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    Subject[PATCH 16/16] tracing: Support for syscall events raw records in perfcounters
    Date
    This bring the support for raw syscall events in perfcounters.
    The arguments or exit value are saved as a raw sample using
    the PERF_SAMPLE_RAW attribute in a perf counter.

    Example (for now you must explicitly set the PERF_SAMPLE_RAW flag
    in perf record):

    perf record -e syscalls:sys_enter_open -f -F 1 -a
    perf report -D

    0x2cbb8 [0x50]: event: 9
    .
    . ... raw event: size 80 bytes
    . 0000: 09 00 00 00 02 00 50 00 20 e9 39 ab 0a 7f 00 00 ......P. .9....
    . 0010: bc 14 00 00 bc 14 00 00 01 00 00 00 00 00 00 00 ...............
    . 0020: 2c 00 00 00 15 01 01 00 bc 14 00 00 bc 14 00 00 ,..............
    ^ ^ ^ ^ ^ ^ ^ ..........................
    Event Size struct trace_entry

    . 0030: 00 00 00 00 46 98 43 02 00 00 00 00 80 08 00 00 ....F.C........
    ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
    ptr to file name open flags

    . 0040: 00 00 00 00 02 00 00 00 00 00 00 00 00 00 00 00 ...............
    ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
    . open mode padding

    0x2cbb8 [0x50]: PERF_EVENT_SAMPLE (IP, 2): 5308: 0x7f0aab39e920 period: 1

    Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
    Cc: Steven Rostedt <rostedt@goodmis.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
    Cc: Jiaying Zhang <jiayingz@google.com>
    Cc: Martin Bligh <mbligh@google.com>
    Cc: Li Zefan <lizf@cn.fujitsu.com>
    Cc: Jason Baron <jbaron@redhat.com>
    Cc: Masami Hiramatsu <mhiramat@redhat.com>
    ---
    kernel/trace/trace_syscalls.c | 39 +++++++++++++++++++++++++++++++++++++--
    1 files changed, 37 insertions(+), 2 deletions(-)

    diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
    index 9ee6386..f837ccc 100644
    --- a/kernel/trace/trace_syscalls.c
    +++ b/kernel/trace/trace_syscalls.c
    @@ -301,6 +301,17 @@ struct trace_event event_syscall_exit = {
    };

    #ifdef CONFIG_EVENT_PROFILE
    +
    +struct syscall_enter_record {
    + struct trace_entry entry;
    + unsigned long args[0];
    +};
    +
    +struct syscall_exit_record {
    + struct trace_entry entry;
    + unsigned long ret;
    +};
    +
    static DECLARE_BITMAP(enabled_prof_enter_syscalls, FTRACE_SYSCALL_MAX);
    static DECLARE_BITMAP(enabled_prof_exit_syscalls, FTRACE_SYSCALL_MAX);
    static int sys_prof_refcount_enter;
    @@ -308,8 +319,10 @@ static int sys_prof_refcount_exit;

    static void prof_syscall_enter(struct pt_regs *regs, long id)
    {
    + struct syscall_enter_record *rec;
    struct syscall_metadata *sys_data;
    int syscall_nr;
    + int size;

    syscall_nr = syscall_get_nr(current, regs);
    if (!test_bit(syscall_nr, enabled_prof_enter_syscalls))
    @@ -319,7 +332,24 @@ static void prof_syscall_enter(struct pt_regs *regs, long id)
    if (!sys_data)
    return;

    - perf_tpcounter_event(sys_data->enter_id, 0, 1, NULL, 0);
    + /* get the size after alignment with the u32 buffer size field */
    + size = sizeof(unsigned long) * sys_data->nb_args + sizeof(*rec);
    + size = ALIGN(size + sizeof(u32), sizeof(u64));
    + size -= sizeof(u32);
    +
    + do {
    + char raw_data[size];
    +
    + /* zero the dead bytes from align to not leak stack to user */
    + *(u64 *)(&raw_data[size - sizeof(u64)]) = 0ULL;
    +
    + rec = (struct syscall_enter_record *) raw_data;
    + tracing_generic_entry_update(&rec->entry, 0, 0);
    + rec->entry.type = sys_data->enter_id;
    + syscall_get_arguments(current, regs, 0, sys_data->nb_args,
    + (unsigned long *)&rec->args);
    + perf_tpcounter_event(sys_data->enter_id, 0, 1, rec, size);
    + } while(0);
    }

    int reg_prof_syscall_enter(char *name)
    @@ -364,6 +394,7 @@ void unreg_prof_syscall_enter(char *name)
    static void prof_syscall_exit(struct pt_regs *regs, long ret)
    {
    struct syscall_metadata *sys_data;
    + struct syscall_exit_record rec;
    int syscall_nr;

    syscall_nr = syscall_get_nr(current, regs);
    @@ -374,7 +405,11 @@ static void prof_syscall_exit(struct pt_regs *regs, long ret)
    if (!sys_data)
    return;

    - perf_tpcounter_event(sys_data->exit_id, 0, 1, NULL, 0);
    + tracing_generic_entry_update(&rec.entry, 0, 0);
    + rec.entry.type = sys_data->exit_id;
    + rec.ret = syscall_get_return_value(current, regs);
    +
    + perf_tpcounter_event(sys_data->exit_id, 0, 1, &rec, sizeof(rec));
    }

    int reg_prof_syscall_exit(char *name)
    --
    1.6.2.3


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