diff --git a/src/arch/i386/image/bzimage.c b/src/arch/i386/image/bzimage.c
index 48b69046..4a9a45ff 100644
--- a/src/arch/i386/image/bzimage.c
+++ b/src/arch/i386/image/bzimage.c
@@ -35,18 +35,36 @@
 
 struct image_type bzimage_image_type __image_type ( PROBE_NORMAL );
 
+/**
+ * bzImage load context
+ */
+struct bzimage_load_context {
+	/** Real-mode kernel portion load segment address */
+	unsigned int rm_kernel_seg;
+	/** Real-mode kernel portion load address */
+	userptr_t rm_kernel;
+	/** Real-mode kernel portion file size */
+	size_t rm_filesz;
+	/** Real-mode heap top (offset from rm_kernel) */
+	size_t rm_heap;
+	/** Command line (offset from rm_kernel) */
+	size_t rm_cmdline;
+	/** Real-mode kernel portion total memory size */
+	size_t rm_memsz;
+	/** Non-real-mode kernel portion load address */
+	userptr_t pm_kernel;
+	/** Non-real-mode kernel portion file and memory size */
+	size_t pm_sz;
+};
+
 /**
  * bzImage execution context
  */
-union bzimage_exec_context {
-	/** Real-mode parameters */
-	struct {
-		/** Kernel real-mode data segment */
-		uint16_t kernel_seg;
-		/** Kernel real-mode stack pointer */
-		uint16_t stack;
-	} rm;
-	unsigned long ul;
+struct bzimage_exec_context {
+	/** Kernel real-mode data segment */
+	uint16_t kernel_seg;
+	/** Kernel real-mode stack pointer */
+	uint16_t stack;
 };
 
 /**
@@ -56,10 +74,13 @@ union bzimage_exec_context {
  * @ret rc		Return status code
  */
 static int bzimage_exec ( struct image *image ) {
-	union bzimage_exec_context context;
+	union {
+		struct bzimage_exec_context bz;
+		unsigned long ul;
+	} exec_ctx;
 
 	/* Retrieve stored execution context */
-	context.ul = image->priv.ul;
+	exec_ctx.ul = image->priv.ul;
 
 	/* Prepare for exiting */
 	shutdown();
@@ -74,9 +95,9 @@ static int bzimage_exec ( struct image *image ) {
 					   "pushw %w2\n\t"
 					   "pushw $0\n\t"
 					   "lret\n\t" )
-			       : : "r" ( context.rm.kernel_seg ),
-			           "r" ( context.rm.stack ),
-			           "r" ( context.rm.kernel_seg + 0x20 ) );
+			       : : "r" ( exec_ctx.bz.kernel_seg ),
+			           "r" ( exec_ctx.bz.stack ),
+			           "r" ( exec_ctx.bz.kernel_seg + 0x20 ) );
 
 	/* There is no way for the image to return, since we provide
 	 * no return address.
@@ -86,6 +107,161 @@ static int bzimage_exec ( struct image *image ) {
 	return -ECANCELED; /* -EIMPOSSIBLE */
 }
 
+/**
+ * Load and parse bzImage header
+ *
+ * @v image		bzImage file
+ * @v load_ctx		Load context
+ * @v bzhdr		Buffer for bzImage header
+ * @ret rc		Return status code
+ */
+static int bzimage_load_header ( struct image *image,
+				 struct bzimage_load_context *load_ctx,
+				 struct bzimage_header *bzhdr ) {
+
+	/* Sanity check */
+	if ( image->len < ( BZI_HDR_OFFSET + sizeof ( *bzhdr ) ) ) {
+		DBGC ( image, "bzImage %p too short for kernel header\n",
+		       image );
+		return -ENOEXEC;
+	}
+
+	/* Read and verify header */
+	copy_from_user ( bzhdr, image->data, BZI_HDR_OFFSET,
+			 sizeof ( *bzhdr ) );
+	if ( bzhdr->header != BZI_SIGNATURE ) {
+		DBGC ( image, "bzImage %p bad signature\n", image );
+		return -ENOEXEC;
+	}
+
+	/* We don't support ancient kernels */
+	if ( bzhdr->version < 0x0200 ) {
+		DBGC ( image, "bzImage %p version %04x not supported\n",
+		       image, bzhdr->version );
+		return -ENOTSUP;
+	}
+
+	/* Calculate load address and size of real-mode portion */
+	load_ctx->rm_kernel_seg = 0x1000; /* place RM kernel at 1000:0000 */
+	load_ctx->rm_kernel = real_to_user ( load_ctx->rm_kernel_seg, 0 );
+	load_ctx->rm_filesz = load_ctx->rm_memsz =
+		( ( bzhdr->setup_sects ? bzhdr->setup_sects : 4 ) + 1 ) << 9;
+	if ( load_ctx->rm_filesz > image->len ) {
+		DBGC ( image, "bzImage %p too short for %zd byte of setup\n",
+		       image, load_ctx->rm_filesz );
+		return -ENOEXEC;
+	}
+
+	/* Calculate load address and size of non-real-mode portion */
+	load_ctx->pm_kernel = ( ( bzhdr->loadflags & BZI_LOAD_HIGH ) ?
+				phys_to_user ( BZI_LOAD_HIGH_ADDR ) :
+				phys_to_user ( BZI_LOAD_LOW_ADDR ) );
+	load_ctx->pm_sz = ( image->len - load_ctx->rm_filesz );
+
+	DBGC ( image, "bzImage %p version %04x RM %#zx bytes PM %#zx bytes\n",
+	       image, bzhdr->version, load_ctx->rm_filesz, load_ctx->pm_sz );
+	return 0;
+}
+
+/**
+ * Load real-mode portion of bzImage
+ *
+ * @v image		bzImage file
+ * @v load_ctx		Load context
+ * @v cmdline		Kernel command line
+ * @ret rc		Return status code
+ */
+static int bzimage_load_real ( struct image *image,
+			       struct bzimage_load_context *load_ctx,
+			       const char *cmdline ) {
+	size_t cmdline_len = ( strlen ( cmdline ) + 1 );
+	int rc;
+
+	/* Allow space for the stack and heap */
+	load_ctx->rm_memsz += BZI_STACK_SIZE;
+	load_ctx->rm_heap = load_ctx->rm_memsz;
+
+	/* Allow space for the command line, if one exists */
+	load_ctx->rm_cmdline = load_ctx->rm_memsz;
+	load_ctx->rm_memsz += cmdline_len;
+
+	/* Prepare, verify, and load the real-mode segment */
+	if ( ( rc = prep_segment ( load_ctx->rm_kernel, load_ctx->rm_filesz,
+				   load_ctx->rm_memsz ) ) != 0 ) {
+		DBGC ( image, "bzImage %p could not prepare RM segment: %s\n",
+		       image, strerror ( rc ) );
+		return rc;
+	}
+	memcpy_user ( load_ctx->rm_kernel, 0, image->data, 0,
+		      load_ctx->rm_filesz );
+
+	/* Copy command line */
+	copy_to_user ( load_ctx->rm_kernel, load_ctx->rm_cmdline,
+		       cmdline, cmdline_len );
+
+	return 0;
+}
+
+/**
+ * Load non-real-mode portion of bzImage
+ *
+ * @v image		bzImage file
+ * @v load_ctx		Load context
+ * @ret rc		Return status code
+ */
+static int bzimage_load_non_real ( struct image *image,
+				   struct bzimage_load_context *load_ctx ) {
+	int rc;
+
+	/* Prepare, verify and load the non-real-mode segment */
+	if ( ( rc = prep_segment ( load_ctx->pm_kernel, load_ctx->pm_sz,
+				   load_ctx->pm_sz ) ) != 0 ) {
+		DBGC ( image, "bzImage %p could not prepare PM segment: %s\n",
+		       image, strerror ( rc ) );
+		return rc;
+	}
+	memcpy_user ( load_ctx->pm_kernel, 0, image->data, load_ctx->rm_filesz,
+		      load_ctx->pm_sz );
+
+	return 0;
+}
+
+
+/**
+ * Update and store bzImage header
+ *
+ * @v image		bzImage file
+ * @v load_ctx		Load context
+ * @v bzhdr		Original bzImage header
+ * @ret rc		Return status code
+ */
+static int bzimage_write_header ( struct image *image __unused,
+				  struct bzimage_load_context *load_ctx,
+				  struct bzimage_header *bzhdr ) {
+	struct bzimage_cmdline cmdline;
+
+	/* Update the header and copy it into the loaded kernel */
+	bzhdr->type_of_loader = BZI_LOADER_TYPE_ETHERBOOT;
+	if ( bzhdr->version >= 0x0201 ) {
+		bzhdr->heap_end_ptr = ( load_ctx->rm_heap - 0x200 );
+		bzhdr->loadflags |= BZI_CAN_USE_HEAP;
+	}
+	if ( bzhdr->version >= 0x0202 ) {
+		bzhdr->cmd_line_ptr = user_to_phys ( load_ctx->rm_kernel,
+						     load_ctx->rm_cmdline );
+	} else {
+		cmdline.magic = BZI_CMDLINE_MAGIC;
+		cmdline.offset = load_ctx->rm_cmdline;
+		copy_to_user ( load_ctx->rm_kernel, BZI_CMDLINE_OFFSET,
+			       &cmdline, sizeof ( cmdline ) );
+		bzhdr->setup_move_size = load_ctx->rm_memsz;
+	}
+	copy_to_user ( load_ctx->rm_kernel, BZI_HDR_OFFSET,
+		       bzhdr, sizeof ( *bzhdr ) );
+
+	return 0;
+}
+
 /**
  * Load bzImage image into memory
  *
@@ -94,112 +270,38 @@ static int bzimage_exec ( struct image *image ) {
  */
 int bzimage_load ( struct image *image ) {
 	struct bzimage_header bzhdr;
-	union bzimage_exec_context context;
-	unsigned int rm_kernel_seg = 0x1000; /* place RM kernel at 1000:0000 */
-	userptr_t rm_kernel = real_to_user ( rm_kernel_seg, 0 );
-	userptr_t pm_kernel;
-	size_t rm_filesz;
-	size_t rm_memsz;
-	size_t pm_filesz;
-	size_t pm_memsz;
-	size_t rm_heap_end;
-	size_t rm_cmdline;
+	struct bzimage_load_context load_ctx;
+	union {
+		struct bzimage_exec_context bz;
+		unsigned long ul;
+	} exec_ctx;
+	const char *cmdline = ( image->cmdline ? image->cmdline : "" );
 	int rc;
 
-	/* Sanity check */
-	if ( image->len < ( BZI_HDR_OFFSET + sizeof ( bzhdr ) ) ) {
-		DBGC ( image, "bzImage %p too short for kernel header\n",
-		       image );
-		return -ENOEXEC;
-	}
-
-	/* Read and verify header */
-	copy_from_user ( &bzhdr, image->data, BZI_HDR_OFFSET,
-			 sizeof ( bzhdr ) );
-	if ( bzhdr.header != BZI_SIGNATURE ) {
-		DBGC ( image, "bzImage %p not a bzImage\n", image );
-		return -ENOEXEC;
-	}
+	/* Load and verify header */
+	if ( ( rc = bzimage_load_header ( image, &load_ctx, &bzhdr ) ) != 0 )
+		return rc;
 
 	/* This is a bzImage image, valid or otherwise */
 	if ( ! image->type )
 		image->type = &bzimage_image_type;
 
-	/* We don't support ancient kernels */
-	if ( bzhdr.version < 0x0200 ) {
-		DBGC ( image, "bzImage %p version %04x not supported\n",
-		       image, bzhdr.version );
-		return -ENOTSUP;
-	}
-	DBGC ( image, "bzImage %p version %04x\n", image, bzhdr.version );
-
-	/* Check size of base memory portions */
-	rm_filesz = ( ( bzhdr.setup_sects ? bzhdr.setup_sects : 4 ) + 1 ) << 9;
-	if ( rm_filesz > image->len ) {
-		DBGC ( image, "bzImage %p too short for %zd byte of setup\n",
-		       image, rm_filesz );
-		return -ENOEXEC;
-	}
-	rm_memsz = rm_filesz;
-
-	/* Allow space for the stack and heap */
-	rm_memsz += BZI_STACK_SIZE;
-	rm_heap_end = rm_memsz;
-
-	/* Allow space for the command line, if one exists */
-	rm_cmdline = rm_memsz;
-	if ( image->cmdline )
-		rm_memsz += ( strlen ( image->cmdline ) + 1 );
-
-	/* Prepare, verify, and load the real-mode segment */
-	if ( ( rc = prep_segment ( rm_kernel, rm_filesz, rm_memsz ) ) != 0 ) {
-		DBGC ( image, "bzImage %p could not prepare RM segment: %s\n",
-		       image, strerror ( rc ) );
+	/* Load real-mode portion */
+	if ( ( rc = bzimage_load_real ( image, &load_ctx, cmdline ) ) != 0 )
 		return rc;
-	}
-	memcpy_user ( rm_kernel, 0, image->data, 0, rm_filesz );
 
-	/* Prepare, verify and load the rest of the kernel */
-	pm_kernel = ( ( bzhdr.loadflags & BZI_LOAD_HIGH ) ?
-		      phys_to_user ( 0x100000 ) : phys_to_user ( 0x10000 ) );
-	pm_filesz = pm_memsz = ( image->len - rm_filesz );
-	if ( ( rc = prep_segment ( pm_kernel, pm_filesz, pm_memsz ) ) != 0 ) {
-		DBGC ( image, "bzImage %p could not prepare PM segment: %s\n",
-		       image, strerror ( rc ) );
+	/* Load non-real-mode portion */
+	if ( ( rc = bzimage_load_non_real ( image, &load_ctx ) ) != 0 )
 		return rc;
-	}
-	memcpy_user ( pm_kernel, 0, image->data, rm_filesz, pm_filesz );
 
-	/* Copy down the command line, if it exists */
-	if ( image->cmdline ) {
-		copy_to_user ( rm_kernel, rm_cmdline, image->cmdline,
-			       strlen ( image->cmdline ) + 1 );
-	}
-
-	/* Update the header and copy it into the loaded kernel */
-	bzhdr.type_of_loader = BZI_LOADER_TYPE_ETHERBOOT;
-	if ( bzhdr.version >= 0x0201 ) {
-		bzhdr.heap_end_ptr = ( rm_heap_end - 0x200 );
-		bzhdr.loadflags |= BZI_CAN_USE_HEAP;
-	}
-	if ( bzhdr.version >= 0x0202 ) {
-		bzhdr.cmd_line_ptr = user_to_phys ( rm_kernel, rm_cmdline );
-	} else {
-		uint16_t cmd_line_magic = BZI_CMD_LINE_MAGIC;
-		uint16_t cmd_line_offset = rm_cmdline;
-
-		put_real ( cmd_line_magic, rm_kernel_seg,
-			   BZI_CMD_LINE_MAGIC_OFFSET );
-		put_real ( cmd_line_offset, rm_kernel_seg,
-			   BZI_CMD_LINE_OFFSET_OFFSET );
-		bzhdr.setup_move_size = rm_memsz;
-	}
-	copy_to_user ( rm_kernel, BZI_HDR_OFFSET, &bzhdr, sizeof ( bzhdr ) );
+	/* Update and write out header */
+	if ( ( rc = bzimage_write_header ( image, &load_ctx, &bzhdr ) ) != 0 )
+		return rc;
 
 	/* Record execution context in image private data field */
-	context.rm.kernel_seg = rm_kernel_seg;
-	context.rm.stack = rm_heap_end;
-	image->priv.ul = context.ul;
+	exec_ctx.bz.kernel_seg = load_ctx.rm_kernel_seg;
+	exec_ctx.bz.stack = load_ctx.rm_heap;
+	image->priv.ul = exec_ctx.ul;
 
 	return 0;
 }
diff --git a/src/arch/i386/include/bzimage.h b/src/arch/i386/include/bzimage.h
index 9b338034..96df180d 100644
--- a/src/arch/i386/include/bzimage.h
+++ b/src/arch/i386/include/bzimage.h
@@ -76,17 +76,30 @@ struct bzimage_header {
 /** bzImage "load high" flag */
 #define BZI_LOAD_HIGH 0x01
 
+/** Load address for high-loaded kernels */
+#define BZI_LOAD_HIGH_ADDR 0x100000
+
+/** Load address for low-loaded kernels */
+#define BZI_LOAD_LOW_ADDR 0x10000
+
 /** bzImage "kernel can use heap" flag */
 #define BZI_CAN_USE_HEAP 0x80
 
+
+/** bzImage command-line structure used by older kernels */
+struct bzimage_cmdline {
+	/** Magic signature */
+	uint16_t magic;
+	/** Offset to command line */
+	uint16_t offset;
+} __attribute__ (( packed ));
+
+/** Offset of bzImage command-line structure within kernel image */
+#define BZI_CMDLINE_OFFSET 0x20
+
 /** bzImage command line present magic marker value */
-#define BZI_CMD_LINE_MAGIC 0xa33f
+#define BZI_CMDLINE_MAGIC 0xa33f
 
-/** bzImage command line present magic marker offset */
-#define BZI_CMD_LINE_MAGIC_OFFSET 0x20
-
-/** bzImage command line offset offset */
-#define BZI_CMD_LINE_OFFSET_OFFSET 0x22
 
 /** Amount of stack space to provide */
 #define BZI_STACK_SIZE 0x1000