ARM32 crt0: Split headers and code

I finally figured out how to best achieve this without breaking GNU ld * Force code to be at known dest of 4096 * Move _start into .text * Load the _start symbol address and then minus 4096 to get the load address This should make the binary more PE32 compatible Change in ncroxon/gnu-efi#45 Signed-off-by: Callum Farmer <[email protected]>
gmbr3 · Sep 26, 2024 · db8677f · db8677f
1 parent e8b286f
commit db8677f
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Showing 2 changed files with 11 additions and 9 deletions.
diff --git a/efi/crt0/crt0-efi-arm.S b/efi/crt0/crt0-efi-arm.S
@@ -45,11 +45,11 @@ optional_header:
 	.2byte	0x10b				// PE32+ format
 	.byte	0x02				// MajorLinkerVersion
 	.byte	0x14				// MinorLinkerVersion
-	.4byte	_etext - _start		// SizeOfCode
+	.4byte	_text_size - ImageBase		// SizeOfCode
 	.4byte	_alldata_size - ImageBase		// SizeOfInitializedData
 	.4byte	0				// SizeOfUninitializedData
 	.4byte	_start - ImageBase		// AddressOfEntryPoint
-	.4byte	_start - ImageBase		// BaseOfCode
+	.4byte	_text - ImageBase		// BaseOfCode
 	.4byte	_reloc - ImageBase		// BaseOfData
 
 extra_header_fields:
@@ -67,7 +67,7 @@ extra_header_fields:
 	.4byte	_image_end - ImageBase		// SizeOfImage
 
 	// Everything before the kernel image is considered part of the header
-	.4byte	_start - ImageBase		// SizeOfHeaders
+	.4byte	_text - ImageBase		// SizeOfHeaders
 	.4byte	0				// CheckSum
 	.2byte	EFI_SUBSYSTEM			// Subsystem
 	.2byte	0				// DllCharacteristics
@@ -100,10 +100,10 @@ extra_header_fields:
 section_table:
 
 	.ascii	".text\0\0\0"
-	.4byte	_evtext - _start // VirtualSize
-	.4byte	_start - ImageBase	// VirtualAddress
-	.4byte	_etext - _start		// SizeOfRawData
-	.4byte	_start - ImageBase	// PointerToRawData
+	.4byte	_text_vsize - ImageBase // VirtualSize
+	.4byte	_text - ImageBase	// VirtualAddress
+	.4byte	_text_size - ImageBase		// SizeOfRawData
+	.4byte	_text - ImageBase	// PointerToRawData
 	.4byte	0		// PointerToRelocations (0 for executables)
 	.4byte	0		// PointerToLineNumbers (0 for executables)
 	.2byte	0		// NumberOfRelocations  (0 for executables)
@@ -173,7 +173,7 @@ section_table:
 	.4byte	0x40000040	// Characteristics (section flags)
 #endif
 
-.balign 256
+.text
 .globl	_start
 .type _start,%function
 _start:
@@ -184,7 +184,8 @@ _start:
 	adr		r1, .L_DYNAMIC
 	ldr		r0, [r1]
 	add		r1, r0, r1
-	adr		r0, ImageBase
+	adr		r0, _start
+	sub		r0, r0, #0x1000
 	bl		_relocate
 	teq		r0, #0
 	bne		0f

diff --git a/efi/lds/elf_arm_efi.lds b/efi/lds/elf_arm_efi.lds
@@ -5,6 +5,7 @@ SECTIONS
 {
   .text 0 : {
     *(.text.head)
+    . = 0x1000;
     _text = .;
     *(.text)
     *(.text.*)