bootvx: x86: Explicitly clear the bootloader image size

VxWorks bootloader stores its size at a pre-defined offset @ 0x5004.
Later when VxWorks kernel boots up and system memory information is
retrieved from the E820 table, the bootloader size will be subtracted
from the total system memory size to calculate the size of available
memory for the OS.

Explicitly clear the bootloader image size otherwise if memory
at this offset happens to contain some garbage data, the final
available memory size for the kernel is insane.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

cmd/elf.c

@@ -348,6 +348,13 @@ int do_bootvx(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 	info->entries = install_e820_map(E820MAX, data);
 	info->addr = (info->entries - 1) * sizeof(struct e820entry) +
 		     E820_DATA_OFFSET;
+
+	/*
+	 * Explicitly clear the bootloader image size otherwise if memory
+	 * at this offset happens to contain some garbage data, the final
+	 * available memory size for the kernel is insane.
+	 */
+	*(u32 *)(base + BOOT_IMAGE_SIZE_OFFSET) = 0;
 #endif
 
 	/*

include/vxworks.h

@@ -43,6 +43,15 @@ struct e820info {
 	u32 error;	/* must be zero */
 };
 
+/*
+ * VxWorks bootloader stores its size at a pre-defined offset @ 0x5004.
+ * Later when VxWorks kernel boots up and system memory information is
+ * retrieved from the E820 table, the bootloader size will be subtracted
+ * from the total system memory size to calculate the size of available
+ * memory for the OS.
+ */
+#define BOOT_IMAGE_SIZE_OFFSET	0x5004
+
 int do_bootvx(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[]);
 void boot_prep_vxworks(bootm_headers_t *images);
 void boot_jump_vxworks(bootm_headers_t *images);