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]>

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";

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);