Re: [PATCH] libbpf: Use the correct fd when attaching to perf events
From: Sultan Alsawaf <hidden>
Date: 2021-03-13 02:23:05
Also in:
bpf, lkml
On Fri, Mar 12, 2021 at 05:31:14PM -0800, Andrii Nakryiko wrote:
On Fri, Mar 12, 2021 at 1:43 PM Sultan Alsawaf [off-list ref] wrote:quoted
From: Sultan Alsawaf <redacted> We should be using the program fd here, not the perf event fd.Why? Can you elaborate on what issue you ran into with the current code?
bpf_link__pin() would fail with -EINVAL when using tracepoints, kprobes, or
uprobes. The failure would happen inside the kernel, in bpf_link_get_from_fd()
right here:
if (f.file->f_op != &bpf_link_fops) {
fdput(f);
return ERR_PTR(-EINVAL);
}
Since bpf wasn't looking for the perf event fd, I swapped it for the program fd
and bpf_link__pin() worked.
Sultan