linux-loongson/arch/riscv/Makefile
Puranjay Mohan c217157bcd
riscv: Implement HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS
This patch enables support for DYNAMIC_FTRACE_WITH_CALL_OPS on RISC-V.
This allows each ftrace callsite to provide an ftrace_ops to the common
ftrace trampoline, allowing each callsite to invoke distinct tracer
functions without the need to fall back to list processing or to
allocate custom trampolines for each callsite. This significantly speeds
up cases where multiple distinct trace functions are used and callsites
are mostly traced by a single tracer.

The idea and most of the implementation is taken from the ARM64's
implementation of the same feature. The idea is to place a pointer to
the ftrace_ops as a literal at a fixed offset from the function entry
point, which can be recovered by the common ftrace trampoline.

We use -fpatchable-function-entry to reserve 8 bytes above the function
entry by emitting 2 4 byte or 4 2 byte  nops depending on the presence of
CONFIG_RISCV_ISA_C. These 8 bytes are patched at runtime with a pointer
to the associated ftrace_ops for that callsite. Functions are aligned to
8 bytes to make sure that the accesses to this literal are atomic.

This approach allows for directly invoking ftrace_ops::func even for
ftrace_ops which are dynamically-allocated (or part of a module),
without going via ftrace_ops_list_func.

We've benchamrked this with the ftrace_ops sample module on Spacemit K1
Jupiter:

Without this patch:

baseline (Linux rivos 6.14.0-09584-g7d06015d936c #3 SMP Sat Mar 29
+-----------------------+-----------------+----------------------------+
|  Number of tracers    | Total time (ns) | Per-call average time      |
|-----------------------+-----------------+----------------------------|
| Relevant | Irrelevant |    100000 calls | Total (ns) | Overhead (ns) |
|----------+------------+-----------------+------------+---------------|
|        0 |          0 |        1357958 |          13 |             - |
|        0 |          1 |        1302375 |          13 |             - |
|        0 |          2 |        1302375 |          13 |             - |
|        0 |         10 |        1379084 |          13 |             - |
|        0 |        100 |        1302458 |          13 |             - |
|        0 |        200 |        1302333 |          13 |             - |
|----------+------------+-----------------+------------+---------------|
|        1 |          0 |       13677833 |         136 |           123 |
|        1 |          1 |       18500916 |         185 |           172 |
|        1 |          2 |       22856459 |         228 |           215 |
|        1 |         10 |       58824709 |         588 |           575 |
|        1 |        100 |      505141584 |        5051 |          5038 |
|        1 |        200 |     1580473126 |       15804 |         15791 |
|----------+------------+-----------------+------------+---------------|
|        1 |          0 |       13561000 |         135 |           122 |
|        2 |          0 |       19707292 |         197 |           184 |
|       10 |          0 |       67774750 |         677 |           664 |
|      100 |          0 |      714123125 |        7141 |          7128 |
|      200 |          0 |     1918065668 |       19180 |         19167 |
+----------+------------+-----------------+------------+---------------+

Note: per-call overhead is estimated relative to the baseline case with
0 relevant tracers and 0 irrelevant tracers.

With this patch:

v4-rc4 (Linux rivos 6.14.0-09598-gd75747611c93 #4 SMP Sat Mar 29
+-----------------------+-----------------+----------------------------+
|  Number of tracers    | Total time (ns) | Per-call average time      |
|-----------------------+-----------------+----------------------------|
| Relevant | Irrelevant |    100000 calls | Total (ns) | Overhead (ns) |
|----------+------------+-----------------+------------+---------------|
|        0 |          0 |         1459917 |         14 |             - |
|        0 |          1 |         1408000 |         14 |             - |
|        0 |          2 |         1383792 |         13 |             - |
|        0 |         10 |         1430709 |         14 |             - |
|        0 |        100 |         1383791 |         13 |             - |
|        0 |        200 |         1383750 |         13 |             - |
|----------+------------+-----------------+------------+---------------|
|        1 |          0 |         5238041 |         52 |            38 |
|        1 |          1 |         5228542 |         52 |            38 |
|        1 |          2 |         5325917 |         53 |            40 |
|        1 |         10 |         5299667 |         52 |            38 |
|        1 |        100 |         5245250 |         52 |            39 |
|        1 |        200 |         5238459 |         52 |            39 |
|----------+------------+-----------------+------------+---------------|
|        1 |          0 |         5239083 |         52 |            38 |
|        2 |          0 |        19449417 |        194 |           181 |
|       10 |          0 |        67718584 |        677 |           663 |
|      100 |          0 |       709840708 |       7098 |          7085 |
|      200 |          0 |      2203580626 |      22035 |         22022 |
+----------+------------+-----------------+------------+---------------+

Note: per-call overhead is estimated relative to the baseline case with
0 relevant tracers and 0 irrelevant tracers.

As can be seen from the above:

 a) Whenever there is a single relevant tracer function associated with a
    tracee, the overhead of invoking the tracer is constant, and does not
    scale with the number of tracers which are *not* associated with that
    tracee.

 b) The overhead for a single relevant tracer has dropped to ~1/3 of the
    overhead prior to this series (from 122ns to 38ns). This is largely
    due to permitting calls to dynamically-allocated ftrace_ops without
    going through ftrace_ops_list_func.

Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>

[update kconfig, asm, refactor]

Signed-off-by: Andy Chiu <andybnac@gmail.com>
Tested-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20250407180838.42877-10-andybnac@gmail.com
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
2025-06-05 11:09:30 -07:00

243 lines
8.2 KiB
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.
#
LDFLAGS_vmlinux := -z norelro
ifeq ($(CONFIG_RELOCATABLE),y)
LDFLAGS_vmlinux += -shared -Bsymbolic -z notext
KBUILD_CFLAGS += -fPIE
endif
ifeq ($(CONFIG_DYNAMIC_FTRACE),y)
LDFLAGS_vmlinux += --no-relax
KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY
ifeq ($(CONFIG_RISCV_ISA_C),y)
CC_FLAGS_FTRACE := -fpatchable-function-entry=8,4
else
CC_FLAGS_FTRACE := -fpatchable-function-entry=4,2
endif
endif
ifeq ($(CONFIG_CMODEL_MEDLOW),y)
KBUILD_CFLAGS_MODULE += -mcmodel=medany
endif
export BITS
ifeq ($(CONFIG_ARCH_RV64I),y)
BITS := 64
UTS_MACHINE := riscv64
KBUILD_CFLAGS += -mabi=lp64
KBUILD_AFLAGS += -mabi=lp64
KBUILD_LDFLAGS += -melf64lriscv
KBUILD_RUSTFLAGS += -Ctarget-cpu=generic-rv64 --target=riscv64imac-unknown-none-elf \
-Cno-redzone
else
BITS := 32
UTS_MACHINE := riscv32
KBUILD_CFLAGS += -mabi=ilp32
KBUILD_AFLAGS += -mabi=ilp32
KBUILD_LDFLAGS += -melf32lriscv
endif
ifndef CONFIG_RISCV_USE_LINKER_RELAXATION
KBUILD_CFLAGS += -mno-relax
KBUILD_AFLAGS += -mno-relax
ifndef CONFIG_AS_IS_LLVM
KBUILD_CFLAGS += -Wa,-mno-relax
KBUILD_AFLAGS += -Wa,-mno-relax
endif
# LLVM has an issue with target-features and LTO: https://github.com/llvm/llvm-project/issues/59350
# Ensure it is aware of linker relaxation with LTO, otherwise relocations may
# be incorrect: https://github.com/llvm/llvm-project/issues/65090
else ifeq ($(CONFIG_LTO_CLANG),y)
KBUILD_LDFLAGS += -mllvm -mattr=+c -mllvm -mattr=+relax
endif
ifeq ($(CONFIG_SHADOW_CALL_STACK),y)
KBUILD_LDFLAGS += --no-relax-gp
endif
# ISA string setting
riscv-march-$(CONFIG_ARCH_RV32I) := rv32ima
riscv-march-$(CONFIG_ARCH_RV64I) := rv64ima
riscv-march-$(CONFIG_FPU) := $(riscv-march-y)fd
riscv-march-$(CONFIG_RISCV_ISA_C) := $(riscv-march-y)c
riscv-march-$(CONFIG_RISCV_ISA_V) := $(riscv-march-y)v
ifneq ($(CONFIG_RISCV_ISA_C),y)
KBUILD_RUSTFLAGS += -Ctarget-feature=-c
endif
ifdef CONFIG_TOOLCHAIN_NEEDS_OLD_ISA_SPEC
KBUILD_CFLAGS += -Wa,-misa-spec=2.2
KBUILD_AFLAGS += -Wa,-misa-spec=2.2
else
riscv-march-$(CONFIG_TOOLCHAIN_NEEDS_EXPLICIT_ZICSR_ZIFENCEI) := $(riscv-march-y)_zicsr_zifencei
endif
# Check if the toolchain supports Zacas
riscv-march-$(CONFIG_TOOLCHAIN_HAS_ZACAS) := $(riscv-march-y)_zacas
# Check if the toolchain supports Zabha
riscv-march-$(CONFIG_TOOLCHAIN_HAS_ZABHA) := $(riscv-march-y)_zabha
# Remove F,D,V from isa string for all. Keep extensions between "fd" and "v" by
# matching non-v and non-multi-letter extensions out with the filter ([^v_]*)
KBUILD_CFLAGS += -march=$(shell echo $(riscv-march-y) | sed -E 's/(rv32ima|rv64ima)fd([^v_]*)v?/\1\2/')
KBUILD_AFLAGS += -march=$(riscv-march-y)
# For C code built with floating-point support, exclude V but keep F and D.
CC_FLAGS_FPU := -march=$(shell echo $(riscv-march-y) | sed -E 's/(rv32ima|rv64ima)([^v_]*)v?/\1\2/')
KBUILD_CFLAGS += -mno-save-restore
ifeq ($(CONFIG_CMODEL_MEDLOW),y)
KBUILD_CFLAGS += -mcmodel=medlow
endif
ifeq ($(CONFIG_CMODEL_MEDANY),y)
KBUILD_CFLAGS += -mcmodel=medany
endif
# Avoid generating .eh_frame sections.
KBUILD_CFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables
# The RISC-V attributes frequently cause compatibility issues and provide no
# information, so just turn them off.
KBUILD_CFLAGS += $(call cc-option,-mno-riscv-attribute)
KBUILD_AFLAGS += $(call cc-option,-mno-riscv-attribute)
KBUILD_CFLAGS += $(call as-option,-Wa$(comma)-mno-arch-attr)
KBUILD_AFLAGS += $(call as-option,-Wa$(comma)-mno-arch-attr)
KBUILD_CFLAGS_MODULE += $(call cc-option,-mno-relax)
KBUILD_AFLAGS_MODULE += $(call as-option,-Wa$(comma)-mno-relax)
# GCC versions that support the "-mstrict-align" option default to allowing
# unaligned accesses. While unaligned accesses are explicitly allowed in the
# RISC-V ISA, they're emulated by machine mode traps on all extant
# architectures. It's faster to have GCC emit only aligned accesses.
ifneq ($(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS),y)
KBUILD_CFLAGS += $(call cc-option,-mstrict-align)
endif
ifeq ($(CONFIG_STACKPROTECTOR_PER_TASK),y)
prepare: stack_protector_prepare
stack_protector_prepare: prepare0
$(eval KBUILD_CFLAGS += -mstack-protector-guard=tls \
-mstack-protector-guard-reg=tp \
-mstack-protector-guard-offset=$(shell \
awk '{if ($$2 == "TSK_STACK_CANARY") print $$3;}' \
$(objtree)/include/generated/asm-offsets.h))
endif
# arch specific predefines for sparse
CHECKFLAGS += -D__riscv -D__riscv_xlen=$(BITS)
# Default target when executing plain make
boot := arch/riscv/boot
ifeq ($(CONFIG_XIP_KERNEL),y)
KBUILD_IMAGE := $(boot)/xipImage
else
ifeq ($(CONFIG_RISCV_M_MODE)$(CONFIG_SOC_CANAAN_K210),yy)
KBUILD_IMAGE := $(boot)/loader.bin
else
ifeq ($(CONFIG_EFI_ZBOOT),)
KBUILD_IMAGE := $(boot)/Image.gz
else
KBUILD_IMAGE := $(boot)/vmlinuz.efi
endif
endif
endif
boot := arch/riscv/boot
boot-image-y := Image
boot-image-$(CONFIG_KERNEL_BZIP2) := Image.bz2
boot-image-$(CONFIG_KERNEL_GZIP) := Image.gz
boot-image-$(CONFIG_KERNEL_LZ4) := Image.lz4
boot-image-$(CONFIG_KERNEL_LZMA) := Image.lzma
boot-image-$(CONFIG_KERNEL_LZO) := Image.lzo
boot-image-$(CONFIG_KERNEL_ZSTD) := Image.zst
boot-image-$(CONFIG_KERNEL_XZ) := Image.xz
ifdef CONFIG_RISCV_M_MODE
boot-image-$(CONFIG_ARCH_CANAAN) := loader.bin
endif
boot-image-$(CONFIG_EFI_ZBOOT) := vmlinuz.efi
boot-image-$(CONFIG_XIP_KERNEL) := xipImage
KBUILD_IMAGE := $(boot)/$(boot-image-y)
libs-y += arch/riscv/lib/
libs-$(CONFIG_EFI_STUB) += $(objtree)/drivers/firmware/efi/libstub/lib.a
ifeq ($(KBUILD_EXTMOD),)
ifeq ($(CONFIG_MMU),y)
prepare: vdso_prepare
vdso_prepare: prepare0
$(Q)$(MAKE) $(build)=arch/riscv/kernel/vdso include/generated/vdso-offsets.h
$(if $(CONFIG_COMPAT),$(Q)$(MAKE) \
$(build)=arch/riscv/kernel/compat_vdso include/generated/compat_vdso-offsets.h)
endif
endif
vdso-install-y += arch/riscv/kernel/vdso/vdso.so.dbg
vdso-install-$(CONFIG_COMPAT) += arch/riscv/kernel/compat_vdso/compat_vdso.so.dbg
BOOT_TARGETS := Image Image.gz Image.bz2 Image.lz4 Image.lzma Image.lzo Image.zst Image.xz loader loader.bin xipImage vmlinuz.efi
all: $(notdir $(KBUILD_IMAGE))
loader.bin: loader
Image.gz Image.bz2 Image.lz4 Image.lzma Image.lzo Image.zst Image.xz loader xipImage vmlinuz.efi: Image
$(BOOT_TARGETS): vmlinux
$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
@$(kecho) ' Kernel: $(boot)/$@ is ready'
# the install target always installs KBUILD_IMAGE (which may be compressed)
# but keep the zinstall target for compatibility with older releases
install zinstall:
$(call cmd,install)
PHONY += rv32_randconfig
rv32_randconfig:
$(Q)$(MAKE) KCONFIG_ALLCONFIG=$(srctree)/arch/riscv/configs/32-bit.config \
-f $(srctree)/Makefile randconfig
PHONY += rv64_randconfig
rv64_randconfig:
$(Q)$(MAKE) KCONFIG_ALLCONFIG=$(srctree)/arch/riscv/configs/64-bit.config \
-f $(srctree)/Makefile randconfig
PHONY += rv32_defconfig
rv32_defconfig:
$(Q)$(MAKE) -f $(srctree)/Makefile defconfig 32-bit.config
PHONY += rv32_nommu_virt_defconfig
rv32_nommu_virt_defconfig:
$(Q)$(MAKE) -f $(srctree)/Makefile nommu_virt_defconfig 32-bit.config
define archhelp
echo ' Image - Uncompressed kernel image (arch/riscv/boot/Image)'
echo ' Image.gz - Compressed kernel image (arch/riscv/boot/Image.gz)'
echo ' Image.bz2 - Compressed kernel image (arch/riscv/boot/Image.bz2)'
echo ' Image.lz4 - Compressed kernel image (arch/riscv/boot/Image.lz4)'
echo ' Image.lzma - Compressed kernel image (arch/riscv/boot/Image.lzma)'
echo ' Image.lzo - Compressed kernel image (arch/riscv/boot/Image.lzo)'
echo ' Image.zst - Compressed kernel image (arch/riscv/boot/Image.zst)'
echo ' Image.xz - Compressed kernel image (arch/riscv/boot/Image.xz)'
echo ' vmlinuz.efi - Compressed EFI kernel image (arch/riscv/boot/vmlinuz.efi)'
echo ' Default when CONFIG_EFI_ZBOOT=y'
echo ' xipImage - Execute-in-place kernel image (arch/riscv/boot/xipImage)'
echo ' Default when CONFIG_XIP_KERNEL=y'
echo ' install - Install kernel using (your) ~/bin/$(INSTALLKERNEL) or'
echo ' (distribution) /sbin/$(INSTALLKERNEL) or install to '
echo ' $$(INSTALL_PATH)'
endef