On Mon, Jul 06, 2020 at 08:33:15AM +0200, Sumanth Korikkar wrote: > Hi Jiri, > > s390 has overlapping address space. As suggested by the commit, > ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE should not be enabled for s390 > kernel. > > This should be changed in bpftrace application. > > Even if we enable ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE, bpf_probe_read > will only work in certain cases like kernel pointer deferences (kprobes). > User pointer deferences in uprobes/kprobes/etc will fail or have some > invalid data > > I am looking forward to this fix: > https://github.com/iovisor/bpftrace/pull/1141 OR probe split in bpftrace. did not see this, will review ;-) thanks a lot! jirka > > (Resending as some cc from my email client failed.) > > Thank you > > Best Regards > Sumanth Korikkar > > Jiri Olsa <jolsa@xxxxxxxxxx> wrote on 07/05/2020 09:42:25 PM: > > > > > Subject: [EXTERNAL] bpf: bpf_probe_read helper restriction on s390x > > > > > > hi, > > > with following commit: > > > 0ebeea8ca8a4 bpf: Restrict bpf_probe_read{, str}() only to archs > > > where they work > > > > > > the bpf_probe_read BPF helper is restricted on architectures that > > > have 'non overlapping address space' and select following config: > > > > > > select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE > > > > > > there's also nice explanation in this commit's changelog: > > > 6ae08ae3dea2 bpf: Add probe_read_{user, kernel} and probe_read_ > > > {user, kernel}_str helpers > > > > > > > > > We have a problem with bpftrace not working properly on s390x because > > > bpf_probe_read is no longer available, and bpftrace does not use > > > bpf_probe_read_(user/kernel) variants yet. > > > > > > My question is if s390x is 'arch with overlapping address space' and we > > > could fix this by adding ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE for > > s390x > > > or we need to fix bpftrace to detect this, which we probably need to do > > > in any case ;-) > > > > > > thanks, > > > jirka > > > > > > -- > Sumanth Korikkar >
