On 4/10/20 3:53 PM, Andrii Nakryiko wrote:
On Fri, Apr 10, 2020 at 3:43 PM Yonghong Song <yhs@xxxxxx> wrote:
On 4/9/20 8:00 PM, Alexei Starovoitov wrote:
On Wed, Apr 08, 2020 at 04:25:26PM -0700, Yonghong Song wrote:
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 0f1cbed446c1..b51d56fc77f9 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -354,6 +354,7 @@ enum {
/* Flags for accessing BPF object from syscall side. */
BPF_F_RDONLY = (1U << 3),
BPF_F_WRONLY = (1U << 4),
+ BPF_F_DUMP = (1U << 5),
...
static int bpf_obj_pin(const union bpf_attr *attr)
{
- if (CHECK_ATTR(BPF_OBJ) || attr->file_flags != 0)
+ if (CHECK_ATTR(BPF_OBJ) || attr->file_flags & ~BPF_F_DUMP)
return -EINVAL;
+ if (attr->file_flags == BPF_F_DUMP)
+ return bpf_dump_create(attr->bpf_fd,
+ u64_to_user_ptr(attr->dumper_name));
+
return bpf_obj_pin_user(attr->bpf_fd, u64_to_user_ptr(attr->pathname));
}
I think kernel can be a bit smarter here. There is no need for user space
to pass BPF_F_DUMP flag to kernel just to differentiate the pinning.
Can prog attach type be used instead?
Think again. I think a flag is still useful.
Suppose that we have the following scenario:
- the current directory /sys/fs/bpf/
- user says pin a tracing/dump (target task) prog to "p1"
It is not really clear whether user wants to pin to
/sys/fs/bpf/p1
or user wants to pin to
/sys/kernel/bpfdump/task/p1
unless we say that a tracing/dump program cannot pin
to /sys/fs/bpf which seems unnecessary restriction.
What do you think?
Instead of special-casing dumper_name, can we require specifying full
path, and then check whether it is in BPF FS vs BPFDUMP FS? If the
latter, additionally check that it is in the right sub-directory
matching its intended target type.
We could. I just think specifying full path for bpfdump is not necessary
since it is a single user mount...
But honestly, just doing everything within BPF FS starts to seem
cleaner at this point...
bpffs is multi mount, which is not a perfect fit for bpfdump,
considering mounting inside namespace, etc, all dumpers are gone.
