[DTrace-devel] [PATCH v2 5/9] Handle stack() and ustack() args in a separate function

[eugene.loh at oracle.com]

From: Eugene Loh <eugene.loh at oracle.com>

Currently, dt_cg_act_stack() and dt_cg_act_ustack() generate BPF code
to implement the stack() and ustack() actions.  However, it should also
be possible to use stack() and ustack() as aggregation keys.  So, it
would be nice to move the main work of the code-generation functions
to separate functions that can be used by different callers.

Therefore, start refactoring these cg functions so that what they do
can be invoked by multiple callers.  Here, simply move the handling of
the stack() and ustack() args out into a separate function.  (Actually,
that handling does not even involve any code generation.)

Signed-off-by: Eugene Loh <eugene.loh at oracle.com>
---
 libdtrace/dt_cg.c | 119 ++++++++++++++++++++++++++--------------------
 1 file changed, 68 insertions(+), 51 deletions(-)

diff --git a/libdtrace/dt_cg.c b/libdtrace/dt_cg.c
index 1e4bb707..084157a0 100644
--- a/libdtrace/dt_cg.c
+++ b/libdtrace/dt_cg.c
@@ -2501,34 +2501,78 @@ dt_cg_act_speculate(dt_pcb_t *pcb, dt_node_t *dnp, dtrace_actkind_t kind)
 	dt_regset_free(drp, dnp->dn_reg);
 }
 
+static int
+dt_cg_stack_nframes(dtrace_hdl_t *dtp, dt_node_t *arg0, int indopt,
+		    int def, int inderr, const char *fname)
+{
+	int nframes;
+
+	/* Get the default number. */
+	nframes = dtp->dt_options[indopt];
+	if (nframes == DTRACEOPT_UNSET)
+		nframes = _dtrace_ustackframes;
+
+	/* Get the specified value, if any. */
+	if (arg0 != NULL) {
+		if (!dt_node_is_posconst(arg0))
+			dnerror(arg0, inderr,
+				"%s( ) argument #1 must be a non-zero positive integer constant\n",
+				fname);
+		nframes = arg0->dn_value;
+	}
+
+	/* If more frames are requested than allowed, silently reduce nframes. */
+	if (nframes > dtp->dt_options[DTRACEOPT_MAXFRAMES])
+		nframes = dtp->dt_options[DTRACEOPT_MAXFRAMES];
+
+	return nframes;
+}
+
+static uint64_t
+dt_cg_stack_arg(dtrace_hdl_t *dtp, dt_node_t *dnp, int user)
+{
+	int		nframes;
+	int		strsize = 0;
+	dt_node_t	*arg0 = dnp->dn_args;
+	dt_node_t	*arg1 = arg0 != NULL ? arg0->dn_list : NULL;
+
+	if (user)
+		nframes = dt_cg_stack_nframes(dtp, arg0, DTRACEOPT_USTACKFRAMES,
+					     _dtrace_ustackframes, D_USTACK_FRAMES, "ustack");
+	else
+		nframes = dt_cg_stack_nframes(dtp, arg0, DTRACEOPT_STACKFRAMES,
+					     _dtrace_stackframes, D_STACK_SIZE, "stack");
+
+	if (!user)
+		return DTRACE_USTACK_ARG(nframes, 0);
+
+	if (arg1 != NULL) {
+		if (arg1->dn_kind != DT_NODE_INT ||
+		    ((arg1->dn_flags & DT_NF_SIGNED) &&
+		    (int64_t)arg1->dn_value < 0))
+			dnerror(arg1, D_USTACK_STRSIZE, "ustack( ) argument #2 "
+				"must be a positive integer constant\n");
+
+		strsize = arg1->dn_value;
+	}
+
+	return DTRACE_USTACK_ARG(nframes, strsize);
+}
+
 static void
 dt_cg_act_stack(dt_pcb_t *pcb, dt_node_t *dnp, dtrace_actkind_t kind)
 {
 	dtrace_hdl_t	*dtp = pcb->pcb_hdl;
 	dt_irlist_t	*dlp = &pcb->pcb_ir;
 	dt_regset_t	*drp = pcb->pcb_regs;
-	dt_node_t	*arg = dnp->dn_args;
-	int		nframes = dtp->dt_options[DTRACEOPT_STACKFRAMES];
+	uint64_t	arg;
+	int		nframes;
 	int		skip = 0;
 	uint_t		off;
 	uint_t		lbl_valid = dt_irlist_label(dlp);
 
-	if (nframes == DTRACEOPT_UNSET)
-		nframes = _dtrace_stackframes;
-
-	if (arg != NULL) {
-		if (!dt_node_is_posconst(arg))
-			dnerror(arg, D_STACK_SIZE, "stack( ) argument #1 must "
-				"be a non-zero positive integer constant\n");
-
-		nframes = arg->dn_value;
-	}
-
-	/*
-	 * If more frames are requested than allowed, silently reduce nframes.
-	 */
-	if (nframes > dtp->dt_options[DTRACEOPT_MAXFRAMES])
-		nframes = dtp->dt_options[DTRACEOPT_MAXFRAMES];
+	arg = dt_cg_stack_arg(dtp, dnp, 0);
+	nframes = DTRACE_USTACK_NFRAMES(arg);
 
 	/* Reserve space in the output buffer. */
 	off = dt_rec_add(dtp, dt_cg_fill_gap, DTRACEACT_STACK,
@@ -2711,46 +2755,19 @@ dt_cg_act_ustack(dt_pcb_t *pcb, dt_node_t *dnp, dtrace_actkind_t kind)
 	dt_irlist_t	*dlp = &pcb->pcb_ir;
 	dt_regset_t	*drp = pcb->pcb_regs;
 	dtrace_hdl_t	*dtp = pcb->pcb_hdl;
-	int		nframes = dtp->dt_options[DTRACEOPT_USTACKFRAMES];
-	int		strsize = 0;
-	int		stacksize;
-	dt_node_t	*arg0 = dnp->dn_args;
-	dt_node_t	*arg1 = arg0 != NULL ? arg0->dn_list : NULL;
+	uint64_t	arg;
+	int		nframes, stacksize;
 	int		skip = 0;
 	uint_t		off;
 	uint_t		lbl_valid = dt_irlist_label(dlp);
 
-	if (nframes == DTRACEOPT_UNSET)
-		nframes = _dtrace_ustackframes;
-
-	if (arg0 != NULL) {
-		if (!dt_node_is_posconst(arg0))
-			dnerror(arg0, D_USTACK_FRAMES, "ustack( ) argument #1 "
-				"must be a non-zero positive integer "
-				"constant\n");
-
-		nframes = arg0->dn_value;
-	}
-
-	if (nframes > dtp->dt_options[DTRACEOPT_MAXFRAMES])
-		nframes = dtp->dt_options[DTRACEOPT_MAXFRAMES];
-
-	/* FIXME: for now, accept non-zero strsize, but it does nothing */
-	if (arg1 != NULL) {
-		if (arg1->dn_kind != DT_NODE_INT ||
-		    ((arg1->dn_flags & DT_NF_SIGNED) &&
-		    (int64_t)arg1->dn_value < 0))
-			dnerror(arg1, D_USTACK_STRSIZE, "ustack( ) argument #2 "
-				"must be a positive integer constant\n");
-
-		strsize = arg1->dn_value;
-	}
+	arg = dt_cg_stack_arg(dtp, dnp, 1);
+	nframes = DTRACE_USTACK_NFRAMES(arg);
+	stacksize = nframes * sizeof(uint64_t);
 
 	/* Reserve space in the output buffer. */
-	stacksize = nframes * sizeof(uint64_t);
 	off = dt_rec_add(pcb->pcb_hdl, dt_cg_fill_gap, DTRACEACT_USTACK,
-			 8 + stacksize, 8, NULL,
-			 DTRACE_USTACK_ARG(nframes, strsize));
+			 8 + stacksize, 8, NULL, arg);
 
 	if (dt_regset_xalloc_args(drp) == -1)
 		longjmp(yypcb->pcb_jmpbuf, EDT_NOREG);
-- 
2.18.4