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* [PATCH v2 0/3] arm64: head: pad Image header to 64 KB and unmap it
@ 2020-11-17 12:47 Ard Biesheuvel
  2020-11-17 12:47 ` [PATCH v2 1/3] arm64: omit [_text, _stext) from permanent kernel mapping Ard Biesheuvel
                   ` (3 more replies)
  0 siblings, 4 replies; 5+ messages in thread
From: Ard Biesheuvel @ 2020-11-17 12:47 UTC (permalink / raw)
  To: linux-arm-kernel
  Cc: mark.rutland, will, catalin.marinas, james.morse, robin.murphy,
	Ard Biesheuvel

The EFI header definition was updated recently to increase the section
alignment to 64 KB, which causes the EFI loader to put the kernel Image
at an offset that is guaranteed to be compatible with the kernel's image
placement policy when CONFIG_RELOCATABLE=y, removing the need to move it
around in DRAM before boot.

This change failed to take into account that the first section in the
PE/COFF description should start at a 64 KB aligned boundary as well,
and so even though EFI loaders don't seem to care, the current PE/COFF
layout is not 100% compliant.

So let's fix this by padding the size of the .head region to 64 KB,
and while at it, removing it from the kernel's executable mapping, which
is now guaranteed to be possible regardless of the page size the kernel
is running with. And if we don't map it, we don't need to reserve it
either.

Changes since v1:
- drop the original first patch that fixed the actual bug - it has already
  been merged
- add Will's acks
- use a better NOP and a better name for the macro that emits it (#3)

Cc: catalin.marinas@arm.com
Cc: will@kernel.org
Cc: mark.rutland@arm.com
Cc: james.morse@arm.com
Cc: robin.murphy@arm.com

Ard Biesheuvel (3):
  arm64: omit [_text, _stext) from permanent kernel mapping
  arm64/head: avoid symbol names pointing into first 64 KB of kernel
    image
  arm64: head: tidy up the Image header definition

 arch/arm64/kernel/efi-header.S  | 84 ++++++++++++--------
 arch/arm64/kernel/head.S        | 19 +----
 arch/arm64/kernel/setup.c       |  4 +-
 arch/arm64/kernel/vmlinux.lds.S |  2 +-
 arch/arm64/mm/init.c            |  2 +-
 arch/arm64/mm/mmu.c             | 10 +--
 6 files changed, 60 insertions(+), 61 deletions(-)

-- 
2.20.1


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^ permalink raw reply	[flat|nested] 5+ messages in thread
* [PATCH v2 1/3] arm64: omit [_text, _stext) from permanent kernel mapping
  2020-11-17 12:47 [PATCH v2 0/3] arm64: head: pad Image header to 64 KB and unmap it Ard Biesheuvel
@ 2020-11-17 12:47 ` Ard Biesheuvel
  2020-11-17 12:47 ` [PATCH v2 2/3] arm64/head: avoid symbol names pointing into first 64 KB of kernel image Ard Biesheuvel
                   ` (2 subsequent siblings)
  3 siblings, 0 replies; 5+ messages in thread
From: Ard Biesheuvel @ 2020-11-17 12:47 UTC (permalink / raw)
  To: linux-arm-kernel
  Cc: mark.rutland, will, catalin.marinas, james.morse, robin.murphy,
	Ard Biesheuvel

In a previous patch, we increased the size of the EFI PE/COFF header
to 64 KB, which resulted in the _stext symbol to appear at a fixed
offset of 64 KB into the image.

Since 64 KB is also the largest page size we support, this completely
removes the need to map the first 64 KB of the kernel image, given that
it only contains the arm64 Image header and the EFI header, neither of
which we ever access again after booting the kernel. More importantly,
we should avoid an executable mapping of non-executable and not entirely
predictable data, to deal with the unlikely event that we inadvertently
emitted something that looks like an opcode that could be used as a
gadget for speculative execution.

So let's limit the kernel mapping of .text to the [_stext, _etext)
region, which matches the view of generic code (such as kallsyms) when
it reasons about the boundaries of the kernel's .text section.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
---
 arch/arm64/kernel/efi-header.S  |  7 -------
 arch/arm64/kernel/setup.c       |  4 ++--
 arch/arm64/kernel/vmlinux.lds.S |  2 +-
 arch/arm64/mm/init.c            |  2 +-
 arch/arm64/mm/mmu.c             | 10 +++++-----
 5 files changed, 9 insertions(+), 16 deletions(-)

diff --git a/arch/arm64/kernel/efi-header.S b/arch/arm64/kernel/efi-header.S
index a71844fb923e..3ad4aecff033 100644
--- a/arch/arm64/kernel/efi-header.S
+++ b/arch/arm64/kernel/efi-header.S
@@ -140,13 +140,6 @@ efi_debug_entry:
 	.set	efi_debug_entry_size, . - efi_debug_entry
 #endif
 
-	/*
-	 * EFI will load .text onwards at the 4k section alignment
-	 * described in the PE/COFF header. To ensure that instruction
-	 * sequences using an adrp and a :lo12: immediate will function
-	 * correctly at this alignment, we must ensure that .text is
-	 * placed at a 4k boundary in the Image to begin with.
-	 */
 	.balign	SEGMENT_ALIGN
 efi_header_end:
 	.endm
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index 133257ffd859..fe1cf52f5f80 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -206,7 +206,7 @@ static void __init request_standard_resources(void)
 	unsigned long i = 0;
 	size_t res_size;
 
-	kernel_code.start   = __pa_symbol(_text);
+	kernel_code.start   = __pa_symbol(_stext);
 	kernel_code.end     = __pa_symbol(__init_begin - 1);
 	kernel_data.start   = __pa_symbol(_sdata);
 	kernel_data.end     = __pa_symbol(_end - 1);
@@ -283,7 +283,7 @@ u64 cpu_logical_map(int cpu)
 
 void __init __no_sanitize_address setup_arch(char **cmdline_p)
 {
-	init_mm.start_code = (unsigned long) _text;
+	init_mm.start_code = (unsigned long) _stext;
 	init_mm.end_code   = (unsigned long) _etext;
 	init_mm.end_data   = (unsigned long) _edata;
 	init_mm.brk	   = (unsigned long) _end;
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 1bda604f4c70..48b222f1c700 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -121,7 +121,7 @@ SECTIONS
 		_text = .;
 		HEAD_TEXT
 	}
-	.text : {			/* Real text segment		*/
+	.text : ALIGN(SEGMENT_ALIGN) {	/* Real text segment		*/
 		_stext = .;		/* Text and read-only data	*/
 			IRQENTRY_TEXT
 			SOFTIRQENTRY_TEXT
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 095540667f0f..aa438b9d7f40 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -367,7 +367,7 @@ void __init arm64_memblock_init(void)
 	 * Register the kernel text, kernel data, initrd, and initial
 	 * pagetables with memblock.
 	 */
-	memblock_reserve(__pa_symbol(_text), _end - _text);
+	memblock_reserve(__pa_symbol(_stext), _end - _stext);
 	if (IS_ENABLED(CONFIG_BLK_DEV_INITRD) && phys_initrd_size) {
 		/* the generic initrd code expects virtual addresses */
 		initrd_start = __phys_to_virt(phys_initrd_start);
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index ca692a815731..9692a81ce6ee 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -464,14 +464,14 @@ void __init mark_linear_text_alias_ro(void)
 	/*
 	 * Remove the write permissions from the linear alias of .text/.rodata
 	 */
-	update_mapping_prot(__pa_symbol(_text), (unsigned long)lm_alias(_text),
-			    (unsigned long)__init_begin - (unsigned long)_text,
+	update_mapping_prot(__pa_symbol(_stext), (unsigned long)lm_alias(_stext),
+			    (unsigned long)__init_begin - (unsigned long)_stext,
 			    PAGE_KERNEL_RO);
 }
 
 static void __init map_mem(pgd_t *pgdp)
 {
-	phys_addr_t kernel_start = __pa_symbol(_text);
+	phys_addr_t kernel_start = __pa_symbol(_stext);
 	phys_addr_t kernel_end = __pa_symbol(__init_begin);
 	phys_addr_t start, end;
 	int flags = 0;
@@ -506,7 +506,7 @@ static void __init map_mem(pgd_t *pgdp)
 	}
 
 	/*
-	 * Map the linear alias of the [_text, __init_begin) interval
+	 * Map the linear alias of the [_stext, __init_begin) interval
 	 * as non-executable now, and remove the write permission in
 	 * mark_linear_text_alias_ro() below (which will be called after
 	 * alternative patching has completed). This makes the contents
@@ -665,7 +665,7 @@ static void __init map_kernel(pgd_t *pgdp)
 	 * Only rodata will be remapped with different permissions later on,
 	 * all other segments are allowed to use contiguous mappings.
 	 */
-	map_kernel_segment(pgdp, _text, _etext, text_prot, &vmlinux_text, 0,
+	map_kernel_segment(pgdp, _stext, _etext, text_prot, &vmlinux_text, 0,
 			   VM_NO_GUARD);
 	map_kernel_segment(pgdp, __start_rodata, __inittext_begin, PAGE_KERNEL,
 			   &vmlinux_rodata, NO_CONT_MAPPINGS, VM_NO_GUARD);
-- 
2.20.1


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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply related	[flat|nested] 5+ messages in thread
* [PATCH v2 2/3] arm64/head: avoid symbol names pointing into first 64 KB of kernel image
  2020-11-17 12:47 [PATCH v2 0/3] arm64: head: pad Image header to 64 KB and unmap it Ard Biesheuvel
  2020-11-17 12:47 ` [PATCH v2 1/3] arm64: omit [_text, _stext) from permanent kernel mapping Ard Biesheuvel
@ 2020-11-17 12:47 ` Ard Biesheuvel
  2020-11-17 12:47 ` [PATCH v2 3/3] arm64: head: tidy up the Image header definition Ard Biesheuvel
  2020-11-17 18:08 ` [PATCH v2 0/3] arm64: head: pad Image header to 64 KB and unmap it Catalin Marinas
  3 siblings, 0 replies; 5+ messages in thread
From: Ard Biesheuvel @ 2020-11-17 12:47 UTC (permalink / raw)
  To: linux-arm-kernel
  Cc: mark.rutland, will, catalin.marinas, james.morse, robin.murphy,
	Ard Biesheuvel

We no longer map the first 64 KB of the kernel image, as there is nothing
there that we ever need to refer back to once the kernel has booted. Even
though facilities like kallsyms are very careful to only refer to the
region that starts at _stext when mapping virtual addresses to symbol
names, let's avoid any confusion by switching to local .L prefixed symbol
names for the EFI header, as none of them have any significance to the
rest of the kernel.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
---
 arch/arm64/kernel/efi-header.S | 46 ++++++++++----------
 1 file changed, 22 insertions(+), 24 deletions(-)

diff --git a/arch/arm64/kernel/efi-header.S b/arch/arm64/kernel/efi-header.S
index 3ad4aecff033..ddaf57d825b5 100644
--- a/arch/arm64/kernel/efi-header.S
+++ b/arch/arm64/kernel/efi-header.S
@@ -9,28 +9,26 @@
 
 	.macro	__EFI_PE_HEADER
 	.long	PE_MAGIC
-coff_header:
 	.short	IMAGE_FILE_MACHINE_ARM64		// Machine
-	.short	section_count				// NumberOfSections
+	.short	.Lsection_count				// NumberOfSections
 	.long	0 					// TimeDateStamp
 	.long	0					// PointerToSymbolTable
 	.long	0					// NumberOfSymbols
-	.short	section_table - optional_header		// SizeOfOptionalHeader
+	.short	.Lsection_table - .Loptional_header	// SizeOfOptionalHeader
 	.short	IMAGE_FILE_DEBUG_STRIPPED | \
 		IMAGE_FILE_EXECUTABLE_IMAGE | \
 		IMAGE_FILE_LINE_NUMS_STRIPPED		// Characteristics
 
-optional_header:
+.Loptional_header:
 	.short	PE_OPT_MAGIC_PE32PLUS			// PE32+ format
 	.byte	0x02					// MajorLinkerVersion
 	.byte	0x14					// MinorLinkerVersion
-	.long	__initdata_begin - efi_header_end	// SizeOfCode
+	.long	__initdata_begin - .Lefi_header_end	// SizeOfCode
 	.long	__pecoff_data_size			// SizeOfInitializedData
 	.long	0					// SizeOfUninitializedData
 	.long	__efistub_efi_pe_entry - _head		// AddressOfEntryPoint
-	.long	efi_header_end - _head			// BaseOfCode
+	.long	.Lefi_header_end - _head		// BaseOfCode
 
-extra_header_fields:
 	.quad	0					// ImageBase
 	.long	SEGMENT_ALIGN				// SectionAlignment
 	.long	PECOFF_FILE_ALIGNMENT			// FileAlignment
@@ -45,7 +43,7 @@ extra_header_fields:
 	.long	_end - _head				// SizeOfImage
 
 	// Everything before the kernel image is considered part of the header
-	.long	efi_header_end - _head			// SizeOfHeaders
+	.long	.Lefi_header_end - _head		// SizeOfHeaders
 	.long	0					// CheckSum
 	.short	IMAGE_SUBSYSTEM_EFI_APPLICATION		// Subsystem
 	.short	0					// DllCharacteristics
@@ -54,7 +52,7 @@ extra_header_fields:
 	.quad	0					// SizeOfHeapReserve
 	.quad	0					// SizeOfHeapCommit
 	.long	0					// LoaderFlags
-	.long	(section_table - .) / 8			// NumberOfRvaAndSizes
+	.long	(.Lsection_table - .) / 8		// NumberOfRvaAndSizes
 
 	.quad	0					// ExportTable
 	.quad	0					// ImportTable
@@ -64,17 +62,17 @@ extra_header_fields:
 	.quad	0					// BaseRelocationTable
 
 #ifdef CONFIG_DEBUG_EFI
-	.long	efi_debug_table - _head			// DebugTable
-	.long	efi_debug_table_size
+	.long	.Lefi_debug_table - _head		// DebugTable
+	.long	.Lefi_debug_table_size
 #endif
 
 	// Section table
-section_table:
+.Lsection_table:
 	.ascii	".text\0\0\0"
-	.long	__initdata_begin - efi_header_end	// VirtualSize
-	.long	efi_header_end - _head			// VirtualAddress
-	.long	__initdata_begin - efi_header_end	// SizeOfRawData
-	.long	efi_header_end - _head			// PointerToRawData
+	.long	__initdata_begin - .Lefi_header_end	// VirtualSize
+	.long	.Lefi_header_end - _head		// VirtualAddress
+	.long	__initdata_begin - .Lefi_header_end	// SizeOfRawData
+	.long	.Lefi_header_end - _head		// PointerToRawData
 
 	.long	0					// PointerToRelocations
 	.long	0					// PointerToLineNumbers
@@ -98,7 +96,7 @@ section_table:
 		IMAGE_SCN_MEM_READ | \
 		IMAGE_SCN_MEM_WRITE			// Characteristics
 
-	.set	section_count, (. - section_table) / 40
+	.set	.Lsection_count, (. - .Lsection_table) / 40
 
 #ifdef CONFIG_DEBUG_EFI
 	/*
@@ -114,21 +112,21 @@ section_table:
 	__INITRODATA
 
 	.align	2
-efi_debug_table:
+.Lefi_debug_table:
 	// EFI_IMAGE_DEBUG_DIRECTORY_ENTRY
 	.long	0					// Characteristics
 	.long	0					// TimeDateStamp
 	.short	0					// MajorVersion
 	.short	0					// MinorVersion
 	.long	IMAGE_DEBUG_TYPE_CODEVIEW		// Type
-	.long	efi_debug_entry_size			// SizeOfData
+	.long	.Lefi_debug_entry_size			// SizeOfData
 	.long	0					// RVA
-	.long	efi_debug_entry - _head			// FileOffset
+	.long	.Lefi_debug_entry - _head		// FileOffset
 
-	.set	efi_debug_table_size, . - efi_debug_table
+	.set	.Lefi_debug_table_size, . - .Lefi_debug_table
 	.previous
 
-efi_debug_entry:
+.Lefi_debug_entry:
 	// EFI_IMAGE_DEBUG_CODEVIEW_NB10_ENTRY
 	.ascii	"NB10"					// Signature
 	.long	0					// Unknown
@@ -137,9 +135,9 @@ efi_debug_entry:
 
 	.asciz	VMLINUX_PATH
 
-	.set	efi_debug_entry_size, . - efi_debug_entry
+	.set	.Lefi_debug_entry_size, . - .Lefi_debug_entry
 #endif
 
 	.balign	SEGMENT_ALIGN
-efi_header_end:
+.Lefi_header_end:
 	.endm
-- 
2.20.1


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linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply related	[flat|nested] 5+ messages in thread
* [PATCH v2 3/3] arm64: head: tidy up the Image header definition
  2020-11-17 12:47 [PATCH v2 0/3] arm64: head: pad Image header to 64 KB and unmap it Ard Biesheuvel
  2020-11-17 12:47 ` [PATCH v2 1/3] arm64: omit [_text, _stext) from permanent kernel mapping Ard Biesheuvel
  2020-11-17 12:47 ` [PATCH v2 2/3] arm64/head: avoid symbol names pointing into first 64 KB of kernel image Ard Biesheuvel
@ 2020-11-17 12:47 ` Ard Biesheuvel
  2020-11-17 18:08 ` [PATCH v2 0/3] arm64: head: pad Image header to 64 KB and unmap it Catalin Marinas
  3 siblings, 0 replies; 5+ messages in thread
From: Ard Biesheuvel @ 2020-11-17 12:47 UTC (permalink / raw)
  To: linux-arm-kernel
  Cc: mark.rutland, will, catalin.marinas, james.morse, robin.murphy,
	Ard Biesheuvel

Even though support for EFI boot remains entirely optional for arm64,
it is unlikely that we will ever be able to repurpose the image header
fields that the EFI loader relies on, i.e., the magic NOP at offset
0x0 and the PE header address at offset 0x3c.

So let's factor out the differences into a 'efi_signature_nop' macro and
a local symbol representing the PE header address, and move the
conditional definitions into efi-header.S, taking into account whether
CONFIG_EFI is enabled or not. While at it, switch to a signature NOP
that behaves more like a NOP, i.e., one that only clobbers the
flags.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
---
 arch/arm64/kernel/efi-header.S | 43 +++++++++++++++-----
 arch/arm64/kernel/head.S       | 19 +--------
 2 files changed, 35 insertions(+), 27 deletions(-)

diff --git a/arch/arm64/kernel/efi-header.S b/arch/arm64/kernel/efi-header.S
index ddaf57d825b5..28d8a5dca5f1 100644
--- a/arch/arm64/kernel/efi-header.S
+++ b/arch/arm64/kernel/efi-header.S
@@ -7,7 +7,27 @@
 #include <linux/pe.h>
 #include <linux/sizes.h>
 
+	.macro	efi_signature_nop
+#ifdef CONFIG_EFI
+.L_head:
+	/*
+	 * This ccmp instruction has no meaningful effect except that
+	 * its opcode forms the magic "MZ" signature required by UEFI.
+	 */
+	ccmp	x18, #0, #0xd, pl
+#else
+	/*
+	 * Bootloaders may inspect the opcode at the start of the kernel
+	 * image to decide if the kernel is capable of booting via UEFI.
+	 * So put an ordinary NOP here, not the "MZ.." pseudo-nop above.
+	 */
+	nop
+#endif
+	.endm
+
 	.macro	__EFI_PE_HEADER
+#ifdef CONFIG_EFI
+	.set	.Lpe_header_offset, . - .L_head
 	.long	PE_MAGIC
 	.short	IMAGE_FILE_MACHINE_ARM64		// Machine
 	.short	.Lsection_count				// NumberOfSections
@@ -26,8 +46,8 @@
 	.long	__initdata_begin - .Lefi_header_end	// SizeOfCode
 	.long	__pecoff_data_size			// SizeOfInitializedData
 	.long	0					// SizeOfUninitializedData
-	.long	__efistub_efi_pe_entry - _head		// AddressOfEntryPoint
-	.long	.Lefi_header_end - _head		// BaseOfCode
+	.long	__efistub_efi_pe_entry - .L_head	// AddressOfEntryPoint
+	.long	.Lefi_header_end - .L_head		// BaseOfCode
 
 	.quad	0					// ImageBase
 	.long	SEGMENT_ALIGN				// SectionAlignment
@@ -40,10 +60,10 @@
 	.short	0					// MinorSubsystemVersion
 	.long	0					// Win32VersionValue
 
-	.long	_end - _head				// SizeOfImage
+	.long	_end - .L_head				// SizeOfImage
 
 	// Everything before the kernel image is considered part of the header
-	.long	.Lefi_header_end - _head		// SizeOfHeaders
+	.long	.Lefi_header_end - .L_head		// SizeOfHeaders
 	.long	0					// CheckSum
 	.short	IMAGE_SUBSYSTEM_EFI_APPLICATION		// Subsystem
 	.short	0					// DllCharacteristics
@@ -62,7 +82,7 @@
 	.quad	0					// BaseRelocationTable
 
 #ifdef CONFIG_DEBUG_EFI
-	.long	.Lefi_debug_table - _head		// DebugTable
+	.long	.Lefi_debug_table - .L_head		// DebugTable
 	.long	.Lefi_debug_table_size
 #endif
 
@@ -70,9 +90,9 @@
 .Lsection_table:
 	.ascii	".text\0\0\0"
 	.long	__initdata_begin - .Lefi_header_end	// VirtualSize
-	.long	.Lefi_header_end - _head		// VirtualAddress
+	.long	.Lefi_header_end - .L_head		// VirtualAddress
 	.long	__initdata_begin - .Lefi_header_end	// SizeOfRawData
-	.long	.Lefi_header_end - _head		// PointerToRawData
+	.long	.Lefi_header_end - .L_head		// PointerToRawData
 
 	.long	0					// PointerToRelocations
 	.long	0					// PointerToLineNumbers
@@ -84,9 +104,9 @@
 
 	.ascii	".data\0\0\0"
 	.long	__pecoff_data_size			// VirtualSize
-	.long	__initdata_begin - _head		// VirtualAddress
+	.long	__initdata_begin - .L_head		// VirtualAddress
 	.long	__pecoff_data_rawsize			// SizeOfRawData
-	.long	__initdata_begin - _head		// PointerToRawData
+	.long	__initdata_begin - .L_head		// PointerToRawData
 
 	.long	0					// PointerToRelocations
 	.long	0					// PointerToLineNumbers
@@ -121,7 +141,7 @@
 	.long	IMAGE_DEBUG_TYPE_CODEVIEW		// Type
 	.long	.Lefi_debug_entry_size			// SizeOfData
 	.long	0					// RVA
-	.long	.Lefi_debug_entry - _head		// FileOffset
+	.long	.Lefi_debug_entry - .L_head		// FileOffset
 
 	.set	.Lefi_debug_table_size, . - .Lefi_debug_table
 	.previous
@@ -140,4 +160,7 @@
 
 	.balign	SEGMENT_ALIGN
 .Lefi_header_end:
+#else
+	.set	.Lpe_header_offset, 0x0
+#endif
 	.endm
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index d8d9caf02834..c1f8f2c5be47 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -58,21 +58,11 @@
  * in the entry routines.
  */
 	__HEAD
-_head:
 	/*
 	 * DO NOT MODIFY. Image header expected by Linux boot-loaders.
 	 */
-#ifdef CONFIG_EFI
-	/*
-	 * This add instruction has no meaningful effect except that
-	 * its opcode forms the magic "MZ" signature required by UEFI.
-	 */
-	add	x13, x18, #0x16
-	b	primary_entry
-#else
+	efi_signature_nop			// special NOP to identity as PE/COFF executable
 	b	primary_entry			// branch to kernel start, magic
-	.long	0				// reserved
-#endif
 	.quad	0				// Image load offset from start of RAM, little-endian
 	le64sym	_kernel_size_le			// Effective size of kernel image, little-endian
 	le64sym	_kernel_flags_le		// Informative flags, little-endian
@@ -80,14 +70,9 @@ _head:
 	.quad	0				// reserved
 	.quad	0				// reserved
 	.ascii	ARM64_IMAGE_MAGIC		// Magic number
-#ifdef CONFIG_EFI
-	.long	pe_header - _head		// Offset to the PE header.
+	.long	.Lpe_header_offset		// Offset to the PE header.
 
-pe_header:
 	__EFI_PE_HEADER
-#else
-	.long	0				// reserved
-#endif
 
 	__INIT
 
-- 
2.20.1


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^ permalink raw reply related	[flat|nested] 5+ messages in thread
* Re: [PATCH v2 0/3] arm64: head: pad Image header to 64 KB and unmap it
  2020-11-17 12:47 [PATCH v2 0/3] arm64: head: pad Image header to 64 KB and unmap it Ard Biesheuvel
                   ` (2 preceding siblings ...)
  2020-11-17 12:47 ` [PATCH v2 3/3] arm64: head: tidy up the Image header definition Ard Biesheuvel
@ 2020-11-17 18:08 ` Catalin Marinas
  3 siblings, 0 replies; 5+ messages in thread
From: Catalin Marinas @ 2020-11-17 18:08 UTC (permalink / raw)
  To: Ard Biesheuvel, linux-arm-kernel
  Cc: mark.rutland, robin.murphy, Will Deacon, james.morse

On Tue, 17 Nov 2020 13:47:26 +0100, Ard Biesheuvel wrote:
> The EFI header definition was updated recently to increase the section
> alignment to 64 KB, which causes the EFI loader to put the kernel Image
> at an offset that is guaranteed to be compatible with the kernel's image
> placement policy when CONFIG_RELOCATABLE=y, removing the need to move it
> around in DRAM before boot.
> 
> This change failed to take into account that the first section in the
> PE/COFF description should start at a 64 KB aligned boundary as well,
> and so even though EFI loaders don't seem to care, the current PE/COFF
> layout is not 100% compliant.
> 
> [...]

Applied to arm64 (for-next/pad-image-header), thanks!

[1/3] arm64: omit [_text, _stext) from permanent kernel mapping
      https://git.kernel.org/arm64/c/e2a073dde921
[2/3] arm64/head: avoid symbol names pointing into first 64 KB of kernel image
      https://git.kernel.org/arm64/c/b50a3225cdff
[3/3] arm64: head: tidy up the Image header definition
      https://git.kernel.org/arm64/c/7919385b9fb3

-- 
Catalin


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^ permalink raw reply	[flat|nested] 5+ messages in thread
end of thread, other threads:[~2020-11-17 18:09 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2020-11-17 12:47 [PATCH v2 0/3] arm64: head: pad Image header to 64 KB and unmap it Ard Biesheuvel
2020-11-17 12:47 ` [PATCH v2 1/3] arm64: omit [_text, _stext) from permanent kernel mapping Ard Biesheuvel
2020-11-17 12:47 ` [PATCH v2 2/3] arm64/head: avoid symbol names pointing into first 64 KB of kernel image Ard Biesheuvel
2020-11-17 12:47 ` [PATCH v2 3/3] arm64: head: tidy up the Image header definition Ard Biesheuvel
2020-11-17 18:08 ` [PATCH v2 0/3] arm64: head: pad Image header to 64 KB and unmap it Catalin Marinas

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