[Patch v4] firmware: dmi-sysfs: add SMBIOS entry point area attribute
From: Ivan Khoronzhuk
Date: Wed Feb 04 2015 - 12:06:40 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. So this patch adds SMBIOS area to
dmi-sysfs in order to allow utils in question to work correctly with
dmi sysfs interface.
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@xxxxxxxxxx>
---
v1: https://lkml.org/lkml/2015/1/23/643
v2: https://lkml.org/lkml/2015/1/26/345
v3: https://lkml.org/lkml/2015/1/28/768
v4..v2:
firmware: dmi_scan: add symbol to get SMBIOS entry area
- used u8 type for smbios_header var
firmware: dmi-sysfs: add SMBIOS entry point area attribute
- replaced -ENODATA on -EINVAL
v3..v2:
firmware: dmi_scan: add symbol to get SMBIOS entry area
firmware: dmi-sysfs: add SMBIOS entry point area attribute
- combined in one patch
- added SMBIOS information to ABI sysfs-dmi documentaton
v2..v1:
firmware: dmi_scan: add symbol to get SMBIOS entry area
- used additional static var to hold SMBIOS raw table size
- changed format of get_smbios_entry_area symbol
returned pointer on const smbios table
firmware: dmi-sysfs: add SMBIOS entry point area attribute
- adopted to updated get_smbios_entry_area symbol
- removed redundant array to save smbios table
Documentation/ABI/testing/sysfs-firmware-dmi | 10 +++++++
drivers/firmware/dmi-sysfs.c | 42 ++++++++++++++++++++++++++++
drivers/firmware/dmi_scan.c | 26 +++++++++++++++++
include/linux/dmi.h | 3 ++
4 files changed, 81 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-firmware-dmi b/Documentation/ABI/testing/sysfs-firmware-dmi
index c78f9ab..3a9ffe8 100644
--- a/Documentation/ABI/testing/sysfs-firmware-dmi
+++ b/Documentation/ABI/testing/sysfs-firmware-dmi
@@ -12,6 +12,16 @@ Description:
cannot ensure that the data as exported to userland is
without error either.
+ 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_raw_header. The format of SMBIOS
+ entry point header can be read in SMBIOS specification.
+
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
diff --git a/drivers/firmware/dmi-sysfs.c b/drivers/firmware/dmi-sysfs.c
index e0f1cb3..9b396d7 100644
--- a/drivers/firmware/dmi-sysfs.c
+++ b/drivers/firmware/dmi-sysfs.c
@@ -29,6 +29,8 @@
#define MAX_ENTRY_TYPE 255 /* Most of these aren't used, but we consider
the top entry type is only 8 bits */
+static const u8 *smbios_raw_header;
+
struct dmi_sysfs_entry {
struct dmi_header dh;
struct kobject kobj;
@@ -646,9 +648,37 @@ static void cleanup_entry_list(void)
}
}
+static ssize_t smbios_entry_area_raw_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_raw_header[pos], size);
+
+ return size;
+}
+
+static struct bin_attribute smbios_raw_area_attr = {
+ .read = smbios_entry_area_raw_read,
+ .attr = {.name = "smbios_raw_header", .mode = 0400},
+};
+
static int __init dmi_sysfs_init(void)
{
int error = -ENOMEM;
+ int size;
int val;
/* Set up our directory */
@@ -669,6 +699,18 @@ static int __init dmi_sysfs_init(void)
goto err;
}
+ smbios_raw_header = dmi_get_smbios_entry_area(&size);
+ if (!smbios_raw_header) {
+ pr_debug("dmi-sysfs: SMBIOS raw data is not available.\n");
+ error = -EINVAL;
+ goto err;
+ }
+
+ /* Create the raw binary file to access the entry area */
+ smbios_raw_area_attr.size = size;
+ if (sysfs_create_bin_file(dmi_kobj, &smbios_raw_area_attr))
+ goto err;
+
pr_debug("dmi-sysfs: loaded.\n");
return 0;
diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
index 420c8d8..99c5f6c 100644
--- a/drivers/firmware/dmi_scan.c
+++ b/drivers/firmware/dmi_scan.c
@@ -113,6 +113,8 @@ static void dmi_table(u8 *buf, int len, int num,
}
}
+static u8 smbios_header[32];
+static int smbios_header_size;
static phys_addr_t dmi_base;
static u16 dmi_len;
static u16 dmi_num;
@@ -474,6 +476,8 @@ 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_header_size = buf[5];
+ memcpy(smbios_header, buf, smbios_header_size);
/* Some BIOS report weird SMBIOS version, fix that up */
switch (smbios_ver) {
@@ -505,6 +509,8 @@ static int __init dmi_present(const u8 *buf)
pr_info("SMBIOS %d.%d present.\n",
dmi_ver >> 8, dmi_ver & 0xFF);
} else {
+ smbios_header_size = 15;
+ memcpy(smbios_header, buf, smbios_header_size);
dmi_ver = (buf[14] & 0xF0) << 4 |
(buf[14] & 0x0F);
pr_info("Legacy DMI %d.%d present.\n",
@@ -531,6 +537,8 @@ 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_header_size = buf[6];
+ memcpy(smbios_header, buf, smbios_header_size);
/*
* The 64-bit SMBIOS 3.0 entry point no longer has a field
@@ -944,3 +952,21 @@ void dmi_memdev_name(u16 handle, const char **bank, const char **device)
}
}
EXPORT_SYMBOL_GPL(dmi_memdev_name);
+
+/**
+ * dmi_get_smbios_entry_area - copy SMBIOS entry point area to array.
+ * @size - pointer to assign actual size of SMBIOS entry point area.
+ *
+ * returns NULL if table is not available, otherwise returns pointer on
+ * SMBIOS entry point area array.
+ */
+const u8 *dmi_get_smbios_entry_area(int *size)
+{
+ if (!smbios_header_size || !dmi_available)
+ return NULL;
+
+ *size = smbios_header_size;
+
+ return smbios_header;
+}
+EXPORT_SYMBOL_GPL(dmi_get_smbios_entry_area);
diff --git a/include/linux/dmi.h b/include/linux/dmi.h
index f820f0a..8e1a28d 100644
--- a/include/linux/dmi.h
+++ b/include/linux/dmi.h
@@ -109,6 +109,7 @@ extern int dmi_walk(void (*decode)(const struct dmi_header *, void *),
void *private_data);
extern bool dmi_match(enum dmi_field f, const char *str);
extern void dmi_memdev_name(u16 handle, const char **bank, const char **device);
+const u8 *dmi_get_smbios_entry_area(int *size);
#else
@@ -140,6 +141,8 @@ static inline void dmi_memdev_name(u16 handle, const char **bank,
const char **device) { }
static inline const struct dmi_system_id *
dmi_first_match(const struct dmi_system_id *list) { return NULL; }
+static inline const u8 *dmi_get_smbios_entry_area(int *size)
+ { return NULL; }
#endif
--
1.9.1
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