libbpf-tools: Allow hardirqs to run on old kernels

This is part of efforts towards iovisor#4231. Fallback to raw tracepoints if tp_btf is not available. With this patch, we also remove manual attach and merge the two irq_handler_entry handlers into one. Signed-off-by: Hengqi Chen <[email protected]>
chenhengqi · Sep 13, 2022 · fcd2187 · fcd2187
1 parent dfb0d98
commit fcd2187
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Showing 2 changed files with 64 additions and 50 deletions.
diff --git a/libbpf-tools/hardirqs.bpf.c b/libbpf-tools/hardirqs.bpf.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 // Copyright (c) 2020 Wenbo Zhang
 #include <vmlinux.h>
+#include <bpf/bpf_core_read.h>
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
 #include "hardirqs.h"
@@ -12,6 +13,7 @@
 const volatile bool filter_cg = false;
 const volatile bool targ_dist = false;
 const volatile bool targ_ns = false;
+const volatile bool do_count = false;
 
 struct {
 	__uint(type, BPF_MAP_TYPE_CGROUP_ARRAY);
@@ -36,59 +38,53 @@ struct {
 
 static struct info zero;
 
-SEC("tracepoint/irq/irq_handler_entry")
-int handle__irq_handler(struct trace_event_raw_irq_handler_entry *ctx)
+static int handle_entry(int irq, struct irqaction *action)
 {
-	struct irq_key key = {};
-	struct info *info;
-
 	if (filter_cg && !bpf_current_task_under_cgroup(&cgroup_map, 0))
 		return 0;
 
-	bpf_probe_read_kernel_str(&key.name, sizeof(key.name), ctx->__data);
-	info = bpf_map_lookup_or_try_init(&infos, &key, &zero);
-	if (!info)
+	if (do_count) {
+		struct irq_key key = {};
+		struct info *info;
+
+		bpf_probe_read_kernel_str(&key.name, sizeof(key.name), BPF_CORE_READ(action, name));
+		info = bpf_map_lookup_or_try_init(&infos, &key, &zero);
+		if (!info)
+			return 0;
+		info->count += 1;
 		return 0;
-	info->count += 1;
-	return 0;
-}
+	} else {
+		u64 ts = bpf_ktime_get_ns();
+		u32 key = 0;
 
-SEC("tp_btf/irq_handler_entry")
-int BPF_PROG(irq_handler_entry)
-{
-	u64 ts = bpf_ktime_get_ns();
-	u32 key = 0;
+		if (filter_cg && !bpf_current_task_under_cgroup(&cgroup_map, 0))
+			return 0;
 
-	if (filter_cg && !bpf_current_task_under_cgroup(&cgroup_map, 0))
+		bpf_map_update_elem(&start, &key, &ts, BPF_ANY);
 		return 0;
-
-	bpf_map_update_elem(&start, &key, &ts, 0);
-	return 0;
+	}
 }
 
-SEC("tp_btf/irq_handler_exit")
-int BPF_PROG(irq_handler_exit_exit, int irq, struct irqaction *action)
+static int handle_exit(int irq, struct irqaction *action)
 {
 	struct irq_key ikey = {};
 	struct info *info;
 	u32 key = 0;
-	s64 delta;
+	u64 delta;
 	u64 *tsp;
 
 	if (filter_cg && !bpf_current_task_under_cgroup(&cgroup_map, 0))
 		return 0;
 
 	tsp = bpf_map_lookup_elem(&start, &key);
-	if (!tsp || !*tsp)
+	if (!tsp)
 		return 0;
 
 	delta = bpf_ktime_get_ns() - *tsp;
-	if (delta < 0)
-		return 0;
 	if (!targ_ns)
 		delta /= 1000U;
 
-	bpf_probe_read_kernel_str(&ikey.name, sizeof(ikey.name), action->name);
+	bpf_probe_read_kernel_str(&ikey.name, sizeof(ikey.name), BPF_CORE_READ(action, name));
 	info = bpf_map_lookup_or_try_init(&infos, &ikey, &zero);
 	if (!info)
 		return 0;
@@ -107,4 +103,28 @@ int BPF_PROG(irq_handler_exit_exit, int irq, struct irqaction *action)
 	return 0;
 }
 
+SEC("tp_btf/irq_handler_entry")
+int BPF_PROG(irq_handler_entry_btf, int irq, struct irqaction *action)
+{
+	return handle_entry(irq, action);
+}
+
+SEC("tp_btf/irq_handler_exit")
+int BPF_PROG(irq_handler_exit_btf, int irq, struct irqaction *action)
+{
+	return handle_exit(irq, action);
+}
+
+SEC("raw_tp/irq_handler_entry")
+int BPF_PROG(irq_handler_entry, int irq, struct irqaction *action)
+{
+	return handle_entry(irq, action);
+}
+
+SEC("raw_tp/irq_handler_exit")
+int BPF_PROG(irq_handler_exit, int irq, struct irqaction *action)
+{
+	return handle_exit(irq, action);
+}
+
 char LICENSE[] SEC("license") = "GPL";
diff --git a/libbpf-tools/hardirqs.c b/libbpf-tools/hardirqs.c
@@ -205,7 +205,20 @@ int main(int argc, char **argv)
 		return 1;
 	}
 
+	if (probe_tp_btf("irq_handler_entry")) {
+		bpf_program__set_autoload(obj->progs.irq_handler_entry, false);
+		bpf_program__set_autoload(obj->progs.irq_handler_exit, false);
+		if (env.count)
+			bpf_program__set_autoload(obj->progs.irq_handler_exit_btf, false);
+	} else {
+		bpf_program__set_autoload(obj->progs.irq_handler_entry_btf, false);
+		bpf_program__set_autoload(obj->progs.irq_handler_exit_btf, false);
+		if (env.count)
+			bpf_program__set_autoload(obj->progs.irq_handler_exit, false);
+	}
+
 	obj->rodata->filter_cg = env.cg;
+	obj->rodata->do_count = env.count;
 
 	/* initialize global data (filtering options) */
 	if (!env.count) {
@@ -234,29 +247,10 @@ int main(int argc, char **argv)
 		}
 	}
 
-	if (env.count) {
-		obj->links.handle__irq_handler = bpf_program__attach(obj->progs.handle__irq_handler);
-		if (!obj->links.handle__irq_handler) {
-			err = -errno;
-			fprintf(stderr,
-				"failed to attach irq/irq_handler_entry: %s\n",
-				strerror(-err));
-		}
-	} else {
-		obj->links.irq_handler_entry = bpf_program__attach(obj->progs.irq_handler_entry);
-		if (!obj->links.irq_handler_entry) {
-			err = -errno;
-			fprintf(stderr,
-				"failed to attach irq_handler_entry: %s\n",
-				strerror(-err));
-		}
-		obj->links.irq_handler_exit_exit = bpf_program__attach(obj->progs.irq_handler_exit_exit);
-		if (!obj->links.irq_handler_exit_exit) {
-			err = -errno;
-			fprintf(stderr,
-				"failed to attach irq_handler_exit: %s\n",
-				strerror(-err));
-		}
+	err = hardirqs_bpf__attach(obj);
+	if (err) {
+		fprintf(stderr, "failed to attach BPF object: %d\n", err);
+		goto cleanup;
 	}
 
 	signal(SIGINT, sig_handler);