[Patch] firmware: dmi_scan: split dmisubsystem from dmi-sysfs

From: Ivan Khoronzhuk
Date: Mon Mar 16 2015 - 16:58:00 EST

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 subsystem 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 were
proposed by Jean Delvare.

Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@xxxxxxxxxxxxxxx>
---

This patch is logical continuation of
"[dmidecode] [Patch v4] firmware: dmi-sysfs: add SMBIOS entry point area attribute"
https://lkml.org/lkml/2015/2/4/475

Pay attention that this includes /sys/firmware/dmi for holding tables instead of
/sys/firmware/dmi/table as were proposed.

Documentation/ABI/testing/sysfs-firmware-dmi | 122 +++------------------
.../ABI/testing/sysfs-firmware-dmi-entries | 110 +++++++++++++++++++
drivers/firmware/dmi-sysfs.c | 12 +-
drivers/firmware/dmi_scan.c | 115 +++++++++++++++++--
include/linux/dmi.h | 2 +
5 files changed, 238 insertions(+), 123 deletions(-)
create mode 100644 Documentation/ABI/testing/sysfs-firmware-dmi-entries

diff --git a/Documentation/ABI/testing/sysfs-firmware-dmi b/Documentation/ABI/testing/sysfs-firmware-dmi
index c78f9ab..6413128 100644
--- a/Documentation/ABI/testing/sysfs-firmware-dmi
+++ b/Documentation/ABI/testing/sysfs-firmware-dmi
@@ -1,110 +1,16 @@
What: /sys/firmware/dmi/
-Date: February 2011
-Contact: Mike Waychison <mikew@xxxxxxxxxx>
+Date: March 2015
+Contact: Ivan Khoronzhuk <ivan.khoronzhuk@xxxxxxxxxxxxxxx>
Description:
- Many machines' firmware (x86 and ia64) export DMI /
- SMBIOS tables to the operating system. Getting at this
- information is often valuable to userland, especially in
- cases where there are OEM extensions used.
-
- The kernel itself does not rely on the majority of the
- information in these tables being correct. It equally
- cannot ensure that the data as exported to userland is
- without error either.
-
- DMI is structured as a large table of entries, where
- each entry has a common header indicating the type and
- length of the entry, as well as a firmware-provided
- 'handle' that is supposed to be unique amongst all
- entries.
-
- Some entries are required by the specification, but many
- others are optional. In general though, users should
- never expect to find a specific entry type on their
- system unless they know for certain what their firmware
- is doing. Machine to machine experiences will vary.
-
- Multiple entries of the same type are allowed. In order
- to handle these duplicate entry types, each entry is
- assigned by the operating system an 'instance', which is
- derived from an entry type's ordinal position. That is
- to say, if there are 'N' multiple entries with the same type
- 'T' in the DMI tables (adjacent or spread apart, it
- doesn't matter), they will be represented in sysfs as
- entries "T-0" through "T-(N-1)":
-
- Example entry directories:
-
- /sys/firmware/dmi/entries/17-0
- /sys/firmware/dmi/entries/17-1
- /sys/firmware/dmi/entries/17-2
- /sys/firmware/dmi/entries/17-3
- ...
-
- Instance numbers are used in lieu of the firmware
- assigned entry handles as the kernel itself makes no
- guarantees that handles as exported are unique, and
- there are likely firmware images that get this wrong in
- the wild.
-
- Each DMI entry in sysfs has the common header values
- exported as attributes:
-
- handle : The 16bit 'handle' that is assigned to this
- entry by the firmware. This handle may be
- referred to by other entries.
- length : The length of the entry, as presented in the
- entry itself. Note that this is _not the
- total count of bytes associated with the
- entry_. This value represents the length of
- the "formatted" portion of the entry. This
- "formatted" region is sometimes followed by
- the "unformatted" region composed of nul
- terminated strings, with termination signalled
- by a two nul characters in series.
- raw : The raw bytes of the entry. This includes the
- "formatted" portion of the entry, the
- "unformatted" strings portion of the entry,
- and the two terminating nul characters.
- type : The type of the entry. This value is the same
- as found in the directory name. It indicates
- how the rest of the entry should be interpreted.
- instance: The instance ordinal of the entry for the
- given type. This value is the same as found
- in the parent directory name.
- position: The ordinal position (zero-based) of the entry
- within the entirety of the DMI entry table.
-
- === Entry Specialization ===
-
- Some entry types may have other information available in
- sysfs. Not all types are specialized.
-
- --- Type 15 - System Event Log ---
-
- This entry allows the firmware to export a log of
- events the system has taken. This information is
- typically backed by nvram, but the implementation
- details are abstracted by this table. This entry's data
- is exported in the directory:
-
- /sys/firmware/dmi/entries/15-0/system_event_log
-
- and has the following attributes (documented in the
- SMBIOS / DMI specification under "System Event Log (Type 15)":
-
- area_length
- header_start_offset
- data_start_offset
- access_method
- status
- change_token
- access_method_address
- header_format
- per_log_type_descriptor_length
- type_descriptors_supported_count
-
- As well, the kernel exports the binary attribute:
-
- raw_event_log : The raw binary bits of the event log
- as described by the DMI entry.
+ 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.
+ That's why SMBIOS entry point is represented in dmi sysfs
+ like a raw attribute and is accessible via
+ /sys/firmware/dmi/smbios_entry_point. The format of SMBIOS
+ entry point header can be read in SMBIOS specification.
+ To simplify access and processing delay in user space,
+ subsystem provides also raw dmi table under
+ /sys/firmware/dmi/dmi_table.
diff --git a/Documentation/ABI/testing/sysfs-firmware-dmi-entries b/Documentation/ABI/testing/sysfs-firmware-dmi-entries
new file mode 100644
index 0000000..c3b4d4c
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-firmware-dmi-entries
@@ -0,0 +1,110 @@
+What: /sys/firmware/dmi/entries
+Date: February 2011
+Contact: Mike Waychison <mikew@xxxxxxxxxx>
+Description:
+ Many machines' firmware (x86 and ia64) export DMI /
+ SMBIOS tables to the operating system. Getting at this
+ information is often valuable to userland, especially in
+ cases where there are OEM extensions used.
+
+ The kernel itself does not rely on the majority of the
+ information in these tables being correct. It equally
+ cannot ensure that the data as exported to userland is
+ without error either.
+
+ DMI is structured as a large table of entries, where
+ each entry has a common header indicating the type and
+ length of the entry, as well as a firmware-provided
+ 'handle' that is supposed to be unique amongst all
+ entries.
+
+ Some entries are required by the specification, but many
+ others are optional. In general though, users should
+ never expect to find a specific entry type on their
+ system unless they know for certain what their firmware
+ is doing. Machine to machine experiences will vary.
+
+ Multiple entries of the same type are allowed. In order
+ to handle these duplicate entry types, each entry is
+ assigned by the operating system an 'instance', which is
+ derived from an entry type's ordinal position. That is
+ to say, if there are 'N' multiple entries with the same type
+ 'T' in the DMI tables (adjacent or spread apart, it
+ doesn't matter), they will be represented in sysfs as
+ entries "T-0" through "T-(N-1)":
+
+ Example entry directories:
+
+ /sys/firmware/dmi/entries/17-0
+ /sys/firmware/dmi/entries/17-1
+ /sys/firmware/dmi/entries/17-2
+ /sys/firmware/dmi/entries/17-3
+ ...
+
+ Instance numbers are used in lieu of the firmware
+ assigned entry handles as the kernel itself makes no
+ guarantees that handles as exported are unique, and
+ there are likely firmware images that get this wrong in
+ the wild.
+
+ Each DMI entry in sysfs has the common header values
+ exported as attributes:
+
+ handle : The 16bit 'handle' that is assigned to this
+ entry by the firmware. This handle may be
+ referred to by other entries.
+ length : The length of the entry, as presented in the
+ entry itself. Note that this is _not the
+ total count of bytes associated with the
+ entry_. This value represents the length of
+ the "formatted" portion of the entry. This
+ "formatted" region is sometimes followed by
+ the "unformatted" region composed of nul
+ terminated strings, with termination signalled
+ by a two nul characters in series.
+ raw : The raw bytes of the entry. This includes the
+ "formatted" portion of the entry, the
+ "unformatted" strings portion of the entry,
+ and the two terminating nul characters.
+ type : The type of the entry. This value is the same
+ as found in the directory name. It indicates
+ how the rest of the entry should be interpreted.
+ instance: The instance ordinal of the entry for the
+ given type. This value is the same as found
+ in the parent directory name.
+ position: The ordinal position (zero-based) of the entry
+ within the entirety of the DMI entry table.
+
+ === Entry Specialization ===
+
+ Some entry types may have other information available in
+ sysfs. Not all types are specialized.
+
+ --- Type 15 - System Event Log ---
+
+ This entry allows the firmware to export a log of
+ events the system has taken. This information is
+ typically backed by nvram, but the implementation
+ details are abstracted by this table. This entry's data
+ is exported in the directory:
+
+ /sys/firmware/dmi/entries/15-0/system_event_log
+
+ and has the following attributes (documented in the
+ SMBIOS / DMI specification under "System Event Log (Type 15)":
+
+ area_length
+ header_start_offset
+ data_start_offset
+ access_method
+ status
+ change_token
+ access_method_address
+ header_format
+ per_log_type_descriptor_length
+ type_descriptors_supported_count
+
+ As well, the kernel exports the binary attribute:
+
+ raw_event_log : The raw binary bits of the event log
+ as described by the DMI entry.
diff --git a/drivers/firmware/dmi-sysfs.c b/drivers/firmware/dmi-sysfs.c
index e0f1cb3..390067d 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 +650,10 @@ 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)
- goto err;
+ if (!dmi_kobj) {
+ pr_err("dmi-sysfs: dmi subsysterm is absent.\n");
+ return -EINVAL;
+ }

dmi_kset = kset_create_and_add("entries", NULL, dmi_kobj);
if (!dmi_kset)
@@ -675,7 +674,6 @@ static int __init dmi_sysfs_init(void)
err:
cleanup_entry_list();
kset_unregister(dmi_kset);
- kobject_put(dmi_kobj);
return error;
}

@@ -685,8 +683,6 @@ 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 c9cb725..3fca52a 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_table(u8 *buf,
}

static phys_addr_t dmi_base;
+static u8 *dmi_tb;

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 +517,8 @@ 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, 15);
dmi_ver = (buf[14] & 0xF0) << 4 |
(buf[14] & 0x0F);
pr_info("Legacy DMI %d.%d present.\n",
@@ -535,6 +546,8 @@ 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 +651,95 @@ void __init dmi_scan_machine(void)
dmi_initialized = 1;
}

+static ssize_t smbios_entry_point_read(struct file *filp,
+ struct kobject *kobj,
+ struct bin_attribute *bin_attr,
+ char *buf, loff_t pos, size_t count)
+{
+ ssize_t size;
+
+ size = bin_attr->size;
+
+ if (size > pos)
+ size -= pos;
+ else
+ return 0;
+
+ if (count < size)
+ size = count;
+
+ memcpy(buf, &smbios_entry_point[pos], size);
+
+ return size;
+}
+
+static ssize_t dmi_table_read(struct file *filp,
+ struct kobject *kobj,
+ struct bin_attribute *bin_attr,
+ char *buf, loff_t pos, size_t count)
+{
+ ssize_t size;
+
+ size = bin_attr->size;
+
+ if (size > pos)
+ size -= pos;
+ else
+ return 0;
+
+ if (count < size)
+ size = count;
+
+ memcpy(buf, &dmi_tb[pos], size);
+
+ return size;
+}
+
+BIN_ATTR_RO(dmi_table, 0);
+BIN_ATTR_RO(smbios_entry_point, 0);
+
+/*
+ * Register the dmi subsystem under the firmware subsysterm
+ */
+static int __init dmisubsys_init(void)
+{
+ int ret = -ENOMEM;
+
+ if (!smbios_entry_point_size || !dmi_available) {
+ ret = -EINVAL;
+ goto err;
+ }
+
+ /* Set up dmi directory at /sys/firmware/dmi */
+ dmi_kobj = kobject_create_and_add("dmi", firmware_kobj);
+ if (!dmi_kobj)
+ goto err;
+
+ bin_attr_smbios_entry_point.size = smbios_entry_point_size;
+ ret = sysfs_create_bin_file(dmi_kobj, &bin_attr_smbios_entry_point);
+ if (ret)
+ goto err;
+
+ if (!dmi_tb) {
+ dmi_tb = dmi_remap(dmi_base, dmi_len);
+ if (!dmi_tb)
+ goto err;
+ }
+
+ bin_attr_dmi_table.size = dmi_len;
+ ret = sysfs_create_bin_file(dmi_kobj, &bin_attr_dmi_table);
+ if (ret)
+ goto err;
+
+ return 0;
+err:
+ pr_err("dmi: Firmware registration failed.\n");
+ kobject_del(dmi_kobj);
+ kobject_put(dmi_kobj);
+ return ret;
+}
+subsys_initcall(dmisubsys_init);
+
/**
* dmi_set_dump_stack_arch_desc - set arch description for dump_stack()
*
@@ -897,18 +999,17 @@ EXPORT_SYMBOL(dmi_get_date);
int dmi_walk(void (*decode)(const struct dmi_header *, void *),
void *private_data)
{
- u8 *buf;
-
if (!dmi_available)
return -1;

- buf = dmi_remap(dmi_base, dmi_len);
- if (buf == NULL)
- return -1;
+ if (!dmi_tb) {
+ dmi_tb = dmi_remap(dmi_base, dmi_len);
+ if (!dmi_tb)
+ return -1;
+ }

- dmi_table(buf, decode, private_data);
+ dmi_table(dmi_tb, decode, private_data);

- dmi_unmap(buf);
return 0;
}
EXPORT_SYMBOL_GPL(dmi_walk);
diff --git a/include/linux/dmi.h b/include/linux/dmi.h
index f820f0a..316293e 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);
@@ -112,6 +113,7 @@ extern void dmi_memdev_name(u16 handle, const char **bank, const char **device);

#else

+extern struct kobject *dmi_kobj;
static inline int dmi_check_system(const struct dmi_system_id *list) { return 0; }
static inline const char * dmi_get_system_info(int field) { return NULL; }
static inline const struct dmi_device * dmi_find_device(int type, const char *name,
--
1.9.1

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