libbpf-tools: Fix renaming of the state field of task_struct

Kernel commit 2f064a59a1 ("sched: Change task_struct::state") changes the name of task_struct::state to task_struct::__state, which breaks several libbpf tools. Fix them by utilizing the libbpf CO-RE support. Signed-off-by: Hengqi Chen <[email protected]>
weibang6liu · Oct 16, 2021 · 8b350fd · 8b350fd
1 parent fb09f59
commit 8b350fd
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Showing 5 changed files with 37 additions and 5 deletions.
diff --git a/libbpf-tools/core_fixes.bpf.h b/libbpf-tools/core_fixes.bpf.h
@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
+/* Copyright (c) 2021 Hengqi Chen */
+
+#ifndef __CORE_FIXES_BPF_H
+#define __CORE_FIXES_BPF_H
+
+#include <vmlinux.h>
+#include <bpf/bpf_core_read.h>
+
+/**
+ * commit 2f064a59a1 ("sched: Change task_struct::state") changes
+ * the name of task_struct::state to task_struct::__state
+ * see:
+ * https://github.com/torvalds/linux/commit/2f064a59a1
+ */
+struct task_struct___x {
+ unsigned int __state;
+};
+
+static __s64 get_task_state(void *task)
+{
+ struct task_struct___x *t = task;
+
+ if (bpf_core_field_exists(t->__state))
+ return t->__state;
+ return ((struct task_struct *)task)->state;
+}
+
+#endif /* __CORE_FIXES_BPF_H */
diff --git a/libbpf-tools/cpudist.bpf.c b/libbpf-tools/cpudist.bpf.c
@@ -6,6 +6,7 @@
 #include <bpf/bpf_tracing.h>
 #include "cpudist.h"
 #include "bits.bpf.h"
+#include "core_fixes.bpf.h"
 
 #define TASK_RUNNING 0
 
@@ -88,7 +89,7 @@ int BPF_PROG(sched_switch, bool preempt, struct task_struct *prev,
  store_start(prev_tgid, prev_pid, ts);
  update_hist(next, tgid, pid, ts);
  } else {
- if (prev->state == TASK_RUNNING)
+ if (get_task_state(prev) == TASK_RUNNING)
  update_hist(prev, prev_tgid, prev_pid, ts);
  store_start(tgid, pid, ts);
  }

diff --git a/libbpf-tools/offcputime.bpf.c b/libbpf-tools/offcputime.bpf.c
@@ -5,6 +5,7 @@
 #include <bpf/bpf_core_read.h>
 #include <bpf/bpf_tracing.h>
 #include "offcputime.h"
+#include "core_fixes.bpf.h"
 
 #define PF_KTHREAD 0x00200000 /* I am a kernel thread */
 #define MAX_ENTRIES 10240
@@ -51,7 +52,7 @@ static bool allow_record(struct task_struct *t)
  return false;
  else if (kernel_threads_only && !(t->flags & PF_KTHREAD))
  return false;
- if (state != -1 && t->state != state)
+ if (state != -1 && get_task_state(t) != state)
  return false;
  return true;
 }

diff --git a/libbpf-tools/runqlat.bpf.c b/libbpf-tools/runqlat.bpf.c
@@ -7,6 +7,7 @@
 #include "runqlat.h"
 #include "bits.bpf.h"
 #include "maps.bpf.h"
+#include "core_fixes.bpf.h"
 
 #define MAX_ENTRIES 10240
 #define TASK_RUNNING 0
@@ -69,7 +70,7 @@ int BPF_PROG(sched_swith, bool preempt, struct task_struct *prev,
  u32 pid, hkey;
  s64 delta;
 
- if (prev->state == TASK_RUNNING)
+ if (get_task_state(prev) == TASK_RUNNING)
  trace_enqueue(prev->tgid, prev->pid);
 
  pid = next->pid;

diff --git a/libbpf-tools/runqslower.bpf.c b/libbpf-tools/runqslower.bpf.c
@@ -3,6 +3,7 @@
 #include <vmlinux.h>
 #include <bpf/bpf_helpers.h>
 #include "runqslower.h"
+#include "core_fixes.bpf.h"
 
 #define TASK_RUNNING 0
 
@@ -69,11 +70,10 @@ int handle__sched_switch(u64 *ctx)
  struct task_struct *next = (struct task_struct *)ctx[2];
  struct event event = {};
  u64 *tsp, delta_us;
- long state;
  u32 pid;
 
  /* ivcsw: treat like an enqueue event and store timestamp */
- if (prev->state == TASK_RUNNING)
+ if (get_task_state(prev) == TASK_RUNNING)
  trace_enqueue(prev->tgid, prev->pid);
 
  pid = next->pid;