[PATCH 1/2] firmware: dmi_scan: add symbol to get SMBIOS entry area

[Ivan Khoronzhuk]

There are situations when code needs to access SMBIOS entry table
area. For example, to pass it via sysfs to userspace when it's not
allowed to get SMBIOS info via /dev/mem.

Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@xxxxxxxxxx>
---
 drivers/firmware/dmi_scan.c | 34 ++++++++++++++++++++++++++++++++++
 include/linux/dmi.h         |  2 ++
 2 files changed, 36 insertions(+)

diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
index 420c8d8..ae9204a 100644
--- a/drivers/firmware/dmi_scan.c
+++ b/drivers/firmware/dmi_scan.c
@@ -113,6 +113,7 @@ static void dmi_table(u8 *buf, int len, int num,
 	}
 }
 
+static unsigned char smbios_header[32];
 static phys_addr_t dmi_base;
 static u16 dmi_len;
 static u16 dmi_num;
@@ -474,6 +475,7 @@ 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);
+		memcpy(smbios_header, buf, buf[5]);
 
 		/* Some BIOS report weird SMBIOS version, fix that up */
 		switch (smbios_ver) {
@@ -505,6 +507,7 @@ static int __init dmi_present(const u8 *buf)
 				pr_info("SMBIOS %d.%d present.\n",
 				       dmi_ver >> 8, dmi_ver & 0xFF);
 			} else {
+				memcpy(smbios_header, buf, 15);
 				dmi_ver = (buf[14] & 0xF0) << 4 |
 					   (buf[14] & 0x0F);
 				pr_info("Legacy DMI %d.%d present.\n",
@@ -531,6 +534,7 @@ 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);
+		memcpy(smbios_header, buf, buf[6]);
 
 		/*
 		 * The 64-bit SMBIOS 3.0 entry point no longer has a field
@@ -944,3 +948,33 @@ 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.
+ * @entry - pointer on array to read area in, current max size is 32 bytes.
+ *
+ * returns -ENODATA if table is not available, otherwise returns actual
+ * size of SMBIOS entry point area.
+ */
+int dmi_get_smbios_entry_area(char *table)
+{
+	int size = 0;
+
+	if (!dmi_available)
+		return -ENODATA;
+
+	if (memcmp(smbios_header, "_SM3_", 5) == 0)
+		size = smbios_header[6];
+	else if (memcmp(smbios_header, "_SM_", 4) == 0)
+		size = smbios_header[5];
+	else if (memcmp(smbios_header, "_DMI_", 5) == 0)
+		size = 15;
+
+	memcpy(table, smbios_header, size);
+
+	if (!size)
+		return -ENODATA;
+
+	return size;
+}
+EXPORT_SYMBOL_GPL(dmi_get_smbios_entry_area);
diff --git a/include/linux/dmi.h b/include/linux/dmi.h
index f820f0a..7cae713 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);
+int dmi_get_smbios_entry_area(char *table);
 
 #else
 
@@ -140,6 +141,7 @@ 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 int dmi_get_smbios_entry_area(char *table) { return -ENODATA; }
 
 #endif
 
-- 
1.9.1

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