From 5febf432df1cfa5b25d99b54c32103fafbdd0eb9 Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Sun, 16 Aug 2026 15:32:33 +0200 Subject: kbuild: rust: keep Rust objects out of Clang LTO with inline helpers Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit `objtool` errors such as: vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a: can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd The reason is that in such builds, the Clang invocation that compiles the combined Rust plus helpers bitcode emits LLVM bitcode (again) -- the final code generation happens in the linker's LTO step, which the `-mllvm` trap options passed to Clang do not reach. This, in turn, means that unreachable traps are missing, and the impossible paths do not merely fallthrough to the next symbol, but past the end of their own section, since LTO builds place each function in its own section. Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always emits machine code directly, with the traps in place. Assisted-by: LLM Cc: Gary Guo Cc: Boqun Feng Cc: Alice Ryhl Cc: Matthew Maurer Cc: Josh Poimboeuf Cc: Peter Zijlstra Cc: stable@vger.kernel.org Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust") Acked-by: Gary Guo Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org Signed-off-by: Miguel Ojeda --- samples/bpf/Makefile | 392 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 392 insertions(+) create mode 100644 samples/bpf/Makefile (limited to 'samples/bpf/Makefile') diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile new file mode 100644 index 000000000..95a4fa1f1 --- /dev/null +++ b/samples/bpf/Makefile @@ -0,0 +1,392 @@ +# SPDX-License-Identifier: GPL-2.0 + +BPF_SAMPLES_PATH ?= $(abspath $(src)) +TOOLS_PATH := $(BPF_SAMPLES_PATH)/../../tools + +pound := \# + +# List of programs to build +tprogs-y := test_lru_dist +tprogs-y += sock_example +tprogs-y += fds_example +tprogs-y += sockex1 +tprogs-y += sockex2 +tprogs-y += sockex3 +tprogs-y += tracex1 +tprogs-y += tracex3 +tprogs-y += tracex4 +tprogs-y += tracex5 +tprogs-y += tracex6 +tprogs-y += trace_output +tprogs-y += lathist +tprogs-y += offwaketime +tprogs-y += spintest +tprogs-y += map_perf_test +tprogs-y += xdp_router_ipv4 +tprogs-y += trace_event +tprogs-y += sampleip +tprogs-y += tc_l2_redirect +tprogs-y += lwt_len_hist +tprogs-y += xdp_tx_iptunnel +tprogs-y += test_map_in_map +tprogs-y += per_socket_stats_example +tprogs-y += syscall_tp +tprogs-y += cpustat +tprogs-y += xdp_adjust_tail +tprogs-y += xdp_fwd +tprogs-y += task_fd_query +tprogs-y += ibumad +tprogs-y += hbm + +# Libbpf dependencies +LIBBPF_SRC = $(TOOLS_PATH)/lib/bpf +LIBBPF_OUTPUT = $(abspath $(BPF_SAMPLES_PATH))/libbpf +LIBBPF_DESTDIR = $(LIBBPF_OUTPUT) +LIBBPF_INCLUDE = $(LIBBPF_DESTDIR)/include +LIBBPF = $(LIBBPF_OUTPUT)/libbpf.a + +CGROUP_HELPERS := ../../tools/testing/selftests/bpf/cgroup_helpers.o +TRACE_HELPERS := ../../tools/testing/selftests/bpf/trace_helpers.o +XDP_SAMPLE := xdp_sample_user.o + +fds_example-objs := fds_example.o +sockex1-objs := sockex1_user.o +sockex2-objs := sockex2_user.o +sockex3-objs := sockex3_user.o +tracex1-objs := tracex1_user.o $(TRACE_HELPERS) +tracex3-objs := tracex3_user.o +tracex4-objs := tracex4_user.o +tracex5-objs := tracex5_user.o $(TRACE_HELPERS) +tracex6-objs := tracex6_user.o +trace_output-objs := trace_output_user.o +lathist-objs := lathist_user.o +offwaketime-objs := offwaketime_user.o $(TRACE_HELPERS) +spintest-objs := spintest_user.o $(TRACE_HELPERS) +map_perf_test-objs := map_perf_test_user.o +test_overhead-objs := test_overhead_user.o +trace_event-objs := trace_event_user.o $(TRACE_HELPERS) +sampleip-objs := sampleip_user.o $(TRACE_HELPERS) +tc_l2_redirect-objs := tc_l2_redirect_user.o +lwt_len_hist-objs := lwt_len_hist_user.o +xdp_tx_iptunnel-objs := xdp_tx_iptunnel_user.o +test_map_in_map-objs := test_map_in_map_user.o +per_socket_stats_example-objs := cookie_uid_helper_example.o +syscall_tp-objs := syscall_tp_user.o +cpustat-objs := cpustat_user.o +xdp_adjust_tail-objs := xdp_adjust_tail_user.o +xdp_fwd-objs := xdp_fwd_user.o +task_fd_query-objs := task_fd_query_user.o $(TRACE_HELPERS) +ibumad-objs := ibumad_user.o +hbm-objs := hbm.o $(CGROUP_HELPERS) + +xdp_router_ipv4-objs := xdp_router_ipv4_user.o $(XDP_SAMPLE) + +# Tell kbuild to always build the programs +always-y := $(tprogs-y) +always-y += sockex1_kern.o +always-y += sockex2_kern.o +always-y += sockex3_kern.o +always-y += tracex1.bpf.o +always-y += tracex3.bpf.o +always-y += tracex4.bpf.o +always-y += tracex5.bpf.o +always-y += tracex6.bpf.o +always-y += trace_output.bpf.o +always-y += tcbpf1_kern.o +always-y += tc_l2_redirect_kern.o +always-y += lathist_kern.o +always-y += offwaketime.bpf.o +always-y += spintest.bpf.o +always-y += map_perf_test.bpf.o +always-y += parse_varlen.o parse_simple.o parse_ldabs.o +always-y += trace_event_kern.o +always-y += sampleip_kern.o +always-y += lwt_len_hist.bpf.o +always-y += xdp_tx_iptunnel_kern.o +always-y += test_map_in_map.bpf.o +always-y += tcp_synrto_kern.o +always-y += tcp_rwnd_kern.o +always-y += tcp_bufs_kern.o +always-y += tcp_cong_kern.o +always-y += tcp_iw_kern.o +always-y += tcp_clamp_kern.o +always-y += tcp_basertt_kern.o +always-y += tcp_tos_reflect_kern.o +always-y += tcp_dumpstats_kern.o +always-y += xdp2skb_meta_kern.o +always-y += syscall_tp_kern.o +always-y += cpustat_kern.o +always-y += xdp_adjust_tail_kern.o +always-y += xdp_fwd_kern.o +always-y += task_fd_query_kern.o +always-y += ibumad_kern.o +always-y += hbm_out_kern.o +always-y += hbm_edt_kern.o + +COMMON_CFLAGS = $(TPROGS_USER_CFLAGS) +TPROGS_LDFLAGS = $(TPROGS_USER_LDFLAGS) + +ifeq ($(ARCH), arm) +# Strip all except -D__LINUX_ARM_ARCH__ option needed to handle linux +# headers when arm instruction set identification is requested. +ARM_ARCH_SELECTOR := $(filter -D__LINUX_ARM_ARCH__%, $(KBUILD_CFLAGS)) +BPF_EXTRA_CFLAGS := $(ARM_ARCH_SELECTOR) +TPROGS_CFLAGS += $(ARM_ARCH_SELECTOR) +endif + +ifeq ($(ARCH), mips) +TPROGS_CFLAGS += -D__SANE_USERSPACE_TYPES__ +ifdef CONFIG_MACH_LOONGSON64 +BPF_EXTRA_CFLAGS += -I$(srctree)/arch/mips/include/asm/mach-loongson64 +BPF_EXTRA_CFLAGS += -I$(srctree)/arch/mips/include/asm/mach-generic +endif +endif + +ifeq ($(ARCH), x86) +BPF_EXTRA_CFLAGS += -fcf-protection +endif + +COMMON_CFLAGS += -Wall -O2 +COMMON_CFLAGS += -Wmissing-prototypes +COMMON_CFLAGS += -Wstrict-prototypes +COMMON_CFLAGS += $(call try-run,\ + printf "int main() { return 0; }" |\ + $(CC) -Werror -fsanitize=bounds -x c - -o "$$TMP",-fsanitize=bounds,) + +TPROGS_CFLAGS += $(COMMON_CFLAGS) +TPROGS_CFLAGS += -I$(objtree)/usr/include +TPROGS_CFLAGS += -I$(srctree)/tools/testing/selftests/bpf/ +TPROGS_CFLAGS += -I$(LIBBPF_INCLUDE) +TPROGS_CFLAGS += -I$(srctree)/tools/include +TPROGS_CFLAGS += -I$(srctree)/tools/perf +TPROGS_CFLAGS += -I$(srctree)/tools/lib +TPROGS_CFLAGS += -DHAVE_ATTR_TEST=0 + +ifdef SYSROOT +COMMON_CFLAGS += --sysroot=$(SYSROOT) +TPROGS_LDFLAGS := -L$(SYSROOT)/usr/lib +endif + +TPROGS_LDLIBS += $(LIBBPF) -lelf -lz +TPROGLDLIBS_xdp_router_ipv4 += -lm -pthread +TPROGLDLIBS_tracex4 += -lrt +TPROGLDLIBS_trace_output += -lrt +TPROGLDLIBS_map_perf_test += -lrt + +# Allows pointing LLC/CLANG to a LLVM backend with bpf support, redefine on cmdline: +# make M=samples/bpf LLC=~/git/llvm-project/llvm/build/bin/llc CLANG=~/git/llvm-project/llvm/build/bin/clang +LLC ?= llc +CLANG ?= clang +OPT ?= opt +LLVM_DIS ?= llvm-dis +LLVM_OBJCOPY ?= llvm-objcopy +LLVM_READELF ?= llvm-readelf +BTF_PAHOLE ?= pahole + +# Detect that we're cross compiling and use the cross compiler +ifdef CROSS_COMPILE +CLANG_ARCH_ARGS = --target=$(notdir $(CROSS_COMPILE:%-=%)) +endif + +# Don't evaluate probes and warnings if we need to run make recursively +ifneq ($(src),) +HDR_PROBE := $(shell printf "$(pound)include \n struct list_head { int a; }; int main() { return 0; }" | \ + $(CC) $(TPROGS_CFLAGS) $(TPROGS_LDFLAGS) -x c - \ + -o /dev/null 2>/dev/null && echo okay) + +ifeq ($(HDR_PROBE),) +$(warning WARNING: Detected possible issues with include path.) +$(warning WARNING: Please install kernel headers locally (make headers_install).) +endif + +BTF_LLC_PROBE := $(shell $(LLC) -march=bpf -mattr=help 2>&1 | grep dwarfris) +BTF_PAHOLE_PROBE := $(shell $(BTF_PAHOLE) --help 2>&1 | grep BTF) +BTF_OBJCOPY_PROBE := $(shell $(LLVM_OBJCOPY) --help 2>&1 | grep -i 'usage.*llvm') +BTF_LLVM_PROBE := $(shell echo "int main() { return 0; }" | \ + $(CLANG) --target=bpf -O2 -g -c -x c - -o ./llvm_btf_verify.o; \ + $(LLVM_READELF) -S ./llvm_btf_verify.o | grep BTF; \ + /bin/rm -f ./llvm_btf_verify.o) + +BPF_EXTRA_CFLAGS += -fno-stack-protector +ifneq ($(BTF_LLVM_PROBE),) + BPF_EXTRA_CFLAGS += -g +else +ifneq ($(and $(BTF_LLC_PROBE),$(BTF_PAHOLE_PROBE),$(BTF_OBJCOPY_PROBE)),) + BPF_EXTRA_CFLAGS += -g + LLC_FLAGS += -mattr=dwarfris + DWARF2BTF = y +endif +endif +endif + +# Trick to allow make to be run from this directory +all: + $(MAKE) -C ../../ M=$(CURDIR) BPF_SAMPLES_PATH=$(CURDIR) + +clean: + $(MAKE) -C ../../ M=$(CURDIR) clean + @find $(CURDIR) -type f -name '*~' -delete + @$(RM) -r $(CURDIR)/libbpf $(CURDIR)/bpftool + +$(LIBBPF): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(LIBBPF_OUTPUT) +# Fix up variables inherited from Kbuild that tools/ build system won't like + $(MAKE) -C $(LIBBPF_SRC) RM='rm -rf' EXTRA_CFLAGS="$(COMMON_CFLAGS)" \ + LDFLAGS="$(TPROGS_LDFLAGS)" srctree=$(BPF_SAMPLES_PATH)/../../ \ + O= OUTPUT=$(LIBBPF_OUTPUT)/ DESTDIR=$(LIBBPF_DESTDIR) prefix= \ + $@ install_headers + +BPFTOOLDIR := $(TOOLS_PATH)/bpf/bpftool +BPFTOOL_OUTPUT := $(abspath $(BPF_SAMPLES_PATH))/bpftool +DEFAULT_BPFTOOL := $(BPFTOOL_OUTPUT)/bootstrap/bpftool +BPFTOOL ?= $(DEFAULT_BPFTOOL) +$(DEFAULT_BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile) | $(BPFTOOL_OUTPUT) + $(MAKE) -C $(BPFTOOLDIR) srctree=$(BPF_SAMPLES_PATH)/../../ \ + OUTPUT=$(BPFTOOL_OUTPUT)/ bootstrap + +$(LIBBPF_OUTPUT) $(BPFTOOL_OUTPUT): + $(call msg,MKDIR,$@) + $(Q)mkdir -p $@ + +$(obj)/syscall_nrs.h: $(obj)/syscall_nrs.s FORCE + $(call filechk,offsets,__SYSCALL_NRS_H__) + +targets += syscall_nrs.s +clean-files += syscall_nrs.h + +FORCE: + + +# Verify LLVM compiler tools are available and bpf target is supported by llc +.PHONY: verify_cmds verify_target_bpf $(CLANG) $(LLC) + +verify_cmds: $(CLANG) $(LLC) + @for TOOL in $^ ; do \ + if ! (which -- "$${TOOL}" > /dev/null 2>&1); then \ + echo "*** ERROR: Cannot find LLVM tool $${TOOL}" ;\ + exit 1; \ + else true; fi; \ + done + +verify_target_bpf: verify_cmds + @if ! (${LLC} -march=bpf -mattr=help > /dev/null 2>&1); then \ + echo "*** ERROR: LLVM (${LLC}) does not support 'bpf' target" ;\ + echo " NOTICE: LLVM version >= 3.7.1 required" ;\ + exit 2; \ + else true; fi + +$(BPF_SAMPLES_PATH)/*.c: verify_target_bpf $(LIBBPF) +$(src)/*.c: verify_target_bpf $(LIBBPF) + +libbpf_hdrs: $(LIBBPF) +$(obj)/$(TRACE_HELPERS) $(obj)/$(CGROUP_HELPERS) $(obj)/$(XDP_SAMPLE): | libbpf_hdrs + +.PHONY: libbpf_hdrs + +$(obj)/xdp_router_ipv4_user.o: $(obj)/xdp_router_ipv4.skel.h + +$(obj)/tracex5.bpf.o: $(obj)/syscall_nrs.h +$(obj)/hbm_out_kern.o: $(src)/hbm.h $(src)/hbm_kern.h +$(obj)/hbm.o: $(src)/hbm.h +$(obj)/hbm_edt_kern.o: $(src)/hbm.h $(src)/hbm_kern.h + +# Override includes for xdp_sample_user.o because $(srctree)/usr/include in +# TPROGS_CFLAGS causes conflicts +XDP_SAMPLE_CFLAGS += -Wall -O2 \ + -I$(src)/../../tools/include \ + -I$(src)/../../tools/include/uapi \ + -I$(LIBBPF_INCLUDE) \ + -I$(src)/../../tools/testing/selftests/bpf + +$(obj)/$(XDP_SAMPLE): TPROGS_CFLAGS = $(XDP_SAMPLE_CFLAGS) $(TPROGS_USER_CFLAGS) +$(obj)/$(XDP_SAMPLE): $(src)/xdp_sample_user.h $(src)/xdp_sample_shared.h +# Override includes for trace_helpers.o because __must_check won't be defined +# in our include path. +$(obj)/$(TRACE_HELPERS): TPROGS_CFLAGS := $(TPROGS_CFLAGS) -D__must_check= + +-include $(BPF_SAMPLES_PATH)/Makefile.target + +VMLINUX_BTF_PATHS ?= $(abspath $(if $(O),$(O)/vmlinux)) \ + $(abspath $(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux)) \ + $(abspath $(objtree)/vmlinux) +VMLINUX_BTF ?= $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS)))) + +$(obj)/vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL) +ifeq ($(VMLINUX_H),) +ifeq ($(VMLINUX_BTF),) + $(error Cannot find a vmlinux for VMLINUX_BTF at any of "$(VMLINUX_BTF_PATHS)",\ + build the kernel or set VMLINUX_BTF like "VMLINUX_BTF=/sys/kernel/btf/vmlinux" or VMLINUX_H variable) +endif + $(Q)$(BPFTOOL) btf dump file $(VMLINUX_BTF) format c > $@ +else + $(Q)cp "$(VMLINUX_H)" $@ +endif + +clean-files += vmlinux.h + +# Get Clang's default includes on this system, as opposed to those seen by +# '--target=bpf'. This fixes "missing" files on some architectures/distros, +# such as asm/byteorder.h, asm/socket.h, asm/sockios.h, sys/cdefs.h etc. +# +# Use '-idirafter': Don't interfere with include mechanics except where the +# build would have failed anyways. +define get_sys_includes +$(shell $(1) -v -E - &1 \ + | sed -n '/<...> search starts here:/,/End of search list./{ s| \(/.*\)|-idirafter \1|p }') \ +$(shell $(1) -dM -E - $@ + +# asm/sysreg.h - inline assembly used by it is incompatible with llvm. +# But, there is no easy way to fix it, so just exclude it since it is +# useless for BPF samples. +# below we use long chain of commands, clang | opt | llvm-dis | llc, +# to generate final object file. 'clang' compiles the source into IR +# with native target, e.g., x64, arm64, etc. 'opt' does bpf CORE IR builtin +# processing (llvm12) and IR optimizations. 'llvm-dis' converts +# 'opt' output to IR, and finally 'llc' generates bpf byte code. +$(obj)/%.o: $(src)/%.c + @echo " CLANG-bpf " $@ + $(Q)$(CLANG) $(NOSTDINC_FLAGS) $(LINUXINCLUDE) $(BPF_EXTRA_CFLAGS) \ + -I$(obj) -I$(srctree)/tools/testing/selftests/bpf/ \ + -I$(LIBBPF_INCLUDE) $(CLANG_SYS_INCLUDES) \ + -D__KERNEL__ -D__BPF_TRACING__ -Wno-unused-value -Wno-pointer-sign \ + -D__TARGET_ARCH_$(SRCARCH) -Wno-compare-distinct-pointer-types \ + -Wno-gnu-variable-sized-type-not-at-end \ + -Wno-address-of-packed-member -Wno-tautological-compare \ + -Wno-unknown-warning-option $(CLANG_ARCH_ARGS) \ + -fno-asynchronous-unwind-tables \ + -I$(srctree)/samples/bpf/ -include asm_goto_workaround.h \ + -O2 -emit-llvm -Xclang -disable-llvm-passes -c $< -o - | \ + $(OPT) -O2 -mtriple=bpf-pc-linux | $(LLVM_DIS) | \ + $(LLC) -march=bpf $(LLC_FLAGS) -filetype=obj -o $@ +ifeq ($(DWARF2BTF),y) + $(BTF_PAHOLE) -J $@ +endif -- cgit v1.3.1