[DTrace-devel] [PATCH 10/19] Remove the is-enabled provider
eugene.loh at oracle.com
eugene.loh at oracle.com
Thu Aug 29 05:25:49 UTC 2024
From: Eugene Loh <eugene.loh at oracle.com>
The trampoline for the is-enabled provider is unnecessarily complicated.
We do not need dt_cg_tramp_copy_regs() since the copied values will not
be used. Nor do we need the (second) copy of regs[arg0] to mst->arg[0].
We can inline copyout_val().
Actually, we can simply consolidate the USDT and is-enabled providers.
Signed-off-by: Eugene Loh <eugene.loh at oracle.com>
---
libdtrace/dt_prov_uprobe.c | 165 ++++++-------------------------------
1 file changed, 26 insertions(+), 139 deletions(-)
diff --git a/libdtrace/dt_prov_uprobe.c b/libdtrace/dt_prov_uprobe.c
index 6403842f..98d7b79b 100644
--- a/libdtrace/dt_prov_uprobe.c
+++ b/libdtrace/dt_prov_uprobe.c
@@ -44,7 +44,6 @@
/* Provider name for the underlying probes. */
static const char prvname[] = "uprobe";
-static const char prvname_is_enabled[] = "uprobe__is_enabled";
#define PP_IS_RETURN 1
#define PP_IS_FUNCALL 2
@@ -82,7 +81,6 @@ static const dtrace_pattr_t pattr = {
{ DTRACE_STABILITY_PRIVATE, DTRACE_STABILITY_PRIVATE, DTRACE_CLASS_UNKNOWN },
};
-dt_provimpl_t dt_uprobe_is_enabled;
dt_provimpl_t dt_pid;
dt_provimpl_t dt_usdt;
@@ -93,8 +91,6 @@ static int populate(dtrace_hdl_t *dtp)
if (dt_provider_create(dtp, dt_uprobe.name, &dt_uprobe, &pattr,
NULL) == NULL ||
- dt_provider_create(dtp, dt_uprobe_is_enabled.name,
- &dt_uprobe_is_enabled, &pattr, NULL) == NULL ||
dt_provider_create(dtp, dt_pid.name, &dt_pid, &pattr,
NULL) == NULL ||
dt_provider_create(dtp, dt_usdt.name, &dt_usdt, &pattr,
@@ -404,7 +400,6 @@ static dt_probe_t *create_underlying(dtrace_hdl_t *dtp,
dtrace_probedesc_t pd;
dt_probe_t *uprp;
dt_uprobe_t *upp;
- int is_enabled = 0;
/*
* The underlying probes (uprobes) represent the tracepoints that pid
@@ -427,8 +422,6 @@ static dt_probe_t *create_underlying(dtrace_hdl_t *dtp,
strcpy(prb, "return");
break;
case DTPPT_IS_ENABLED:
- is_enabled = 1;
- /* Fallthrough. */
case DTPPT_ENTRY:
case DTPPT_OFFSETS:
snprintf(prb, sizeof(prb), "%lx", psp->pps_off);
@@ -439,7 +432,7 @@ static dt_probe_t *create_underlying(dtrace_hdl_t *dtp,
}
pd.id = DTRACE_IDNONE;
- pd.prv = is_enabled ? prvname_is_enabled : prvname;
+ pd.prv = prvname;
pd.mod = mod;
pd.fun = psp->pps_fun;
pd.prb = prb;
@@ -631,21 +624,6 @@ static void enable(dtrace_hdl_t *dtp, dt_probe_t *prp, int is_usdt)
dt_probe_enable(dtp, uprp);
}
- /*
- * If necessary, we need to enable is-enabled probes too (if they
- * exist).
- */
- if (is_usdt) {
- dtrace_probedesc_t pd;
- dt_probe_t *iep;
-
- memcpy(&pd, &prp->desc, sizeof(pd));
- pd.prv = prvname_is_enabled;
- iep = dt_probe_lookup(dtp, &pd);
- if (iep != NULL)
- dt_probe_enable(dtp, iep);
- }
-
/*
* Finally, ensure we're in the list of enablings as well.
* (This ensures that, among other things, the probes map
@@ -790,6 +768,29 @@ static int trampoline(dt_pcb_t *pcb, uint_t exitlbl)
emit(dlp, BPF_CALL_HELPER(BPF_FUNC_map_lookup_elem));
emit(dlp, BPF_BRANCH_IMM(BPF_JEQ, BPF_REG_0, 0, lbl_exit));
+ if (upp->flags & PP_IS_ENABLED) {
+ /*
+ * Generate a BPF trampoline for an is-enabled probe. The is-enabled probe
+ * prototype looks like:
+ *
+ * int is_enabled(int *arg)
+ *
+ * The trampoline writes 1 into the location pointed to by the passed-in arg.
+ */
+ emit(dlp, BPF_STORE_IMM(BPF_W, BPF_REG_FP, DT_TRAMP_SP_SLOT(0), 1));
+ emit(dlp, BPF_LOAD(BPF_DW, BPF_REG_1, BPF_REG_8, PT_REGS_ARG0));
+ emit(dlp, BPF_MOV_REG(BPF_REG_2, BPF_REG_FP));
+ emit(dlp, BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, DT_TRAMP_SP_SLOT(0)));
+ emit(dlp, BPF_MOV_IMM(BPF_REG_3, sizeof(uint32_t)));
+ emit(dlp, BPF_CALL_HELPER(BPF_FUNC_probe_write_user));
+
+ goto out;
+ }
+
+ /*
+ * Continue with normal USDT probes.
+ */
+
/* Read the PRID from the table lookup and store to mst->prid. */
emit(dlp, BPF_LOAD(BPF_W, BPF_REG_1, BPF_REG_0, 0));
emit(dlp, BPF_STORE(BPF_W, BPF_REG_7, DMST_PRID, BPF_REG_1));
@@ -839,110 +840,11 @@ out:
return 0;
}
-/*
- * Copy the given immediate value into the address given by the specified probe
- * argument.
- */
-static void
-copyout_val(dt_pcb_t *pcb, uint_t lbl, uint32_t val, int arg)
-{
- dt_regset_t *drp = pcb->pcb_regs;
- dt_irlist_t *dlp = &pcb->pcb_ir;
-
- emitl(dlp, lbl, BPF_STORE_IMM(BPF_DW, BPF_REG_FP, DT_TRAMP_SP_SLOT(0),
- val));
-
- if (dt_regset_xalloc_args(drp) == -1)
- longjmp(yypcb->pcb_jmpbuf, EDT_NOREG);
- emit(dlp, BPF_LOAD(BPF_DW, BPF_REG_1, BPF_REG_7, DMST_ARG(arg)));
- emit(dlp, BPF_MOV_REG(BPF_REG_2, BPF_REG_FP));
- emit(dlp, BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, DT_TRAMP_SP_SLOT(0)));
- emit(dlp, BPF_MOV_IMM(BPF_REG_3, sizeof(uint32_t)));
- dt_regset_xalloc(drp, BPF_REG_0);
- emit(dlp, BPF_CALL_HELPER(BPF_FUNC_probe_write_user));
-
- /* XXX any point error-checking here? What can we possibly do? */
- dt_regset_free(drp, BPF_REG_0);
- dt_regset_free_args(drp);
-}
-
-/*
- * Generate a BPF trampoline for an is-enabled probe. The is-enabled probe
- * prototype looks like:
- *
- * int is_enabled(int *arg)
- *
- * The trampoline dereferences the passed-in arg and writes 1 into it if this is
- * one of the processes for which the probe is enabled.
- */
-static int trampoline_is_enabled(dt_pcb_t *pcb, uint_t exitlbl)
-{
- dt_irlist_t *dlp = &pcb->pcb_ir;
- const dt_probe_t *uprp = pcb->pcb_probe;
- dt_ident_t *usdt_prids = dt_dlib_get_map(pcb->pcb_hdl, "usdt_prids");
-
- assert(usdt_prids != NULL);
-
- dt_cg_tramp_prologue(pcb);
-
- /*
- * After the dt_cg_tramp_prologue() call, we have:
- * // (%r7 = dctx->mst)
- * // (%r8 = dctx->ctx)
- */
- dt_cg_tramp_copy_regs(pcb);
-
- /*
- * Copy in the first function argument, a pointer value to which
- * the is-enabled state of the probe will be written (necessarily
- * 1 if this probe is running at all).
- */
- emit(dlp, BPF_LOAD(BPF_DW, BPF_REG_0, BPF_REG_8, PT_REGS_ARG0));
- emit(dlp, BPF_STORE(BPF_DW, BPF_REG_7, DMST_ARG(0), BPF_REG_0));
-
- /*
- * Retrieve the PID of the process that caused the probe to fire.
- */
- emit(dlp, BPF_CALL_HELPER(BPF_FUNC_get_current_pid_tgid));
- emit(dlp, BPF_ALU64_IMM(BPF_RSH, BPF_REG_0, 32));
-
- /*
- * Look up in the BPF 'usdt_prids' map. Space for the look-up key
- * will be used on the BPF stack:
- *
- * offset value
- *
- * -sizeof(usdt_prids_map_key_t) pid (in %r0)
- *
- * -sizeof(usdt_prids_map_key_t) + sizeof(pid_t)
- * ==
- * -sizeof(dtrace_id_t) underlying-probe prid
- */
- emit(dlp, BPF_STORE(BPF_W, BPF_REG_9, (int)(-sizeof(usdt_prids_map_key_t)), BPF_REG_0));
- emit(dlp, BPF_STORE_IMM(BPF_W, BPF_REG_9, (int)(-sizeof(dtrace_id_t)), uprp->desc->id));
- dt_cg_xsetx(dlp, usdt_prids, DT_LBL_NONE, BPF_REG_1, usdt_prids->di_id);
- emit(dlp, BPF_MOV_REG(BPF_REG_2, BPF_REG_9));
- emit(dlp, BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, (int)(-sizeof(usdt_prids_map_key_t))));
- emit(dlp, BPF_CALL_HELPER(BPF_FUNC_map_lookup_elem));
- emit(dlp, BPF_BRANCH_IMM(BPF_JEQ, BPF_REG_0, 0, pcb->pcb_exitlbl));
-
- /*
- * If we succeeded, then we use copyout_val() above to assign:
- * *arg0 = 1;
- */
- copyout_val(pcb, DT_LBL_NONE, 1, 0);
-
- dt_cg_tramp_return(pcb);
-
- return 0;
-}
-
static char *uprobe_name(dev_t dev, ino_t ino, uint64_t addr, int flags)
{
char *name;
- if (asprintf(&name, "dt_pid%s/%c_%llx_%llx_%lx",
- flags & PP_IS_ENABLED ? "_is_enabled" : "",
+ if (asprintf(&name, "dt_pid/%c_%llx_%llx_%lx",
flags & PP_IS_RETURN ? 'r' : 'p', (unsigned long long)dev,
(unsigned long long)ino, (unsigned long)addr) < 0)
return NULL;
@@ -952,7 +854,7 @@ static char *uprobe_name(dev_t dev, ino_t ino, uint64_t addr, int flags)
/*
* Create a uprobe for a given dev/ino, mapping filename, and address: the
- * uprobe may be a uretprobe or an is-enabled probe. Return the probe's name as
+ * uprobe may be a uretprobe. Return the probe's name as
* a new dynamically-allocated string, or NULL on error.
*/
static char *uprobe_create(dev_t dev, ino_t ino, const char *mapping_fn,
@@ -1114,21 +1016,6 @@ dt_provimpl_t dt_uprobe = {
.update = &update_uprobe,
};
-/*
- * Used for underlying is-enabled uprobes.
- */
-dt_provimpl_t dt_uprobe_is_enabled = {
- .name = prvname_is_enabled,
- .prog_type = BPF_PROG_TYPE_KPROBE,
- .populate = &populate,
- .load_prog = &dt_bpf_prog_load,
- .trampoline = &trampoline_is_enabled,
- .attach = &attach,
- .probe_info = &probe_info,
- .detach = &detach,
- .probe_destroy = &probe_destroy_underlying,
-};
-
/*
* Used for pid probes.
*/
--
2.43.5
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