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perf augmented_raw_syscalls: Change helper to consider just the augmented_filename part

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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 <adrian.hunter@intel.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Luis Cláudio Gonçalves <lclaudio@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-deyvqi39um6gp6hux6jovos8@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Arnaldo Carvalho de Melo 2019-06-04 15:57:28 -03:00
parent 0c95a7ff76
commit deaf4da48a
1 changed files with 33 additions and 13 deletions
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46
tools/perf/examples/bpf/augmented_raw_syscalls.c
View File

@ -47,7 +47,7 @@ struct syscall_exit_args {
struct augmented_filename { struct augmented_filename {
unsigned int size; unsigned int size;
int reserved; int err;
char value[PATH_MAX]; 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); bpf_map(augmented_filename_map, PERCPU_ARRAY, int, struct augmented_args_filename, 1);
static inline static inline
unsigned int augmented_args__read_filename(struct augmented_args_filename *augmented_args, unsigned int augmented_filename__read(struct augmented_filename *augmented_filename,
const void *filename_arg, unsigned int filename_len) 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_filename->size = augmented_filename->err = 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)) { * probe_read_str may return < 0, e.g. -EFAULT
len -= sizeof(augmented_args->filename.value) - augmented_args->filename.size; * So we leave that in the augmented_filename->size that userspace will
len &= sizeof(augmented_args->filename.value) - 1; */
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; return len;
@ -80,7 +92,17 @@ SEC("raw_syscalls:sys_enter")
int sys_enter(struct syscall_enter_args *args) int sys_enter(struct syscall_enter_args *args)
{ {
struct augmented_args_filename *augmented_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; const void *filename_arg = NULL;
struct syscall *syscall; struct syscall *syscall;
int key = 0; 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) loop_iter_last(5)
if (filename_arg != NULL && filename_len <= sizeof(augmented_args->filename.value)) { if (filename_arg != NULL && filename_len <= sizeof(augmented_args->filename.value)) {
len = augmented_args__read_filename(augmented_args, filename_arg, filename_len); len += augmented_filename__read(&augmented_args->filename, filename_arg, filename_len);
} else {
len = sizeof(augmented_args->args);
} }
/* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */ /* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */