Allowing one to hook into the syscalls:sys_enter_NAME tracepoints,
an example is provided that hooks into the 'openat' syscall.
Using it with the probe:vfs_getname probe into getname_flags to get the
filename args as it is copied from userspace:
# perf probe -l
probe:vfs_getname (on getname_flags:73@acme/git/linux/fs/namei.c with pathname)
# perf trace -e probe:*getname,tools/perf/examples/bpf/sys_enter_openat.c cat /etc/passwd > /dev/null
0.000 probe:vfs_getname:(ffffffffbd2a8983) pathname="/etc/ld.so.preload"
0.022 syscalls:sys_enter_openat:dfd: CWD, filename: 0xafbe8da8, flags: CLOEXEC
0.027 probe:vfs_getname:(ffffffffbd2a8983) pathname="/etc/ld.so.cache"
0.054 syscalls:sys_enter_openat:dfd: CWD, filename: 0xafdf0ce0, flags: CLOEXEC
0.057 probe:vfs_getname:(ffffffffbd2a8983) pathname="/lib64/libc.so.6"
0.316 probe:vfs_getname:(ffffffffbd2a8983) pathname="/usr/lib/locale/locale-archive"
0.375 syscalls:sys_enter_openat:dfd: CWD, filename: 0xe2b2b0b4
0.379 probe:vfs_getname:(ffffffffbd2a8983) pathname="/etc/passwd"
#
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-2po9jcqv1qgj0koxlg8kkg30@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
