Ubuntu reports incorrect kernel version through uname(), which on older kernels leads to kprobe BPF programs failing to load due to the version check mismatch. Accommodate Ubuntu's quirks with LINUX_VERSION_CODE by using Ubuntu-specific /proc/version_code to fetch major/minor/patch versions to form LINUX_VERSION_CODE. While at it, consolide libbpf's kernel version detection code between libbpf.c and libbpf_probes.c. [0] Closes: https://github.com/libbpf/libbpf/issues/421 Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx> --- tools/lib/bpf/libbpf.c | 27 ++++++++++++++++++++++++++- tools/lib/bpf/libbpf_internal.h | 2 ++ tools/lib/bpf/libbpf_probes.c | 16 ---------------- 3 files changed, 28 insertions(+), 17 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index cf862a19222b..9cb99d1e2385 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -795,11 +795,36 @@ bpf_object__add_programs(struct bpf_object *obj, Elf_Data *sec_data, return 0; } -static __u32 get_kernel_version(void) +__u32 get_kernel_version(void) { + /* On Ubuntu LINUX_VERSION_CODE doesn't correspond to info.release, + * but Ubuntu provides /proc/version_signature file, as described at + * https://ubuntu.com/kernel, with an example contents below, which we + * can use to get a proper LINUX_VERSION_CODE. + * + * Ubuntu 5.4.0-12.15-generic 5.4.8 + * + * In the above, 5.4.8 is what kernel is actually expecting, while + * uname() call will return 5.4.0 in info.release. + */ + const char *ubuntu_kver_file = "/proc/version_signature"; __u32 major, minor, patch; struct utsname info; + if (access(ubuntu_kver_file, R_OK) == 0) { + FILE *f; + + f = fopen(ubuntu_kver_file, "r"); + if (f) { + if (fscanf(f, "%*s %*s %d.%d.%d\n", &major, &minor, &patch) == 3) { + fclose(f); + return KERNEL_VERSION(major, minor, patch); + } + fclose(f); + } + /* something went wrong, fall back to uname() approach */ + } + uname(&info); if (sscanf(info.release, "%u.%u.%u", &major, &minor, &patch) != 3) return 0; diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h index 5dbe4f463880..1565679eb432 100644 --- a/tools/lib/bpf/libbpf_internal.h +++ b/tools/lib/bpf/libbpf_internal.h @@ -188,6 +188,8 @@ static inline void libbpf_strlcpy(char *dst, const char *src, size_t sz) dst[i] = '\0'; } +__u32 get_kernel_version(void); + struct btf; struct btf_type; diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c index 9d3985283dfc..97b06cede56f 100644 --- a/tools/lib/bpf/libbpf_probes.c +++ b/tools/lib/bpf/libbpf_probes.c @@ -48,22 +48,6 @@ static int get_vendor_id(int ifindex) return strtol(buf, NULL, 0); } -static int get_kernel_version(void) -{ - int version, subversion, patchlevel; - struct utsname utsn; - - /* Return 0 on failure, and attempt to probe with empty kversion */ - if (uname(&utsn)) - return 0; - - if (sscanf(utsn.release, "%d.%d.%d", - &version, &subversion, &patchlevel) != 3) - return 0; - - return (version << 16) + (subversion << 8) + patchlevel; -} - static int probe_prog_load(enum bpf_prog_type prog_type, const struct bpf_insn *insns, size_t insns_cnt, char *log_buf, size_t log_buf_sz, -- 2.30.2
