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/fds_example.c | 195 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 195 insertions(+) create mode 100644 samples/bpf/fds_example.c (limited to 'samples/bpf/fds_example.c') diff --git a/samples/bpf/fds_example.c b/samples/bpf/fds_example.c new file mode 100644 index 000000000..88a26f3ce --- /dev/null +++ b/samples/bpf/fds_example.c @@ -0,0 +1,195 @@ +#include +#include + +#include +#include +#include +#include +#include +#include +#include + +#include +#include + +#include + +#include +#include "bpf_insn.h" +#include "sock_example.h" +#include "bpf_util.h" + +#define BPF_F_PIN (1 << 0) +#define BPF_F_GET (1 << 1) +#define BPF_F_PIN_GET (BPF_F_PIN | BPF_F_GET) + +#define BPF_F_KEY (1 << 2) +#define BPF_F_VAL (1 << 3) +#define BPF_F_KEY_VAL (BPF_F_KEY | BPF_F_VAL) + +#define BPF_M_UNSPEC 0 +#define BPF_M_MAP 1 +#define BPF_M_PROG 2 + +char bpf_log_buf[BPF_LOG_BUF_SIZE]; + +static void usage(void) +{ + printf("Usage: fds_example [...]\n"); + printf(" -F File to pin/get object\n"); + printf(" -P |- pin object\n"); + printf(" -G `- get object\n"); + printf(" -m eBPF map mode\n"); + printf(" -k |- map key\n"); + printf(" -v `- map value\n"); + printf(" -p eBPF prog mode\n"); + printf(" -o `- object file\n"); + printf(" -h Display this help.\n"); +} + +static int bpf_prog_create(const char *object) +{ + static struct bpf_insn insns[] = { + BPF_MOV64_IMM(BPF_REG_0, 1), + BPF_EXIT_INSN(), + }; + size_t insns_cnt = ARRAY_SIZE(insns); + struct bpf_object *obj; + int err; + + if (object) { + obj = bpf_object__open_file(object, NULL); + assert(!libbpf_get_error(obj)); + err = bpf_object__load(obj); + assert(!err); + return bpf_program__fd(bpf_object__next_program(obj, NULL)); + } else { + LIBBPF_OPTS(bpf_prog_load_opts, opts, + .log_buf = bpf_log_buf, + .log_size = BPF_LOG_BUF_SIZE, + ); + + return bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, NULL, "GPL", + insns, insns_cnt, &opts); + } +} + +static int bpf_do_map(const char *file, uint32_t flags, uint32_t key, + uint32_t value) +{ + int fd, ret; + + if (flags & BPF_F_PIN) { + fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, NULL, sizeof(uint32_t), + sizeof(uint32_t), 1024, NULL); + printf("bpf: map fd:%d (%s)\n", fd, strerror(errno)); + assert(fd > 0); + + ret = bpf_obj_pin(fd, file); + printf("bpf: pin ret:(%d,%s)\n", ret, strerror(errno)); + assert(ret == 0); + } else { + fd = bpf_obj_get(file); + printf("bpf: get fd:%d (%s)\n", fd, strerror(errno)); + assert(fd > 0); + } + + if ((flags & BPF_F_KEY_VAL) == BPF_F_KEY_VAL) { + ret = bpf_map_update_elem(fd, &key, &value, 0); + printf("bpf: fd:%d u->(%u:%u) ret:(%d,%s)\n", fd, key, value, + ret, strerror(errno)); + assert(ret == 0); + } else if (flags & BPF_F_KEY) { + ret = bpf_map_lookup_elem(fd, &key, &value); + printf("bpf: fd:%d l->(%u):%u ret:(%d,%s)\n", fd, key, value, + ret, strerror(errno)); + assert(ret == 0); + } + + return 0; +} + +static int bpf_do_prog(const char *file, uint32_t flags, const char *object) +{ + int fd, sock, ret; + + if (flags & BPF_F_PIN) { + fd = bpf_prog_create(object); + printf("bpf: prog fd:%d (%s)\n", fd, strerror(errno)); + assert(fd > 0); + + ret = bpf_obj_pin(fd, file); + printf("bpf: pin ret:(%d,%s)\n", ret, strerror(errno)); + assert(ret == 0); + } else { + fd = bpf_obj_get(file); + printf("bpf: get fd:%d (%s)\n", fd, strerror(errno)); + assert(fd > 0); + } + + sock = open_raw_sock("lo"); + assert(sock > 0); + + ret = setsockopt(sock, SOL_SOCKET, SO_ATTACH_BPF, &fd, sizeof(fd)); + printf("bpf: sock:%d <- fd:%d attached ret:(%d,%s)\n", sock, fd, + ret, strerror(errno)); + assert(ret == 0); + + return 0; +} + +int main(int argc, char **argv) +{ + const char *file = NULL, *object = NULL; + uint32_t key = 0, value = 0, flags = 0; + int opt, mode = BPF_M_UNSPEC; + + while ((opt = getopt(argc, argv, "F:PGmk:v:po:")) != -1) { + switch (opt) { + /* General args */ + case 'F': + file = optarg; + break; + case 'P': + flags |= BPF_F_PIN; + break; + case 'G': + flags |= BPF_F_GET; + break; + /* Map-related args */ + case 'm': + mode = BPF_M_MAP; + break; + case 'k': + key = strtoul(optarg, NULL, 0); + flags |= BPF_F_KEY; + break; + case 'v': + value = strtoul(optarg, NULL, 0); + flags |= BPF_F_VAL; + break; + /* Prog-related args */ + case 'p': + mode = BPF_M_PROG; + break; + case 'o': + object = optarg; + break; + default: + goto out; + } + } + + if (!(flags & BPF_F_PIN_GET) || !file) + goto out; + + switch (mode) { + case BPF_M_MAP: + return bpf_do_map(file, flags, key, value); + case BPF_M_PROG: + return bpf_do_prog(file, flags, object); + } +out: + usage(); + return -1; +} -- cgit v1.3.1