On Thu, Jun 20, 2019 at 5:04 PM Stanislav Fomichev <sdf@xxxxxxxxxxx> wrote:
>
> On 06/20, Andrii Nakryiko wrote:
> > Add ability to attach to kernel and user probes and retprobes.
> > Implementation depends on perf event support for kprobes/uprobes.
> >
> > Signed-off-by: Andrii Nakryiko <andriin@xxxxxx>
> > ---
> > tools/lib/bpf/libbpf.c | 207 +++++++++++++++++++++++++++++++++++++++
> > tools/lib/bpf/libbpf.h | 8 ++
> > tools/lib/bpf/libbpf.map | 2 +
> > 3 files changed, 217 insertions(+)
> >
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index 2bb1fa008be3..11329e05530e 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -3969,6 +3969,213 @@ int bpf_program__attach_perf_event(struct bpf_program *prog, int pfd)
> > return 0;
> > }
> >
> > +static int parse_uint(const char *buf)
> > +{
> > + int ret;
> > +
> > + errno = 0;
> > + ret = (int)strtol(buf, NULL, 10);
> > + if (errno) {
> > + ret = -errno;
> > + pr_debug("failed to parse '%s' as unsigned int\n", buf);
> > + return ret;
> > + }
> > + if (ret < 0) {
> > + pr_debug("failed to parse '%s' as unsigned int\n", buf);
> > + return -EINVAL;
> > + }
> > + return ret;
> > +}
> > +
> > +static int parse_uint_from_file(const char* file)
> > +{
> > + char buf[STRERR_BUFSIZE];
> > + int fd, ret;
> > +
> > + fd = open(file, O_RDONLY);
> > + if (fd < 0) {
> > + ret = -errno;
> > + pr_debug("failed to open '%s': %s\n", file,
> > + libbpf_strerror_r(ret, buf, sizeof(buf)));
> > + return ret;
> > + }
> > + ret = read(fd, buf, sizeof(buf));
> > + close(fd);
> > + if (ret < 0) {
> > + ret = -errno;
> Is -errno still valid here after a close(fd) above? Do we have any
> guarantee of errno preservation when we do another syscall?
Good catch! No, close() can change errno. Fixed. Also fixed for
parse_config_from_file below.
>
> > + pr_debug("failed to read '%s': %s\n", file,
> > + libbpf_strerror_r(ret, buf, sizeof(buf)));
> > + return ret;
> > + }
> > + if (ret == 0 || ret >= sizeof(buf)) {
> > + buf[sizeof(buf) - 1] = 0;
> > + pr_debug("unexpected input from '%s': '%s'\n", file, buf);
> > + return -EINVAL;
> > + }
> > + return parse_uint(buf);
> > +}
> > +
> > +static int determine_kprobe_perf_type(void)
> > +{
> > + const char *file = "/sys/bus/event_source/devices/kprobe/type";
> > + return parse_uint_from_file(file);
> > +}
> > +
> > +static int determine_uprobe_perf_type(void)
> > +{
> > + const char *file = "/sys/bus/event_source/devices/uprobe/type";
> > + return parse_uint_from_file(file);
> > +}
> > +
> > +static int parse_config_from_file(const char *file)
> > +{
> > + char buf[STRERR_BUFSIZE];
> > + int fd, ret;
> > +
> > + fd = open(file, O_RDONLY);
> > + if (fd < 0) {
> > + ret = -errno;
> > + pr_debug("failed to open '%s': %s\n", file,
> > + libbpf_strerror_r(ret, buf, sizeof(buf)));
> > + return ret;
> > + }
> > + ret = read(fd, buf, sizeof(buf));
> > + close(fd);
> > + if (ret < 0) {
> > + ret = -errno;
> > + pr_debug("failed to read '%s': %s\n", file,
> > + libbpf_strerror_r(ret, buf, sizeof(buf)));
> > + return ret;
> > + }
> > + if (ret == 0 || ret >= sizeof(buf)) {
> > + buf[sizeof(buf) - 1] = 0;
> > + pr_debug("unexpected input from '%s': '%s'\n", file, buf);
> > + return -EINVAL;
> > + }
> > + if (strncmp(buf, "config:", 7)) {
> > + pr_debug("expected 'config:' prefix, found '%s'\n", buf);
> > + return -EINVAL;
> > + }
> > + return parse_uint(buf + 7);
> > +}
> > +
<snip>
