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authorArd Biesheuvel <ard.biesheuvel@linaro.org>2015-10-08 19:02:04 (GMT)
committerCatalin Marinas <catalin.marinas@arm.com>2015-10-12 15:20:12 (GMT)
commite8f3010f7326c00368dbc057bd052bec80dfc072 (patch)
tree111ad1d750410588ecd346fc257c05565963f0fd /arch
parent207918461eb0aca720fddec5da79bc71c133b9f1 (diff)
downloadlinux-e8f3010f7326c00368dbc057bd052bec80dfc072.tar.xz
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 <ard.biesheuvel@linaro.org> Reviewed-by: Matt Fleming <matt.fleming@intel.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/arm64/kernel/Makefile12
-rw-r--r--arch/arm64/kernel/efi-entry.S10
-rw-r--r--arch/arm64/kernel/head.S14
-rw-r--r--arch/arm64/kernel/image.h27
4 files changed, 49 insertions, 14 deletions
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index 22dc9bc..7b17f62 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 8ce9b05..a773db9 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 90d09ed..28a81e9 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 8fae075..e083af0 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 */