x86: Export x86 boot_params to sysfs

kexec-tools use boot_params for getting the 1st kernel hardware_subarch,
the kexec kernel EFI runtime support also needs to 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 "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)*/

Signed-off-by: Dave Young <dyoung@redhat.com>
Acked-by: Borislav Petkov <bp@suse.de>
Tested-by: Toshi Kani <toshi.kani@hp.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>

3 files changed, 378 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-kernel-boot_params b/Documentation/ABI/testing/sysfs-kernel-boot_params
new file mode 100644
index 000000000000..eca38ce2852d
--- /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@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 9b0a34e2cd79..510cca5c5390 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 000000000000..eb53d153f307
--- /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@intel.com>
+ * Copyright (C) 2013, 2013 Red Hat, Inc.
+ *      Dave Young <dyoung@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);