From 97da9aea78ab71e92778649bf9d1071f30e260f0 Mon Sep 17 00:00:00 2001
From: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Date: Mon, 26 Feb 2024 22:24:08 +0100
Subject: [PATCH] arm: separate .data and .text sections of EFI binaries
EFI binaries should not contain sections that are both writable and
executable. Separate the RX .text section from the RW .data section.
We currently don't created relocation sections (.rel.*) for our EFI
binaries. Anyway these would have to be converted to PE/COFF relocations.
Enumerate them under DISCARD and add a comment.
Correct the characteristics of the sections.
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
---
arch/arm/lib/crt0_arm_efi.S | 40 ++++++++++++++++++++++++++++--------
arch/arm/lib/elf_arm_efi.lds | 28 ++++++++++++++++++-------
2 files changed, 52 insertions(+), 16 deletions(-)
diff --git a/arch/arm/lib/crt0_arm_efi.S b/arch/arm/lib/crt0_arm_efi.S
index b45c034c23..b5dfd4e381 100644
--- a/arch/arm/lib/crt0_arm_efi.S
+++ b/arch/arm/lib/crt0_arm_efi.S
@@ -23,7 +23,7 @@ pe_header:
.long IMAGE_NT_SIGNATURE /* 'PE' */
coff_header:
.short IMAGE_FILE_MACHINE_THUMB /* Mixed ARM/Thumb */
- .short 2 /* nr_sections */
+ .short 3 /* nr_sections */
.long 0 /* TimeDateStamp */
.long 0 /* PointerToSymbolTable */
.long 0 /* NumberOfSymbols */
@@ -102,22 +102,44 @@ section_table:
.long 0 /* PointerToLineNumbers */
.short 0 /* NumberOfRelocations */
.short 0 /* NumberOfLineNumbers */
- .long 0x42100040 /* Characteristics (section flags) */
+ /* Characteristics (section flags) */
+ .long (IMAGE_SCN_MEM_READ | \
+ IMAGE_SCN_MEM_DISCARDABLE | \
+ IMAGE_SCN_CNT_INITIALIZED_DATA)
.ascii ".text"
.byte 0
.byte 0
.byte 0 /* end of 0 padding of section name */
- .long _edata - _start /* VirtualSize */
+ .long _text_size /* VirtualSize */
.long _start - image_base /* VirtualAddress */
- .long _edata - _start /* SizeOfRawData */
+ .long _text_size /* SizeOfRawData */
.long _start - image_base /* PointerToRawData */
+ .long 0 /* PointerToRelocations */
+ .long 0 /* PointerToLineNumbers */
+ .short 0 /* NumberOfRelocations */
+ .short 0 /* NumberOfLineNumbers */
+ /* Characteristics (section flags) */
+ .long (IMAGE_SCN_MEM_READ | \
+ IMAGE_SCN_MEM_EXECUTE | \
+ IMAGE_SCN_CNT_CODE)
- .long 0 /* PointerToRelocations (0 for executables) */
- .long 0 /* PointerToLineNumbers (0 for executables) */
- .short 0 /* NumberOfRelocations (0 for executables) */
- .short 0 /* NumberOfLineNumbers (0 for executables) */
- .long 0xe0500020 /* Characteristics (section flags) */
+ .ascii ".data"
+ .byte 0
+ .byte 0
+ .byte 0 /* end of 0 padding of section name */
+ .long _data_size /* VirtualSize */
+ .long _data - image_base /* VirtualAddress */
+ .long _data_size /* SizeOfRawData */
+ .long _data - image_base /* PointerToRawData */
+ .long 0 /* PointerToRelocations */
+ .long 0 /* PointerToLineNumbers */
+ .short 0 /* NumberOfRelocations */
+ .short 0 /* NumberOfLineNumbers */
+ /* Characteristics (section flags) */
+ .long (IMAGE_SCN_MEM_WRITE | \
+ IMAGE_SCN_MEM_READ | \
+ IMAGE_SCN_CNT_INITIALIZED_DATA)
.align 12
_start:
diff --git a/arch/arm/lib/elf_arm_efi.lds b/arch/arm/lib/elf_arm_efi.lds
index 767ebda635..41440594aa 100644
--- a/arch/arm/lib/elf_arm_efi.lds
+++ b/arch/arm/lib/elf_arm_efi.lds
@@ -7,6 +7,12 @@
OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm")
OUTPUT_ARCH(arm)
+
+PHDRS
+{
+ data PT_LOAD FLAGS(3); /* PF_W | PF_X */
+}
+
ENTRY(_start)
SECTIONS
{
@@ -18,11 +24,13 @@ SECTIONS
*(.gnu.linkonce.t.*)
*(.srodata)
*(.rodata*)
+ . = ALIGN(16);
+ *(.dynamic);
. = ALIGN(512);
}
_etext = .;
_text_size = . - _text;
- .dynamic : { *(.dynamic) }
+ . = ALIGN(4096);
.data : {
_data = .;
*(.sdata)
@@ -47,14 +55,20 @@ SECTIONS
. = ALIGN(512);
_bss_end = .;
_edata = .;
- }
- .rel.dyn : { *(.rel.dyn) }
- .rel.plt : { *(.rel.plt) }
- .rel.got : { *(.rel.got) }
- .rel.data : { *(.rel.data) *(.rel.data*) }
- _data_size = . - _etext;
+ } :data
+ _data_size = . - _data;
/DISCARD/ : {
+ /*
+ * We don't support relocations. These would have to be
+ * translated from ELF to PE format and added to the .reloc
+ * section.
+ */
+ *(.rel.dyn)
+ *(.rel.plt)
+ *(.rel.got)
+ *(.rel.data)
+ *(.rel.data*)
*(.rel.reloc)
*(.eh_frame)
*(.note.GNU-stack)
--
2.39.5