On Sun, Jan 28, 2024 at 06:24:05PM -0700, Daniel Xu wrote: > === Description === > > This is a bpf-treewide change that annotates all kfuncs as such inside > .BTF_ids. This annotation eventually allows us to automatically generate > kfunc prototypes from bpftool. > > We store this metadata inside a yet-unused flags field inside struct > btf_id_set8 (thanks Kumar!). pahole will be taught where to look. > > More details about the full chain of events are available in commit 3's > description. > > The accompanying pahole and bpftool changes can be viewed > here on these "frozen" branches [0][1]. > > [0]: https://github.com/danobi/pahole/tree/kfunc_btf-v3-mailed > [1]: https://github.com/danobi/linux/tree/kfunc_bpftool-mailed I hit a similar issue to [0] on master 943b043aeecc ("selftests/bpf: Fix bench runner SIGSEGV") when cross-compiling on x86_64 (LE) to s390x (BE). I do have CONFIG_DEBUG_INFO_BTF enable and the issue would not trigger if I disabled CONFIG_DEBUG_INFO_BTF (and with the fix mentioned in [0]). What seems to happen is that `tools/resolve_btfids` is ran in the context of the host endianess and if I printk before the WARN_ON: diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index ef380e546952..a9ed7a1a4936 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -8128,6 +8128,7 @@ int register_btf_kfunc_id_set(enum bpf_prog_type prog_type, * WARN() for initcall registrations that do not check errors. */ if (!(kset->set->flags & BTF_SET8_KFUNCS)) { + printk("Flag 0x%08X, expected 0x%08X\n", kset->set->flags, BTF_SET8_KFUNCS); WARN_ON(!kset->owner); return -EINVAL; } the boot logs would show: Flag 0x01000000, expected 0x00000001 The issue did not happen prior to 6f3189f38a3e ("bpf: treewide: Annotate BPF kfuncs in BTF") has only 0 was written before. It seems [1] will be addressing cross-compilation, but it did not fix it as is by just applying on top of master, so probably some of the changes will also need to be ported to `tools/include/linux/btf_ids.h`? A hacky workaround to cross-compilation I have is to apply: diff --git a/tools/bpf/resolve_btfids/Makefile b/tools/bpf/resolve_btfids/Makefile index 4b8079f294f6..b706e7ab066f 100644 --- a/tools/bpf/resolve_btfids/Makefile +++ b/tools/bpf/resolve_btfids/Makefile @@ -22,10 +22,10 @@ HOST_OVERRIDES := AR="$(HOSTAR)" CC="$(HOSTCC)" LD="$(HOSTLD)" ARCH="$(HOSTARCH) CROSS_COMPILE="" EXTRA_CFLAGS="$(HOSTCFLAGS)" RM ?= rm -HOSTCC ?= gcc -HOSTLD ?= ld -HOSTAR ?= ar -CROSS_COMPILE = +HOSTCC = $(CC) +HOSTLD = $(LD) +HOSTAR = $(AR) +#CROSS_COMPILE = OUTPUT ?= $(srctree)/tools/bpf/resolve_btfids/ @@ -56,16 +56,16 @@ $(OUTPUT) $(OUTPUT)/libsubcmd $(LIBBPF_OUT): $(SUBCMDOBJ): fixdep FORCE | $(OUTPUT)/libsubcmd $(Q)$(MAKE) -C $(SUBCMD_SRC) OUTPUT=$(SUBCMD_OUT) \ - DESTDIR=$(SUBCMD_DESTDIR) $(HOST_OVERRIDES) prefix= subdir= \ + DESTDIR=$(SUBCMD_DESTDIR) prefix= subdir= \ $(abspath $@) install_headers $(BPFOBJ): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(LIBBPF_OUT) $(Q)$(MAKE) $(submake_extras) -C $(LIBBPF_SRC) OUTPUT=$(LIBBPF_OUT) \ - DESTDIR=$(LIBBPF_DESTDIR) $(HOST_OVERRIDES) prefix= subdir= \ + DESTDIR=$(LIBBPF_DESTDIR) prefix= subdir= \ $(abspath $@) install_headers -LIBELF_FLAGS := $(shell $(HOSTPKG_CONFIG) libelf --cflags 2>/dev/null) -LIBELF_LIBS := $(shell $(HOSTPKG_CONFIG) libelf --libs 2>/dev/null || echo -lelf) +LIBELF_FLAGS := $(shell $(PKG_CONFIG) libelf --cflags 2>/dev/null) +LIBELF_LIBS := $(shell $(PKG_CONFIG) libelf --libs 2>/dev/null || echo -lelf) HOSTCFLAGS_resolve_btfids += -g \ -I$(srctree)/tools/include \ @@ -84,7 +84,7 @@ $(BINARY_IN): fixdep FORCE prepare | $(OUTPUT) $(BINARY): $(BPFOBJ) $(SUBCMDOBJ) $(BINARY_IN) $(call msg,LINK,$@) - $(Q)$(HOSTCC) $(BINARY_IN) $(KBUILD_HOSTLDFLAGS) -o $@ $(BPFOBJ) $(SUBCMDOBJ) $(LIBS) + $(Q)$(CC) $(BINARY_IN) $(KBUILD_HOSTLDFLAGS) -o $@ $(BPFOBJ) $(SUBCMDOBJ) $(LIBS) clean_objects := $(wildcard $(OUTPUT)/*.o \ $(OUTPUT)/.*.o.cmd \ diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile index a38a3001527c..5cd193c04448 100644 --- a/tools/testing/selftests/bpf/Makefile +++ b/tools/testing/selftests/bpf/Makefile @@ -171,7 +171,7 @@ INCLUDE_DIR := $(SCRATCH_DIR)/include BPFOBJ := $(BUILD_DIR)/libbpf/libbpf.a ifneq ($(CROSS_COMPILE),) HOST_BUILD_DIR := $(BUILD_DIR)/host -HOST_SCRATCH_DIR := $(OUTPUT)/host-tools +HOST_SCRATCH_DIR := $(SCRATCH_DIR) HOST_INCLUDE_DIR := $(HOST_SCRATCH_DIR)/include else HOST_BUILD_DIR := $(BUILD_DIR) This causes `resolve_btfids` to be compiled in the target endianess and gets magically run provided that the hosts has `qemu-s390x-static` and a functional binfmt_misc [2] on the host, but having this using host architecture per [1] is likely better. Here are steps to reproduce the issue on Ubuntu 23.10 and assuming danobi/vmtest [3] is installed: XPLATFORM="s390x" XARCH="s390" # Set up repo for s390x cat <<EOF >> /etc/apt/sources.list.d/s390x.list deb [arch=s390x] http://ports.ubuntu.com/ubuntu-ports mantic main restricted deb [arch=s390x] http://ports.ubuntu.com/ubuntu-ports mantic-updates main restricted EOF sudo dpkg --add-architecture s390x apt install qemu-system-s390x qemu-user-static g{cc,++}-"${XARCH}-linux-gnu" {libelf-dev,libssl-dev,pkgconf}:s390x KBUILD_OUTPUT_DIR="/tmp/kbuild-${XPLATFORM}" mkdir "${KBUILD_OUTPUT_DIR}" cat tools/testing/selftests/bpf/config{,.vm,.${XPLATFORM}} > ${KBUILD_OUTPUT_DIR}/.config make ARCH="${XARCH}" CROSS_COMPILE="${XPLATFORM}-linux-gnu-" O="${KBUILD_OUTPUT_DIR}" -j$((4 * $(nproc))) olddefconfig make ARCH="${XARCH}" CROSS_COMPILE="${XPLATFORM}-linux-gnu-" O="${KBUILD_OUTPUT_DIR}" -j$((4 * $(nproc))) all # No need for a s390x ubuntu 23.10 rootfs, we only care about booting the kernel vmtest -k "${KBUILD_OUTPUT_DIR}/arch/s390/boot/bzImage" -a s390x "uname -m" | cat For the chroot route, see [4]. [0] https://lore.kernel.org/linux-kernel/20240201155339.2b5936be@xxxxxxxxxxxxxxxx/T/ [1] https://lore.kernel.org/bpf/cover.1706717857.git.vmalik@xxxxxxxxxx/ [2] https://en.wikipedia.org/wiki/Binfmt_misc [3] https://github.com/danobi/vmtest [4] https://chantra.github.io/bpfcitools/bpf-cross-compile.html Manu > > === Changelog === > > Changes from v3: > * Rebase to bpf-next and add missing annotation on new kfunc > > Changes from v2: > * Only WARN() for vmlinux kfuncs > > Changes from v1: > * Move WARN_ON() up a call level > * Also return error when kfunc set is not properly tagged > * Use BTF_KFUNCS_START/END instead of flags > * Rename BTF_SET8_KFUNC to BTF_SET8_KFUNCS > > Daniel Xu (3): > bpf: btf: Support flags for BTF_SET8 sets > bpf: btf: Add BTF_KFUNCS_START/END macro pair > bpf: treewide: Annotate BPF kfuncs in BTF > > Documentation/bpf/kfuncs.rst | 8 +++---- > drivers/hid/bpf/hid_bpf_dispatch.c | 8 +++---- > fs/verity/measure.c | 4 ++-- > include/linux/btf_ids.h | 21 +++++++++++++++---- > kernel/bpf/btf.c | 8 +++++++ > kernel/bpf/cpumask.c | 4 ++-- > kernel/bpf/helpers.c | 8 +++---- > kernel/bpf/map_iter.c | 4 ++-- > kernel/cgroup/rstat.c | 4 ++-- > kernel/trace/bpf_trace.c | 8 +++---- > net/bpf/test_run.c | 8 +++---- > net/core/filter.c | 20 +++++++++--------- > net/core/xdp.c | 4 ++-- > net/ipv4/bpf_tcp_ca.c | 4 ++-- > net/ipv4/fou_bpf.c | 4 ++-- > net/ipv4/tcp_bbr.c | 4 ++-- > net/ipv4/tcp_cubic.c | 4 ++-- > net/ipv4/tcp_dctcp.c | 4 ++-- > net/netfilter/nf_conntrack_bpf.c | 4 ++-- > net/netfilter/nf_nat_bpf.c | 4 ++-- > net/xfrm/xfrm_interface_bpf.c | 4 ++-- > net/xfrm/xfrm_state_bpf.c | 4 ++-- > .../selftests/bpf/bpf_testmod/bpf_testmod.c | 8 +++---- > 23 files changed, 87 insertions(+), 66 deletions(-) > > -- > 2.42.1 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
