[patch 0/3] Dynamic Debug providing early boot debug messages via boot parameter

[patch 0/3] Dynamic Debug providing early boot debug messages via boot parameter

[trenn]

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Sorry about the first post, missing two patches, please ignore...

this patch is against 2.6.35-rc5. Not sure whether Jason's latest fix is
in there already and whether it conflicts with this series,
but it should patch.

Please tell me if I should (have to) re-diff and against which branch
I should do that.

The patches got boot tested via ddebug_query="file ec.c +p" which worked
out fine.

Would be great to see these in the next kernel cycle (2.6.36).

Thanks,

     Thomas

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[patch 1/3] Dynamic Debug: Split out query string parsing/setup from proc_write

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[-- Attachment #1: patches.drivers/dynamic_debug_split_up_query_exec.patch --]
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The parsing and applying of dynamic debug strings is not only useful for
/sys/../dynamic_debug/control write access, but can also be used for
boot parameter parsing.
The boot parameter is introduced in a follow up patch.

Signed-off-by: Thomas Renninger <trenn@suse.de>
CC: jbaron@redhat.com
CC: linux-kernel@vger.kernel.org
CC: yehuda@hq.newdream.net

---
 lib/dynamic_debug.c |   40 +++++++++++++++++++++++++---------------
 1 file changed, 25 insertions(+), 15 deletions(-)

Index: linux-2.6.34-master/lib/dynamic_debug.c
===================================================================
--- linux-2.6.34-master.orig/lib/dynamic_debug.c
+++ linux-2.6.34-master/lib/dynamic_debug.c
@@ -429,6 +429,27 @@ static int ddebug_parse_flags(const char
 	return 0;
 }
 
+static int ddebug_exec_query(char *query_string)
+{
+	unsigned int flags = 0, mask = 0;
+	struct ddebug_query query;
+#define MAXWORDS 9
+	int nwords;
+	char *words[MAXWORDS];
+
+	nwords = ddebug_tokenize(query_string, words, MAXWORDS);
+	if (nwords <= 0)
+		return -EINVAL;
+	if (ddebug_parse_query(words, nwords-1, &query))
+		return -EINVAL;
+	if (ddebug_parse_flags(words[nwords-1], &flags, &mask))
+		return -EINVAL;
+
+	/* actually go and implement the change */
+	ddebug_change(&query, flags, mask);
+	return 0;
+}
+
 /*
  * File_ops->write method for <debugfs>/dynamic_debug/conrol.  Gathers the
  * command text from userspace, parses and executes it.
@@ -436,12 +457,8 @@ static int ddebug_parse_flags(const char
 static ssize_t ddebug_proc_write(struct file *file, const char __user *ubuf,
 				  size_t len, loff_t *offp)
 {
-	unsigned int flags = 0, mask = 0;
-	struct ddebug_query query;
-#define MAXWORDS 9
-	int nwords;
-	char *words[MAXWORDS];
 	char tmpbuf[256];
+	int ret;
 
 	if (len == 0)
 		return 0;
@@ -455,16 +472,9 @@ static ssize_t ddebug_proc_write(struct
 		printk(KERN_INFO "%s: read %d bytes from userspace\n",
 			__func__, (int)len);
 
-	nwords = ddebug_tokenize(tmpbuf, words, MAXWORDS);
-	if (nwords <= 0)
-		return -EINVAL;
-	if (ddebug_parse_query(words, nwords-1, &query))
-		return -EINVAL;
-	if (ddebug_parse_flags(words[nwords-1], &flags, &mask))
-		return -EINVAL;
-
-	/* actually go and implement the change */
-	ddebug_change(&query, flags, mask);
+	ret = ddebug_exec_query(tmpbuf);
+	if (ret)
+		return ret;
 
 	*offp += len;
 	return len;

[patch 2/3] Dynamic Debug: Introduce ddebug_query= boot parameter

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[-- Attachment #1: patches.drivers/dynamic_debug_boot_param_enhance.patch --]
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Dynamic debug lacks the ability to enable debug messages at boot time.
One could patch initramfs or service startup scripts to write to
/sys/../dynamic_debug/control, but this sucks.

This patch makes it possible to pass a query in the same format one can
write to /sys/../dynamic_debug/control via boot param.
When dynamic debug gets initialized, this query will automatically be
applied.


Signed-off-by: Thomas Renninger <trenn@suse.de>
CC: jbaron@redhat.com
CC: linux-kernel@vger.kernel.org
CC: yehuda@hq.newdream.net

---
 Documentation/dynamic-debug-howto.txt |   22 +++++++++++++++++++++-
 Documentation/kernel-parameters.txt   |    7 ++++++-
 lib/dynamic_debug.c                   |   25 +++++++++++++++++++++++++
 3 files changed, 52 insertions(+), 2 deletions(-)

Index: linux-2.6.34-master/lib/dynamic_debug.c
===================================================================
--- linux-2.6.34-master.orig/lib/dynamic_debug.c
+++ linux-2.6.34-master/lib/dynamic_debug.c
@@ -450,6 +450,19 @@ static int ddebug_exec_query(char *query
 	return 0;
 }
 
+static __initdata char ddebug_setup_string[1024];
+static __init int ddebug_setup_query(char *str)
+{
+	if (strlen(str) >= 1024) {
+		pr_warning("ddebug boot param string too large\n");
+		return 0;
+	}
+	strcpy(ddebug_setup_string, str);
+	return 1;
+}
+
+__setup("ddebug_query=", ddebug_setup_query);
+
 /*
  * File_ops->write method for <debugfs>/dynamic_debug/conrol.  Gathers the
  * command text from userspace, parses and executes it.
@@ -769,6 +782,18 @@ static int __init dynamic_debug_init(voi
 		}
 		ret = ddebug_add_module(iter_start, n, modname);
 	}
+
+	/* ddebug_query boot param got passed -> set it up */
+	if (ddebug_setup_string[0] != '\0') {
+		ret = ddebug_exec_query(ddebug_setup_string);
+		if (ret)
+			pr_warning("Invalid ddebug boot param %s",
+				   ddebug_setup_string);
+		else
+			pr_info("ddebug initialized with string %s",
+				ddebug_setup_string);
+	}
+
 out_free:
 	if (ret) {
 		ddebug_remove_all_tables();
Index: linux-2.6.34-master/Documentation/dynamic-debug-howto.txt
===================================================================
--- linux-2.6.34-master.orig/Documentation/dynamic-debug-howto.txt
+++ linux-2.6.34-master/Documentation/dynamic-debug-howto.txt
@@ -24,7 +24,7 @@ Dynamic debug has even more useful featu
    read to display the complete list of known debug statements, to help guide you
 
 Controlling dynamic debug Behaviour
-===============================
+===================================
 
 The behaviour of pr_debug()/dev_debug()s are controlled via writing to a
 control file in the 'debugfs' filesystem. Thus, you must first mount the debugfs
@@ -212,6 +212,26 @@ Note the regexp ^[-+=][scp]+$ matches a
 Note also that there is no convenient syntax to remove all
 the flags at once, you need to use "-psc".
 
+
+Debug messages during boot process
+==================================
+
+To be able to activate debug messages during the boot process,
+even before userspace and debugfs exists, use the boot parameter:
+ddebug_query="QUERY"
+
+QUERY follows the syntax described above, but must not exceed 1023
+characters. The enablement of debug messages is done as an arch_initcall.
+Thus you can enable debug messages in all code processed after this
+arch_initcall via this boot parameter.
+On an x86 system for example ACPI enablement is a subsys_initcall and
+ddebug_query="file ec.c +p"
+will show early Embedded Controller transactions during ACPI setup if
+your machine (typically a laptop) has an Embedded Controller.
+PCI (or other devices) initialization also is a hot candidate for using
+this boot parameter for debugging purposes.
+
+
 Examples
 ========
 
Index: linux-2.6.34-master/Documentation/kernel-parameters.txt
===================================================================
--- linux-2.6.34-master.orig/Documentation/kernel-parameters.txt
+++ linux-2.6.34-master/Documentation/kernel-parameters.txt
@@ -43,10 +43,11 @@ parameter is applicable:
 	AVR32	AVR32 architecture is enabled.
 	AX25	Appropriate AX.25 support is enabled.
 	BLACKFIN Blackfin architecture is enabled.
-	DRM	Direct Rendering Management support is enabled.
 	EDD	BIOS Enhanced Disk Drive Services (EDD) is enabled
 	EFI	EFI Partitioning (GPT) is enabled
 	EIDE	EIDE/ATAPI support is enabled.
+	DRM	Direct Rendering Management support is enabled.
+	DYNAMIC_DEBUG Build in debug messages and enable them at runtime
 	FB	The frame buffer device is enabled.
 	GCOV	GCOV profiling is enabled.
 	HW	Appropriate hardware is enabled.
@@ -601,6 +602,10 @@ and is between 256 and 4096 characters.
 			Format: <port#>,<type>
 			See also Documentation/input/joystick-parport.txt
 
+	ddebug_query=   [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
+			time. See Documentation/dynamic-debug-howto.txt for
+			details.
+
 	debug		[KNL] Enable kernel debugging (events log level).
 
 	debug_locks_verbose=

[patch 3/3] Dynamic Debug: Initialize dynamic debug earlier via arch_initcall

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[-- Attachment #1: patches.drivers/dynamic_debug_make_arch_initcall.patch --]
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Having the ddebug_query= boot parameter it makes sense to set up
dynamic debug as soon as possible.

I expect sysfs files cannot be set up via an arch_initcall, because
this one is even before fs_initcall. Therefore I splitted the
dynamic_debug_init function into an early one and a later one providing
/sys/../dynamic_debug/control file.

Possibly dynamic_debug can be initialized even earlier, not sure whether
this still makes sense then. I picked up arch_initcall as it covers
quite a lot already.

Dynamic debug seem to not need memory (kmalloc) set up yet.
If it is possible to move initialization even before __setup boot
parameter processing, the temporary variable to copy away the boot paramter
and later use it in dynamic_debug_init() is not needed anymore.

This has been tested with ddebug_query="file ec.c +p"
and I could retrieve pr_debug() messages early at boot during ACPI setup:
ACPI: EC: Look up EC in DSDT
ACPI: EC: ---> status = 0x08
ACPI: EC: transaction start
ACPI: EC: <--- command = 0x80
ACPI: EC: ~~~> interrupt
ACPI: EC: ---> status = 0x08
ACPI: EC: <--- data = 0xa4
...
ACPI: Interpreter enabled
ACPI: (supports S0 S3 S4 S5)
ACPI: Using IOAPIC for interrupt routing
ACPI: EC: ---> status = 0x00
ACPI: EC: transaction start
ACPI: EC: <--- command = 0x80


Signed-off-by: Thomas Renninger <trenn@suse.de>
CC: jbaron@redhat.com
CC: linux-kernel@vger.kernel.org
CC: yehuda@hq.newdream.net
CC: astarikovskiy@novell.com


---
 lib/dynamic_debug.c |   33 +++++++++++++++++++++++----------
 1 file changed, 23 insertions(+), 10 deletions(-)

Index: linux-2.6.34-master/lib/dynamic_debug.c
===================================================================
--- linux-2.6.34-master.orig/lib/dynamic_debug.c
+++ linux-2.6.34-master/lib/dynamic_debug.c
@@ -748,13 +748,14 @@ static void ddebug_remove_all_tables(voi
 	mutex_unlock(&ddebug_lock);
 }
 
-static int __init dynamic_debug_init(void)
+static __initdata int ddebug_init_success;
+
+static int __init dynamic_debug_init_debugfs(void)
 {
 	struct dentry *dir, *file;
-	struct _ddebug *iter, *iter_start;
-	const char *modname = NULL;
-	int ret = 0;
-	int n = 0;
+
+	if (!ddebug_init_success)
+		return -ENODEV;
 
 	dir = debugfs_create_dir("dynamic_debug", NULL);
 	if (!dir)
@@ -765,6 +766,16 @@ static int __init dynamic_debug_init(voi
 		debugfs_remove(dir);
 		return -ENOMEM;
 	}
+	return 0;
+}
+
+static int __init dynamic_debug_init(void)
+{
+	struct _ddebug *iter, *iter_start;
+	const char *modname = NULL;
+	int ret = 0;
+	int n = 0;
+
 	if (__start___verbose != __stop___verbose) {
 		iter = __start___verbose;
 		modname = iter->modname;
@@ -795,11 +806,13 @@ static int __init dynamic_debug_init(voi
 	}
 
 out_free:
-	if (ret) {
+	if (ret)
 		ddebug_remove_all_tables();
-		debugfs_remove(dir);
-		debugfs_remove(file);
-	}
+	else
+		ddebug_init_success = 1;
 	return 0;
 }
-module_init(dynamic_debug_init);
+/* Allow early initialization for boot messages via boot param */
+arch_initcall(dynamic_debug_init);
+/* Debugfs setup must be done later */
+module_init(dynamic_debug_init_debugfs);