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Subject[PATCH -mm -v3] x86 boot : export boot_params via sysfs
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Date
This patch export the boot parameters via sysfs. This can be used for
debugging and kexec.

The files added are as follow:

/sys/kernel/boot_params/data : binary file for struct boot_params
/sys/kernel/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 platoform.

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


v3:

- Use updated API: kobject_create_and_add.

v2:

- Add document in Document/ABI.


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

---
Documentation/ABI/testing/sysfs-kernel-boot_params | 14 +++
arch/x86/kernel/Makefile_32 | 1
arch/x86/kernel/Makefile_64 | 1
arch/x86/kernel/ksysfs.c | 88 +++++++++++++++++++++
arch/x86/kernel/setup64.c | 2
arch/x86/kernel/setup_32.c | 2
6 files changed, 106 insertions(+), 2 deletions(-)
--- a/arch/x86/kernel/Makefile_64
+++ b/arch/x86/kernel/Makefile_64
@@ -40,6 +40,7 @@ obj-$(CONFIG_X86_VSMP) += vsmp_64.o
obj-$(CONFIG_K8_NB) += k8.o
obj-$(CONFIG_AUDIT) += audit_64.o
obj-$(CONFIG_EFI) += efi.o efi_64.o efi_stub_64.o
+obj-$(CONFIG_SYSFS) += ksysfs.o

obj-$(CONFIG_MODULES) += module_64.o
obj-$(CONFIG_PCI) += early-quirks.o
--- a/arch/x86/kernel/setup64.c
+++ b/arch/x86/kernel/setup64.c
@@ -24,7 +24,7 @@
#include <asm/sections.h>
#include <asm/setup.h>

-struct boot_params __initdata boot_params;
+struct boot_params boot_params;

cpumask_t cpu_initialized __cpuinitdata = CPU_MASK_NONE;

--- /dev/null
+++ b/arch/x86/kernel/ksysfs.c
@@ -0,0 +1,88 @@
+/*
+ * Architecture specific sysfs attributes in /sys/kernel
+ *
+ * Copyright (C) 2007, Intel Corp.
+ * Huang Ying <ying.huang@intel.com>
+ *
+ * This file is released under the GPLv2
+ */
+
+#include <linux/kobject.h>
+#include <linux/string.h>
+#include <linux/sysfs.h>
+#include <linux/init.h>
+#include <linux/stat.h>
+#include <linux/mm.h>
+
+#include <asm/setup.h>
+
+static ssize_t boot_params_version_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "0x%04x\n", boot_params.hdr.version);
+}
+
+static struct kobj_attribute boot_params_version_attr =
+ __ATTR(version, S_IRUGO, boot_params_version_show, NULL);
+
+static struct attribute *boot_params_attrs[] = {
+ &boot_params_version_attr.attr,
+ NULL
+};
+
+static struct attribute_group boot_params_attr_group = {
+ .attrs = boot_params_attrs,
+};
+
+static ssize_t boot_params_data_read(struct kobject *kobj,
+ struct bin_attribute *bin_attr,
+ char *buf, loff_t off, size_t count)
+{
+ memcpy(buf, (void *)&boot_params + off, count);
+ return count;
+}
+
+static struct bin_attribute boot_params_data_attr = {
+ .attr = {
+ .name = "data",
+ .mode = S_IRUGO,
+ },
+ .read = boot_params_data_read,
+ .size = sizeof(boot_params),
+};
+
+static int __init boot_params_ksysfs_init(void)
+{
+ int error;
+ struct kobject *boot_params_kobj;
+
+ boot_params_kobj = kobject_create_and_add("boot_params", kernel_kobj);
+ if (!boot_params_kobj) {
+ error = -ENOMEM;
+ goto err_return;
+ }
+ error = sysfs_create_group(boot_params_kobj,
+ &boot_params_attr_group);
+ if (error)
+ goto err_boot_params_subsys_unregister;
+ error = sysfs_create_bin_file(boot_params_kobj,
+ &boot_params_data_attr);
+ if (error)
+ goto err_boot_params_subsys_unregister;
+ return 0;
+err_boot_params_subsys_unregister:
+ kobject_unregister(boot_params_kobj);
+err_return:
+ return error;
+}
+
+static int __init arch_ksysfs_init(void)
+{
+ int error;
+
+ error = boot_params_ksysfs_init();
+
+ return error;
+}
+
+arch_initcall(arch_ksysfs_init);
--- a/arch/x86/kernel/Makefile_32
+++ b/arch/x86/kernel/Makefile_32
@@ -45,6 +45,7 @@ obj-$(CONFIG_EARLY_PRINTK) += early_prin
obj-$(CONFIG_HPET_TIMER) += hpet.o
obj-$(CONFIG_K8_NB) += k8.o
obj-$(CONFIG_MGEODE_LX) += geode_32.o mfgpt_32.o
+obj-$(CONFIG_SYSFS) += ksysfs.o

obj-$(CONFIG_VMI) += vmi_32.o vmiclock_32.o
obj-$(CONFIG_PARAVIRT) += paravirt_32.o
--- a/arch/x86/kernel/setup_32.c
+++ b/arch/x86/kernel/setup_32.c
@@ -194,7 +194,7 @@ unsigned long saved_videomode;

static char __initdata command_line[COMMAND_LINE_SIZE];

-struct boot_params __initdata boot_params;
+struct boot_params boot_params;

#if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE)
struct edd edd;
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-kernel-boot_params
@@ -0,0 +1,14 @@
+What: /sys/kernel/boot_params
+Date: December 2007
+Contact: Huang Ying <ying.huang@intel.com>
+Description:
+ The /sys/kernel/boot_params directory contains two
+ files: "data" and "version". It is used to export the
+ kernel boot parameters of x86 platform to user space
+ for debugging and kexec. The "data" file is the binary
+ representation of struct boot_params. The "version"
+ file is the string representation of boot protocol
+ version.
+
+Users:
+ Kexec Mailing List <kexec@lists.infradead.org>


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