MFC r316754: loader/multiboot: fix multiboot loading

Sponsored by: Citrix Systems R&D

1 files changed, 42 insertions, 0 deletions

diff --git a/sys/boot/i386/libi386/multiboot.c b/sys/boot/i386/libi386/multiboot.c
index 00e36f2..9aac640 100644
--- a/sys/boot/i386/libi386/multiboot.c
+++ b/sys/boot/i386/libi386/multiboot.c
@@ -267,7 +267,39 @@ multiboot_exec(struct preloaded_file *fp)
 	 * information is placed at the start of the second module and
 	 * the original modulep value is saved together with the other
 	 * metadata, so we can relocate everything.
+	 *
+	 * Native layout:
+	 *           fp->f_addr + fp->f_size
+	 * +---------+----------------+------------+
+	 * |         |                |            |
+	 * | Kernel  |    Modules     |  Metadata  |
+	 * |         |                |            |
+	 * +---------+----------------+------------+
+	 * fp->f_addr                 modulep      kernend
+	 *
+	 * Xen layout:
+	 *
+	 * Initial:
+	 *                      fp->f_addr + fp->f_size
+	 * +---------+----------+----------------+------------+
+	 * |         |          |                |            |
+	 * | Kernel  | Reserved |    Modules     |  Metadata  |
+	 * |         |          |                |  dry run   |
+	 * +---------+----------+----------------+------------+
+	 * fp->f_addr
+	 *
+	 * After metadata polacement (ie: final):
+	 *                                  fp->f_addr + fp->f_size
+	 * +-----------+---------+----------+----------------+
+	 * |           |         |          |                |
+	 * |  Kernel   |  Free   | Metadata |    Modules     |
+	 * |           |         |          |                |
+	 * +-----------+---------+----------+----------------+
+	 * fp->f_addr            modulep                     kernend
+	 * \__________/          \__________________________/
+	 *  Multiboot module 0    Multiboot module 1
 	 */
+
 	fp = file_findfile(NULL, "elf kernel");
 	if (fp == NULL) {
 		printf("No FreeBSD kernel provided, aborting\n");
@@ -275,6 +307,13 @@ multiboot_exec(struct preloaded_file *fp)
 		goto error;
 	}
 
+	if (fp->f_metadata != NULL) {
+		printf("FreeBSD kernel already contains metadata, aborting\n");
+		error = EINVAL;
+		goto error;
+	}
+
+
 	mb_mod = malloc(sizeof(struct multiboot_mod_list) * NUM_MODULES);
 	if (mb_mod == NULL) {
 		error = ENOMEM;
@@ -312,6 +351,9 @@ multiboot_exec(struct preloaded_file *fp)
 		goto error;
 	}
 
+	/* Clean the metadata added to the kernel in the bi_load64 dry run */
+	file_removemetadata(fp);
+
 	/*
 	 * This is the position where the second multiboot module
 	 * will be placed.