On Mon, Jun 05, 2023 at 04:30:29PM -0700, Alexei Starovoitov wrote:
On Mon, Jun 5, 2023 at 9:50 AM Krister Johansen kjlx@templeofstupid.com wrote:
if (!aux->func[i]->aux->num_exentries ||aux->func[i]->aux->extable == NULL)continue;e = search_extable(aux->func[i]->aux->extable,aux->func[i]->aux->num_exentries, addr);}}something odd here. We do bpf_prog_kallsyms_add(func[i]); for each subprog. So bpf_prog_ksym_find() in search_bpf_extables() should be finding ksym and extable of the subprog and not the main prog. The bug is probably elsewhere.
I have a kdump (or more) of this bug so if there's additional state you'd like me to share, let me know. With your comments in mind, I took another look at the ksym fields in the aux structs. I have this in the main program:
ksym = { start = 18446744072638420852, end = 18446744072638423040, name = <...> lnode = { next = 0xffff88d9c1065168, prev = 0xffff88da91609168 }, tnode = { node = {{ __rb_parent_color = 18446613068361611640, rb_right = 0xffff88da91609178, rb_left = 0xffff88d9f0c5a578 }, { __rb_parent_color = 18446613068361611664, rb_right = 0xffff88da91609190, rb_left = 0xffff88d9f0c5a590 }} }, prog = true },
and this in the func[0] subprogram:
ksym = { start = 18446744072638420852, end = 18446744072638423040, name = <...> lnode = { next = 0xffff88da91609168, prev = 0xffffffff981f8990 <bpf_kallsyms> }, tnode = { node = {{ __rb_parent_color = 18446613068361606520, rb_right = 0x0, rb_left = 0x0 }, { __rb_parent_color = 18446613068361606544, rb_right = 0x0, rb_left = 0x0 }} }, prog = true },
That sure looks like func[0] is a leaf in the rbtree and the main program is an intermediate node with leaves. If that's the case, then bpf_prog_ksym_find may have found the main program instead of the subprogram. In that case, do you think it's better to skip the main program's call to bpf_prog_ksym_set_addr() if it has subprograms instead of searching for subprograms if the main program is found?
-K