From 5b3d72987701d51bf31823b39db49d10970f5c2d Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Wed, 22 Dec 2021 15:10:03 -0800 Subject: libbpf: Improve LINUX_VERSION_CODE detection 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 Signed-off-by: Alexei Starovoitov Acked-by: Yonghong Song Link: https://lore.kernel.org/bpf/20211222231003.2334940-1-andrii@kernel.org --- 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(-) (limited to 'tools') 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, -- cgit v1.2.3