x86 boot : export boot_params via debugfs for debugging

This patch export the boot parameters via debugfs for debugging.

The files added are as follow:

boot_params/data    :  binary file for struct boot_params
boot_params/version :  boot protocol version

This patch is based on 2.6.24-rc5-mm1 and has been tested on i386 and
x86_64 platform.

This patch is based on the Peter Anvin's proposal.

Signed-off-by: Huang Ying <ying.huang@intel.com>

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/Kconfig.debug

@@ -185,4 +185,11 @@ config DEFAULT_IO_DELAY_TYPE
 	default IO_DELAY_TYPE_NONE
 endif
 
+config DEBUG_BOOT_PARAMS
+	bool "Debug boot parameters"
+	depends on DEBUG_KERNEL
+	depends on DEBUG_FS
+	help
+	  This option will cause struct boot_params to be exported via debugfs.
+
 endmenu

arch/x86/kernel/Makefile

@@ -16,7 +16,7 @@ obj-$(CONFIG_X86_32)	+= sys_i386_32.o i386_ksyms_32.o
 obj-$(CONFIG_X86_64)	+= sys_x86_64.o x8664_ksyms_64.o
 obj-$(CONFIG_X86_64)	+= syscall_64.o vsyscall_64.o setup64.o
 obj-y			+= pci-dma_$(BITS).o  bootflag.o e820_$(BITS).o
-obj-y			+= quirks.o i8237.o topology.o
+obj-y			+= quirks.o i8237.o topology.o kdebugfs.o
 obj-y			+= alternative.o i8253.o
 obj-$(CONFIG_X86_64)	+= pci-nommu_64.o bugs_64.o
 obj-y			+= tsc_$(BITS).o io_delay.o rtc.o

arch/x86/kernel/kdebugfs.c

@@ -0,0 +1,65 @@
+/*
+ * Architecture specific debugfs files
+ *
+ * Copyright (C) 2007, Intel Corp.
+ *	Huang Ying <ying.huang@intel.com>
+ *
+ * This file is released under the GPLv2.
+ */
+
+#include <linux/debugfs.h>
+#include <linux/stat.h>
+#include <linux/init.h>
+
+#include <asm/setup.h>
+
+#ifdef CONFIG_DEBUG_BOOT_PARAMS
+static struct debugfs_blob_wrapper boot_params_blob = {
+	.data = &boot_params,
+	.size = sizeof(boot_params),
+};
+
+static int __init boot_params_kdebugfs_init(void)
+{
+	int error;
+	struct dentry *dbp, *version, *data;
+
+	dbp = debugfs_create_dir("boot_params", NULL);
+	if (!dbp) {
+		error = -ENOMEM;
+		goto err_return;
+	}
+	version = debugfs_create_x16("version", S_IRUGO, dbp,
+				     &boot_params.hdr.version);
+	if (!version) {
+		error = -ENOMEM;
+		goto err_dir;
+	}
+	data = debugfs_create_blob("data", S_IRUGO, dbp,
+				   &boot_params_blob);
+	if (!data) {
+		error = -ENOMEM;
+		goto err_version;
+	}
+	return 0;
+err_version:
+	debugfs_remove(version);
+err_dir:
+	debugfs_remove(dbp);
+err_return:
+	return error;
+}
+#endif
+
+static int __init arch_kdebugfs_init(void)
+{
+	int error = 0;
+
+#ifdef CONFIG_DEBUG_BOOT_PARAMS
+	error = boot_params_kdebugfs_init();
+#endif
+
+	return error;
+}
+
+arch_initcall(arch_kdebugfs_init);

arch/x86/kernel/setup64.c

@@ -24,7 +24,11 @@
 #include <asm/sections.h>
 #include <asm/setup.h>
 
+#ifndef CONFIG_DEBUG_BOOT_PARAMS
 struct boot_params __initdata boot_params;
+#else
+struct boot_params boot_params;
+#endif
 
 cpumask_t cpu_initialized __cpuinitdata = CPU_MASK_NONE;
 

arch/x86/kernel/setup_32.c

@@ -194,7 +194,11 @@ unsigned long saved_videomode;
 
 static char __initdata command_line[COMMAND_LINE_SIZE];
 
+#ifndef CONFIG_DEBUG_BOOT_PARAMS
 struct boot_params __initdata boot_params;
+#else
+struct boot_params boot_params;
+#endif
 
 #if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE)
 struct edd edd;