[PATCH v2 1/4] cg, providers: refactor clearing probe arguments

Signed-off-by: Kris Van Hees <[email protected]>
---
 libdtrace/dt_cg.c           | 34 +++++++++++++++++++++++++++++++---
 libdtrace/dt_cg.h           |  1 +
 libdtrace/dt_prov_cpc.c     | 17 -----------------
 libdtrace/dt_prov_dtrace.c  |  8 ++------
 libdtrace/dt_prov_profile.c | 23 +----------------------
 libdtrace/dt_prov_syscall.c | 10 ++--------
 6 files changed, 37 insertions(+), 56 deletions(-)

diff --git a/libdtrace/dt_cg.c b/libdtrace/dt_cg.c
index ec4e3123..b3084ddb 100644
--- a/libdtrace/dt_cg.c
+++ b/libdtrace/dt_cg.c
@@ -454,6 +454,32 @@ dt_cg_tramp_copy_regs(dt_pcb_t *pcb)
 	}
 }
 
+/*
+ * Clear the content of the 'argv' member of the machine state, from the given
+ * index (idx).
+ *
+ * The caller must ensure that %r7 contains the value set by the
+ * dt_cg_tramp_prologue*() functions.
+ */
+void
+dt_cg_tramp_clear_argv(dt_pcb_t *pcb, int idx)
+{
+	dt_irlist_t	*dlp = &pcb->pcb_ir;
+	int		i, argc = ARRAY_SIZE(((dt_mstate_t *)0)->argv);
+
+	if (idx >= argc)
+		return;
+
+	/*
+	 *	memset(&dctx->mst->argv[idx], 0, sizeof(dt_pt_regs);
+	 *				// stdw [%7 + DMST_ARG(idx)], 0
+	 *				// stdw [%7 + DMST_ARG(idx + 1)], 0
+	 *				//     (...)
+	 */
+	for (i = idx; i < argc; i++)
+		emit(dlp, BPF_STORE_IMM(BPF_DW, BPF_REG_7, DMST_ARG(i), 0));
+}
+
 /*
  * Copy arguments from a dt_pt_regs structure referenced by %r8.
  * If 'called' is nonzero, the registers are laid out as when inside the
@@ -626,6 +652,10 @@ dt_cg_tramp_copy_pc_from_regs(dt_pcb_t *pcb)
 	/* done */
 	emitl(dlp, Ldone,
 	      BPF_NOP());
+
+	/* clear the rest of the arguments */
+	dt_cg_tramp_clear_argv(pcb, 2);
+
 	dt_regset_free_args(drp);
 }
 
@@ -640,15 +670,13 @@ void
 dt_cg_tramp_copy_rval_from_regs(dt_pcb_t *pcb)
 {
 	dt_irlist_t	*dlp = &pcb->pcb_ir;
-	int		i;
 
 	emit(dlp, BPF_STORE_IMM(BPF_DW, BPF_REG_7, DMST_ARG(0), 0));
 
 	emit(dlp, BPF_LOAD(BPF_DW, BPF_REG_0, BPF_REG_8, PT_REGS_RET));
 	emit(dlp, BPF_STORE(BPF_DW, BPF_REG_7, DMST_ARG(1), BPF_REG_0));
 
-	for (i = 2; i < ARRAY_SIZE(((dt_mstate_t *)0)->argv); i++)
-		emit(dlp, BPF_STORE_IMM(BPF_DW, BPF_REG_7, DMST_ARG(i), 0));
+	dt_cg_tramp_clear_argv(pcb, 2);
 }
 
 /*
diff --git a/libdtrace/dt_cg.h b/libdtrace/dt_cg.h
index 9493edbb..401ac0e0 100644
--- a/libdtrace/dt_cg.h
+++ b/libdtrace/dt_cg.h
@@ -26,6 +26,7 @@ extern void dt_cg_tramp_prologue_cpu(dt_pcb_t *pcb);
 extern void dt_cg_tramp_prologue(dt_pcb_t *pcb);
 extern void dt_cg_tramp_clear_regs(dt_pcb_t *pcb);
 extern void dt_cg_tramp_copy_regs(dt_pcb_t *pcb);
+extern void dt_cg_tramp_clear_argv(dt_pcb_t *pcb, int i);
 extern void dt_cg_tramp_copy_args_from_regs(dt_pcb_t *pcb, int called);
 extern void dt_cg_tramp_copy_pc_from_regs(dt_pcb_t *pcb);
 extern void dt_cg_tramp_copy_rval_from_regs(dt_pcb_t *pcb);
diff --git a/libdtrace/dt_prov_cpc.c b/libdtrace/dt_prov_cpc.c
index 57b11b13..fd33990f 100644
--- a/libdtrace/dt_prov_cpc.c
+++ b/libdtrace/dt_prov_cpc.c
@@ -393,26 +393,9 @@ static int provide(dtrace_hdl_t *dtp, const dtrace_probedesc_t *pdp)
  */
 static int trampoline(dt_pcb_t *pcb, uint_t exitlbl)
 {
-	int		i;
-	dt_irlist_t	*dlp = &pcb->pcb_ir;
-
 	dt_cg_tramp_prologue_cpu(pcb);
-
-	/*
-	 * After the dt_cg_tramp_prologue_cpu() call, we have:
-	 *				//     (%r7 = dctx->mst)
-	 *				//     (%r8 = dctx->ctx)
-	 */
-
 	dt_cg_tramp_copy_regs(pcb);
-
-	/*
-	 * Use the PC to set arg0 and arg1, then clear the other args.
-	 */
 	dt_cg_tramp_copy_pc_from_regs(pcb);
-	for (i = 2; i < ARRAY_SIZE(((dt_mstate_t *)0)->argv); i++)
-		emit(dlp, BPF_STORE_IMM(BPF_DW, BPF_REG_7, DMST_ARG(i), 0));
-
 	dt_cg_tramp_epilogue(pcb);
 
 	return 0;
diff --git a/libdtrace/dt_prov_dtrace.c b/libdtrace/dt_prov_dtrace.c
index 34b5d8e2..453d3e58 100644
--- a/libdtrace/dt_prov_dtrace.c
+++ b/libdtrace/dt_prov_dtrace.c
@@ -83,7 +83,7 @@ static int trampoline(dt_pcb_t *pcb, uint_t exitlbl)
 {
 	dt_irlist_t	*dlp = &pcb->pcb_ir;
 	dt_activity_t	act = DT_ACTIVITY_ACTIVE;
-	uint32_t	i, key = 0;
+	uint32_t	key = 0;
 
 	/*
 	 * The ERROR probe isn't really a trace event that a BPF program is
@@ -174,11 +174,7 @@ static int trampoline(dt_pcb_t *pcb, uint_t exitlbl)
 	emit(dlp, BPF_CALL_HELPER(BPF_FUNC_map_update_elem));
 
 	dt_cg_tramp_copy_regs(pcb);
-
-	/* zero the probe args */
-	for (i = 0; i < ARRAY_SIZE(((dt_mstate_t *)0)->argv); i++)
-		emit(dlp, BPF_STORE_IMM(BPF_DW, BPF_REG_7, DMST_ARG(i), 0));
-
+	dt_cg_tramp_clear_argv(pcb, 0);
 	dt_cg_tramp_epilogue_advance(pcb, act);
 
 	return 0;
diff --git a/libdtrace/dt_prov_profile.c b/libdtrace/dt_prov_profile.c
index e1369ca9..cb65ca43 100644
--- a/libdtrace/dt_prov_profile.c
+++ b/libdtrace/dt_prov_profile.c
@@ -216,24 +216,9 @@ static int provide(dtrace_hdl_t *dtp, const dtrace_probedesc_t *pdp)
  */
 static int trampoline(dt_pcb_t *pcb, uint_t exitlbl)
 {
-	int		i;
-	dt_irlist_t	*dlp = &pcb->pcb_ir;
-
 	dt_cg_tramp_prologue_cpu(pcb);
-
-	/*
-	 * After the dt_cg_tramp_prologue_cpu() call, we have:
-	 *				//     (%r7 = dctx->mst)
-	 *				//     (%r8 = dctx->ctx)
-	 */
-
 	dt_cg_tramp_copy_regs(pcb);
-
-	/*
-	 * dctx->mst->argv[0] = kernel PC
-	 * dctx->mst->argv[1] = userspace PC
-	 */
-        dt_cg_tramp_copy_pc_from_regs(pcb);
+	dt_cg_tramp_copy_pc_from_regs(pcb);
 
 	/*
 	 * TODO: For profile-n probes:
@@ -246,12 +231,6 @@ static int trampoline(dt_pcb_t *pcb, uint_t exitlbl)
 	 * and update expected+=interval.
 	 */
 
-	/*
-	 *     (we clear dctx->mst->argv[2] and on)
-	 */
-	for (i = 2; i < ARRAY_SIZE(((dt_mstate_t *)0)->argv); i++)
-		emit(dlp, BPF_STORE_IMM(BPF_DW, BPF_REG_7, DMST_ARG(i), 0));
-
 	dt_cg_tramp_epilogue(pcb);
 
 	return 0;
diff --git a/libdtrace/dt_prov_syscall.c b/libdtrace/dt_prov_syscall.c
index 20843c6f..237f2728 100644
--- a/libdtrace/dt_prov_syscall.c
+++ b/libdtrace/dt_prov_syscall.c
@@ -159,14 +159,8 @@ static int trampoline(dt_pcb_t *pcb, uint_t exitlbl)
 		emit(dlp, BPF_STORE(BPF_DW, BPF_REG_7, DMST_ARG(i), BPF_REG_0));
 	}
 
-	/*
-	 * Zero the remaining probe args.
-	 *	for ( ; i < ARRAY_SIZE(((dt_mstate_t *)0)->argv); i++)
-	 *		dctx->mst->argv[i] = 0;
-	 *				// stdw [%r7 + DMST_ARG(i)], 0
-	 */
-	for ( ; i < ARRAY_SIZE(((dt_mstate_t *)0)->argv); i++)
-		emit(dlp, BPF_STORE_IMM(BPF_DW, BPF_REG_7, DMST_ARG(i), 0));
+	/* Zero the remaining probe args. */
+	dt_cg_tramp_clear_argv(pcb, i);
 
 	/*
 	 * For return probes, store the errno.  That is, examine arg0.
-- 
2.51.0