[Patch 2/3] firmware: dmi_scan: add SBMIOS entry and DMI tables

Ivan Khoronzhuk
2015-04-02T12:57:02Z

Some utils, like dmidecode and smbios, need to access SMBIOS entry
table area in order to get information like SMBIOS version, size, etc.
Currently it's done via /dev/mem. But for situation when /dev/mem
usage is disabled, the utils have to use dmi sysfs instead, which
doesn't represent SMBIOS entry and adds code/delay redundancy when direct
access for table is needed.

So this patch creates dmi/tables and adds SMBIOS entry point to allow
utils in question to work correctly without /dev/mem. Also patch adds
raw dmi table to simplify dmi table processing in user space, as
proposed by Jean Delvare.

Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk-hExfYMNmJl/Cnp4W7fqMDg@public.gmane.org>
---
.../ABI/testing/sysfs-firmware-dmi-tables | 22 ++++++
drivers/firmware/dmi-sysfs.c | 11 ++-
drivers/firmware/dmi_scan.c | 80 ++++++++++++++++++++++
include/linux/dmi.h | 1 +
4 files changed, 107 insertions(+), 7 deletions(-)
create mode 100644 Documentation/ABI/testing/sysfs-firmware-dmi-tables

diff --git a/Documentation/ABI/testing/sysfs-firmware-dmi-tables b/Documentation/ABI/testing/sysfs-firmware-dmi-tables
new file mode 100644
index 0000000..f46158c
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-firmware-dmi-tables
@@ -0,0 +1,22 @@
+What: /sys/firmware/dmi/tables/
+Date: April 2015
+Contact: Ivan Khoronzhuk <ivan.khoronzhuk-hExfYMNmJl/Cnp4W7fqMDg@public.gmane.org>
+Description:
+ The firmware provides DMI structures as a packed list of
+ data referenced by a SMBIOS table entry point. The SMBIOS
+ entry point contains general information, like SMBIOS
+ version, DMI table size, etc. The structure, content and
+ size of SMBIOS entry point is dependent on SMBIOS version.
+ The format of SMBIOS entry point, equal as DMI structures
+ can be read in SMBIOS specification.
+
+ The dmi/tables provides raw SMBIOS entry point and DMI tables
+ through sysfs as an alternative to utilities reading them
+ from /dev/mem. The raw SMBIOS entry point and DMI table are
+ presented as raw attributes and are accessible via:
+
+ /sys/firmware/dmi/tables/smbios_entry_point
+ /sys/firmware/dmi/tables/DMI
+
+ The complete DMI information can be taken using these two
+ tables.
diff --git a/drivers/firmware/dmi-sysfs.c b/drivers/firmware/dmi-sysfs.c
index e0f1cb3..8e1a411 100644
--- a/drivers/firmware/dmi-sysfs.c
+++ b/drivers/firmware/dmi-sysfs.c
@@ -566,7 +566,6 @@ static struct kobj_type dmi_sysfs_entry_ktype = {
.default_attrs = dmi_sysfs_entry_attrs,
};

-static struct kobject *dmi_kobj;
static struct kset *dmi_kset;

/* Global count of all instances seen. Only for setup */
@@ -651,10 +650,11 @@ static int __init dmi_sysfs_init(void)
int error = -ENOMEM;
int val;

- /* Set up our directory */
- dmi_kobj = kobject_create_and_add("dmi", firmware_kobj);
- if (!dmi_kobj)
+ if (!dmi_kobj) {
+ pr_err("dmi-sysfs: dmi entry is absent.\n");
+ error = -ENOSYS;
goto err;
+ }

dmi_kset = kset_create_and_add("entries", NULL, dmi_kobj);
if (!dmi_kset)
@@ -675,7 +675,6 @@ static int __init dmi_sysfs_init(void)
err:
cleanup_entry_list();
kset_unregister(dmi_kset);
- kobject_put(dmi_kobj);
return error;
}

@@ -685,8 +684,6 @@ static void __exit dmi_sysfs_exit(void)
pr_debug("dmi-sysfs: unloading.\n");
cleanup_entry_list();
kset_unregister(dmi_kset);
- kobject_del(dmi_kobj);
- kobject_put(dmi_kobj);
}

module_init(dmi_sysfs_init);
diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
index d3aae09..bb19f8b 100644
--- a/drivers/firmware/dmi_scan.c
+++ b/drivers/firmware/dmi_scan.c
@@ -10,6 +10,9 @@
#include <asm/dmi.h>
#include <asm/unaligned.h>

+struct kobject *dmi_kobj;
+EXPORT_SYMBOL_GPL(dmi_kobj);
+
/*
* DMI stands for "Desktop Management Interface". It is part
* of and an antecedent to, SMBIOS, which stands for System
@@ -20,6 +23,9 @@ static const char dmi_empty_string[] = " ";
static u32 dmi_ver __initdata;
static u32 dmi_len;
static u16 dmi_num;
+static u8 smbios_entry_point[32];
+static int smbios_entry_point_size;
+
/*
* Catch too early calls to dmi_check_system():
*/
@@ -118,6 +124,7 @@ static void dmi_decode_table(u8 *buf,
}

static phys_addr_t dmi_base;
+static u8 *dmi_table;

static int __init dmi_walk_early(void (*decode)(const struct dmi_header *,
void *))
@@ -476,6 +483,8 @@ static int __init dmi_present(const u8 *buf)
if (memcmp(buf, "_SM_", 4) == 0 &&
buf[5] < 32 && dmi_checksum(buf, buf[5])) {
smbios_ver = get_unaligned_be16(buf + 6);
+ smbios_entry_point_size = buf[5];
+ memcpy(smbios_entry_point, buf, smbios_entry_point_size);

/* Some BIOS report weird SMBIOS version, fix that up */
switch (smbios_ver) {
@@ -508,6 +517,9 @@ static int __init dmi_present(const u8 *buf)
dmi_ver >> 8, dmi_ver & 0xFF,
(dmi_ver < 0x0300) ? "" : ".x");
} else {
+ smbios_entry_point_size = 15;
+ memcpy(smbios_entry_point, buf,
+ smbios_entry_point_size);
dmi_ver = (buf[14] & 0xF0) << 4 |
(buf[14] & 0x0F);
pr_info("Legacy DMI %d.%d present.\n",
@@ -535,6 +547,8 @@ static int __init dmi_smbios3_present(const u8 *buf)
dmi_ver &= 0xFFFFFF;
dmi_len = get_unaligned_le32(buf + 12);
dmi_base = get_unaligned_le64(buf + 16);
+ smbios_entry_point_size = buf[6];
+ memcpy(smbios_entry_point, buf, smbios_entry_point_size);

/*
* The 64-bit SMBIOS 3.0 entry point no longer has a field
@@ -638,6 +652,72 @@ void __init dmi_scan_machine(void)
dmi_initialized = 1;
}

+static ssize_t raw_table_read(struct file *file, struct kobject *kobj,
+ struct bin_attribute *attr, char *buf,
+ loff_t pos, size_t count)
+{
+ memcpy(buf, attr->private + pos, count);
+ return count;
+}
+
+static BIN_ATTR(smbios_entry_point, S_IRUSR, raw_table_read, NULL, 0);
+struct bin_attribute bin_attr_dmi_table =
+ __BIN_ATTR(DMI, S_IRUSR, raw_table_read, NULL, 0);
+
+static int __init dmi_init(void)
+{
+ int ret = -ENOMEM;
+ struct kobject *tables_kobj = NULL;
+
+ if (!dmi_available) {
+ ret = -ENOSYS;
+ goto err;
+ }
+
+ /* Set up dmi directory at /sys/firmware/dmi */
+ dmi_kobj = kobject_create_and_add("dmi", firmware_kobj);
+ if (!dmi_kobj)
+ goto err;
+
+ tables_kobj = kobject_create_and_add("tables", dmi_kobj);
+ if (!tables_kobj)
+ goto err;
+
+ bin_attr_smbios_entry_point.size = smbios_entry_point_size;
+ bin_attr_smbios_entry_point.private = smbios_entry_point;
+ ret = sysfs_create_bin_file(tables_kobj, &bin_attr_smbios_entry_point);
+ if (ret)
+ goto err;
+
+ dmi_table = dmi_remap(dmi_base, dmi_len);
+ if (!dmi_table)
+ goto err;
+
+ bin_attr_dmi_table.size = dmi_len;
+ bin_attr_dmi_table.private = dmi_table;
+ ret = sysfs_create_bin_file(tables_kobj, &bin_attr_dmi_table);
+ if (ret) {
+ dmi_unmap(dmi_table);
+ goto err;
+ }
+
+ return 0;
+err:
+ pr_err("dmi: Firmware registration failed.\n");
+
+ if (tables_kobj)
+ sysfs_remove_bin_file(tables_kobj,
+ &bin_attr_smbios_entry_point);
+ kobject_del(tables_kobj);
+ kobject_put(tables_kobj);
+ kobject_del(dmi_kobj);
+ kobject_put(dmi_kobj);
+ dmi_kobj = NULL;
+
+ return ret;
+}
+subsys_initcall(dmi_init);
+
/**
* dmi_set_dump_stack_arch_desc - set arch description for dump_stack()
*
diff --git a/include/linux/dmi.h b/include/linux/dmi.h
index f820f0a..9f55f46 100644
--- a/include/linux/dmi.h
+++ b/include/linux/dmi.h
@@ -93,6 +93,7 @@ struct dmi_dev_onboard {
int devfn;
};

+extern struct kobject *dmi_kobj;
extern int dmi_check_system(const struct dmi_system_id *list);
const struct dmi_system_id *dmi_first_match(const struct dmi_system_id *list);
extern const char * dmi_get_system_info(int field);
--
1.9.1