x86, boot: Sanitize boot_params if not zeroed on creation

Use the new sentinel field to detect bootloaders which fail to follow
protocol and don't initialize fields in struct boot_params that they
do not explicitly initialize to zero.

Based on an original patch and research by Yinghai Lu.
Changed by hpa to be invoked both in the decompression path and in the
kernel proper; the latter for the case where a bootloader takes over
decompression.

Originally-by: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1359058816-7615-26-git-send-email-yinghai@kernel.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

arch/x86/kernel/head32.c

@@ -18,6 +18,7 @@
 #include <asm/io_apic.h>
 #include <asm/bios_ebda.h>
 #include <asm/tlbflush.h>
+#include <asm/bootparam_utils.h>
 
 static void __init i386_default_early_setup(void)
 {
@@ -30,6 +31,8 @@ static void __init i386_default_early_setup(void)
 
 void __init i386_start_kernel(void)
 {
+	sanitize_boot_params(&boot_params);
+
 	memblock_reserve(__pa_symbol(&_text),
 			 __pa_symbol(&__bss_stop) - __pa_symbol(&_text));
 

arch/x86/kernel/head64.c

@@ -25,6 +25,7 @@
 #include <asm/kdebug.h>
 #include <asm/e820.h>
 #include <asm/bios_ebda.h>
+#include <asm/bootparam_utils.h>
 
 static void __init zap_identity_mappings(void)
 {
@@ -46,6 +47,7 @@ static void __init copy_bootdata(char *real_mode_data)
 	char * command_line;
 
 	memcpy(&boot_params, real_mode_data, sizeof boot_params);
+	sanitize_boot_params(&boot_params);
 	if (boot_params.hdr.cmd_line_ptr) {
 		command_line = __va(boot_params.hdr.cmd_line_ptr);
 		memcpy(boot_command_line, command_line, COMMAND_LINE_SIZE);