On 11/22/22 11:53 AM, Yonghong Song wrote:
+SEC("?fentry.s/" SYS_PREFIX "sys_nanosleep")
+int task_acquire(void *ctx)
+{
+ struct task_struct *task, *real_parent;
+
+ task = bpf_get_current_task_btf();
+ bpf_rcu_read_lock();
+ real_parent = task->real_parent;
+ /* acquire a reference which can be used outside rcu read lock region */
+ real_parent = bpf_task_acquire(real_parent);
Does the bpf_task_acquire() kfunc need a change to do refcount_inc_not_zero()
and KF_RET_NULL?
Also, some more 'skip' checks in prog_tests/rcu_read_lock.c is needed for gcc.
This is failing in gcc CI:
https://github.com/kernel-patches/bpf/actions/runs/3527747280/jobs/5917628248#step:6:5624
; bpf_rcu_read_lock();
2: (85) call bpf_rcu_read_lock#26650
; real_parent = task->real_parent;
3: (79) r1 = *(u64 *)(r6 +1416) ; R1_w=ptr_task_struct(off=0,imm=0)
R6_w=trusted_ptr_task_struct(off=0,imm=0)
; real_parent = bpf_task_acquire(real_parent);
4: (85) call bpf_task_acquire#26666
R1 must be referenced or trusted
processed 5 insns (limit 1000000) max_states_per_insn 0 total_states 0
peak_states 0 mark_read 0
-- END PROG LOAD LOG --
libbpf: prog 'task_acquire': failed to load: -22
+ bpf_rcu_read_unlock();
+ (void)bpf_task_storage_get(&map_a, real_parent, 0, 0);
+ bpf_task_release(real_parent);
+ return 0;
+}
+
+SEC("?fentry.s/" SYS_PREFIX "sys_nanosleep")
+int no_lock(void *ctx)
+{
+ struct task_struct *task, *real_parent;
+
+ /* no bpf_rcu_read_lock(), old code still works */
+ task = bpf_get_current_task_btf();
+ real_parent = task->real_parent;
+ bpf_printk("pid %u\n", real_parent->pid);
nit. Can bpf_printk be avoided here?
Others lgtm.
