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>

diff --git a/Documentation/ABI/testing/sysfs-kernel-boot_params b/Documentation/ABI/testing/sysfs-kernel-boot_params
new file mode 100644 (file)
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@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 (file)
--- 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 (file)
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@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);