netdev - Re: pull-request: bpf-next 2023-09-16

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Date: Mon, 18 Sep 2023 16:23:44 +0200
From: Kumar Kartikeya Dwivedi <memxor@...il.com>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Eric Dumazet <edumazet@...gle.com>, "David S. Miller" <davem@...emloft.net>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, 
	Network Development <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>, 
	Kernel Team <kernel-team@...com>
Subject: Re: pull-request: bpf-next 2023-09-16

On Mon, 18 Sept 2023 at 16:15, Kumar Kartikeya Dwivedi <memxor@...il.com> wrote:
>
> On Mon, 18 Sept 2023 at 15:56, Alexei Starovoitov
> <alexei.starovoitov@...il.com> wrote:
> >
> > On Mon, Sep 18, 2023 at 6:54 AM Eric Dumazet <edumazet@...gle.com> wrote:
> > >
> > > On Mon, Sep 18, 2023 at 3:41 PM Alexei Starovoitov
> > > <alexei.starovoitov@...il.com> wrote:
> > > >
> > > > On Mon, Sep 18, 2023 at 6:25 AM Eric Dumazet <edumazet@...gle.com> wrote:
> > > > >
> > > > > On Sat, Sep 16, 2023 at 6:59 PM Alexei Starovoitov
> > > > > <alexei.starovoitov@...il.com> wrote:
> > > > > >
> > > > > > Hi David, hi Jakub, hi Paolo, hi Eric,
> > > > > >
> > > > > > The following pull-request contains BPF updates for your *net-next* tree.
> > > > > >
> > > > > > We've added 73 non-merge commits during the last 9 day(s) which contain
> > > > > > a total of 79 files changed, 5275 insertions(+), 600 deletions(-).
> > > > > >
> > > > > > The main changes are:
> > > > > >
> > > > > > 1) Basic BTF validation in libbpf, from Andrii Nakryiko.
> > > > > >
> > > > > > 2) bpf_assert(), bpf_throw(), exceptions in bpf progs, from Kumar Kartikeya Dwivedi.
> > > > > >
> > > > > > 3) next_thread cleanups, from Oleg Nesterov.
> > > > > >
> > > > > > 4) Add mcpu=v4 support to arm32, from Puranjay Mohan.
> > > > > >
> > > > > > 5) Add support for __percpu pointers in bpf progs, from Yonghong Song.
> > > > > >
> > > > > > 6) Fix bpf tailcall interaction with bpf trampoline, from Leon Hwang.
> > > > > >
> > > > > > 7) Raise irq_work in bpf_mem_alloc while irqs are disabled to improve refill probabablity, from Hou Tao.
> > > > > >
> > > > > > Please consider pulling these changes from:
> > > > > >
> > > > > >   git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git
> > > > > >
> > > > >
> > > > > This might have been raised already, but bpf on x86 now depends on
> > > > > CONFIG_UNWINDER_ORC ?
> > > > >
> > > > > $ grep CONFIG_UNWINDER_ORC .config
> > > > > # CONFIG_UNWINDER_ORC is not set
> > > > >
> > > > > $ make ...
> > > > > arch/x86/net/bpf_jit_comp.c:3022:58: error: no member named 'sp' in
> > > > > 'struct unwind_state'
> > > > >                 if (!addr || !consume_fn(cookie, (u64)addr,
> > > > > (u64)state.sp, (u64)state.bp))
> > > > >                                                                  ~~~~~ ^
> > > > > 1 error generated.
> > > >
> > > > Kumar,
> > > > can probably explain better,
> > > > but no the bpf as whole doesn't depend.
> > > > One feature needs either ORC or frame unwinder.
> > > > It won't work with unwinder_guess.
> > > > The build error is a separate issue.
> > > > It hasn't been reported before.
> > >
> > > In my builds, I do have CONFIG_UNWINDER_FRAME_POINTER=y
> > >
> > > $ grep UNWIND .config
> > > # CONFIG_UNWINDER_ORC is not set
> > > CONFIG_UNWINDER_FRAME_POINTER=y
> > >
> > >
> > > I note state.sp is only available to CONFIG_UNWINDER_ORC
> > >
> > > arch/x86/include/asm/unwind.h
> > >
> > > #if defined(CONFIG_UNWINDER_ORC)
> > >     bool signal, full_regs;
> > >     unsigned long sp, bp, ip;
> > >     struct pt_regs *regs, *prev_regs;
> > > #elif defined(CONFIG_UNWINDER_FRAME_POINTER)
> > >    bool got_irq;
> > >    unsigned long *bp, *orig_sp, ip;   // this is orig_sp , not sp.
> >
> > Right. Our replies crossed.
> > Please ignore this PR. We need to fix this first.
>
> Hello,
> This is my bad. I totally missed it since I initially wrote this patch
> and never looked at it again.
> I suggest that I send a fix to disable this feature with
> CONFIG_UNWINDER_FRAME_POINTER=y, while I work on reenabling it again
> for it with a follow up.

Hi, I've attached a fix that should disable it for now. I'll work on a
follow up to reenable it for this config option.
Really sorry about this, I'll try to be more careful going forward.

View attachment "0001-bpf-Disable-exceptions-when-CONFIG_UNWINDER_FRAME_PO.patch" of type "text/x-patch" (1805 bytes)