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From: Steven Rostedt on 23 Jun 2010 11:10
On Wed, 2010-06-23 at 20:02 +1000, Ian Munsie wrote:
> From: Ian Munsie <imunsie(a)au1.ibm.com>
>
> 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(a)au1.ibm.com>
> ---
> 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 7f614ce..86f082b 100644
> --- a/include/linux/syscalls.h
> +++ b/include/linux/syscalls.h
> @@ -159,6 +159,7 @@ extern struct trace_event_functions exit_syscall_print_funcs;
> __attribute__((section("__syscalls_metadata"))) \
> __syscall_meta_##sname = { \
> .name = "sys"#sname, \
> + .syscall_nr = -1, /* Filled in at boot */ \
> .nb_args = nb, \
> .types = types_##sname, \
> .args = args_##sname, \
> @@ -176,6 +177,7 @@ extern struct trace_event_functions exit_syscall_print_funcs;
> __attribute__((section("__syscalls_metadata"))) \
> __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 34e3580..82246ce 100644
> --- a/kernel/trace/trace_syscalls.c
> +++ b/kernel/trace/trace_syscalls.c
> @@ -431,6 +431,14 @@ 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;
> + }

Perhaps this should be:

if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls)
return -ENOSYS;

-- Steve

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


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