tools: readnote: Add bzImage kernel support

Add the check of bzImage kernel and make it work
with RHEL 6 big zImage kernel

Signed-off-by: Xuesen Guo <Xuesen.Guo@hitachiconsulting.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>

tools/xcutils/readnotes.c

@@ -18,6 +18,48 @@
 
 static xc_interface *xch;
 
+/* According to the implemation of xc_dom_probe_bzimage_kernel() function */
+/* We add support of bzImage kernel */
+/* Copied from tools/libxc/xc_doom_bzImageloader.c */
+struct setup_header {
+	uint8_t  _pad0[0x1f1];  /* skip uninteresting stuff */
+	uint8_t  setup_sects;
+	uint16_t root_flags;
+	uint32_t syssize;
+	uint16_t ram_size;
+	uint16_t vid_mode;
+	uint16_t root_dev;
+	uint16_t boot_flag;
+	uint16_t jump;
+	uint32_t header;
+#define HDR_MAGIC  "HdrS"
+#define HDR_MAGIC_SZ 4
+	uint16_t version;
+#define VERSION(h,l) (((h)<<8) | (l))
+	uint32_t realmode_swtch;
+	uint16_t start_sys;
+	uint16_t kernel_version;
+	uint8_t  type_of_loader;
+	uint8_t  loadflags;
+	uint16_t setup_move_size;
+	uint32_t code32_start;
+	uint32_t ramdisk_image;
+	uint32_t ramdisk_size;
+	uint32_t bootsect_kludge;
+	uint16_t heap_end_ptr;
+	uint16_t _pad1;
+	uint32_t cmd_line_ptr;
+	uint32_t initrd_addr_max;
+	uint32_t kernel_alignment;
+	uint8_t  relocatable_kernel;
+	uint8_t  _pad2[3];
+	uint32_t cmdline_size;
+	uint32_t hardware_subarch;
+	uint64_t hardware_subarch_data;
+	uint32_t payload_offset;
+	uint32_t payload_length;
+} __attribute__((packed));
+
 static void print_string_note(const char *prefix, struct elf_binary *elf,
 			      const elf_note *note)
 {
@@ -131,6 +173,9 @@ int main(int argc, char **argv)
 	const elf_shdr *shdr;
 	int notes_found = 0;
 
+	struct setup_header *hdr;
+	uint64_t payload_offset, payload_length;
+
 	if (argc != 2)
 	{
 		fprintf(stderr, "Usage: readnotes <elfimage>\n");
@@ -159,13 +204,45 @@ int main(int argc, char **argv)
 		fprintf(stderr, "Unable to map %s: %s\n", f, strerror(errno));
 		return 1;
 	}
-	size = st.st_size;
+	
+	/* Check the magic of bzImage kernel */
+	hdr = (struct setup_header *)image;
+	if ( memcmp(&hdr->header, HDR_MAGIC, HDR_MAGIC_SZ) == 0 )
+	{
+		if ( hdr->version < VERSION(2,8) )
+		{
+			printf("%s: boot protocol too old (%04x)", __FUNCTION__, hdr->version);
+			return 1;
+		}
 
-	usize = xc_dom_check_gzip(xch, image, st.st_size);
+		/* upcast to 64 bits to avoid overflow */
+		/* setup_sects is u8 and so cannot overflow */
+		payload_offset = (hdr->setup_sects + 1) * 512;
+		payload_offset += hdr->payload_offset;
+		payload_length = hdr->payload_length;
+		
+		if ( payload_offset >= st.st_size )
+		{
+			printf("%s: payload offset overflow", __FUNCTION__);
+			return 1;
+		}
+		if ( (payload_offset + payload_length) > st.st_size )
+		{
+			printf("%s: payload length overflow", __FUNCTION__);
+			return 1;
+		}
+
+		image = image + payload_offset;
+		size = payload_length;
+	} else {
+		size = st.st_size;
+	}
+
+	usize = xc_dom_check_gzip(xch, image, size);
 	if (usize)
 	{
 		tmp = malloc(usize);
-		xc_dom_do_gunzip(xch, image, st.st_size, tmp, usize);
+		xc_dom_do_gunzip(xch, image, size, tmp, usize);
 		image = tmp;
 		size = usize;
 	}