linux-kernel - [tip: x86/boot] x86/boot: Split off PE/COFF .data section

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Date:   Sun, 17 Sep 2023 18:12:49 -0000
From:   "tip-bot2 for Ard Biesheuvel" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Ard Biesheuvel <ardb@...nel.org>, Ingo Molnar <mingo@...nel.org>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/boot] x86/boot: Split off PE/COFF .data section

The following commit has been merged into the x86/boot branch of tip:

Commit-ID:     34951f3c28bdf6481d949a20413b2ce7693687b2
Gitweb:        https://git.kernel.org/tip/34951f3c28bdf6481d949a20413b2ce7693687b2
Author:        Ard Biesheuvel <ardb@...nel.org>
AuthorDate:    Fri, 15 Sep 2023 17:16:31 
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Sun, 17 Sep 2023 19:48:43 +02:00

x86/boot: Split off PE/COFF .data section

Describe the code and data of the decompressor binary using separate
.text and .data PE/COFF sections, so that we will be able to map them
using restricted permissions once we increase the section and file
alignment sufficiently. This avoids the need for memory mappings that
are writable and executable at the same time, which is something that
is best avoided for security reasons.

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Link: https://lore.kernel.org/r/20230915171623.655440-17-ardb@google.com
---
 arch/x86/boot/Makefile |  2 +-
 arch/x86/boot/header.S | 19 +++++++++++++++----
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile
index cc04917..3cece19 100644
--- a/arch/x86/boot/Makefile
+++ b/arch/x86/boot/Makefile
@@ -89,7 +89,7 @@ $(obj)/vmlinux.bin: $(obj)/compressed/vmlinux FORCE
 
 SETUP_OBJS = $(addprefix $(obj)/,$(setup-y))
 
-sed-zoffset := -e 's/^\([0-9a-fA-F]*\) [a-zA-Z] \(startup_32\|efi.._stub_entry\|efi\(32\)\?_pe_entry\|input_data\|kernel_info\|_end\|_ehead\|_text\|_edata\|z_.*\)$$/\#define ZO_\2 0x\1/p'
+sed-zoffset := -e 's/^\([0-9a-fA-F]*\) [a-zA-Z] \(startup_32\|efi.._stub_entry\|efi\(32\)\?_pe_entry\|input_data\|kernel_info\|_end\|_ehead\|_text\|_e\?data\|z_.*\)$$/\#define ZO_\2 0x\1/p'
 
 quiet_cmd_zoffset = ZOFFSET $@
       cmd_zoffset = $(NM) $< | sed -n $(sed-zoffset) > $@
diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
index 9e9641e..a1f9861 100644
--- a/arch/x86/boot/header.S
+++ b/arch/x86/boot/header.S
@@ -75,9 +75,9 @@ optional_header:
 	.byte	0x02				# MajorLinkerVersion
 	.byte	0x14				# MinorLinkerVersion
 
-	.long	setup_size + ZO__end - 0x200	# SizeOfCode
+	.long	ZO__data			# SizeOfCode
 
-	.long	0				# SizeOfInitializedData
+	.long	ZO__end - ZO__data		# SizeOfInitializedData
 	.long	0				# SizeOfUninitializedData
 
 	.long	setup_size + ZO_efi_pe_entry	# AddressOfEntryPoint
@@ -178,9 +178,9 @@ section_table:
 	.byte	0
 	.byte	0
 	.byte	0
-	.long	ZO__end
+	.long	ZO__data
 	.long	setup_size
-	.long	ZO__edata			# Size of initialized data
+	.long	ZO__data			# Size of initialized data
 						# on disk
 	.long	setup_size
 	.long	0				# PointerToRelocations
@@ -191,6 +191,17 @@ section_table:
 		IMAGE_SCN_MEM_READ		| \
 		IMAGE_SCN_MEM_EXECUTE		# Characteristics
 
+	.ascii	".data\0\0\0"
+	.long	ZO__end - ZO__data		# VirtualSize
+	.long	setup_size + ZO__data		# VirtualAddress
+	.long	ZO__edata - ZO__data		# SizeOfRawData
+	.long	setup_size + ZO__data		# PointerToRawData
+
+	.long	0, 0, 0
+	.long	IMAGE_SCN_CNT_INITIALIZED_DATA	| \
+		IMAGE_SCN_MEM_READ		| \
+		IMAGE_SCN_MEM_WRITE		# Characteristics
+
 	.set	section_count, (. - section_table) / 40
 #endif /* CONFIG_EFI_STUB */