Merge branch 'x86-boot-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 bootup changes from Ingo Molnar:
 "Deal with bootloaders which fail to initialize unknown fields in
  boot_params to zero, by sanitizing boot params passed in.

  This unbreaks versions of kexec-utils.  Other bootloaders do not
  appear to show sensitivity to this change, but it's a possibility for
  breakage nevertheless."

* 'x86-boot-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86, boot: Sanitize boot_params if not zeroed on creation

5 files changed, 46 insertions, 0 deletions

diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 88f7ff6da404..7cb56c6ca351 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -325,6 +325,8 @@ asmlinkage void decompress_kernel(void *rmode, memptr heap,
 {
 	real_mode = rmode;
 
+	sanitize_boot_params(real_mode);
+
 	if (real_mode->screen_info.orig_video_mode == 7) {
 		vidmem = (char *) 0xb0000;
 		vidport = 0x3b4;
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 0e6dc0ee0eea..674019d8e235 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -18,6 +18,7 @@
 #include <asm/page.h>
 #include <asm/boot.h>
 #include <asm/bootparam.h>
+#include <asm/bootparam_utils.h>
 
 #define BOOT_BOOT_H
 #include "../ctype.h"
diff --git a/arch/x86/include/asm/bootparam_utils.h b/arch/x86/include/asm/bootparam_utils.h
new file mode 100644
index 000000000000..5b5e9cb774b5
--- /dev/null
+++ b/arch/x86/include/asm/bootparam_utils.h
@@ -0,0 +1,38 @@
+#ifndef _ASM_X86_BOOTPARAM_UTILS_H
+#define _ASM_X86_BOOTPARAM_UTILS_H
+
+#include <asm/bootparam.h>
+
+/*
+ * This file is included from multiple environments.  Do not
+ * add completing #includes to make it standalone.
+ */
+
+/*
+ * Deal with bootloaders which fail to initialize unknown fields in
+ * boot_params to zero.  The list fields in this list are taken from
+ * analysis of kexec-tools; if other broken bootloaders initialize a
+ * different set of fields we will need to figure out how to disambiguate.
+ *
+ */
+static void sanitize_boot_params(struct boot_params *boot_params)
+{
+	if (boot_params->sentinel) {
+		/*fields in boot_params are not valid, clear them */
+		memset(&boot_params->olpc_ofw_header, 0,
+		       (char *)&boot_params->alt_mem_k -
+			(char *)&boot_params->olpc_ofw_header);
+		memset(&boot_params->kbd_status, 0,
+		       (char *)&boot_params->hdr -
+		       (char *)&boot_params->kbd_status);
+		memset(&boot_params->_pad7[0], 0,
+		       (char *)&boot_params->edd_mbr_sig_buffer[0] -
+			(char *)&boot_params->_pad7[0]);
+		memset(&boot_params->_pad8[0], 0,
+		       (char *)&boot_params->eddbuf[0] -
+			(char *)&boot_params->_pad8[0]);
+		memset(&boot_params->_pad9[0], 0, sizeof(boot_params->_pad9));
+	}
+}
+
+#endif /* _ASM_X86_BOOTPARAM_UTILS_H */
diff --git a/arch/x86/kernel/head32.c b/arch/x86/kernel/head32.c
index c18f59d10101..6773c918b8cc 100644
--- a/arch/x86/kernel/head32.c
+++ b/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));
 
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 037df57a99ac..849fc9e63c2f 100644
--- a/arch/x86/kernel/head64.c
+++ b/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);