powerpc/tracing: tracepoints for RTAS entry and exit

Add two sets of tracepoints to be used around RTAS entry:

* rtas_input/rtas_output, which emit the function name, its inputs,
  the returned status, and any other outputs. These produce an API-level
  record of OS<->RTAS activity.

* rtas_ll_entry/rtas_ll_exit, which are lower-level and emit the
  entire contents of the parameter block (aka rtas_args) on entry and
  exit. Likely useful only for debugging.

With uses of these tracepoints in do_enter_rtas() to be added in the
following patch, examples of get-time-of-day and event-scan functions
as rendered by trace-cmd (with some multi-line formatting manually
imposed on the rtas_ll_* entries to avoid extremely long lines in the
commit message):

cat-36800 [059]  4978.518303: rtas_input:           get-time-of-day arguments:
cat-36800 [059]  4978.518306: rtas_ll_entry:        token=3 nargs=0 nret=8
                                                    params: [0]=0x00000000 [1]=0x00000000 [2]=0x00000000 [3]=0x00000000
                                                            [4]=0x00000000 [5]=0x00000000 [6]=0x00000000 [7]=0x00000000
							    [8]=0x00000000 [9]=0x00000000 [10]=0x00000000 [11]=0x00000000
							    [12]=0x00000000 [13]=0x00000000 [14]=0x00000000 [15]=0x00000000
cat-36800 [059]  4978.518366: rtas_ll_exit:         token=3 nargs=0 nret=8
                                                    params: [0]=0x00000000 [1]=0x000007e6 [2]=0x0000000b [3]=0x00000001
						            [4]=0x00000000 [5]=0x0000000e [6]=0x00000008 [7]=0x2e0dac40
							    [8]=0x00000000 [9]=0x00000000 [10]=0x00000000 [11]=0x00000000
							    [12]=0x00000000 [13]=0x00000000 [14]=0x00000000 [15]=0x00000000
cat-36800 [059]  4978.518366: rtas_output:          get-time-of-day status: 0, other outputs: 2022 11 1 0 14 8 772648000

kworker/39:1-336   [039]  4982.731623: rtas_input:           event-scan arguments: 4294967295 0 80484920 2048
kworker/39:1-336   [039]  4982.731626: rtas_ll_entry:        token=6 nargs=4 nret=1
                                                             params: [0]=0xffffffff [1]=0x00000000 [2]=0x04cc1a38 [3]=0x00000800
							             [4]=0x00000000 [5]=0x0000000e [6]=0x00000008 [7]=0x2e0dac40
								     [8]=0x00000000 [9]=0x00000000 [10]=0x00000000 [11]=0x00000000
								     [12]=0x00000000 [13]=0x00000000 [14]=0x00000000 [15]=0x00000000
kworker/39:1-336   [039]  4982.731676: rtas_ll_exit:         token=6 nargs=4 nret=1
                                                             params: [0]=0xffffffff [1]=0x00000000 [2]=0x04cc1a38 [3]=0x00000800
							             [4]=0x00000001 [5]=0x0000000e [6]=0x00000008 [7]=0x2e0dac40
								     [8]=0x00000000 [9]=0x00000000 [10]=0x00000000 [11]=0x00000000
								     [12]=0x00000000 [13]=0x00000000 [14]=0x00000000 [15]=0x00000000
kworker/39:1-336   [039]  4982.731677: rtas_output:          event-scan status: 1, other outputs:

Signed-off-by: Nathan Lynch <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

arch/powerpc/include/asm/trace.h

@@ -119,6 +119,109 @@ TRACE_EVENT_FN_COND(hcall_exit,
 );
 #endif
 
+#ifdef CONFIG_PPC_RTAS
+
+#include <asm/rtas-types.h>
+
+TRACE_EVENT(rtas_input,
+
+	TP_PROTO(struct rtas_args *rtas_args, const char *name),
+
+	TP_ARGS(rtas_args, name),
+
+	TP_STRUCT__entry(
+		__field(__u32, nargs)
+		__string(name, name)
+		__dynamic_array(__u32, inputs, be32_to_cpu(rtas_args->nargs))
+	),
+
+	TP_fast_assign(
+		__entry->nargs = be32_to_cpu(rtas_args->nargs);
+		__assign_str(name, name);
+		be32_to_cpu_array(__get_dynamic_array(inputs), rtas_args->args, __entry->nargs);
+	),
+
+	TP_printk("%s arguments: %s", __get_str(name),
+		  __print_array(__get_dynamic_array(inputs), __entry->nargs, 4)
+	)
+);
+
+TRACE_EVENT(rtas_output,
+
+	TP_PROTO(struct rtas_args *rtas_args, const char *name),
+
+	TP_ARGS(rtas_args, name),
+
+	TP_STRUCT__entry(
+		__field(__u32, nr_other)
+		__field(__s32, status)
+		__string(name, name)
+		__dynamic_array(__u32, other_outputs, be32_to_cpu(rtas_args->nret) - 1)
+	),
+
+	TP_fast_assign(
+		__entry->nr_other = be32_to_cpu(rtas_args->nret) - 1;
+		__entry->status = be32_to_cpu(rtas_args->rets[0]);
+		__assign_str(name, name);
+		be32_to_cpu_array(__get_dynamic_array(other_outputs),
+				  &rtas_args->rets[1], __entry->nr_other);
+	),
+
+	TP_printk("%s status: %d, other outputs: %s", __get_str(name), __entry->status,
+		  __print_array(__get_dynamic_array(other_outputs),
+				__entry->nr_other, 4)
+	)
+);
+
+DECLARE_EVENT_CLASS(rtas_parameter_block,
+
+	TP_PROTO(struct rtas_args *rtas_args),
+
+	TP_ARGS(rtas_args),
+
+	TP_STRUCT__entry(
+		__field(u32, token)
+		__field(u32, nargs)
+		__field(u32, nret)
+		__array(__u32, params, 16)
+	),
+
+	TP_fast_assign(
+		__entry->token = be32_to_cpu(rtas_args->token);
+		__entry->nargs = be32_to_cpu(rtas_args->nargs);
+		__entry->nret = be32_to_cpu(rtas_args->nret);
+		be32_to_cpu_array(__entry->params, rtas_args->args, ARRAY_SIZE(rtas_args->args));
+	),
+
+	TP_printk("token=%u nargs=%u nret=%u params:"
+		  " [0]=0x%08x [1]=0x%08x [2]=0x%08x [3]=0x%08x"
+		  " [4]=0x%08x [5]=0x%08x [6]=0x%08x [7]=0x%08x"
+		  " [8]=0x%08x [9]=0x%08x [10]=0x%08x [11]=0x%08x"
+		  " [12]=0x%08x [13]=0x%08x [14]=0x%08x [15]=0x%08x",
+		  __entry->token, __entry->nargs, __entry->nret,
+		  __entry->params[0], __entry->params[1], __entry->params[2], __entry->params[3],
+		  __entry->params[4], __entry->params[5], __entry->params[6], __entry->params[7],
+		  __entry->params[8], __entry->params[9], __entry->params[10], __entry->params[11],
+		  __entry->params[12], __entry->params[13], __entry->params[14], __entry->params[15]
+	)
+);
+
+DEFINE_EVENT(rtas_parameter_block, rtas_ll_entry,
+
+	TP_PROTO(struct rtas_args *rtas_args),
+
+	TP_ARGS(rtas_args)
+);
+
+DEFINE_EVENT(rtas_parameter_block, rtas_ll_exit,
+
+	TP_PROTO(struct rtas_args *rtas_args),
+
+	TP_ARGS(rtas_args)
+);
+
+#endif /* CONFIG_PPC_RTAS */
+
 #ifdef CONFIG_PPC_POWERNV
 extern int opal_tracepoint_regfunc(void);
 extern void opal_tracepoint_unregfunc(void);