);
+
 	if (configured != 1)
 		return;
 
@@ -190,9 +237,10 @@ static int configure_kgdboc(void)
 	kgdb_tty_line = tty_line;
 
 do_register:
-	err = kgdb_register_io_module(&kgdboc_io_ops);
+	err = kgdb_register_io_module(&kgdboc_io_ops, earlycon != NULL);
 	if (err)
 		goto noconfig;
+	cleanup_earlycon(false);
 
 	err = kgdb_register_nmi_console();
 	if (err)
@@ -208,6 +256,14 @@ static int configure_kgdboc(void)
 	kgdboc_unregister_kbd();
 	configured = 0;
 
+	/*
+	 * Each time we run configure_kgdboc() but don't find a console, use
+	 * that as a chance to validate that our earlycon didn't vanish on
+	 * us.  If it vanished we should unregister which will disable kgdb
+	 * if we're the last I/O module.
+	 */
+	cleanup_earlycon_if_invalid();
+
 	return err;
 }
 
@@ -415,6 +471,88 @@ static int __init kgdboc_early_init(char *opt)
 }
 
 early_param("ekgdboc", kgdboc_early_init);
+
+static int earlycon_kgdboc_get_char(void)
+{
+	char c;
+
+	if (earlycon_neutered || !earlycon->read(earlycon, &c, 1))
+		return NO_POLL_CHAR;
+
+	return c;
+}
+
+static void earlycon_kgdboc_put_char(u8 chr)
+{
+	if (!earlycon_neutered)
+		earlycon->write(earlycon, &chr, 1);
+}
+
+static void earlycon_kgdboc_pre_exp_handler(void)
+{
+	atomic_inc(&ignore_console_lock_warning);
+
+	/*
+	 * We don't get notified when the boot console is unregistered.
+	 * Double-check when we enter the debugger.  Unfortunately we
+	 * can't really unregister ourselves now, but at least don't crash.
+	 */
+	if (earlycon && !earlycon_neutered && !is_earlycon_still_valid()) {
+		pr_warn("Neutering kgdb since boot console vanished\n");
+		earlycon_neutered = true;
+	}
+}
+
+static void earlycon_kgdboc_post_exp_handler(void)
+{
+	atomic_dec(&ignore_console_lock_warning);
+}
+
+static struct kgdb_io earlycon_kgdboc_io_ops = {
+	.name			= "earlycon_kgdboc",
+	.read_char		= earlycon_kgdboc_get_char,
+	.write_char		= earlycon_kgdboc_put_char,
+	.pre_exception		= earlycon_kgdboc_pre_exp_handler,
+	.post_exception		= earlycon_kgdboc_post_exp_handler,
+	.is_console		= true,
+};
+
+static int __init earlycon_kgdboc_init(char *opt)
+{
+	struct console *con;
+
+	kdb_init(KDB_INIT_EARLY);
+
+	/*
+	 * Look for a matching console, or if the name was left blank just
+	 * pick the first one we find.
+	 */
+	console_lock();
+	for_each_console(con) {
+		if (con->write && con->read &&
+		    (con->flags & (CON_BOOT | CON_ENABLED)) &&
+		    (!opt || !opt[0] || strcmp(con->name, opt) == 0))
+			break;
+	}
+	console_unlock();
+
+	if (!con) {
+		pr_info("Couldn't find kgdb earlycon\n");
+		return 0;
+	}
+
+	earlycon = con;
+	pr_info("Going to register kgdb with earlycon '%s'\n", con->name);
+	if (kgdb_register_io_module(&earlycon_kgdboc_io_ops, false) != 0) {
+		earlycon = NULL;
+		pr_info("Failed to register kgdb with earlycon\n");
+		return 0;
+	}
+
+	return 0;
+}
+
+early_param("earlycon_kgdboc", earlycon_kgdboc_init);
 #endif /* CONFIG_KGDB_SERIAL_CONSOLE */
 
 module_init(init_kgdboc);
diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h
index 7371517aeacc..2e86307f2683 100644
--- a/include/linux/kgdb.h
+++ b/include/linux/kgdb.h
@@ -323,7 +323,8 @@ static inline int kgdb_unregister_nmi_console(void) { return 0; }
 static inline bool kgdb_nmi_poll_knock(void) { return 1; }
 #endif
 
-extern int kgdb_register_io_module(struct kgdb_io *local_kgdb_io_ops);
+extern int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops,
+				   bool replace);
 extern void kgdb_unregister_io_module(struct kgdb_io *local_kgdb_io_ops);
 extern struct kgdb_io *dbg_io_ops;
 
diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index 9a4551a0fb4b..82a9af56a0b5 100644
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -1070,16 +1070,21 @@ EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
 /**
  *	kgdb_register_io_module - register KGDB IO module
  *	@new_dbg_io_ops: the io ops vector
+ *	@replace: If true it's OK if there were old ops.  This is used
+ *		  to transition from early kgdb to normal kgdb.  It's
+ *		  assumed these are the same device so kgdb can continue.
  *
  *	Register it with the KGDB core.
  */
-int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
+int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops, bool replace)
 {
+	struct kgdb_io *old_dbg_io_ops;
 	int err;
 
 	spin_lock(&kgdb_registration_lock);
 
-	if (dbg_io_ops) {
+	old_dbg_io_ops = dbg_io_ops;
+	if (dbg_io_ops && !replace) {
 		spin_unlock(&kgdb_registration_lock);
 
 		pr_err("Another I/O driver is already registered with KGDB\n");
@@ -1098,6 +1103,12 @@ int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
 
 	spin_unlock(&kgdb_registration_lock);
 
+	if (replace) {
+		pr_info("Replaced I/O driver %s with %s\n",
+			old_dbg_io_ops->name, new_dbg_io_ops->name);
+		return 0;
+	}
+
 	pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name);
 
 	/* Arm KGDB now. */
-- 
2.26.0.110.g2183baf09c-goog

[PATCH 5/7] Documentation: kgdboc: Document new earlycon_kgdboc parameter

[Douglas Anderson]

The recent patch ("kgdboc: Add earlycon_kgdboc to support early kgdb
using boot consoles") adds a new kernel command line parameter.
Document it.

Note that the patch adding the feature does some comparing/contrasting
of "earlycon_kgdboc" vs. the existing "ekgdboc".  See that patch for
more details, but briefly "ekgdboc" can be used _instead_ of "kgdboc"
and just makes "kgdboc" do its normal initialization early (only works
if your tty driver is already ready).  The new "earlycon_kgdboc" works
in combination with "kgdboc" and is backed by boot consoles.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

 .../admin-guide/kernel-parameters.txt         | 20 +++++++++++++++++++
 Documentation/dev-tools/kgdb.rst              | 14 +++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index c07815d230bc..37dc2db13743 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1124,6 +1124,22 @@
 			address must be provided, and the serial port must
 			already be setup and configured.
 
+	earlycon_kgdboc=	[KGDB,HW]
+			If the boot console provides the ability to read
+			characters and can work in polling mode, you can use
+			this parameter to tell kgdb to use it as a backend
+			until the normal console is registered. Intended to
+			be used together with the kgdboc parameter which
+			specifies the normal console to transition to.
+
+			The the name of the early console should be specified
+			as the value of this parameter. Note that the name of
+			the early console might be different than the tty
+			name passed to kgdboc. If only one boot console with
+			a read() function is enabled it's OK to leave the
+			value blank and the first boot console that implements
+			read() will be picked.
+
 	earlyprintk=	[X86,SH,ARM,M68k,S390]
 			earlyprintk=vga
 			earlyprintk=sclp
@@ -1182,6 +1198,10 @@
 			This is designed to be used in conjunction with
 			the boot argument: earlyprintk=vga
 
+			This parameter works in place of the kgdboc parameter
+			but can only be used if the backing tty is available
+			very early in the boot process.
+
 	edd=		[EDD]
 			Format: {"off" | "on" | "skip[mbr]"}
 
diff --git a/Documentation/dev-tools/kgdb.rst b/Documentation/dev-tools/kgdb.rst
index d38be58f872a..c0b321403d9a 100644
--- a/Documentation/dev-tools/kgdb.rst
+++ b/Documentation/dev-tools/kgdb.rst
@@ -274,6 +274,20 @@ don't like this are to hack gdb to send the :kbd:`SysRq-G` for you as well as
 on the initial connect, or to use a debugger proxy that allows an
 unmodified gdb to do the debugging.
 
+Kernel parameter: ``earlycon_kgdboc``
+-------------------------------------
+
+If you specify the kernel parameter ``earlycon_kgdboc`` and your serial
+driver registers a boot console that supports polling (doesn't need
+interrupts and implements a nonblocking read() function) kgdb will attempt
+to work using the boot console until it can transition to the regular
+tty driver specified by the ``kgdboc`` parameter.
+
+Normally there is only one boot console (especially that implements the
+read() function) so just adding ``earlycon_kgdboc`` on its own is
+sufficient to make this work.  If you have more than one boot console you
+can add the boot console's name to differentiate.
+
 Kernel parameter: ``kgdbwait``
 ------------------------------
 
-- 
2.26.0.110.g2183baf09c-goog

[PATCH 6/7] serial: qcom_geni_serial: Support earlycon_kgdboc

[Douglas Anderson]

Implement the read() function in the early console driver.  With
recent kgdb patches this allows you to use kgdb to debug fairly early
into the system boot.

We only bother implementing this if polling is enabled since kgdb
can't be enabled without that.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

 drivers/tty/serial/qcom_geni_serial.c | 32 +++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
index 0bd1684cabb3..e3bb90404ab5 100644
--- a/drivers/tty/serial/qcom_geni_serial.c
+++ b/drivers/tty/serial/qcom_geni_serial.c
@@ -1084,6 +1084,36 @@ static void qcom_geni_serial_earlycon_write(struct console *con,
 	__qcom_geni_serial_console_write(&dev->port, s, n);
 }
 
+#ifdef CONFIG_CONSOLE_POLL
+static int qcom_geni_serial_earlycon_read(struct console *con,
+					  char *s, unsigned int n)
+{
+	struct earlycon_device *dev = con->data;
+	struct uart_port *uport = &dev->port;
+	int num_read = 0;
+	int ch;
+
+	while (num_read < n) {
+		ch = qcom_geni_serial_get_char(uport);
+		if (ch == NO_POLL_CHAR)
+			break;
+		s[num_read++] = ch;
+	}
+
+	return num_read;
+}
+
+static void __init qcom_geni_serial_enable_early_read(struct geni_se *se,
+						      struct console *con)
+{
+	geni_se_setup_s_cmd(se, UART_START_READ, 0);
+	con->read = qcom_geni_serial_earlycon_read;
+}
+#else
+static inline void qcom_geni_serial_enable_early_read(struct geni_se *se,
+						      struct console *con) { ; }
+#endif
+
 static int __init qcom_geni_serial_earlycon_setup(struct earlycon_device *dev,
 								const char *opt)
 {
@@ -1130,6 +1160,8 @@ static int __init qcom_geni_serial_earlycon_setup(struct earlycon_device *dev,
 
 	dev->con->write = qcom_geni_serial_earlycon_write;
 	dev->con->setup = NULL;
+	qcom_geni_serial_enable_early_read(&se, dev->con);
+
 	return 0;
 }
 OF_EARLYCON_DECLARE(qcom_geni, "qcom,geni-debug-uart",
-- 
2.26.0.110.g2183baf09c-goog

[PATCH 7/7] serial: 8250_early: Support earlycon_kgdboc

[Douglas Anderson]

Implement the read() function in the early console driver.  With
recent kgdb patches this allows you to use kgdb to debug fairly early
into the system boot.

We only bother implementing this if polling is enabled since kgdb
can't be enabled without that.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

 drivers/tty/serial/8250/8250_early.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c
index 5cd8c36c8fcc..70d7826788f5 100644
--- a/drivers/tty/serial/8250/8250_early.c
+++ b/drivers/tty/serial/8250/8250_early.c
@@ -109,6 +109,28 @@ static void early_serial8250_write(struct console *console,
 	uart_console_write(port, s, count, serial_putc);
 }
 
+#ifdef CONFIG_CONSOLE_POLL
+static int early_serial8250_read(struct console *console,
+				 char *s, unsigned int count)
+{
+	struct earlycon_device *device = console->data;
+	struct uart_port *port = &device->port;
+	unsigned int status;
+	int num_read = 0;
+
+	while (num_read < count) {
+		status = serial8250_early_in(port, UART_LSR);
+		if (!(status & UART_LSR_DR))
+			break;
+		s[num_read++] = serial8250_early_in(port, UART_RX);
+	}
+
+	return num_read;
+}
+#else
+#define early_serial8250_read NULL
+#endif
+
 static void __init init_port(struct earlycon_device *device)
 {
 	struct uart_port *port = &device->port;
@@ -149,6 +171,7 @@ int __init early_serial8250_setup(struct earlycon_device *device,
 		init_port(device);
 
 	device->con->write = early_serial8250_write;
+	device->con->read = early_serial8250_read;
 	return 0;
 }
 EARLYCON_DECLARE(uart8250, early_serial8250_setup);
-- 
2.26.0.110.g2183baf09c-goog

Re: [PATCH 4/7] kgdboc: Add earlycon_kgdboc to support early kgdb using boot consoles

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 3736 bytes --]

Hi Douglas,

I love your patch! Yet something to improve:

[auto build test ERROR on arm64/for-next/core]
[also build test ERROR on tty/tty-testing v5.6 next-20200410]
[cannot apply to kgdb/kgdb-next]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Douglas-Anderson/kgdb-Support-late-serial-drivers-enable-early-debug-w-boot-consoles/20200411-062123
base:   https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-next/core
config: microblaze-mmu_defconfig (attached as .config)
compiler: microblaze-linux-gcc (GCC) 9.3.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        GCC_VERSION=9.3.0 make.cross ARCH=microblaze 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   drivers/misc/kgdbts.c: In function 'configure_kgdbts':
>> drivers/misc/kgdbts.c:1080:8: error: too few arguments to function 'kgdb_register_io_module'
    1080 |  err = kgdb_register_io_module(&kgdbts_io_ops);
         |        ^~~~~~~~~~~~~~~~~~~~~~~
   In file included from drivers/misc/kgdbts.c:86:
   include/linux/kgdb.h:326:12: note: declared here
     326 | extern int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops,
         |            ^~~~~~~~~~~~~~~~~~~~~~~

vim +/kgdb_register_io_module +1080 drivers/misc/kgdbts.c

e8d31c204e36e0 Jason Wessel 2008-03-07  1069  
e8d31c204e36e0 Jason Wessel 2008-03-07  1070  static int configure_kgdbts(void)
e8d31c204e36e0 Jason Wessel 2008-03-07  1071  {
e8d31c204e36e0 Jason Wessel 2008-03-07  1072  	int err = 0;
e8d31c204e36e0 Jason Wessel 2008-03-07  1073  
e8d31c204e36e0 Jason Wessel 2008-03-07  1074  	if (!strlen(config) || isspace(config[0]))
e8d31c204e36e0 Jason Wessel 2008-03-07  1075  		goto noconfig;
e8d31c204e36e0 Jason Wessel 2008-03-07  1076  
e8d31c204e36e0 Jason Wessel 2008-03-07  1077  	final_ack = 0;
e8d31c204e36e0 Jason Wessel 2008-03-07  1078  	run_plant_and_detach_test(1);
e8d31c204e36e0 Jason Wessel 2008-03-07  1079  
e8d31c204e36e0 Jason Wessel 2008-03-07 @1080  	err = kgdb_register_io_module(&kgdbts_io_ops);
e8d31c204e36e0 Jason Wessel 2008-03-07  1081  	if (err) {
e8d31c204e36e0 Jason Wessel 2008-03-07  1082  		configured = 0;
e8d31c204e36e0 Jason Wessel 2008-03-07  1083  		return err;
e8d31c204e36e0 Jason Wessel 2008-03-07  1084  	}
e8d31c204e36e0 Jason Wessel 2008-03-07  1085  	configured = 1;
e8d31c204e36e0 Jason Wessel 2008-03-07  1086  	kgdbts_run_tests();
e8d31c204e36e0 Jason Wessel 2008-03-07  1087  
e8d31c204e36e0 Jason Wessel 2008-03-07  1088  	return err;
e8d31c204e36e0 Jason Wessel 2008-03-07  1089  
e8d31c204e36e0 Jason Wessel 2008-03-07  1090  noconfig:
e8d31c204e36e0 Jason Wessel 2008-03-07  1091  	config[0] = 0;
e8d31c204e36e0 Jason Wessel 2008-03-07  1092  	configured = 0;
e8d31c204e36e0 Jason Wessel 2008-03-07  1093  
e8d31c204e36e0 Jason Wessel 2008-03-07  1094  	return err;
e8d31c204e36e0 Jason Wessel 2008-03-07  1095  }
e8d31c204e36e0 Jason Wessel 2008-03-07  1096  

:::::: The code at line 1080 was first introduced by commit
:::::: e8d31c204e36e019b9134f2a11926cac0fcf9b19 kgdb: add kgdb internal test suite

:::::: TO: Jason Wessel <jason.wessel@windriver.com>
:::::: CC: Ingo Molnar <mingo@elte.hu>

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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Re: [PATCH 4/7] kgdboc: Add earlycon_kgdboc to support early kgdb using boot consoles

[kbuild test robot]

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Hi Douglas,

I love your patch! Yet something to improve:

[auto build test ERROR on arm64/for-next/core]
[also build test ERROR on tty/tty-testing v5.6 next-20200410]
[cannot apply to kgdb/kgdb-next]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Douglas-Anderson/kgdb-Support-late-serial-drivers-enable-early-debug-w-boot-consoles/20200411-062123
base:   https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-next/core
config: i386-allyesconfig (attached as .config)
compiler: gcc-7 (Ubuntu 7.5.0-6ubuntu2) 7.5.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   drivers/usb/early/ehci-dbgp.c: In function 'kgdbdbgp_parse_config':
>> drivers/usb/early/ehci-dbgp.c:1060:2: error: too few arguments to function 'kgdb_register_io_module'
     kgdb_register_io_module(&kgdbdbgp_io_ops);
     ^~~~~~~~~~~~~~~~~~~~~~~
   In file included from drivers/usb/early/ehci-dbgp.c:24:0:
   include/linux/kgdb.h:326:12: note: declared here
    extern int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops,
               ^~~~~~~~~~~~~~~~~~~~~~~

vim +/kgdb_register_io_module +1060 drivers/usb/early/ehci-dbgp.c

4fe1da4ebc18c4 Jason Wessel 2010-05-20  1046  
4fe1da4ebc18c4 Jason Wessel 2010-05-20  1047  static int __init kgdbdbgp_parse_config(char *str)
4fe1da4ebc18c4 Jason Wessel 2010-05-20  1048  {
4fe1da4ebc18c4 Jason Wessel 2010-05-20  1049  	char *ptr;
4fe1da4ebc18c4 Jason Wessel 2010-05-20  1050  
4fe1da4ebc18c4 Jason Wessel 2010-05-20  1051  	if (!ehci_debug) {
4fe1da4ebc18c4 Jason Wessel 2010-05-20  1052  		if (early_dbgp_init(str))
4fe1da4ebc18c4 Jason Wessel 2010-05-20  1053  			return -1;
4fe1da4ebc18c4 Jason Wessel 2010-05-20  1054  	}
4fe1da4ebc18c4 Jason Wessel 2010-05-20  1055  	ptr = strchr(str, ',');
4fe1da4ebc18c4 Jason Wessel 2010-05-20  1056  	if (ptr) {
4fe1da4ebc18c4 Jason Wessel 2010-05-20  1057  		ptr++;
4fe1da4ebc18c4 Jason Wessel 2010-05-20  1058  		kgdbdbgp_wait_time = simple_strtoul(ptr, &ptr, 10);
4fe1da4ebc18c4 Jason Wessel 2010-05-20  1059  	}
4fe1da4ebc18c4 Jason Wessel 2010-05-20 @1060  	kgdb_register_io_module(&kgdbdbgp_io_ops);
4fe1da4ebc18c4 Jason Wessel 2010-05-20  1061  	kgdbdbgp_io_ops.is_console = early_dbgp_console.index != -1;
4fe1da4ebc18c4 Jason Wessel 2010-05-20  1062  
4fe1da4ebc18c4 Jason Wessel 2010-05-20  1063  	return 0;
4fe1da4ebc18c4 Jason Wessel 2010-05-20  1064  }
4fe1da4ebc18c4 Jason Wessel 2010-05-20  1065  early_param("kgdbdbgp", kgdbdbgp_parse_config);
4fe1da4ebc18c4 Jason Wessel 2010-05-20  1066  

:::::: The code at line 1060 was first introduced by commit
:::::: 4fe1da4ebc18c4c42fa56c228447f68033fce5f0 echi-dbgp: Add kernel debugger support for the usb debug port

:::::: TO: Jason Wessel <jason.wessel@windriver.com>
:::::: CC: Jason Wessel <jason.wessel@windriver.com>

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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Re: [PATCH 4/7] kgdboc: Add earlycon_kgdboc to support early kgdb using boot consoles

[Doug Anderson]

Hi,

On Fri, Apr 10, 2020 at 4:56 PM kbuild test robot <lkp@intel.com> wrote:
>
> Hi Douglas,
>
> I love your patch! Yet something to improve:
>
> [auto build test ERROR on arm64/for-next/core]
> [also build test ERROR on tty/tty-testing v5.6 next-20200410]
> [cannot apply to kgdb/kgdb-next]
> [if your patch is applied to the wrong git tree, please drop us a note to help
> improve the system. BTW, we also suggest to use '--base' option to specify the
> base tree in git format-patch, please see https://stackoverflow.com/a/37406982]
>
> url:    https://github.com/0day-ci/linux/commits/Douglas-Anderson/kgdb-Support-late-serial-drivers-enable-early-debug-w-boot-consoles/20200411-062123
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-next/core
> config: microblaze-mmu_defconfig (attached as .config)
> compiler: microblaze-linux-gcc (GCC) 9.3.0
> reproduce:
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # save the attached .config to linux build tree
>         GCC_VERSION=9.3.0 make.cross ARCH=microblaze
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kbuild test robot <lkp@intel.com>
>
> All errors (new ones prefixed by >>):
>
>    drivers/misc/kgdbts.c: In function 'configure_kgdbts':
> >> drivers/misc/kgdbts.c:1080:8: error: too few arguments to function 'kgdb_register_io_module'
>     1080 |  err = kgdb_register_io_module(&kgdbts_io_ops);

Sigh, I knew I'd forget something stupid.  I have a fix for this and
have confirmed that "kgdbts" continues to work after I fix it.
Running it also found splats similar to what I fixed for "kgdboc" in
commit 81eaadcae81b ("kgdboc: disable the console lock when in kgdb").
I'll att a commit to my next version to move that fix into the kgdb
core and then remove it from "kgdboc".

I'm not setup to use kgdb over EHCI so I'll just fix that so it
compiles and trust that it continues to work.

For now I'll hold up on sending a new version to await feedback on v1.
If I don't hear anything after a little while I'll send a v2 with just
these fixes.

-Doug