Hello,
在 2023/10/24 01:14, Alexei Starovoitov 写道:
On Mon, Oct 23, 2023 at 6:50 AM Chuyi Zhou <zhouchuyi@xxxxxxxxxxxxx> wrote:
R1_w=ptr_task_struct(off=0,imm=0) R7_w=ptr_task_struct(off=0,imm=0)
18: (85) call bpf_task_acquire#26990
R1 must be a rcu pointer
I will try to figure out it.
Thanks. That would be great.
So far it looks like a regression.
I'm guessing __bpf_md_ptr wrapping is confusing the verifier.
Since it's more complicated than I thought, please respin
the current set with fixes to patch 1 and leave the patch 2 as-is.
That can be another follow up.
After adding this change:
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 15d71d2986d3..4565e5457754 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -6071,6 +6071,8 @@ bool btf_ctx_access(int off, int size, enum
bpf_access_type type,
info->reg_type = ctx_arg_info->reg_type;
info->btf = btf_vmlinux;
info->btf_id = ctx_arg_info->btf_id;
+ if (prog_args_trusted(prog))
+ info->reg_type |= PTR_TRUSTED;
return true;
}
}
the task pointer would be recognized as 'trusted_ptr_or_null_task_struct'.
The VERIFIER LOG:
=============
reg type unsupported for arg#0 function dump_task#7
0: R1=ctx(off=0,imm=0) R10=fp0
; struct task_struct *task = ctx->task;
0: (79) r1 = *(u64 *)(r1 +8) ;
R1_w=trusted_ptr_or_null_task_struct(id=1,off=0,imm=0)
The following BPF Prog works well.
SEC("iter/task")
int dump_task(struct bpf_iter__task *ctx)
{
struct task_struct *task = ctx->task;
struct task_struct *acq;
if (task == NULL)
return 0;
acq = bpf_task_acquire(task);
if (!acq)
return 0;
bpf_task_release(acq);
return 0;
}
Do you think this change is correct ?
Or do you have better ideas ?
Thanks.
