linux-kernel - Re: [PATCH v2 3/3] x86/boot: Introduce the kernel_info.setup_type

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Date:   Fri, 12 Jul 2019 08:59:43 -0700
From:   hpa@...or.com
To:     Daniel Kiper <daniel.kiper@...cle.com>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, x86@...nel.org
CC:     bp@...en8.de, corbet@....net, dpsmith@...rtussolutions.com,
        eric.snowberg@...cle.com, kanth.ghatraju@...cle.com,
        konrad.wilk@...cle.com, mingo@...hat.com,
        ross.philipson@...cle.com, tglx@...utronix.de
Subject: Re: [PATCH v2 3/3] x86/boot: Introduce the kernel_info.setup_type_max

On July 4, 2019 9:36:12 AM PDT, Daniel Kiper <daniel.kiper@...cle.com> wrote:
>This field contains maximal allowed type for setup_data and
>setup_indirect structs.
>
>And finally bump setup_header version in arch/x86/boot/header.S.
>
>Suggested-by: H. Peter Anvin <hpa@...or.com>
>Signed-off-by: Daniel Kiper <daniel.kiper@...cle.com>
>Reviewed-by: Ross Philipson <ross.philipson@...cle.com>
>Reviewed-by: Eric Snowberg <eric.snowberg@...cle.com>
>---
> Documentation/x86/boot.rst             | 10 +++++++++-
> arch/x86/boot/compressed/kernel_info.S |  4 ++++
> arch/x86/boot/header.S                 |  2 +-
> arch/x86/include/uapi/asm/bootparam.h  |  3 +++
> 4 files changed, 17 insertions(+), 2 deletions(-)
>
>diff --git a/Documentation/x86/boot.rst b/Documentation/x86/boot.rst
>index 23d3726d54fc..63609fd0517f 100644
>--- a/Documentation/x86/boot.rst
>+++ b/Documentation/x86/boot.rst
>@@ -73,7 +73,8 @@ Protocol 2.14:	BURNT BY INCORRECT COMMIT
>ae7e1238e68f2a472a125673ab506d49158c188
> 		(x86/boot: Add ACPI RSDP address to setup_header)
> 		DO NOT USE!!! ASSUME SAME AS 2.13.
> 
>-Protocol 2.15:	(Kernel 5.3) Added the kernel_info and setup_indirect.
>+Protocol 2.15:	(Kernel 5.3) Added the kernel_info,
>kernel_info.setup_type_max
>+		and setup_indirect.
>=============	============================================================
> 
> .. note::
>@@ -980,6 +981,13 @@ Offset/size:	0x0004/4
>This field contains the size of the kernel_info including
>kernel_info.header.
>It should be used by the boot loader to detect supported fields in the
>kernel_info.
> 
>+============	==============
>+Field name:	setup_type_max
>+Offset/size:	0x0008/4
>+============	==============
>+
>+  This field contains maximal allowed type for setup_data and
>setup_indirect structs.
>+
> 
> The Image Checksum
> ==================
>diff --git a/arch/x86/boot/compressed/kernel_info.S
>b/arch/x86/boot/compressed/kernel_info.S
>index 3f1cb301b9ff..2f28aabf6558 100644
>--- a/arch/x86/boot/compressed/kernel_info.S
>+++ b/arch/x86/boot/compressed/kernel_info.S
>@@ -1,5 +1,7 @@
> /* SPDX-License-Identifier: GPL-2.0 */
> 
>+#include <asm/bootparam.h>
>+
> 	.section ".rodata.kernel_info", "a"
> 
> 	.global kernel_info
>@@ -9,4 +11,6 @@ kernel_info:
> 	.ascii	"InfO"
>         /* Size. */
> 	.long	kernel_info_end - kernel_info
>+        /* Maximal allowed type for setup_data and setup_indirect
>structs. */
>+	.long	SETUP_TYPE_MAX
> kernel_info_end:
>diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
>index ec6a25a43148..893a456663ab 100644
>--- a/arch/x86/boot/header.S
>+++ b/arch/x86/boot/header.S
>@@ -300,7 +300,7 @@ _start:
> 	# Part 2 of the header, from the old setup.S
> 
> 		.ascii	"HdrS"		# header signature
>-		.word	0x020d		# header version number (>= 0x0105)
>+		.word	0x020f		# header version number (>= 0x0105)
> 					# or else old loadlin-1.5 will fail)
> 		.globl realmode_swtch
> realmode_swtch:	.word	0, 0		# default_switch, SETUPSEG
>diff --git a/arch/x86/include/uapi/asm/bootparam.h
>b/arch/x86/include/uapi/asm/bootparam.h
>index aaaa17fa6ad6..2ba870dae6f3 100644
>--- a/arch/x86/include/uapi/asm/bootparam.h
>+++ b/arch/x86/include/uapi/asm/bootparam.h
>@@ -12,6 +12,9 @@
> #define SETUP_JAILHOUSE			6
> #define SETUP_INDIRECT			7
> 
>+/* max(SETUP_*) */
>+#define SETUP_TYPE_MAX			SETUP_INDIRECT
>+
> /* ram_size flags */
> #define RAMDISK_IMAGE_START_MASK	0x07FF
> #define RAMDISK_PROMPT_FLAG		0x8000

Bump the version number and add setup_max before adding the indirect stuff. That will nicely double as at the very least a first-order validity check.

-- 
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