[DTrace-devel] [PATCH 1/3] Allocate exit label in dt_cg_tramp_prologue rather than each provider

[Kris Van Hees]

Every provider implementation was allocating an id for the exit label
that is used in the trampoline prologue and epilogue.  Now the label
id is allocated in and returned by dt_cg_tramp_prologue() (and its
*_act() variant).  That id is to be passed to dt_cg_tramp_epilogue()
(or the *_advance() variant) to ensure that the same label is used
throughout the trampoline.

Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
---
 libdtrace/dt_cg.c           | 15 ++++++++++-----
 libdtrace/dt_cg.h           |  5 ++---
 libdtrace/dt_prov_dtrace.c  |  4 ++--
 libdtrace/dt_prov_fbt.c     |  4 ++--
 libdtrace/dt_prov_profile.c |  4 ++--
 libdtrace/dt_prov_sdt.c     |  4 ++--
 libdtrace/dt_prov_syscall.c |  4 ++--
 7 files changed, 22 insertions(+), 18 deletions(-)

diff --git a/libdtrace/dt_cg.c b/libdtrace/dt_cg.c
index f5ed3f2e..d43cea41 100644
--- a/libdtrace/dt_cg.c
+++ b/libdtrace/dt_cg.c
@@ -38,13 +38,16 @@ static void dt_cg_node(dt_node_t *, dt_irlist_t *, dt_regset_t *);
  *
  * The caller should NOT depend on any register values that exist at the end of
  * the trampoline prologue.
+ *
+ * This function returns a label id to be passed to dt_cg_tramp_epilogue().
  */
-void
-dt_cg_tramp_prologue_act(dt_pcb_t *pcb, uint_t lbl_exit, dt_activity_t act)
+uint_t
+dt_cg_tramp_prologue_act(dt_pcb_t *pcb, dt_activity_t act)
 {
 	dt_irlist_t	*dlp = &pcb->pcb_ir;
 	dt_ident_t	*mem = dt_dlib_get_map(pcb->pcb_hdl, "mem");
 	dt_ident_t	*state = dt_dlib_get_map(pcb->pcb_hdl, "state");
+	uint_t		lbl_exit = dt_irlist_label(dlp);
 	struct bpf_insn	instr;
 
 	assert(mem != NULL);
@@ -143,12 +146,14 @@ dt_cg_tramp_prologue_act(dt_pcb_t *pcb, uint_t lbl_exit, dt_activity_t act)
 	dt_irlist_append(dlp, dt_cg_node_alloc(DT_LBL_NONE, instr));
 	instr = BPF_STORE(BPF_DW, BPF_REG_FP, DCTX_FP(DCTX_BUF), BPF_REG_0);
 	dt_irlist_append(dlp, dt_cg_node_alloc(DT_LBL_NONE, instr));
+
+	return lbl_exit;
 }
 
-void
-dt_cg_tramp_prologue(dt_pcb_t *pcb, uint_t lbl_exit)
+uint_t
+dt_cg_tramp_prologue(dt_pcb_t *pcb)
 {
-	dt_cg_tramp_prologue_act(pcb, lbl_exit, DT_ACTIVITY_ACTIVE);
+	return dt_cg_tramp_prologue_act(pcb, DT_ACTIVITY_ACTIVE);
 }
 
 static int
diff --git a/libdtrace/dt_cg.h b/libdtrace/dt_cg.h
index a4c6fb28..29678e2f 100644
--- a/libdtrace/dt_cg.h
+++ b/libdtrace/dt_cg.h
@@ -19,9 +19,8 @@ extern "C" {
 extern void dt_cg(dt_pcb_t *, dt_node_t *);
 extern void dt_cg_xsetx(dt_irlist_t *, dt_ident_t *, uint_t, int, uint64_t);
 extern dt_irnode_t *dt_cg_node_alloc(uint_t, struct bpf_insn);
-extern void dt_cg_tramp_prologue_act(dt_pcb_t *pcb, uint_t lbl_exit,
-				     dt_activity_t act);
-extern void dt_cg_tramp_prologue(dt_pcb_t *pcb, uint_t lbl_exit);
+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);
 
diff --git a/libdtrace/dt_prov_dtrace.c b/libdtrace/dt_prov_dtrace.c
index a0c8d007..1de99ab5 100644
--- a/libdtrace/dt_prov_dtrace.c
+++ b/libdtrace/dt_prov_dtrace.c
@@ -75,7 +75,7 @@ static void trampoline(dt_pcb_t *pcb)
 	int		i;
 	dt_irlist_t	*dlp = &pcb->pcb_ir;
 	struct bpf_insn	instr;
-	uint_t		lbl_exit = dt_irlist_label(dlp);
+	uint_t		lbl_exit;
 	dt_activity_t	act;
 	int		adv_act;
 	uint32_t	key = 0;
@@ -114,7 +114,7 @@ static void trampoline(dt_pcb_t *pcb)
 		adv_act = 0;
 	}
 
-	dt_cg_tramp_prologue_act(pcb, lbl_exit, act);
+	lbl_exit = dt_cg_tramp_prologue_act(pcb, act);
 
 	if (key) {
 		/*
diff --git a/libdtrace/dt_prov_fbt.c b/libdtrace/dt_prov_fbt.c
index 842ba53b..1ba144a5 100644
--- a/libdtrace/dt_prov_fbt.c
+++ b/libdtrace/dt_prov_fbt.c
@@ -164,9 +164,9 @@ static void trampoline(dt_pcb_t *pcb)
 	int		i;
 	dt_irlist_t	*dlp = &pcb->pcb_ir;
 	struct bpf_insn	instr;
-	uint_t		lbl_exit = dt_irlist_label(dlp);
+	uint_t		lbl_exit;
 
-	dt_cg_tramp_prologue(pcb, lbl_exit);
+	lbl_exit = dt_cg_tramp_prologue(pcb);
 
 	/*
 	 * We cannot assume anything about the state of any registers so set up
diff --git a/libdtrace/dt_prov_profile.c b/libdtrace/dt_prov_profile.c
index 0e90351f..8541bee6 100644
--- a/libdtrace/dt_prov_profile.c
+++ b/libdtrace/dt_prov_profile.c
@@ -218,9 +218,9 @@ static void trampoline(dt_pcb_t *pcb)
 	int		i;
 	dt_irlist_t	*dlp = &pcb->pcb_ir;
 	struct bpf_insn	instr;
-	uint_t		lbl_exit = dt_irlist_label(dlp);
+	uint_t		lbl_exit;
 
-	dt_cg_tramp_prologue(pcb, lbl_exit);
+	lbl_exit = dt_cg_tramp_prologue(pcb);
 
 	/*
 	 * We cannot assume anything about the state of any registers so set up
diff --git a/libdtrace/dt_prov_sdt.c b/libdtrace/dt_prov_sdt.c
index fbfdb7fe..4b2ac31b 100644
--- a/libdtrace/dt_prov_sdt.c
+++ b/libdtrace/dt_prov_sdt.c
@@ -396,9 +396,9 @@ static void trampoline(dt_pcb_t *pcb)
 	int		i;
 	dt_irlist_t	*dlp = &pcb->pcb_ir;
 	struct bpf_insn	instr;
-	uint_t		lbl_exit = dt_irlist_label(dlp);
+	uint_t		lbl_exit;
 
-	dt_cg_tramp_prologue(pcb, lbl_exit);
+	lbl_exit = dt_cg_tramp_prologue(pcb);
 
 	/*
 	 * We cannot assume anything about the state of any registers so set up
diff --git a/libdtrace/dt_prov_syscall.c b/libdtrace/dt_prov_syscall.c
index b817f528..341a18c8 100644
--- a/libdtrace/dt_prov_syscall.c
+++ b/libdtrace/dt_prov_syscall.c
@@ -149,9 +149,9 @@ static void trampoline(dt_pcb_t *pcb)
 	int		i;
 	dt_irlist_t	*dlp = &pcb->pcb_ir;
 	struct bpf_insn	instr;
-	uint_t		lbl_exit = dt_irlist_label(dlp);
+	uint_t		lbl_exit;
 
-	dt_cg_tramp_prologue(pcb, lbl_exit);
+	lbl_exit = dt_cg_tramp_prologue(pcb);
 
 	/*
 	 * We cannot assume anything about the state of any registers so set up
-- 
2.28.0