From 97eb31384af943d6b97eb5947262cee4ef25cb87 Mon Sep 17 00:00:00 2001 From: Martynas Pumputis Date: Mon, 12 Jul 2021 14:55:51 +0200 Subject: libbpf: Fix reuse of pinned map on older kernel When loading a BPF program with a pinned map, the loader checks whether the pinned map can be reused, i.e. their properties match. To derive such of the pinned map, the loader invokes BPF_OBJ_GET_INFO_BY_FD and then does the comparison. Unfortunately, on < 4.12 kernels the BPF_OBJ_GET_INFO_BY_FD is not available, so loading the program fails with the following error: libbpf: failed to get map info for map FD 5: Invalid argument libbpf: couldn't reuse pinned map at '/sys/fs/bpf/tc/globals/cilium_call_policy': parameter mismatch" libbpf: map 'cilium_call_policy': error reusing pinned map libbpf: map 'cilium_call_policy': failed to create: Invalid argument(-22) libbpf: failed to load object 'bpf_overlay.o' To fix this, fallback to derivation of the map properties via /proc/$PID/fdinfo/$MAP_FD if BPF_OBJ_GET_INFO_BY_FD fails with EINVAL, which can be used as an indicator that the kernel doesn't support the latter. Signed-off-by: Martynas Pumputis Signed-off-by: Andrii Nakryiko Acked-by: John Fastabend Link: https://lore.kernel.org/bpf/20210712125552.58705-1-m@lambda.lt --- tools/lib/bpf/libbpf.c | 48 +++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 45 insertions(+), 3 deletions(-) (limited to 'tools/lib/bpf/libbpf.c') diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 1e04ce724240..88b99401040c 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -3894,6 +3894,42 @@ static int bpf_map_find_btf_info(struct bpf_object *obj, struct bpf_map *map) return 0; } +static int bpf_get_map_info_from_fdinfo(int fd, struct bpf_map_info *info) +{ + char file[PATH_MAX], buff[4096]; + FILE *fp; + __u32 val; + int err; + + snprintf(file, sizeof(file), "/proc/%d/fdinfo/%d", getpid(), fd); + memset(info, 0, sizeof(*info)); + + fp = fopen(file, "r"); + if (!fp) { + err = -errno; + pr_warn("failed to open %s: %d. No procfs support?\n", file, + err); + return err; + } + + while (fgets(buff, sizeof(buff), fp)) { + if (sscanf(buff, "map_type:\t%u", &val) == 1) + info->type = val; + else if (sscanf(buff, "key_size:\t%u", &val) == 1) + info->key_size = val; + else if (sscanf(buff, "value_size:\t%u", &val) == 1) + info->value_size = val; + else if (sscanf(buff, "max_entries:\t%u", &val) == 1) + info->max_entries = val; + else if (sscanf(buff, "map_flags:\t%i", &val) == 1) + info->map_flags = val; + } + + fclose(fp); + + return 0; +} + int bpf_map__reuse_fd(struct bpf_map *map, int fd) { struct bpf_map_info info = {}; @@ -3902,6 +3938,8 @@ int bpf_map__reuse_fd(struct bpf_map *map, int fd) char *new_name; err = bpf_obj_get_info_by_fd(fd, &info, &len); + if (err && errno == EINVAL) + err = bpf_get_map_info_from_fdinfo(fd, &info); if (err) return libbpf_err(err); @@ -4381,12 +4419,16 @@ static bool map_is_reuse_compat(const struct bpf_map *map, int map_fd) struct bpf_map_info map_info = {}; char msg[STRERR_BUFSIZE]; __u32 map_info_len; + int err; map_info_len = sizeof(map_info); - if (bpf_obj_get_info_by_fd(map_fd, &map_info, &map_info_len)) { - pr_warn("failed to get map info for map FD %d: %s\n", - map_fd, libbpf_strerror_r(errno, msg, sizeof(msg))); + err = bpf_obj_get_info_by_fd(map_fd, &map_info, &map_info_len); + if (err && errno == EINVAL) + err = bpf_get_map_info_from_fdinfo(map_fd, &map_info); + if (err) { + pr_warn("failed to get map info for map FD %d: %s\n", map_fd, + libbpf_strerror_r(errno, msg, sizeof(msg))); return false; } -- cgit v1.2.3 From ac0ed488297a9850b0c285646b7854228368ba6b Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Wed, 14 Jul 2021 11:43:58 +0200 Subject: libbpf: Add bpf_program__attach_kprobe_opts function Adding bpf_program__attach_kprobe_opts that does the same as bpf_program__attach_kprobe, but takes opts argument. Currently opts struct holds just retprobe bool, but we will add new field in following patch. The function is not exported, so there's no need to add size to the struct bpf_program_attach_kprobe_opts for now. Signed-off-by: Jiri Olsa Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20210714094400.396467-7-jolsa@kernel.org --- tools/lib/bpf/libbpf.c | 34 +++++++++++++++++++++++++--------- 1 file changed, 25 insertions(+), 9 deletions(-) (limited to 'tools/lib/bpf/libbpf.c') diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 88b99401040c..d93a6f9408d1 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -10346,19 +10346,24 @@ static int perf_event_open_probe(bool uprobe, bool retprobe, const char *name, return pfd; } -struct bpf_link *bpf_program__attach_kprobe(struct bpf_program *prog, - bool retprobe, - const char *func_name) +struct bpf_program_attach_kprobe_opts { + bool retprobe; +}; + +static struct bpf_link* +bpf_program__attach_kprobe_opts(struct bpf_program *prog, + const char *func_name, + struct bpf_program_attach_kprobe_opts *opts) { char errmsg[STRERR_BUFSIZE]; struct bpf_link *link; int pfd, err; - pfd = perf_event_open_probe(false /* uprobe */, retprobe, func_name, + pfd = perf_event_open_probe(false /* uprobe */, opts->retprobe, func_name, 0 /* offset */, -1 /* pid */); if (pfd < 0) { pr_warn("prog '%s': failed to create %s '%s' perf event: %s\n", - prog->name, retprobe ? "kretprobe" : "kprobe", func_name, + prog->name, opts->retprobe ? "kretprobe" : "kprobe", func_name, libbpf_strerror_r(pfd, errmsg, sizeof(errmsg))); return libbpf_err_ptr(pfd); } @@ -10367,23 +10372,34 @@ struct bpf_link *bpf_program__attach_kprobe(struct bpf_program *prog, if (err) { close(pfd); pr_warn("prog '%s': failed to attach to %s '%s': %s\n", - prog->name, retprobe ? "kretprobe" : "kprobe", func_name, + prog->name, opts->retprobe ? "kretprobe" : "kprobe", func_name, libbpf_strerror_r(err, errmsg, sizeof(errmsg))); return libbpf_err_ptr(err); } return link; } +struct bpf_link *bpf_program__attach_kprobe(struct bpf_program *prog, + bool retprobe, + const char *func_name) +{ + struct bpf_program_attach_kprobe_opts opts = { + .retprobe = retprobe, + }; + + return bpf_program__attach_kprobe_opts(prog, func_name, &opts); +} + static struct bpf_link *attach_kprobe(const struct bpf_sec_def *sec, struct bpf_program *prog) { + struct bpf_program_attach_kprobe_opts opts; const char *func_name; - bool retprobe; func_name = prog->sec_name + sec->len; - retprobe = strcmp(sec->sec, "kretprobe/") == 0; + opts.retprobe = strcmp(sec->sec, "kretprobe/") == 0; - return bpf_program__attach_kprobe(prog, retprobe, func_name); + return bpf_program__attach_kprobe_opts(prog, func_name, &opts); } struct bpf_link *bpf_program__attach_uprobe(struct bpf_program *prog, -- cgit v1.2.3 From a2488b5f483f18e6e34be2a15eb4a79f4a0d8728 Mon Sep 17 00:00:00 2001 From: Alan Maguire Date: Wed, 14 Jul 2021 11:43:59 +0200 Subject: libbpf: Allow specification of "kprobe/function+offset" kprobes can be placed on most instructions in a function, not just entry, and ftrace and bpftrace support the function+offset notification for probe placement. Adding parsing of func_name into func+offset to bpf_program__attach_kprobe() allows the user to specify SEC("kprobe/bpf_fentry_test5+0x6") ...for example, and the offset can be passed to perf_event_open_probe() to support kprobe attachment. Signed-off-by: Alan Maguire Signed-off-by: Jiri Olsa Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20210714094400.396467-8-jolsa@kernel.org --- tools/lib/bpf/libbpf.c | 24 ++++++++++++++++++++++-- 1 file changed, 22 insertions(+), 2 deletions(-) (limited to 'tools/lib/bpf/libbpf.c') diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index d93a6f9408d1..abe6d4842bb0 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -10348,6 +10348,7 @@ static int perf_event_open_probe(bool uprobe, bool retprobe, const char *name, struct bpf_program_attach_kprobe_opts { bool retprobe; + unsigned long offset; }; static struct bpf_link* @@ -10360,7 +10361,7 @@ bpf_program__attach_kprobe_opts(struct bpf_program *prog, int pfd, err; pfd = perf_event_open_probe(false /* uprobe */, opts->retprobe, func_name, - 0 /* offset */, -1 /* pid */); + opts->offset, -1 /* pid */); if (pfd < 0) { pr_warn("prog '%s': failed to create %s '%s' perf event: %s\n", prog->name, opts->retprobe ? "kretprobe" : "kprobe", func_name, @@ -10394,12 +10395,31 @@ static struct bpf_link *attach_kprobe(const struct bpf_sec_def *sec, struct bpf_program *prog) { struct bpf_program_attach_kprobe_opts opts; + unsigned long offset = 0; + struct bpf_link *link; const char *func_name; + char *func; + int n, err; func_name = prog->sec_name + sec->len; opts.retprobe = strcmp(sec->sec, "kretprobe/") == 0; - return bpf_program__attach_kprobe_opts(prog, func_name, &opts); + n = sscanf(func_name, "%m[a-zA-Z0-9_.]+%lx", &func, &offset); + if (n < 1) { + err = -EINVAL; + pr_warn("kprobe name is invalid: %s\n", func_name); + return libbpf_err_ptr(err); + } + if (opts.retprobe && offset != 0) { + err = -EINVAL; + pr_warn("kretprobes do not support offset specification\n"); + return libbpf_err_ptr(err); + } + + opts.offset = offset; + link = bpf_program__attach_kprobe_opts(prog, func, &opts); + free(func); + return link; } struct bpf_link *bpf_program__attach_uprobe(struct bpf_program *prog, -- cgit v1.2.3