[DTrace-devel] [PATCH 1/4] cg, providers: refactor clearing probe arguments
Kris Van Hees
kris.van.hees at oracle.com
Wed Dec 17 05:09:57 UTC 2025
Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
---
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
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