sysfs: add /sys/firmware/memmap

This patch adds /sys/firmware/memmap interface that represents the BIOS
(or Firmware) provided memory map. The tree looks like:

    /sys/firmware/memmap/0/start   (hex number)
                           end     (hex number)
                           type    (string)
    ...                 /1/start
                           end
                           type

With the following shell snippet one can print the memory map in the same form
the kernel prints itself when booting on x86 (the E820 map).

  --------- 8< --------------------------
    #!/bin/sh
    cd /sys/firmware/memmap
    for dir in * ; do
        start=$(cat $dir/start)
        end=$(cat $dir/end)
        type=$(cat $dir/type)
        printf "%016x-%016x (%s)\n" $start $[ $end +1] "$type"
    done
  --------- >8 --------------------------

That patch only provides the needed interface:

 1. The sysfs interface.
 2. The structure and enumeration definition.
 3. The function firmware_map_add() and firmware_map_add_early()
    that should be called from architecture code (E820/EFI, for
    example) to add the contents to the interface.

If the kernel is compiled without CONFIG_FIRMWARE_MEMMAP, the interface does
nothing without cluttering the architecture-specific code with #ifdef's.

The purpose of the new interface is kexec: While /proc/iomem represents
the *used* memory map (e.g. modified via kernel parameters like 'memmap'
and 'mem'), the /sys/firmware/memmap tree represents the unmodified memory
map provided via the firmware. So kexec can:

 - use the original memory map for rebooting,
 - use the /proc/iomem for setting up the ELF core headers for kdump
   case that should only represent the memory of the system.

The patch has been tested on i386 and x86_64.

Signed-off-by: Bernhard Walle <bwalle@suse.de>
Acked-by: Greg KH <gregkh@suse.de>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Cc: kexec@lists.infradead.org
Cc: yhlu.kernel@gmail.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

3 files changed, 216 insertions, 0 deletions

diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
index dc2cec6127d1..ebb9e51deb0c 100644
--- a/drivers/firmware/Kconfig
+++ b/drivers/firmware/Kconfig
@@ -26,6 +26,16 @@ config EDD_OFF
           kernel. Say N if you want EDD enabled by default. EDD can be dynamically set
           using the kernel parameter 'edd={on|skipmbr|off}'.
 
+config FIRMWARE_MEMMAP
+    bool "Add firmware-provided memory map to sysfs" if EMBEDDED
+    default (X86_64 || X86_32)
+    help
+      Add the firmware-provided (unmodified) memory map to /sys/firmware/memmap.
+      That memory map is used for example by kexec to set up parameter area
+      for the next kernel, but can also be used for debugging purposes.
+
+      See also Documentation/ABI/testing/sysfs-firmware-memmap.
+
 config EFI_VARS
         tristate "EFI Variable Support via sysfs"
         depends on EFI
diff --git a/drivers/firmware/Makefile b/drivers/firmware/Makefile
index 4c9147154df8..1c3c17343dbe 100644
--- a/drivers/firmware/Makefile
+++ b/drivers/firmware/Makefile
@@ -10,3 +10,4 @@ obj-$(CONFIG_DCDBAS)		+= dcdbas.o
 obj-$(CONFIG_DMIID)             += dmi-id.o
 obj-$(CONFIG_ISCSI_IBFT_FIND)   += iscsi_ibft_find.o
 obj-$(CONFIG_ISCSI_IBFT)        += iscsi_ibft.o
+obj-$(CONFIG_FIRMWARE_MEMMAP)   += memmap.o
diff --git a/drivers/firmware/memmap.c b/drivers/firmware/memmap.c
new file mode 100644
index 000000000000..e23399c7f773
--- /dev/null
+++ b/drivers/firmware/memmap.c
@@ -0,0 +1,205 @@
+/*
+ * linux/drivers/firmware/memmap.c
+ *  Copyright (C) 2008 SUSE LINUX Products GmbH
+ *  by Bernhard Walle <bwalle@suse.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License v2.0 as published by
+ * the Free Software Foundation
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/string.h>
+#include <linux/firmware-map.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/bootmem.h>
+
+/*
+ * Data types ------------------------------------------------------------------
+ */
+
+/*
+ * Firmware map entry. Because firmware memory maps are flat and not
+ * hierarchical, it's ok to organise them in a linked list. No parent
+ * information is necessary as for the resource tree.
+ */
+struct firmware_map_entry {
+        resource_size_t         start;  /* start of the memory range */
+        resource_size_t         end;    /* end of the memory range (incl.) */
+        const char              *type;  /* type of the memory range */
+        struct list_head        list;   /* entry for the linked list */
+        struct kobject          kobj;   /* kobject for each entry */
+};
+
+/*
+ * Forward declarations --------------------------------------------------------
+ */
+static ssize_t memmap_attr_show(struct kobject *kobj,
+                                struct attribute *attr, char *buf);
+static ssize_t start_show(struct firmware_map_entry *entry, char *buf);
+static ssize_t end_show(struct firmware_map_entry *entry, char *buf);
+static ssize_t type_show(struct firmware_map_entry *entry, char *buf);
+
+/*
+ * Static data -----------------------------------------------------------------
+ */
+
+struct memmap_attribute {
+        struct attribute attr;
+        ssize_t (*show)(struct firmware_map_entry *entry, char *buf);
+};
+
+struct memmap_attribute memmap_start_attr = __ATTR_RO(start);
+struct memmap_attribute memmap_end_attr   = __ATTR_RO(end);
+struct memmap_attribute memmap_type_attr  = __ATTR_RO(type);
+
+/*
+ * These are default attributes that are added for every memmap entry.
+ */
+static struct attribute *def_attrs[] = {
+        &memmap_start_attr.attr,
+        &memmap_end_attr.attr,
+        &memmap_type_attr.attr,
+        NULL
+};
+
+static struct sysfs_ops memmap_attr_ops = {
+        .show = memmap_attr_show,
+};
+
+static struct kobj_type memmap_ktype = {
+        .sysfs_ops      = &memmap_attr_ops,
+        .default_attrs  = def_attrs,
+};
+
+/*
+ * Registration functions ------------------------------------------------------
+ */
+
+/*
+ * Firmware memory map entries
+ */
+static LIST_HEAD(map_entries);
+
+/**
+ * Common implementation of firmware_map_add() and firmware_map_add_early()
+ * which expects a pre-allocated struct firmware_map_entry.
+ *
+ * @start: Start of the memory range.
+ * @end:   End of the memory range (inclusive).
+ * @type:  Type of the memory range.
+ * @entry: Pre-allocated (either kmalloc() or bootmem allocator), uninitialised
+ *         entry.
+ */
+static int firmware_map_add_entry(resource_size_t start, resource_size_t end,
+                                  const char *type,
+                                  struct firmware_map_entry *entry)
+{
+        BUG_ON(start > end);
+
+        entry->start = start;
+        entry->end = end;
+        entry->type = type;
+        INIT_LIST_HEAD(&entry->list);
+        kobject_init(&entry->kobj, &memmap_ktype);
+
+        list_add_tail(&entry->list, &map_entries);
+
+        return 0;
+}
+
+/*
+ * See <linux/firmware-map.h> for documentation.
+ */
+int firmware_map_add(resource_size_t start, resource_size_t end,
+                     const char *type)
+{
+        struct firmware_map_entry *entry;
+
+        entry = kmalloc(sizeof(struct firmware_map_entry), GFP_ATOMIC);
+        WARN_ON(!entry);
+        if (!entry)
+                return -ENOMEM;
+
+        return firmware_map_add_entry(start, end, type, entry);
+}
+
+/*
+ * See <linux/firmware-map.h> for documentation.
+ */
+int __init firmware_map_add_early(resource_size_t start, resource_size_t end,
+                                  const char *type)
+{
+        struct firmware_map_entry *entry;
+
+        entry = alloc_bootmem_low(sizeof(struct firmware_map_entry));
+        WARN_ON(!entry);
+        if (!entry)
+                return -ENOMEM;
+
+        return firmware_map_add_entry(start, end, type, entry);
+}
+
+/*
+ * Sysfs functions -------------------------------------------------------------
+ */
+
+static ssize_t start_show(struct firmware_map_entry *entry, char *buf)
+{
+        return snprintf(buf, PAGE_SIZE, "0x%llx\n", entry->start);
+}
+
+static ssize_t end_show(struct firmware_map_entry *entry, char *buf)
+{
+        return snprintf(buf, PAGE_SIZE, "0x%llx\n", entry->end);
+}
+
+static ssize_t type_show(struct firmware_map_entry *entry, char *buf)
+{
+        return snprintf(buf, PAGE_SIZE, "%s\n", entry->type);
+}
+
+#define to_memmap_attr(_attr) container_of(_attr, struct memmap_attribute, attr)
+#define to_memmap_entry(obj) container_of(obj, struct firmware_map_entry, kobj)
+
+static ssize_t memmap_attr_show(struct kobject *kobj,
+                                struct attribute *attr, char *buf)
+{
+        struct firmware_map_entry *entry = to_memmap_entry(kobj);
+        struct memmap_attribute *memmap_attr = to_memmap_attr(attr);
+
+        return memmap_attr->show(entry, buf);
+}
+
+/*
+ * Initialises stuff and adds the entries in the map_entries list to
+ * sysfs. Important is that firmware_map_add() and firmware_map_add_early()
+ * must be called before late_initcall.
+ */
+static int __init memmap_init(void)
+{
+        int i = 0;
+        struct firmware_map_entry *entry;
+        struct kset *memmap_kset;
+
+        memmap_kset = kset_create_and_add("memmap", NULL, firmware_kobj);
+        WARN_ON(!memmap_kset);
+        if (!memmap_kset)
+                return -ENOMEM;
+
+        list_for_each_entry(entry, &map_entries, list) {
+                entry->kobj.kset = memmap_kset;
+                kobject_add(&entry->kobj, NULL, "%d", i++);
+        }
+
+        return 0;
+}
+late_initcall(memmap_init);
+