[linux] Provide access to SMBIOS via /dev/mem

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

src/interface/linux/linux_smbios.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2010 Piotr Jaroszyński <p.jaroszynski@gmail.com>
+ * Copyright (C) 2013 Michael Brown <mbrown@fensystems.co.uk>.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
@@ -13,25 +13,103 @@
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
  */
 
-FILE_LICENCE(GPL2_OR_LATER);
+FILE_LICENCE ( GPL2_OR_LATER );
 
 #include <errno.h>
+#include <linux_api.h>
+#include <ipxe/linux.h>
 #include <ipxe/smbios.h>
 
+/** SMBIOS filename */
+static const char smbios_filename[] = "/dev/mem";
+
+/** SMBIOS entry point scan region start address */
+#define SMBIOS_ENTRY_START 0xf0000
+
+/** SMBIOS entry point scan region length */
+#define SMBIOS_ENTRY_LEN 0x10000
+
+/** SMBIOS mapping alignment */
+#define SMBIOS_ALIGN 0x1000
+
 /**
  * Find SMBIOS
  *
- * Not implemented currently.
- *
  * @v smbios		SMBIOS entry point descriptor structure to fill in
  * @ret rc		Return status code
  */
-static int linux_find_smbios(struct smbios *smbios __unused)
-{
-	return -ENODEV;
+static int linux_find_smbios ( struct smbios *smbios ) {
+	struct smbios_entry entry;
+	void *entry_mem;
+	void *smbios_mem;
+	size_t smbios_offset;
+	size_t smbios_indent;
+	size_t smbios_len;
+	int fd;
+	int rc;
+
+	/* Open SMBIOS file */
+	fd = linux_open ( smbios_filename, O_RDONLY );
+	if ( fd < 0 ) {
+		rc = -ELINUX ( linux_errno );
+		DBGC ( smbios, "SMBIOS could not open %s: %s\n",
+		       smbios_filename, linux_strerror ( linux_errno ) );
+		goto err_open;
+	}
+
+	/* Map the region potentially containing the SMBIOS entry point */
+	entry_mem = linux_mmap ( NULL, SMBIOS_ENTRY_LEN, PROT_READ, MAP_SHARED,
+				 fd, SMBIOS_ENTRY_START );
+	if ( entry_mem == MAP_FAILED ) {
+		rc = -ELINUX ( linux_errno );
+		DBGC ( smbios, "SMBIOS could not mmap %s (%#x+%#x): %s\n",
+		       smbios_filename, SMBIOS_ENTRY_START, SMBIOS_ENTRY_LEN,
+		       linux_strerror ( linux_errno ) );
+		goto err_mmap_entry;
+	}
+
+	/* Scan for the SMBIOS entry point */
+	if ( ( rc = find_smbios_entry ( virt_to_user ( entry_mem ),
+					SMBIOS_ENTRY_LEN, &entry ) ) != 0 )
+		goto err_find_entry;
+
+	/* Map the region containing the SMBIOS structures */
+	smbios_indent = ( entry.smbios_address & ( SMBIOS_ALIGN - 1 ) );
+	smbios_offset = ( entry.smbios_address - smbios_indent );
+	smbios_len = ( entry.smbios_len + smbios_indent );
+	smbios_mem = linux_mmap ( NULL, smbios_len, PROT_READ, MAP_SHARED,
+				  fd, smbios_offset );
+	if ( smbios_mem == MAP_FAILED ) {
+		rc = -ELINUX ( linux_errno );
+		DBGC ( smbios, "SMBIOS could not mmap %s (%#zx+%#zx): %s\n",
+		       smbios_filename, smbios_offset, smbios_len,
+		       linux_strerror ( linux_errno ) );
+		goto err_mmap_smbios;
+	}
+
+	/* Fill in entry point descriptor structure */
+	smbios->address = virt_to_user ( smbios_mem + smbios_indent );
+	smbios->len = entry.smbios_len;
+	smbios->count = entry.smbios_count;
+	smbios->version = SMBIOS_VERSION ( entry.major, entry.minor );
+
+	/* Unmap the entry point region (no longer required) */
+	linux_munmap ( entry_mem, SMBIOS_ENTRY_LEN );
+
+	return 0;
+
+	linux_munmap ( smbios_mem, smbios_len );
+ err_mmap_smbios:
+ err_find_entry:
+	linux_munmap ( entry_mem, SMBIOS_ENTRY_LEN );
+ err_mmap_entry:
+	linux_close ( fd );
+ err_open:
+	return rc;
 }
 
-PROVIDE_SMBIOS(linux, find_smbios, linux_find_smbios);
+PROVIDE_SMBIOS ( linux, find_smbios, linux_find_smbios );

src/interface/smbios/smbios.c

@@ -37,6 +37,54 @@ static struct smbios smbios = {
 	.address = UNULL,
 };
 
+/**
+ * Scan for SMBIOS 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_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 ) {
+
+		/* 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 ) {
+			DBG ( "SMBIOS at %08lx has bad checksum %02x\n",
+			      user_to_phys ( start, offset ), sum );
+			continue;
+		}
+
+		/* Fill result structure */
+		DBG ( "Found SMBIOS v%d.%d entry point at %08lx\n",
+		      entry->major, entry->minor,
+		      user_to_phys ( start, offset ) );
+		return 0;
+	}
+
+	DBG ( "No SMBIOS found\n" );
+	return -ENODEV;
+}
+
 /**
  * Find SMBIOS strings terminator
  *