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>

diff --git a/arch/arm/lib/crt0_arm_efi.S b/arch/arm/lib/crt0_arm_efi.S
index b45c034c23cb7ae62a513a37aaf165f07d77d93a..b5dfd4e381955a105fedd55b4a7e234ea4035a3e 100644 (file)
--- 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 767ebda6351b5463ecb1958b8a791ccd58dc708b..41440594aa61f2e96183f9e74a2f2bae5b35cbff 100644 (file)
--- 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)