linux/arch/arm64/Makefile
Torsten Duwe 3b23e4991f arm64: implement ftrace with regs
This patch implements FTRACE_WITH_REGS for arm64, which allows a traced
function's arguments (and some other registers) to be captured into a
struct pt_regs, allowing these to be inspected and/or modified. This is
a building block for live-patching, where a function's arguments may be
forwarded to another function. This is also necessary to enable ftrace
and in-kernel pointer authentication at the same time, as it allows the
LR value to be captured and adjusted prior to signing.

Using GCC's -fpatchable-function-entry=N option, we can have the
compiler insert a configurable number of NOPs between the function entry
point and the usual prologue. This also ensures functions are AAPCS
compliant (e.g. disabling inter-procedural register allocation).

For example, with -fpatchable-function-entry=2, GCC 8.1.0 compiles the
following:

| unsigned long bar(void);
|
| unsigned long foo(void)
| {
|         return bar() + 1;
| }

... to:

| <foo>:
|         nop
|         nop
|         stp     x29, x30, [sp, #-16]!
|         mov     x29, sp
|         bl      0 <bar>
|         add     x0, x0, #0x1
|         ldp     x29, x30, [sp], #16
|         ret

This patch builds the kernel with -fpatchable-function-entry=2,
prefixing each function with two NOPs. To trace a function, we replace
these NOPs with a sequence that saves the LR into a GPR, then calls an
ftrace entry assembly function which saves this and other relevant
registers:

| mov	x9, x30
| bl	<ftrace-entry>

Since patchable functions are AAPCS compliant (and the kernel does not
use x18 as a platform register), x9-x18 can be safely clobbered in the
patched sequence and the ftrace entry code.

There are now two ftrace entry functions, ftrace_regs_entry (which saves
all GPRs), and ftrace_entry (which saves the bare minimum). A PLT is
allocated for each within modules.

Signed-off-by: Torsten Duwe <duwe@suse.de>
[Mark: rework asm, comments, PLTs, initialization, commit message]
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Torsten Duwe <duwe@suse.de>
Tested-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Tested-by: Torsten Duwe <duwe@suse.de>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Julien Thierry <jthierry@redhat.com>
Cc: Will Deacon <will@kernel.org>
2019-11-06 14:17:35 +00:00

179 lines
5.8 KiB
Makefile

#
# arch/arm64/Makefile
#
# This file is included by the global makefile so that you can add your own
# architecture-specific flags and dependencies.
#
# This file is subject to the terms and conditions of the GNU General Public
# License. See the file "COPYING" in the main directory of this archive
# for more details.
#
# Copyright (C) 1995-2001 by Russell King
LDFLAGS_vmlinux :=--no-undefined -X
CPPFLAGS_vmlinux.lds = -DTEXT_OFFSET=$(TEXT_OFFSET)
GZFLAGS :=-9
ifeq ($(CONFIG_RELOCATABLE), y)
# Pass --no-apply-dynamic-relocs to restore pre-binutils-2.27 behaviour
# for relative relocs, since this leads to better Image compression
# with the relocation offsets always being zero.
LDFLAGS_vmlinux += -shared -Bsymbolic -z notext -z norelro \
$(call ld-option, --no-apply-dynamic-relocs)
endif
ifeq ($(CONFIG_ARM64_ERRATUM_843419),y)
ifeq ($(call ld-option, --fix-cortex-a53-843419),)
$(warning ld does not support --fix-cortex-a53-843419; kernel may be susceptible to erratum)
else
LDFLAGS_vmlinux += --fix-cortex-a53-843419
endif
endif
# Check for binutils support for specific extensions
lseinstr := $(call as-instr,.arch_extension lse,-DCONFIG_AS_LSE=1)
ifeq ($(CONFIG_ARM64_LSE_ATOMICS), y)
ifeq ($(lseinstr),)
$(warning LSE atomics not supported by binutils)
endif
endif
cc_has_k_constraint := $(call try-run,echo \
'int main(void) { \
asm volatile("and w0, w0, %w0" :: "K" (4294967295)); \
return 0; \
}' | $(CC) -S -x c -o "$$TMP" -,,-DCONFIG_CC_HAS_K_CONSTRAINT=1)
ifeq ($(CONFIG_ARM64), y)
brokengasinst := $(call as-instr,1:\n.inst 0\n.rept . - 1b\n\nnop\n.endr\n,,-DCONFIG_BROKEN_GAS_INST=1)
ifneq ($(brokengasinst),)
$(warning Detected assembler with broken .inst; disassembly will be unreliable)
endif
endif
KBUILD_CFLAGS += -mgeneral-regs-only $(lseinstr) $(brokengasinst) \
$(compat_vdso) $(cc_has_k_constraint)
KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
KBUILD_CFLAGS += $(call cc-disable-warning, psabi)
KBUILD_AFLAGS += $(lseinstr) $(brokengasinst) $(compat_vdso)
KBUILD_CFLAGS += $(call cc-option,-mabi=lp64)
KBUILD_AFLAGS += $(call cc-option,-mabi=lp64)
ifeq ($(CONFIG_STACKPROTECTOR_PER_TASK),y)
prepare: stack_protector_prepare
stack_protector_prepare: prepare0
$(eval KBUILD_CFLAGS += -mstack-protector-guard=sysreg \
-mstack-protector-guard-reg=sp_el0 \
-mstack-protector-guard-offset=$(shell \
awk '{if ($$2 == "TSK_STACK_CANARY") print $$3;}' \
include/generated/asm-offsets.h))
endif
ifeq ($(CONFIG_CPU_BIG_ENDIAN), y)
KBUILD_CPPFLAGS += -mbig-endian
CHECKFLAGS += -D__AARCH64EB__
AS += -EB
# Prefer the baremetal ELF build target, but not all toolchains include
# it so fall back to the standard linux version if needed.
KBUILD_LDFLAGS += -EB $(call ld-option, -maarch64elfb, -maarch64linuxb)
UTS_MACHINE := aarch64_be
else
KBUILD_CPPFLAGS += -mlittle-endian
CHECKFLAGS += -D__AARCH64EL__
AS += -EL
# Same as above, prefer ELF but fall back to linux target if needed.
KBUILD_LDFLAGS += -EL $(call ld-option, -maarch64elf, -maarch64linux)
UTS_MACHINE := aarch64
endif
CHECKFLAGS += -D__aarch64__
ifeq ($(CONFIG_ARM64_MODULE_PLTS),y)
KBUILD_LDS_MODULE += $(srctree)/arch/arm64/kernel/module.lds
endif
ifeq ($(CONFIG_DYNAMIC_FTRACE_WITH_REGS),y)
KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY
CC_FLAGS_FTRACE := -fpatchable-function-entry=2
endif
# Default value
head-y := arch/arm64/kernel/head.o
# The byte offset of the kernel image in RAM from the start of RAM.
ifeq ($(CONFIG_ARM64_RANDOMIZE_TEXT_OFFSET), y)
TEXT_OFFSET := $(shell awk "BEGIN {srand(); printf \"0x%06x\n\", \
int(2 * 1024 * 1024 / (2 ^ $(CONFIG_ARM64_PAGE_SHIFT)) * \
rand()) * (2 ^ $(CONFIG_ARM64_PAGE_SHIFT))}")
else
TEXT_OFFSET := 0x00080000
endif
ifeq ($(CONFIG_KASAN_SW_TAGS), y)
KASAN_SHADOW_SCALE_SHIFT := 4
else
KASAN_SHADOW_SCALE_SHIFT := 3
endif
KBUILD_CFLAGS += -DKASAN_SHADOW_SCALE_SHIFT=$(KASAN_SHADOW_SCALE_SHIFT)
KBUILD_CPPFLAGS += -DKASAN_SHADOW_SCALE_SHIFT=$(KASAN_SHADOW_SCALE_SHIFT)
KBUILD_AFLAGS += -DKASAN_SHADOW_SCALE_SHIFT=$(KASAN_SHADOW_SCALE_SHIFT)
export TEXT_OFFSET GZFLAGS
core-y += arch/arm64/
libs-y := arch/arm64/lib/ $(libs-y)
core-$(CONFIG_EFI_STUB) += $(objtree)/drivers/firmware/efi/libstub/lib.a
# Default target when executing plain make
boot := arch/arm64/boot
KBUILD_IMAGE := $(boot)/Image.gz
all: Image.gz
Image: vmlinux
$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
Image.%: Image
$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
zinstall install:
$(Q)$(MAKE) $(build)=$(boot) $@
PHONY += vdso_install
vdso_install:
$(Q)$(MAKE) $(build)=arch/arm64/kernel/vdso $@
# We use MRPROPER_FILES and CLEAN_FILES now
archclean:
$(Q)$(MAKE) $(clean)=$(boot)
ifeq ($(KBUILD_EXTMOD),)
# We need to generate vdso-offsets.h before compiling certain files in kernel/.
# In order to do that, we should use the archprepare target, but we can't since
# asm-offsets.h is included in some files used to generate vdso-offsets.h, and
# asm-offsets.h is built in prepare0, for which archprepare is a dependency.
# Therefore we need to generate the header after prepare0 has been made, hence
# this hack.
prepare: vdso_prepare
vdso_prepare: prepare0
$(Q)$(MAKE) $(build)=arch/arm64/kernel/vdso include/generated/vdso-offsets.h
$(if $(CONFIG_COMPAT_VDSO),$(Q)$(MAKE) \
$(build)=arch/arm64/kernel/vdso32 \
include/generated/vdso32-offsets.h)
endif
define archhelp
echo '* Image.gz - Compressed kernel image (arch/$(ARCH)/boot/Image.gz)'
echo ' Image - Uncompressed kernel image (arch/$(ARCH)/boot/Image)'
echo ' install - Install uncompressed kernel'
echo ' zinstall - Install compressed kernel'
echo ' Install using (your) ~/bin/installkernel or'
echo ' (distribution) /sbin/installkernel or'
echo ' install to $$(INSTALL_PATH) and run lilo'
endef