[DTrace-devel] [PATCH 3/3] Verify the activity state before calling each clause

[Kris Van Hees]

When a clause contains an exit() action, processing of all other
clauses (even for the same probe firing) must not be executed
anymore.  The activity state check therefore needs to not just happen
in the trampoline, but also before every clause within the program.

Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
---
 libdtrace/dt_cg.c          | 33 ++++++++++++++++++++++++---------
 libdtrace/dt_cg.h          |  3 ++-
 libdtrace/dt_prov_dtrace.c |  2 +-
 3 files changed, 27 insertions(+), 11 deletions(-)

diff --git a/libdtrace/dt_cg.c b/libdtrace/dt_cg.c
index 707c368c..9966af90 100644
--- a/libdtrace/dt_cg.c
+++ b/libdtrace/dt_cg.c
@@ -160,16 +160,33 @@ dt_cg_tramp_prologue(dt_pcb_t *pcb)
 	return dt_cg_tramp_prologue_act(pcb, DT_ACTIVITY_ACTIVE);
 }
 
+typedef struct {
+	dt_irlist_t	*dlp;
+	dt_activity_t	act;
+	uint_t		lbl_exit;
+} dt_clause_arg_t;
+
 static int
-dt_cg_call_clause(dtrace_hdl_t *dtp, dt_ident_t *idp, dt_irlist_t *dlp)
+dt_cg_call_clause(dtrace_hdl_t *dtp, dt_ident_t *idp, dt_clause_arg_t *arg)
 {
 	struct bpf_insn	instr;
+	dt_irlist_t	*dlp = arg->dlp;
 
 	/*
+	 *	if (*dctx.act != act)	// ldw %r0, [%fp + DCTX_FP(DCTX_ACT)]
+	 *		goto exit;	// ldw %r0, [%r0 + 0]
+	 *				// jne %r0, act, lbl_exit
 	 *	dt_clause(dctx);	// mov %r1, %fp
 	 *				// add %r1, DCTX_FP(0)
 	 *				// call dt_program
 	 */
+	instr = BPF_LOAD(BPF_DW, BPF_REG_0, BPF_REG_FP, DCTX_FP(DCTX_ACT));
+	dt_irlist_append(dlp, dt_cg_node_alloc(DT_LBL_NONE, instr));
+	instr = BPF_LOAD(BPF_W, BPF_REG_0, BPF_REG_0, 0);
+	dt_irlist_append(dlp, dt_cg_node_alloc(DT_LBL_NONE, instr));
+	instr = BPF_BRANCH_IMM(BPF_JNE, BPF_REG_0, arg->act, arg->lbl_exit);
+	dt_irlist_append(dlp, dt_cg_node_alloc(DT_LBL_NONE, instr));
+
 	instr = BPF_MOV_REG(BPF_REG_1, BPF_REG_FP);
 	dt_irlist_append(dlp, dt_cg_node_alloc(DT_LBL_NONE, instr));
 	instr = BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, DCTX_FP(0));
@@ -182,15 +199,13 @@ dt_cg_call_clause(dtrace_hdl_t *dtp, dt_ident_t *idp, dt_irlist_t *dlp)
 }
 
 static void
-dt_cg_tramp_call_clauses(dt_pcb_t *pcb)
+dt_cg_tramp_call_clauses(dt_pcb_t *pcb, uint_t lbl_exit, dt_activity_t act)
 {
 	dt_irlist_t	*dlp = &pcb->pcb_ir;
+	dt_clause_arg_t	arg = { dlp, act, lbl_exit };
 
-	/*
-	 *	dt_clause(dctx);	//     (repeated for each clause)
-	 */
 	dt_probe_clause_iter(pcb->pcb_hdl, pcb->pcb_probe,
-			     (dt_clause_f *)dt_cg_call_clause, dlp);
+			     (dt_clause_f *)dt_cg_call_clause, &arg);
 }
 
 static void
@@ -214,17 +229,17 @@ dt_cg_tramp_return(dt_pcb_t *pcb, uint_t lbl_exit)
 void
 dt_cg_tramp_epilogue(dt_pcb_t *pcb, uint_t lbl_exit)
 {
-	dt_cg_tramp_call_clauses(pcb);
+	dt_cg_tramp_call_clauses(pcb, lbl_exit, DT_ACTIVITY_ACTIVE);
 	dt_cg_tramp_return(pcb, lbl_exit);
 }
 
 void
-dt_cg_tramp_epilogue_advance(dt_pcb_t *pcb, uint_t lbl_exit)
+dt_cg_tramp_epilogue_advance(dt_pcb_t *pcb, uint_t lbl_exit, dt_activity_t act)
 {
 	dt_irlist_t	*dlp = &pcb->pcb_ir;
 	struct bpf_insn	instr;
 
-	dt_cg_tramp_call_clauses(pcb);
+	dt_cg_tramp_call_clauses(pcb, lbl_exit, act);
 
 	/*
 	 *	(*dctx.act)++;		// lddw %r0, [%fp + DCTX_FP(DCTX_ACT)]
diff --git a/libdtrace/dt_cg.h b/libdtrace/dt_cg.h
index 29678e2f..54e01df7 100644
--- a/libdtrace/dt_cg.h
+++ b/libdtrace/dt_cg.h
@@ -22,7 +22,8 @@ extern dt_irnode_t *dt_cg_node_alloc(uint_t, struct bpf_insn);
 extern uint_t dt_cg_tramp_prologue_act(dt_pcb_t *pcb, dt_activity_t act);
 extern uint_t dt_cg_tramp_prologue(dt_pcb_t *pcb);
 extern void dt_cg_tramp_epilogue(dt_pcb_t *pcb, uint_t lbl_exit);
-extern void dt_cg_tramp_epilogue_advance(dt_pcb_t *pcb, uint_t lbl_exit);
+extern void dt_cg_tramp_epilogue_advance(dt_pcb_t *pcb, uint_t lbl_exit,
+					 dt_activity_t act);
 
 #ifdef	__cplusplus
 }
diff --git a/libdtrace/dt_prov_dtrace.c b/libdtrace/dt_prov_dtrace.c
index 1de99ab5..8b98d44a 100644
--- a/libdtrace/dt_prov_dtrace.c
+++ b/libdtrace/dt_prov_dtrace.c
@@ -242,7 +242,7 @@ static void trampoline(dt_pcb_t *pcb)
 	}
 
 	if (adv_act)
-		dt_cg_tramp_epilogue_advance(pcb, lbl_exit);
+		dt_cg_tramp_epilogue_advance(pcb, lbl_exit, act);
 	else
 		dt_cg_tramp_epilogue(pcb, lbl_exit);
 }
-- 
2.28.0