From be3245e22d227ad68ab97785d506561374daa028 Mon Sep 17 00:00:00 2001 From: Quentin Monnet Date: Tue, 18 Dec 2018 10:13:18 +0000 Subject: tools: bpftool: attempt to mount tracefs if required for tracelog cmd As a follow-up to commit 30da46b5dc3a ("tools: bpftool: add a command to dump the trace pipe"), attempt to mount the tracefs virtual file system if it is not detected on the system before trying to dump content of the tracing pipe on an invocation of "bpftool prog tracelog". Usually, tracefs in automatically mounted by debugfs when the user tries to access it (e.g. "ls /sys/kernel/debug/tracing" mounts the tracefs). So if we failed to find it, it is probably that debugfs is not here either. Therefore, we just attempt a single mount, at a location that does not involve debugfs: /sys/kernel/tracing. Suggested-by: Daniel Borkmann Signed-off-by: Quentin Monnet Reviewed-by: Jakub Kicinski Signed-off-by: Daniel Borkmann --- tools/bpf/bpftool/common.c | 25 ++++++++++++++++++++----- 1 file changed, 20 insertions(+), 5 deletions(-) (limited to 'tools/bpf/bpftool/common.c') diff --git a/tools/bpf/bpftool/common.c b/tools/bpf/bpftool/common.c index 24582e8a96fb..1bad6602a282 100644 --- a/tools/bpf/bpftool/common.c +++ b/tools/bpf/bpftool/common.c @@ -76,7 +76,8 @@ void set_max_rlimit(void) setrlimit(RLIMIT_MEMLOCK, &rinf); } -static int mnt_bpffs(const char *target, char *buff, size_t bufflen) +static int +mnt_fs(const char *target, const char *type, char *buff, size_t bufflen) { bool bind_done = false; @@ -98,15 +99,29 @@ static int mnt_bpffs(const char *target, char *buff, size_t bufflen) bind_done = true; } - if (mount("bpf", target, "bpf", 0, "mode=0700")) { - snprintf(buff, bufflen, "mount -t bpf bpf %s failed: %s", - target, strerror(errno)); + if (mount(type, target, type, 0, "mode=0700")) { + snprintf(buff, bufflen, "mount -t %s %s %s failed: %s", + type, type, target, strerror(errno)); return -1; } return 0; } +int mount_tracefs(const char *target) +{ + char err_str[ERR_MAX_LEN]; + int err; + + err = mnt_fs(target, "tracefs", err_str, ERR_MAX_LEN); + if (err) { + err_str[ERR_MAX_LEN - 1] = '\0'; + p_err("can't mount tracefs: %s", err_str); + } + + return err; +} + int open_obj_pinned(char *path, bool quiet) { int fd; @@ -162,7 +177,7 @@ int mount_bpffs_for_pin(const char *name) /* nothing to do if already mounted */ goto out_free; - err = mnt_bpffs(dir, err_str, ERR_MAX_LEN); + err = mnt_fs(dir, "bpf", err_str, ERR_MAX_LEN); if (err) { err_str[ERR_MAX_LEN - 1] = '\0'; p_err("can't mount BPF file system to pin the object (%s): %s", -- cgit v1.2.3