Re: [PATCH v2 1/2] perf: Fix user attribute access in kprobes

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Tue, Jun 09, 2020 at 10:10:18AM +0200, Sumanth Korikkar escreveu:
> Issue:
> perf probe -a 'do_sched_setscheduler  pid policy
> param->sched_priority@user' did not work before.
> 
> Fix:
> Make (perf probe -a 'do_sched_setscheduler  pid policy
> param->sched_priority@user') output equivalent to ftrace
> ('p:probe/do_sched_setscheduler _text+517384 pid=%r2:s32 policy=%r3:s32
> sched_priority=+u0(%r4):s32' > kprobe_events)
> 
> Other:
> 1. Right now, __match_glob() does not handle [u]<offset>. For now, use
>   *u]<offset>.
> 2. @user attribute was introduced in commit 1e032f7cfa14 ("perf-probe:
>    Add user memory access attribute support")
> 
> Test:
> 1. perf probe -a 'do_sched_setscheduler  pid policy
>    param->sched_priority@user'
> 
> 2 ./perf script
>    sched 305669 [000] 1614458.838675: perf_bpf_probe:func: (2904e508)
>    pid=261614 policy=2 sched_priority=1
> 
> 3. cat /sys/kernel/debug/tracing/trace
>    <...>-309956 [006] .... 1616098.093957: 0: prio: 1

Thanks, I'm adding this:

Fixes: 1e032f7cfa14 ("perf-probe: Add user memory access attribute support")
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>

So that the stable guys pick this up eventually,

That first hunk with the strcmp() return check could have gone into a
separate patch, but I'll process it as-is for expediency,

- Arnaldo
 
> Signed-off-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
> Reviewed-by: Thomas Richter <tmricht@linux.ibm.com>
> Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
> ---
>  tools/perf/util/probe-event.c | 7 +++++--
>  tools/perf/util/probe-file.c  | 2 +-
>  2 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> index a08f373d3305..df713a5d1e26 100644
> --- a/tools/perf/util/probe-event.c
> +++ b/tools/perf/util/probe-event.c
> @@ -1575,7 +1575,7 @@ static int parse_perf_probe_arg(char *str, struct perf_probe_arg *arg)
>  	}
>  
>  	tmp = strchr(str, '@');
> -	if (tmp && tmp != str && strcmp(tmp + 1, "user")) { /* user attr */
> +	if (tmp && tmp != str && !strcmp(tmp + 1, "user")) { /* user attr */
>  		if (!user_access_is_supported()) {
>  			semantic_error("ftrace does not support user access\n");
>  			return -EINVAL;
> @@ -1995,7 +1995,10 @@ static int __synthesize_probe_trace_arg_ref(struct probe_trace_arg_ref *ref,
>  		if (depth < 0)
>  			return depth;
>  	}
> -	err = strbuf_addf(buf, "%+ld(", ref->offset);
> +	if (ref->user_access)
> +		err = strbuf_addf(buf, "%s%ld(", "+u", ref->offset);
> +	else
> +		err = strbuf_addf(buf, "%+ld(", ref->offset);
>  	return (err < 0) ? err : depth;
>  }
>  
> diff --git a/tools/perf/util/probe-file.c b/tools/perf/util/probe-file.c
> index 8c852948513e..064b63a6a3f3 100644
> --- a/tools/perf/util/probe-file.c
> +++ b/tools/perf/util/probe-file.c
> @@ -1044,7 +1044,7 @@ static struct {
>  	DEFINE_TYPE(FTRACE_README_PROBE_TYPE_X, "*type: * x8/16/32/64,*"),
>  	DEFINE_TYPE(FTRACE_README_KRETPROBE_OFFSET, "*place (kretprobe): *"),
>  	DEFINE_TYPE(FTRACE_README_UPROBE_REF_CTR, "*ref_ctr_offset*"),
> -	DEFINE_TYPE(FTRACE_README_USER_ACCESS, "*[u]<offset>*"),
> +	DEFINE_TYPE(FTRACE_README_USER_ACCESS, "*u]<offset>*"),
>  	DEFINE_TYPE(FTRACE_README_MULTIPROBE_EVENT, "*Create/append/*"),
>  	DEFINE_TYPE(FTRACE_README_IMMEDIATE_VALUE, "*\\imm-value,*"),
>  };
> -- 
> 2.17.1
> 

-- 

- Arnaldo