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

[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 separate functions.  (Actually,
that handling does not even involve any code generation.)

Signed-off-by: Eugene Loh <eugene.loh at oracle.com>
---
 libdtrace/dt_cg.c | 61 +++++++++++++++++++++++++++++++----------------
 1 file changed, 40 insertions(+), 21 deletions(-)

diff --git a/libdtrace/dt_cg.c b/libdtrace/dt_cg.c
index cef41e6a..389e4dba 100644
--- a/libdtrace/dt_cg.c
+++ b/libdtrace/dt_cg.c
@@ -2163,17 +2163,11 @@ dt_cg_act_speculate(dt_pcb_t *pcb, dt_node_t *dnp, dtrace_actkind_t kind)
 	dt_regset_free(drp, dnp->dn_reg);
 }
 
-static void
-dt_cg_act_stack(dt_pcb_t *pcb, dt_node_t *dnp, dtrace_actkind_t kind)
+static int
+dt_cg_stack_nframes(dtrace_hdl_t *dtp, dt_node_t *dnp)
 {
-	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];
-	int		skip = 0;
-	uint_t		off;
-	uint_t		lbl_valid = dt_irlist_label(dlp);
 
 	if (nframes == DTRACEOPT_UNSET)
 		nframes = _dtrace_stackframes;
@@ -2192,6 +2186,22 @@ dt_cg_act_stack(dt_pcb_t *pcb, dt_node_t *dnp, dtrace_actkind_t kind)
 	if (nframes > dtp->dt_options[DTRACEOPT_MAXFRAMES])
 		nframes = dtp->dt_options[DTRACEOPT_MAXFRAMES];
 
+	return nframes;
+}
+
+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;
+	int		nframes;
+	int		skip = 0;
+	uint_t		off;
+	uint_t		lbl_valid = dt_irlist_label(dlp);
+
+	nframes = dt_cg_stack_nframes(dtp, dnp);
+
 	/* Reserve space in the output buffer. */
 	off = dt_rec_add(dtp, dt_cg_fill_gap, DTRACEACT_STACK,
 			 sizeof(uint64_t) * nframes, sizeof(uint64_t),
@@ -2368,20 +2378,13 @@ dt_cg_act_trunc(dt_pcb_t *pcb, dt_node_t *dnp, dtrace_actkind_t kind)
 	dt_cg_store_val(pcb, trunc, DTRACEACT_LIBACT, NULL, DT_ACT_TRUNC);
 }
 
-static void
-dt_cg_act_ustack(dt_pcb_t *pcb, dt_node_t *dnp, dtrace_actkind_t kind)
+static uint64_t
+dt_cg_ustack_arg(dtrace_hdl_t *dtp, dt_node_t *dnp)
 {
-	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;
-	int		skip = 0;
-	uint_t		off;
-	uint_t		lbl_valid = dt_irlist_label(dlp);
 
 	if (nframes == DTRACEOPT_UNSET)
 		nframes = _dtrace_ustackframes;
@@ -2398,7 +2401,6 @@ dt_cg_act_ustack(dt_pcb_t *pcb, dt_node_t *dnp, dtrace_actkind_t kind)
 	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) &&
@@ -2409,11 +2411,28 @@ dt_cg_act_ustack(dt_pcb_t *pcb, dt_node_t *dnp, dtrace_actkind_t kind)
 		strsize = arg1->dn_value;
 	}
 
-	/* Reserve space in the output buffer. */
+	return DTRACE_USTACK_ARG(nframes, strsize);
+}
+
+static void
+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;
+	uint64_t	arg;
+	int		nframes, stacksize;
+	int		skip = 0;
+	uint_t		off;
+	uint_t		lbl_valid = dt_irlist_label(dlp);
+
+	arg = dt_cg_ustack_arg(dtp, dnp);
+	nframes = DTRACE_USTACK_NFRAMES(arg);
 	stacksize = nframes * sizeof(uint64_t);
+
+	/* Reserve space in the output buffer. */
 	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