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    Subject[tip:perf/core] tracing/syscalls: Don't add events for unmapped syscalls
    Commit-ID:  ba976970c79fd2fbfe1a4b3b6766a318f4eb9d4c
    Gitweb: http://git.kernel.org/tip/ba976970c79fd2fbfe1a4b3b6766a318f4eb9d4c
    Author: Ian Munsie <imunsie@au1.ibm.com>
    AuthorDate: Thu, 3 Feb 2011 14:27:20 +1100
    Committer: Steven Rostedt <rostedt@goodmis.org>
    CommitDate: Mon, 7 Feb 2011 21:24:44 -0500

    tracing/syscalls: Don't add events for unmapped syscalls

    FTRACE_SYSCALLS would create events for each and every system call, even
    if it had failed to map the system call's name with it's number. This
    resulted in a number of events being created that would not behave as
    expected.

    This could happen, for example, on architectures who's symbol names are
    unusual and will not match the system call name. It could also happen
    with system calls which were mapped to sys_ni_syscall.

    This patch changes the default system call number in the metadata to -1.
    If the system call name from the metadata is not successfully mapped to
    a system call number during boot, than the event initialisation routine
    will now return an error, preventing the event from being created.

    Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
    LKML-Reference: <1296703645-18718-2-git-send-email-imunsie@au1.ibm.com>
    Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
    ---
    include/linux/syscalls.h | 2 ++
    kernel/trace/trace_syscalls.c | 8 ++++++++
    2 files changed, 10 insertions(+), 0 deletions(-)

    diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
    index 98664db..8e8968e 100644
    --- a/include/linux/syscalls.h
    +++ b/include/linux/syscalls.h
    @@ -158,6 +158,7 @@ extern struct trace_event_functions exit_syscall_print_funcs;
    static struct syscall_metadata __used \
    __syscall_meta_##sname = { \
    .name = "sys"#sname, \
    + .syscall_nr = -1, /* Filled in at boot */ \
    .nb_args = nb, \
    .types = types_##sname, \
    .args = args_##sname, \
    @@ -175,6 +176,7 @@ extern struct trace_event_functions exit_syscall_print_funcs;
    static struct syscall_metadata __used \
    __syscall_meta__##sname = { \
    .name = "sys_"#sname, \
    + .syscall_nr = -1, /* Filled in at boot */ \
    .nb_args = 0, \
    .enter_event = &event_enter__##sname, \
    .exit_event = &event_exit__##sname, \
    diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
    index 5c9fe08..a9ceabd 100644
    --- a/kernel/trace/trace_syscalls.c
    +++ b/kernel/trace/trace_syscalls.c
    @@ -424,6 +424,14 @@ void unreg_event_syscall_exit(struct ftrace_event_call *call)
    int init_syscall_trace(struct ftrace_event_call *call)
    {
    int id;
    + int num;
    +
    + num = ((struct syscall_metadata *)call->data)->syscall_nr;
    + if (num < 0 || num >= NR_syscalls) {
    + pr_debug("syscall %s metadata not mapped, disabling ftrace event\n",
    + ((struct syscall_metadata *)call->data)->name);
    + return -ENOSYS;
    + }

    if (set_syscall_print_fmt(call) < 0)
    return -ENOMEM;

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