From deaf4da48a67f73eb7d5d1802c14eaf58d33f2da Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Tue, 4 Jun 2019 15:57:28 -0300 Subject: [PATCH] perf augmented_raw_syscalls: Change helper to consider just the augmented_filename part MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit So that we can use it for multiple args, baby steps not to step into the verifier toes. In the process make sure we handle -EFAULT from bpf_prog_read_str(), as this really is needed now that we'll handle more than one augmented argument, i.e. if there is failure, then we have the argument that fails have: (size = 0, err = -EFAULT, value = [] ) followed by the next, lets say that worked for a second pathname: (size = 4, err = 0, value = "/tmp" ) So we can skip the first while telling the user about the problem and then process the second. Cc: Adrian Hunter Cc: Brendan Gregg Cc: Jiri Olsa Cc: Luis Cláudio Gonçalves Cc: Namhyung Kim Link: https://lkml.kernel.org/n/tip-deyvqi39um6gp6hux6jovos8@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- .../examples/bpf/augmented_raw_syscalls.c | 46 +++++++++++++------ 1 file changed, 33 insertions(+), 13 deletions(-) diff --git a/tools/perf/examples/bpf/augmented_raw_syscalls.c b/tools/perf/examples/bpf/augmented_raw_syscalls.c index 356513e81ec1..5054b4bc9e55 100644 --- a/tools/perf/examples/bpf/augmented_raw_syscalls.c +++ b/tools/perf/examples/bpf/augmented_raw_syscalls.c @@ -47,7 +47,7 @@ struct syscall_exit_args { struct augmented_filename { unsigned int size; - int reserved; + int err; char value[PATH_MAX]; }; @@ -61,16 +61,28 @@ struct augmented_args_filename { bpf_map(augmented_filename_map, PERCPU_ARRAY, int, struct augmented_args_filename, 1); static inline -unsigned int augmented_args__read_filename(struct augmented_args_filename *augmented_args, - const void *filename_arg, unsigned int filename_len) +unsigned int augmented_filename__read(struct augmented_filename *augmented_filename, + const void *filename_arg, unsigned int filename_len) { - unsigned int len = sizeof(*augmented_args); + unsigned int len = sizeof(*augmented_filename); + int size = probe_read_str(&augmented_filename->value, filename_len, filename_arg); - augmented_args->filename.reserved = 0; - augmented_args->filename.size = probe_read_str(&augmented_args->filename.value, filename_len, filename_arg); - if (augmented_args->filename.size < sizeof(augmented_args->filename.value)) { - len -= sizeof(augmented_args->filename.value) - augmented_args->filename.size; - len &= sizeof(augmented_args->filename.value) - 1; + augmented_filename->size = augmented_filename->err = 0; + /* + * probe_read_str may return < 0, e.g. -EFAULT + * So we leave that in the augmented_filename->size that userspace will + */ + if (size > 0) { + len -= sizeof(augmented_filename->value) - size; + len &= sizeof(augmented_filename->value) - 1; + augmented_filename->size = size; + } else { + /* + * So that username notice the error while still being able + * to skip this augmented arg record + */ + augmented_filename->err = size; + len = offsetof(struct augmented_filename, value); } return len; @@ -80,7 +92,17 @@ SEC("raw_syscalls:sys_enter") int sys_enter(struct syscall_enter_args *args) { struct augmented_args_filename *augmented_args; - unsigned int len, filename_len; + /* + * We start len, the amount of data that will be in the perf ring + * buffer, if this is not filtered out by one of pid_filter__has(), + * syscall->enabled, etc, with the non-augmented raw syscall payload, + * i.e. sizeof(augmented_args->args). + * + * We'll add to this as we add augmented syscalls right after that + * initial, non-augmented raw_syscalls:sys_enter payload. + */ + unsigned int len = sizeof(augmented_args->args); + unsigned int filename_len; const void *filename_arg = NULL; struct syscall *syscall; int key = 0; @@ -198,9 +220,7 @@ processed 46 insns (limit 1000000) max_states_per_insn 0 total_states 12 peak_st loop_iter_last(5) if (filename_arg != NULL && filename_len <= sizeof(augmented_args->filename.value)) { - len = augmented_args__read_filename(augmented_args, filename_arg, filename_len); - } else { - len = sizeof(augmented_args->args); + len += augmented_filename__read(&augmented_args->filename, filename_arg, filename_len); } /* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */ -- 2.30.2