From e8f3010f7326c00368dbc057bd052bec80dfc072 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Thu, 8 Oct 2015 20:02:04 +0100 Subject: arm64/efi: isolate EFI stub from the kernel proper Since arm64 does not use a builtin decompressor, the EFI stub is built into the kernel proper. So far, this has been working fine, but actually, since the stub is in fact a PE/COFF relocatable binary that is executed at an unknown offset in the 1:1 mapping provided by the UEFI firmware, we should not be seamlessly sharing code with the kernel proper, which is a position dependent executable linked at a high virtual offset. So instead, separate the contents of libstub and its dependencies, by putting them into their own namespace by prefixing all of its symbols with __efistub. This way, we have tight control over what parts of the kernel proper are referenced by the stub. Signed-off-by: Ard Biesheuvel Reviewed-by: Matt Fleming Signed-off-by: Catalin Marinas --- arch/arm64/kernel/Makefile | 12 ++++++++++-- arch/arm64/kernel/efi-entry.S | 10 +++++----- arch/arm64/kernel/head.S | 14 +++++++------- arch/arm64/kernel/image.h | 27 +++++++++++++++++++++++++++ 4 files changed, 49 insertions(+), 14 deletions(-) (limited to 'arch/arm64/kernel') diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index 22dc9bc781be..7b17f6245f1e 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -20,6 +20,14 @@ arm64-obj-y := debug-monitors.o entry.o irq.o fpsimd.o \ cpufeature.o alternative.o cacheinfo.o \ smp.o smp_spin_table.o topology.o +stub-obj := efi-stub.o efi-entry.o +extra-y := $(stub-obj) +stub-obj := $(patsubst %.o,%.stub.o,$(stub-obj)) + +OBJCOPYFLAGS := --prefix-symbols=__efistub_ +$(obj)/%.stub.o: $(obj)/%.o FORCE + $(call if_changed,objcopy) + arm64-obj-$(CONFIG_COMPAT) += sys32.o kuser32.o signal32.o \ sys_compat.o entry32.o \ ../../arm/kernel/opcodes.o @@ -32,7 +40,7 @@ arm64-obj-$(CONFIG_CPU_PM) += sleep.o suspend.o arm64-obj-$(CONFIG_CPU_IDLE) += cpuidle.o arm64-obj-$(CONFIG_JUMP_LABEL) += jump_label.o arm64-obj-$(CONFIG_KGDB) += kgdb.o -arm64-obj-$(CONFIG_EFI) += efi.o efi-stub.o efi-entry.o +arm64-obj-$(CONFIG_EFI) += efi.o $(stub-obj) arm64-obj-$(CONFIG_PCI) += pci.o arm64-obj-$(CONFIG_ARMV8_DEPRECATED) += armv8_deprecated.o arm64-obj-$(CONFIG_ACPI) += acpi.o @@ -40,7 +48,7 @@ arm64-obj-$(CONFIG_ACPI) += acpi.o obj-y += $(arm64-obj-y) vdso/ obj-m += $(arm64-obj-m) head-y := head.o -extra-y := $(head-y) vmlinux.lds +extra-y += $(head-y) vmlinux.lds # vDSO - this must be built first to generate the symbol offsets $(call objectify,$(arm64-obj-y)): $(obj)/vdso/vdso-offsets.h diff --git a/arch/arm64/kernel/efi-entry.S b/arch/arm64/kernel/efi-entry.S index 8ce9b0577442..a773db92908b 100644 --- a/arch/arm64/kernel/efi-entry.S +++ b/arch/arm64/kernel/efi-entry.S @@ -29,7 +29,7 @@ * we want to be. The kernel image wants to be placed at TEXT_OFFSET * from start of RAM. */ -ENTRY(efi_stub_entry) +ENTRY(entry) /* * Create a stack frame to save FP/LR with extra space * for image_addr variable passed to efi_entry(). @@ -86,8 +86,8 @@ ENTRY(efi_stub_entry) * entries for the VA range of the current image, so no maintenance is * necessary. */ - adr x0, efi_stub_entry - adr x1, efi_stub_entry_end + adr x0, entry + adr x1, entry_end sub x1, x1, x0 bl __flush_dcache_area @@ -120,5 +120,5 @@ efi_load_fail: ldp x29, x30, [sp], #32 ret -efi_stub_entry_end: -ENDPROC(efi_stub_entry) +entry_end: +ENDPROC(entry) diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 90d09eddd5b2..28a81e948df9 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -120,8 +120,8 @@ efi_head: #endif #ifdef CONFIG_EFI - .globl stext_offset - .set stext_offset, stext - efi_head + .globl __efistub_stext_offset + .set __efistub_stext_offset, stext - efi_head .align 3 pe_header: .ascii "PE" @@ -144,8 +144,8 @@ optional_header: .long _end - stext // SizeOfCode .long 0 // SizeOfInitializedData .long 0 // SizeOfUninitializedData - .long efi_stub_entry - efi_head // AddressOfEntryPoint - .long stext_offset // BaseOfCode + .long __efistub_entry - efi_head // AddressOfEntryPoint + .long __efistub_stext_offset // BaseOfCode extra_header_fields: .quad 0 // ImageBase @@ -162,7 +162,7 @@ extra_header_fields: .long _end - efi_head // SizeOfImage // Everything before the kernel image is considered part of the header - .long stext_offset // SizeOfHeaders + .long __efistub_stext_offset // SizeOfHeaders .long 0 // CheckSum .short 0xa // Subsystem (EFI application) .short 0 // DllCharacteristics @@ -207,9 +207,9 @@ section_table: .byte 0 .byte 0 // end of 0 padding of section name .long _end - stext // VirtualSize - .long stext_offset // VirtualAddress + .long __efistub_stext_offset // VirtualAddress .long _edata - stext // SizeOfRawData - .long stext_offset // PointerToRawData + .long __efistub_stext_offset // PointerToRawData .long 0 // PointerToRelocations (0 for executables) .long 0 // PointerToLineNumbers (0 for executables) diff --git a/arch/arm64/kernel/image.h b/arch/arm64/kernel/image.h index 8fae0756e175..e083af0dd546 100644 --- a/arch/arm64/kernel/image.h +++ b/arch/arm64/kernel/image.h @@ -59,4 +59,31 @@ _kernel_offset_le = DATA_LE64(TEXT_OFFSET); \ _kernel_flags_le = DATA_LE64(__HEAD_FLAGS); +#ifdef CONFIG_EFI + +/* + * The EFI stub has its own symbol namespace prefixed by __efistub_, to + * isolate it from the kernel proper. The following symbols are legally + * accessed by the stub, so provide some aliases to make them accessible. + * Only include data symbols here, or text symbols of functions that are + * guaranteed to be safe when executed at another offset than they were + * linked at. The routines below are all implemented in assembler in a + * position independent manner + */ +__efistub_memcmp = __pi_memcmp; +__efistub_memchr = __pi_memchr; +__efistub_memcpy = __pi_memcpy; +__efistub_memmove = __pi_memmove; +__efistub_memset = __pi_memset; +__efistub_strlen = __pi_strlen; +__efistub_strcmp = __pi_strcmp; +__efistub_strncmp = __pi_strncmp; +__efistub___flush_dcache_area = __pi___flush_dcache_area; + +__efistub__text = _text; +__efistub__end = _end; +__efistub__edata = _edata; + +#endif + #endif /* __ASM_IMAGE_H */ -- cgit v1.2.3