trace.py: fix compiler warning (#2094)

Compiler shows warning "incompatible integer to pointer conversion
initializing" while compiling bpf program.
This patch adds necessary typecast when assigning PT_REGS_PARAM vaules
to struct pt_regs pointer

tools/trace.py

@@ -216,17 +216,17 @@ class Probe(object):
         }
 
         aliases_indarg = {
-                "arg1": "({u64 _val; struct pt_regs *_ctx = PT_REGS_PARM1(ctx);"
+                "arg1": "({u64 _val; struct pt_regs *_ctx = (struct pt_regs *)PT_REGS_PARM1(ctx);"
                         "  bpf_probe_read(&_val, sizeof(_val), &(PT_REGS_PARM1(_ctx))); _val;})",
-                "arg2": "({u64 _val; struct pt_regs *_ctx = PT_REGS_PARM2(ctx);"
+                "arg2": "({u64 _val; struct pt_regs *_ctx = (struct pt_regs *)PT_REGS_PARM2(ctx);"
                         "  bpf_probe_read(&_val, sizeof(_val), &(PT_REGS_PARM2(_ctx))); _val;})",
-                "arg3": "({u64 _val; struct pt_regs *_ctx = PT_REGS_PARM3(ctx);"
+                "arg3": "({u64 _val; struct pt_regs *_ctx = (struct pt_regs *)PT_REGS_PARM3(ctx);"
                         "  bpf_probe_read(&_val, sizeof(_val), &(PT_REGS_PARM3(_ctx))); _val;})",
-                "arg4": "({u64 _val; struct pt_regs *_ctx = PT_REGS_PARM4(ctx);"
+                "arg4": "({u64 _val; struct pt_regs *_ctx = (struct pt_regs *)PT_REGS_PARM4(ctx);"
                         "  bpf_probe_read(&_val, sizeof(_val), &(PT_REGS_PARM4(_ctx))); _val;})",
-                "arg5": "({u64 _val; struct pt_regs *_ctx = PT_REGS_PARM5(ctx);"
+                "arg5": "({u64 _val; struct pt_regs *_ctx = (struct pt_regs *)PT_REGS_PARM5(ctx);"
                         "  bpf_probe_read(&_val, sizeof(_val), &(PT_REGS_PARM5(_ctx))); _val;})",
-                "arg6": "({u64 _val; struct pt_regs *_ctx = PT_REGS_PARM6(ctx);"
+                "arg6": "({u64 _val; struct pt_regs *_ctx = (struct pt_regs *)PT_REGS_PARM6(ctx);"
                         "  bpf_probe_read(&_val, sizeof(_val), &(PT_REGS_PARM6(_ctx))); _val;})",
         }