[smbios] Support scanning for the 64-bit SMBIOS3 entry point

Support scanning for the 64-bit SMBIOS3 entry point in addition to the
32-bit SMBIOS2 entry point.

Prefer use of the 32-bit entry point if present, since this is
guaranteed to be within accessible memory.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

1 files changed, 65 insertions, 13 deletions

diff --git a/src/interface/smbios/smbios.c b/src/interface/smbios/smbios.c
index 12a080da2..fdd14499f 100644
--- a/src/interface/smbios/smbios.c
+++ b/src/interface/smbios/smbios.c
@@ -42,7 +42,27 @@ static struct smbios smbios = {
 };
 
 /**
- * Scan for SMBIOS entry point structure
+ * Calculate SMBIOS entry point structure checksum
+ *
+ * @v start		Start address of region
+ * @v offset		Offset of SMBIOS entry point structure
+ * @v len		Length of entry point structure
+ * @ret sum		Byte checksum
+ */
+static uint8_t smbios_checksum ( userptr_t start, size_t offset, size_t len ) {
+	size_t end = ( offset + len );
+	uint8_t sum;
+	uint8_t byte;
+
+	for ( sum = 0 ; offset < end ; offset++ ) {
+		copy_from_user ( &byte, start, offset, sizeof ( byte ) );
+		sum += byte;
+	}
+	return sum;
+}
+
+/**
+ * Scan for SMBIOS 32-bit entry point structure
  *
  * @v start		Start address of region to scan
  * @v len		Length of region to scan
@@ -51,28 +71,20 @@ static struct smbios smbios = {
  */
 int find_smbios_entry ( userptr_t start, size_t len,
 			struct smbios_entry *entry ) {
-	uint8_t buf[256]; /* 256 is maximum length possible */
 	static size_t offset = 0; /* Avoid repeated attempts to locate SMBIOS */
-	size_t entry_len;
-	unsigned int i;
 	uint8_t sum;
 
 	/* Try to find SMBIOS */
-	for ( ; offset < len ; offset += 0x10 ) {
+	for ( ; ( offset + sizeof ( *entry ) ) <= len ; offset += 0x10 ) {
 
 		/* Read start of header and verify signature */
 		copy_from_user ( entry, start, offset, sizeof ( *entry ) );
 		if ( entry->signature != SMBIOS_SIGNATURE )
 			continue;
 
-		/* Read whole header and verify checksum */
-		entry_len = entry->len;
-		assert ( entry_len <= sizeof ( buf ) );
-		copy_from_user ( buf, start, offset, entry_len );
-		for ( i = 0, sum = 0 ; i < entry_len ; i++ ) {
-			sum += buf[i];
-		}
-		if ( sum != 0 ) {
+		/* Verify checksum */
+		if ( ( sum = smbios_checksum ( start, offset,
+					       entry->len ) ) != 0 ) {
 			DBG ( "SMBIOS at %08lx has bad checksum %02x\n",
 			      user_to_phys ( start, offset ), sum );
 			continue;
@@ -90,6 +102,46 @@ int find_smbios_entry ( userptr_t start, size_t len,
 }
 
 /**
+ * Scan for SMBIOS 64-bit entry point structure
+ *
+ * @v start		Start address of region to scan
+ * @v len		Length of region to scan
+ * @v entry		SMBIOS entry point structure to fill in
+ * @ret rc		Return status code
+ */
+int find_smbios3_entry ( userptr_t start, size_t len,
+			 struct smbios3_entry *entry ) {
+	static size_t offset = 0; /* Avoid repeated attempts to locate SMBIOS */
+	uint8_t sum;
+
+	/* Try to find SMBIOS */
+	for ( ; ( offset + sizeof ( *entry ) ) <= len ; offset += 0x10 ) {
+
+		/* Read start of header and verify signature */
+		copy_from_user ( entry, start, offset, sizeof ( *entry ) );
+		if ( entry->signature != SMBIOS3_SIGNATURE )
+			continue;
+
+		/* Verify checksum */
+		if ( ( sum = smbios_checksum ( start, offset,
+					       entry->len ) ) != 0 ) {
+			DBG ( "SMBIOS3 at %08lx has bad checksum %02x\n",
+			      user_to_phys ( start, offset ), sum );
+			continue;
+		}
+
+		/* Fill result structure */
+		DBG ( "Found SMBIOS3 v%d.%d entry point at %08lx\n",
+		      entry->major, entry->minor,
+		      user_to_phys ( start, offset ) );
+		return 0;
+	}
+
+	DBG ( "No SMBIOS3 found\n" );
+	return -ENODEV;
+}
+
+/**
  * Find SMBIOS strings terminator
  *
  * @v offset		Offset to start of strings