Capable of loading a multiboot image into memory

src/arch/i386/image/multiboot.c

@@ -0,0 +1,235 @@
+/*
+ * Copyright (C) 2007 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
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+/**
+ * @file
+ *
+ * Multiboot image format
+ *
+ */
+
+#include <errno.h>
+#include <multiboot.h>
+#include <gpxe/uaccess.h>
+#include <gpxe/image.h>
+#include <gpxe/segment.h>
+#include <gpxe/elf.h>
+
+/** Boot modules must be page aligned */
+#define MB_FLAG_PGALIGN 0x00000001
+
+/** Memory map must be provided */
+#define MB_FLAG_MEMMAP 0x00000002
+
+/** Video mode information must be provided */
+#define MB_FLAG_VIDMODE 0x00000004
+
+/** Image is a raw multiboot image (not ELF) */
+#define MB_FLAG_RAW 0x00010000
+
+/** Multiboot flags that we support */
+#define MB_SUPPORTED_FLAGS ( MB_FLAG_PGALIGN | MB_FLAG_MEMMAP | \
+			     MB_FLAG_VIDMODE | MB_FLAG_RAW )
+
+/** Compulsory feature multiboot flags */
+#define MB_COMPULSORY_FLAGS 0x0000ffff
+
+/** Optional feature multiboot flags */
+#define MB_OPTIONAL_FLAGS 0xffff0000
+
+/**
+ * Multiboot flags that we don't support
+ *
+ * We only care about the compulsory feature flags (bits 0-15); we are
+ * allowed to ignore the optional feature flags.
+ */
+#define MB_UNSUPPORTED_FLAGS ( MB_COMPULSORY_FLAGS & ~MB_SUPPORTED_FLAGS )
+
+/** A multiboot header descriptor */
+struct multiboot_header_info {
+	/** The actual multiboot header */
+	struct multiboot_header mb;
+	/** Offset of header within the multiboot image */
+	size_t offset;
+};
+
+/**
+ * Execute multiboot image
+ *
+ * @v image		ELF file
+ * @ret rc		Return status code
+ */
+static int multiboot_execute ( struct image *image __unused ) {
+	return -ENOTSUP;
+}
+
+/**
+ * Find multiboot header
+ *
+ * @v image		Multiboot file
+ * @v hdr		Multiboot header descriptor to fill in
+ * @ret rc		Return status code
+ */
+static int multiboot_find_header ( struct image *image,
+				   struct multiboot_header_info *hdr ) {
+	uint32_t buf[64];
+	size_t offset;
+	unsigned int buf_idx;
+	uint32_t checksum;
+
+	/* Scan through first 8kB of image file 256 bytes at a time.
+	 * (Use the buffering to avoid the overhead of a
+	 * copy_from_user() for every dword.)
+	 */
+	for ( offset = 0 ; offset < 8192 ; offset += sizeof ( buf[0] ) ) {
+		/* Check for end of image */
+		if ( offset > image->len )
+			break;
+		/* Refill buffer if applicable */
+		buf_idx = ( ( offset % sizeof ( buf ) ) / sizeof ( buf[0] ) );
+		if ( buf_idx == 0 ) {
+			copy_from_user ( buf, image->data, offset,
+					 sizeof ( buf ) );
+		}
+		/* Check signature */
+		if ( buf[buf_idx] != MULTIBOOT_HEADER_MAGIC )
+			continue;
+		/* Copy header and verify checksum */
+		copy_from_user ( &hdr->mb, image->data, offset,
+				 sizeof ( hdr->mb ) );
+		checksum = ( hdr->mb.magic + hdr->mb.flags +
+			     hdr->mb.checksum );
+		if ( checksum != 0 )
+			continue;
+		/* Record offset of multiboot header and return */
+		hdr->offset = offset;
+		return 0;
+	}
+
+	/* No multiboot header found */
+	return -ENOEXEC;
+}
+
+/**
+ * Load raw multiboot image into memory
+ *
+ * @v image		Multiboot file
+ * @v hdr		Multiboot header descriptor
+ * @ret rc		Return status code
+ */
+static int multiboot_load_raw ( struct image *image,
+				struct multiboot_header_info *hdr ) {
+	size_t offset;
+	size_t filesz;
+	size_t memsz;
+	userptr_t buffer;
+	int rc;
+
+	/* Verify and prepare segment */
+	offset = ( hdr->offset - hdr->mb.header_addr + hdr->mb.load_addr );
+	filesz = ( hdr->mb.load_end_addr - hdr->mb.load_addr );
+	memsz = ( hdr->mb.bss_end_addr - hdr->mb.load_addr );
+	buffer = phys_to_user ( hdr->mb.load_addr );
+	if ( ( rc = prep_segment ( buffer, filesz, memsz ) ) != 0 ) {
+		DBG ( "Multiboot could not prepare segment: %s\n",
+		      strerror ( rc ) );
+		return rc;
+	}
+
+	/* Copy image to segment */
+	copy_user ( buffer, 0, image->data, offset, filesz );
+
+	/* Record execution entry point */
+	image->entry = hdr->mb.entry_addr;
+	image->execute = multiboot_execute;
+
+	return 0;
+}
+
+/**
+ * Load ELF multiboot image into memory
+ *
+ * @v image		Multiboot file
+ * @ret rc		Return status code
+ */
+static int multiboot_load_elf ( struct image *image ) {
+	int rc;
+
+	/* Load ELF image*/
+	if ( ( rc = elf_load ( image ) ) != 0 ) {
+		DBG ( "Multiboot ELF image failed to load: %s\n",
+		      strerror ( rc ) );
+		/* We must translate "not an ELF image" (i.e. ENOEXEC)
+		 * into "invalid multiboot image", to avoid screwing
+		 * up the image probing logic.
+		 */
+		if ( rc == -ENOEXEC ) {
+			return -ENOTSUP;
+		} else {
+			return rc;
+		}
+	}
+
+	/* Capture execution method */
+	if ( image->execute )
+		image->execute = multiboot_execute;
+
+	return 0;
+}
+
+/**
+ * Load multiboot image into memory
+ *
+ * @v image		Multiboot file
+ * @ret rc		Return status code
+ */
+int multiboot_load ( struct image *image ) {
+	struct multiboot_header_info hdr;
+	int rc;
+
+	/* Locate multiboot header, if present */
+	if ( ( rc = multiboot_find_header ( image, &hdr ) ) != 0 ) {
+		DBG ( "No multiboot header\n" );
+		return rc;
+	}
+	DBG ( "Found multiboot header with flags %08lx\n", hdr.mb.flags );
+
+	/* Abort if we detect flags that we cannot support */
+	if ( hdr.mb.flags & MB_UNSUPPORTED_FLAGS ) {
+		DBG ( "Multiboot flags %08lx not supported\n",
+		      ( hdr.mb.flags & MB_UNSUPPORTED_FLAGS ) );
+		return -ENOTSUP;
+	}
+
+	/* Load the actual image */
+	if ( hdr.mb.flags & MB_FLAG_RAW ) {
+		if ( ( rc = multiboot_load_raw ( image, &hdr ) ) != 0 )
+			return rc;
+	} else {
+		if ( ( rc = multiboot_load_elf ( image ) ) != 0 )
+			return rc;
+	}
+
+	return 0;
+}
+
+/** Multiboot image type */
+struct image_type multiboot_image_type __image_type = {
+	.name = "Multiboot",
+	.load = multiboot_load,
+};