From 3c4aff6b9a183b4f24eb7b8dd6c8a92cdba3bc75 Mon Sep 17 00:00:00 2001 From: Peter Jones Date: Wed, 6 Mar 2013 13:00:23 -0500 Subject: [PATCH] x86, doc: Be explicit about what the x86 struct boot_params requires If the sentinel triggers, we do not want the boot loader authors to just poke it and make the error go away, we want them to actually fix the problem. This should help avoid making the incorrect change in non-compliant bootloaders. [ hpa: dropped the Documentation/x86/boot.txt hunk pending clarifications ] Signed-off-by: Peter Jones Link: http://lkml.kernel.org/r/1362592823-28967-1-git-send-email-pjones@redhat.com Signed-off-by: H. Peter Anvin --- arch/x86/include/asm/bootparam_utils.h | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/bootparam_utils.h b/arch/x86/include/asm/bootparam_utils.h index ff808ef4fdb4..653668d140f9 100644 --- a/arch/x86/include/asm/bootparam_utils.h +++ b/arch/x86/include/asm/bootparam_utils.h @@ -19,8 +19,22 @@ */ 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->efi_info - (char *)&boot_params->olpc_ofw_header); -- 2.30.2