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>

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 b45c034c23c..b5dfd4e3819 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 767ebda6351..41440594aa6 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)