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    Subject[PATCH 5.7 385/477] perf probe: Fix user attribute access in kprobes
    Date
    From: Sumanth Korikkar <sumanthk@linux.ibm.com>

    [ Upstream commit 9256c3031eb9beafa3957c61093104c3c75a6148 ]

    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:

    # echo 'p:probe/do_sched_setscheduler _text+517384 pid=%r2:s32 policy=%r3:s32 sched_priority=+u0(%r4):s32' > /sys/kernel/debug/tracing/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

    Committer testing:

    Before:

    # perf probe -a 'do_sched_setscheduler pid policy param->sched_priority@user'
    param(type:sched_param) has no member sched_priority@user.
    Error: Failed to add events.
    # pahole sched_param
    struct sched_param {
    int sched_priority; /* 0 4 */

    /* size: 4, cachelines: 1, members: 1 */
    /* last cacheline: 4 bytes */
    };
    #

    After:

    # perf probe -a 'do_sched_setscheduler pid policy param->sched_priority@user'
    Added new event:
    probe:do_sched_setscheduler (on do_sched_setscheduler with pid policy sched_priority=param->sched_priority)

    You can now use it in all perf tools, such as:

    perf record -e probe:do_sched_setscheduler -aR sleep 1

    # cat /sys/kernel/debug/tracing/kprobe_events
    p:probe/do_sched_setscheduler _text+1113792 pid=%di:s32 policy=%si:s32 sched_priority=+u0(%dx):s32
    #

    Fixes: 1e032f7cfa14 ("perf-probe: Add user memory access attribute support")
    Signed-off-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
    Reviewed-by: Thomas Richter <tmricht@linux.ibm.com>
    Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
    Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
    Cc: Ilya Leoshkevich <iii@linux.ibm.com>
    Cc: Jiri Olsa <jolsa@redhat.com>
    Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
    Cc: bpf@vger.kernel.org
    LPU-Reference: 20200609081019.60234-2-sumanthk@linux.ibm.com
    Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    Signed-off-by: Sasha Levin <sashal@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 a08f373d33056..df713a5d1e26a 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 8c852948513e3..064b63a6a3f31 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,*"),
    };
    --
    2.25.1


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