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Diffstat (limited to 'arch/x86/include/asm/bootparam_utils.h')
-rw-r--r--arch/x86/include/asm/bootparam_utils.h20
1 files changed, 18 insertions, 2 deletions
diff --git a/arch/x86/include/asm/bootparam_utils.h b/arch/x86/include/asm/bootparam_utils.h
index 5b5e9cb774b..653668d140f 100644
--- a/arch/x86/include/asm/bootparam_utils.h
+++ b/arch/x86/include/asm/bootparam_utils.h
@@ -14,13 +14,29 @@
* analysis of kexec-tools; if other broken bootloaders initialize a
* different set of fields we will need to figure out how to disambiguate.
*
+ * Note: efi_info is commonly left uninitialized, but that field has a
+ * private magic, so it is better to leave it unchanged.
*/
static void sanitize_boot_params(struct boot_params *boot_params)
{
+ /*
+ * IMPORTANT NOTE TO BOOTLOADER AUTHORS: do not simply clear
+ * this field. The purpose of this field is to guarantee
+ * compliance with the x86 boot spec located in
+ * Documentation/x86/boot.txt . That spec says that the
+ * *whole* structure should be cleared, after which only the
+ * portion defined by struct setup_header (boot_params->hdr)
+ * should be copied in.
+ *
+ * If you're having an issue because the sentinel is set, you
+ * need to change the whole structure to be cleared, not this
+ * (or any other) individual field, or you will soon have
+ * problems again.
+ */
if (boot_params->sentinel) {
- /*fields in boot_params are not valid, clear them */
+ /* fields in boot_params are left uninitialized, clear them */
memset(&boot_params->olpc_ofw_header, 0,
- (char *)&boot_params->alt_mem_k -
+ (char *)&boot_params->efi_info -
(char *)&boot_params->olpc_ofw_header);
memset(&boot_params->kbd_status, 0,
(char *)&boot_params->hdr -