tracing/syscalls: Pass in hardcoded 6 into syscall_get_arguments()

The only users that calls syscall_get_arguments() with a variable and not a
hard coded '6' is ftrace_syscall_enter(). syscall_get_arguments() can be
optimized by removing a variable input, and always grabbing 6 arguments
regardless of what the system call actually uses.

Change ftrace_syscall_enter() to pass the 6 args into a local stack array
and copy the necessary arguments into the trace event as needed.

This is needed to remove two parameters from syscall_get_arguments().

Link: http://lkml.kernel.org/r/20161107213233.627583542@goodmis.org
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index f93a56d2db275be64df083344b68ec65f3c32473..e9f5bbbad6d94cf1e6c3ee284b79e2a86c897cda 100644 (file)
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -314,6 +314,7 @@ static void ftrace_syscall_enter(void *data, struct pt_regs *regs, long id)
        struct ring_buffer_event *event;
        struct ring_buffer *buffer;
        unsigned long irq_flags;
+       unsigned long args[6];
        int pc;
        int syscall_nr;
        int size;
@@ -347,7 +348,8 @@ static void ftrace_syscall_enter(void *data, struct pt_regs *regs, long id)
 
        entry = ring_buffer_event_data(event);
        entry->nr = syscall_nr;
-       syscall_get_arguments(current, regs, 0, sys_data->nb_args, entry->args);
+       syscall_get_arguments(current, regs, 0, 6, args);
+       memcpy(entry->args, args, sizeof(unsigned long) * sys_data->nb_args);
 
        event_trigger_unlock_commit(trace_file, buffer, event, entry,
                                    irq_flags, pc);
@@ -583,6 +585,7 @@ static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
        struct syscall_metadata *sys_data;
        struct syscall_trace_enter *rec;
        struct hlist_head *head;
+       unsigned long args[6];
        bool valid_prog_array;
        int syscall_nr;
        int rctx;
@@ -613,8 +616,8 @@ static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
                return;
 
        rec->nr = syscall_nr;
-       syscall_get_arguments(current, regs, 0, sys_data->nb_args,
-                              (unsigned long *)&rec->args);
+       syscall_get_arguments(current, regs, 0, 6, args);
+       memcpy(&rec->args, args, sizeof(unsigned long) * sys_data->nb_args);
 
        if ((valid_prog_array &&
             !perf_call_bpf_enter(sys_data->enter_event, regs, sys_data, rec)) ||