[PATCH bpf-next] bpftool: add kernel.kptr_restrict hint for no instructions

[PATCH bpf-next] bpftool: add kernel.kptr_restrict hint for no instructions

[Vincent Li]

from bpftool github repo issue [0], when Linux distribution
kernel.kptr_restrict is set to 2, bpftool prog dump jited returns "no
instructions returned", this message can be puzzling to bpftool users
who is not familiar with kernel BPF internal, so add small hint for
bpftool users to check kernel.kptr_restrict setting. Set
kernel.kptr_restrict to expose kernel address to allow bpftool prog
dump jited to dump the jited bpf program instructions.

[0]: https://github.com/libbpf/bpftool/issues/184

Signed-off-by: Vincent Li <vincent.mc.li@gmail.com.
---
 tools/bpf/bpftool/prog.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index 9722d841abc0..cf18c3879680 100644
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -714,7 +714,7 @@ prog_dump(struct bpf_prog_info *info, enum dump_mode mode,
 
 	if (mode == DUMP_JITED) {
 		if (info->jited_prog_len == 0 || !info->jited_prog_insns) {
-			p_info("no instructions returned");
+			p_err("error retrieving jit dump: no instructions returned or kernel.kptr_restrict set?");
 			return -1;
 		}
 		buf = u64_to_ptr(info->jited_prog_insns);
-- 
2.38.1

Re: [PATCH bpf-next] bpftool: add kernel.kptr_restrict hint for no instructions

[Daniel Borkmann]

On 8/18/25 6:51 PM, Vincent Li wrote:
> from bpftool github repo issue [0], when Linux distribution
> kernel.kptr_restrict is set to 2, bpftool prog dump jited returns "no
> instructions returned", this message can be puzzling to bpftool users
> who is not familiar with kernel BPF internal, so add small hint for
> bpftool users to check kernel.kptr_restrict setting. Set
> kernel.kptr_restrict to expose kernel address to allow bpftool prog
> dump jited to dump the jited bpf program instructions.
> 
> [0]: https://github.com/libbpf/bpftool/issues/184
> 
> Signed-off-by: Vincent Li <vincent.mc.li@gmail.com.

I fixed up the email typo and rewrote the commit message a bit when applying
to bpf-next.

Thanks,
Daniel

Re: [PATCH bpf-next] bpftool: add kernel.kptr_restrict hint for no instructions

[Vincent Li]

On Tue, Aug 19, 2025 at 1:12 AM Daniel Borkmann <daniel@iogearbox.net> wrote:
>
> On 8/18/25 6:51 PM, Vincent Li wrote:
> > from bpftool github repo issue [0], when Linux distribution
> > kernel.kptr_restrict is set to 2, bpftool prog dump jited returns "no
> > instructions returned", this message can be puzzling to bpftool users
> > who is not familiar with kernel BPF internal, so add small hint for
> > bpftool users to check kernel.kptr_restrict setting. Set
> > kernel.kptr_restrict to expose kernel address to allow bpftool prog
> > dump jited to dump the jited bpf program instructions.
> >
> > [0]: https://github.com/libbpf/bpftool/issues/184
> >
> > Signed-off-by: Vincent Li <vincent.mc.li@gmail.com.
>
> I fixed up the email typo and rewrote the commit message a bit when applying
> to bpf-next.
>
Sorry about the typo, maybe I should have asked AI first to write a
commit message for me :).

> Thanks,
> Daniel