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Message-ID: <20231208172152.GD36716@noisy.programming.kicks-ass.net>
Date: Fri, 8 Dec 2023 18:21:52 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Jiri Olsa <olsajiri@...il.com>, Song Liu <song@...nel.org>,
Song Liu <songliubraving@...a.com>,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>, X86 ML <x86@...nel.org>,
"H. Peter Anvin" <hpa@...or.com>,
"David S. Miller" <davem@...emloft.net>,
David Ahern <dsahern@...nel.org>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <martin.lau@...ux.dev>,
Yonghong Song <yonghong.song@...ux.dev>,
John Fastabend <john.fastabend@...il.com>,
KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...gle.com>,
Hao Luo <haoluo@...gle.com>, Arnd Bergmann <arnd@...db.de>,
Sami Tolvanen <samitolvanen@...gle.com>,
Kees Cook <keescook@...omium.org>,
Nathan Chancellor <nathan@...nel.org>,
Nick Desaulniers <ndesaulniers@...gle.com>,
linux-riscv <linux-riscv@...ts.infradead.org>,
LKML <linux-kernel@...r.kernel.org>,
Network Development <netdev@...r.kernel.org>,
bpf <bpf@...r.kernel.org>, linux-arch <linux-arch@...r.kernel.org>,
clang-built-linux <llvm@...ts.linux.dev>,
Josh Poimboeuf <jpoimboe@...nel.org>,
Joao Moreira <joao@...rdrivepizza.com>,
Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v2 2/2] x86/cfi,bpf: Fix BPF JIT call
On Fri, Dec 08, 2023 at 02:40:41PM +0100, Peter Zijlstra wrote:
> On Fri, Dec 08, 2023 at 11:29:40AM +0100, Peter Zijlstra wrote:
> > The only problem I now have is the one XXX, I'm not entirely sure what
> > signature to use there.
>
> > @@ -119,6 +119,7 @@ int bpf_struct_ops_test_run(struct bpf_p
> > op_idx = prog->expected_attach_type;
> > err = bpf_struct_ops_prepare_trampoline(tlinks, link,
> > &st_ops->func_models[op_idx],
> > + /* XXX */ NULL,
> > image, image + PAGE_SIZE);
> > if (err < 0)
> > goto out;
>
> Duh, that should ofcourse be something of dummy_ops_test_ret_fn type.
> Let me go fix that.
Next one.. bpf_obj_free_fields: field->kptr.dtor(xchg_field);
The one that trips is bpf_cgroup_release().
objtool doesn't think the address of that function 'escapes' and
'helpfully' seals that function, and then BPF thinks it does escape and
manages the above indirect call and *boom*.
How can I tell which functions escape according to BPF such that I might
teach objtool this?
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