[PATCH v7 11/12] x86: export x86 boot_params to sysfs
Dave Young
dyoung at redhat.com
Fri Dec 20 05:02:21 EST 2013
kexec-tools use boot_params for getting the 1st kernel hardware_subarch,
the kexec kernel efi runtime support also need read the old efi_info from
boot_params. Currently it exists in debugfs which is not a good place for
such infomation. Per HPA, we should avoid of "sploit debugfs".
In this patch /sys/kernel/boot_params are exported, also the setup_data is
exported as a subdirectory. kexec-tools is using debugfs for hardware_subarch
for a long time now so we're not removing it yet.
Structure is like below:
/sys/kernel/boot_params
|__ data /* boot_params in binary*/
|__ setup_data
| |__ 0 /* the first setup_data node */
| | |__ data /* setup_data node 0 in binary*/
| | |__ type /* setup_data type of setup_data node 0, hex string */
[snip]
|__ version /* boot protocal version (in hex, "0x" prefixed)*/
Changelog:
Greg: use __ATTR_RO() and group attr.
Matt and Boris: Documentation improvement, code indentation.
Documentation fix.
Signed-off-by: Dave Young <dyoung at redhat.com>
Acked-by: Borislav Petkov <bp at suse.de>
---
Documentation/ABI/testing/sysfs-kernel-boot_params | 38 +++
arch/x86/kernel/Makefile | 1 +
arch/x86/kernel/ksysfs.c | 339 +++++++++++++++++++++
3 files changed, 378 insertions(+)
create mode 100644 Documentation/ABI/testing/sysfs-kernel-boot_params
create mode 100644 arch/x86/kernel/ksysfs.c
diff --git a/Documentation/ABI/testing/sysfs-kernel-boot_params b/Documentation/ABI/testing/sysfs-kernel-boot_params
new file mode 100644
index 0000000..eca38ce
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-kernel-boot_params
@@ -0,0 +1,38 @@
+What: /sys/kernel/boot_params
+Date: December 2013
+Contact: Dave Young <dyoung at redhat.com>
+Description: The /sys/kernel/boot_params directory contains two
+ files: "data" and "version" and one subdirectory "setup_data".
+ It is used to export the kernel boot parameters of an x86
+ platform to userspace for kexec and debugging purpose.
+
+ If there's no setup_data in boot_params the subdirectory will
+ not be created.
+
+ "data" file is the binary representation of struct boot_params.
+
+ "version" file is the string representation of boot
+ protocol version.
+
+ "setup_data" subdirectory contains the setup_data data
+ structure in boot_params. setup_data is maintained in kernel
+ as a link list. In "setup_data" subdirectory there's one
+ subdirectory for each link list node named with the number
+ of the list nodes. The list node subdirectory contains two
+ files "type" and "data". "type" file is the string
+ representation of setup_data type. "data" file is the binary
+ representation of setup_data payload.
+
+ The whole boot_params directory structure is like below:
+ /sys/kernel/boot_params
+ |__ data
+ |__ setup_data
+ | |__ 0
+ | | |__ data
+ | | |__ type
+ | |__ 1
+ | |__ data
+ | |__ type
+ |__ version
+
+Users: Kexec
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 9b0a34e..510cca5 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -29,6 +29,7 @@ obj-$(CONFIG_X86_64) += sys_x86_64.o x8664_ksyms_64.o
obj-y += syscall_$(BITS).o
obj-$(CONFIG_X86_64) += vsyscall_64.o
obj-$(CONFIG_X86_64) += vsyscall_emu_64.o
+obj-$(CONFIG_SYSFS) += ksysfs.o
obj-y += bootflag.o e820.o
obj-y += pci-dma.o quirks.o topology.o kdebugfs.o
obj-y += alternative.o i8253.o pci-nommu.o hw_breakpoint.o
diff --git a/arch/x86/kernel/ksysfs.c b/arch/x86/kernel/ksysfs.c
new file mode 100644
index 0000000..eb53d15
--- /dev/null
+++ b/arch/x86/kernel/ksysfs.c
@@ -0,0 +1,339 @@
+/*
+ * Architecture specific sysfs attributes in /sys/kernel
+ *
+ * Copyright (C) 2007, Intel Corp.
+ * Huang Ying <ying.huang at intel.com>
+ * Copyright (C) 2013, 2013 Red Hat, Inc.
+ * Dave Young <dyoung at redhat.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/slab.h>
+#include <linux/mm.h>
+
+#include <asm/setup.h>
+
+static ssize_t 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_RO(version);
+
+static ssize_t boot_params_data_read(struct file *fp, 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 struct attribute *boot_params_version_attrs[] = {
+ &boot_params_version_attr.attr,
+ NULL,
+};
+
+static struct bin_attribute *boot_params_data_attrs[] = {
+ &boot_params_data_attr,
+ NULL,
+};
+
+static struct attribute_group boot_params_attr_group = {
+ .attrs = boot_params_version_attrs,
+ .bin_attrs = boot_params_data_attrs,
+};
+
+static int kobj_to_setup_data_nr(struct kobject *kobj, int *nr)
+{
+ const char *name;
+
+ name = kobject_name(kobj);
+ return kstrtoint(name, 10, nr);
+}
+
+static int get_setup_data_paddr(int nr, u64 *paddr)
+{
+ int i = 0;
+ struct setup_data *data;
+ u64 pa_data = boot_params.hdr.setup_data;
+
+ while (pa_data) {
+ if (nr == i) {
+ *paddr = pa_data;
+ return 0;
+ }
+ data = ioremap_cache(pa_data, sizeof(*data));
+ if (!data)
+ return -ENOMEM;
+
+ pa_data = data->next;
+ iounmap(data);
+ i++;
+ }
+ return -EINVAL;
+}
+
+static int __init get_setup_data_size(int nr, size_t *size)
+{
+ int i = 0;
+ struct setup_data *data;
+ u64 pa_data = boot_params.hdr.setup_data;
+
+ while (pa_data) {
+ data = ioremap_cache(pa_data, sizeof(*data));
+ if (!data)
+ return -ENOMEM;
+ if (nr == i) {
+ *size = data->len;
+ iounmap(data);
+ return 0;
+ }
+
+ pa_data = data->next;
+ iounmap(data);
+ i++;
+ }
+ return -EINVAL;
+}
+
+static ssize_t type_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ int nr, ret;
+ u64 paddr;
+ struct setup_data *data;
+
+ ret = kobj_to_setup_data_nr(kobj, &nr);
+ if (ret)
+ return ret;
+
+ ret = get_setup_data_paddr(nr, &paddr);
+ if (ret)
+ return ret;
+ data = ioremap_cache(paddr, sizeof(*data));
+ if (!data)
+ return -ENOMEM;
+
+ ret = sprintf(buf, "0x%x\n", data->type);
+ iounmap(data);
+ return ret;
+}
+
+static ssize_t setup_data_data_read(struct file *fp,
+ struct kobject *kobj,
+ struct bin_attribute *bin_attr,
+ char *buf,
+ loff_t off, size_t count)
+{
+ int nr, ret = 0;
+ u64 paddr;
+ struct setup_data *data;
+ void *p;
+
+ ret = kobj_to_setup_data_nr(kobj, &nr);
+ if (ret)
+ return ret;
+
+ ret = get_setup_data_paddr(nr, &paddr);
+ if (ret)
+ return ret;
+ data = ioremap_cache(paddr, sizeof(*data));
+ if (!data)
+ return -ENOMEM;
+
+ if (off > data->len) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ if (count > data->len - off)
+ count = data->len - off;
+
+ if (!count)
+ goto out;
+
+ ret = count;
+ p = ioremap_cache(paddr + sizeof(*data), data->len);
+ if (!p) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ memcpy(buf, p + off, count);
+ iounmap(p);
+out:
+ iounmap(data);
+ return ret;
+}
+
+static struct kobj_attribute type_attr = __ATTR_RO(type);
+
+static struct bin_attribute data_attr = {
+ .attr = {
+ .name = "data",
+ .mode = S_IRUGO,
+ },
+ .read = setup_data_data_read,
+};
+
+static struct attribute *setup_data_type_attrs[] = {
+ &type_attr.attr,
+ NULL,
+};
+
+static struct bin_attribute *setup_data_data_attrs[] = {
+ &data_attr,
+ NULL,
+};
+
+static struct attribute_group setup_data_attr_group = {
+ .attrs = setup_data_type_attrs,
+ .bin_attrs = setup_data_data_attrs,
+};
+
+static int __init create_setup_data_node(struct kobject *parent,
+ struct kobject **kobjp, int nr)
+{
+ int ret = 0;
+ size_t size;
+ struct kobject *kobj;
+ char name[16]; /* should be enough for setup_data nodes numbers */
+ snprintf(name, 16, "%d", nr);
+
+ kobj = kobject_create_and_add(name, parent);
+ if (!kobj)
+ return -ENOMEM;
+
+ ret = get_setup_data_size(nr, &size);
+ if (ret)
+ goto out_kobj;
+
+ data_attr.size = size;
+ ret = sysfs_create_group(kobj, &setup_data_attr_group);
+ if (ret)
+ goto out_kobj;
+ *kobjp = kobj;
+
+ return 0;
+out_kobj:
+ kobject_put(kobj);
+ return ret;
+}
+
+static void __init cleanup_setup_data_node(struct kobject *kobj)
+{
+ sysfs_remove_group(kobj, &setup_data_attr_group);
+ kobject_put(kobj);
+}
+
+static int __init get_setup_data_total_num(u64 pa_data, int *nr)
+{
+ int ret = 0;
+ struct setup_data *data;
+
+ *nr = 0;
+ while (pa_data) {
+ *nr += 1;
+ data = ioremap_cache(pa_data, sizeof(*data));
+ if (!data) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ pa_data = data->next;
+ iounmap(data);
+ }
+
+out:
+ return ret;
+}
+
+static int __init create_setup_data_nodes(struct kobject *parent)
+{
+ struct kobject *setup_data_kobj, **kobjp;
+ u64 pa_data;
+ int i, j, nr, ret = 0;
+
+ pa_data = boot_params.hdr.setup_data;
+ if (!pa_data)
+ return 0;
+
+ setup_data_kobj = kobject_create_and_add("setup_data", parent);
+ if (!setup_data_kobj) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ ret = get_setup_data_total_num(pa_data, &nr);
+ if (ret)
+ goto out_setup_data_kobj;
+
+ kobjp = kmalloc(sizeof(*kobjp) * nr, GFP_KERNEL);
+ if (!kobjp) {
+ ret = -ENOMEM;
+ goto out_setup_data_kobj;
+ }
+
+ for (i = 0; i < nr; i++) {
+ ret = create_setup_data_node(setup_data_kobj, kobjp + i, i);
+ if (ret)
+ goto out_clean_nodes;
+ }
+
+ kfree(kobjp);
+ return 0;
+
+out_clean_nodes:
+ for (j = i - 1; j > 0; j--)
+ cleanup_setup_data_node(*(kobjp + j));
+ kfree(kobjp);
+out_setup_data_kobj:
+ kobject_put(setup_data_kobj);
+out:
+ return ret;
+}
+
+static int __init boot_params_ksysfs_init(void)
+{
+ int ret;
+ struct kobject *boot_params_kobj;
+
+ boot_params_kobj = kobject_create_and_add("boot_params",
+ kernel_kobj);
+ if (!boot_params_kobj) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ ret = sysfs_create_group(boot_params_kobj, &boot_params_attr_group);
+ if (ret)
+ goto out_boot_params_kobj;
+
+ ret = create_setup_data_nodes(boot_params_kobj);
+ if (ret)
+ goto out_create_group;
+
+ return 0;
+out_create_group:
+ sysfs_remove_group(boot_params_kobj, &boot_params_attr_group);
+out_boot_params_kobj:
+ kobject_put(boot_params_kobj);
+out:
+ return ret;
+}
+
+arch_initcall(boot_params_ksysfs_init);
--
1.8.3.1
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