From: Jean-Philippe Brucker <jean-philippe@linaro.org>
To: Xu Kuohai <xukuohai@huawei.com>
Cc: bpf@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
Mark Rutland <mark.rutland@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Alexei Starovoitov <ast@kernel.org>,
Zi Shen Lim <zlim.lnx@gmail.com>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
"David S . Miller" <davem@davemloft.net>,
Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
David Ahern <dsahern@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
Jakub Kicinski <kuba@kernel.org>,
Jesper Dangaard Brouer <hawk@kernel.org>,
Russell King <rmk+kernel@armlinux.org.uk>,
James Morse <james.morse@arm.com>, Hou Tao <houtao1@huawei.com>,
Jason Wang <wangborong@cdjrlc.com>
Subject: Re: [PATCH bpf-next v6 3/4] bpf, arm64: Impelment bpf_arch_text_poke() for arm64
Date: Fri, 8 Jul 2022 09:25:58 +0100 [thread overview]
Message-ID: <YsfqFp+IkhvXPoDl@myrica> (raw)
In-Reply-To: <b2d21d18-2fc1-be68-f8ac-d185fcfadbbd@huawei.com>
On Fri, Jul 08, 2022 at 10:41:46AM +0800, Xu Kuohai wrote:
> >> +/* generated prologue:
> >> + * bti c // if CONFIG_ARM64_BTI_KERNEL
> >> + * mov x9, lr
> >> + * nop // POKE_OFFSET
> >> + * paciasp // if CONFIG_ARM64_PTR_AUTH_KERNEL
> >
> > Any reason for the change regarding BTI and pointer auth? We used to put
> > 'bti c' at the function entry if (BTI && !PA), or 'paciasp' if (BTI && PA),
> > because 'paciasp' is an implicit BTI.
> >
>
> Assuming paciasp is the first instruction if (BTI && PA), when a
> trampoline with BPF_TRAMP_F_CALL_ORIG flag attached, we'll encounter the
> following scenario.
>
> bpf_prog:
> paciasp // LR1
> mov x9, lr
> bl <trampoline> ----> trampoline:
> ....
> mov x10, <entry_for_CALL_ORIG>
> blr x10
> |
> CALL_ORIG_entry: |
> bti c <------------------|
> stp x29, lr, [sp, #- 16]!
> ...
> autiasp // LR2
> ret
>
> Because LR1 and LR2 are not equal, the autiasp will fail!
>
> To make this scenario work properly, the first instruction should be
> 'bti c'.
Right my mistake, this layout is also what GCC generates for normal kernel
functions when (BTI && PA), so it makes sense to use the same
Thanks,
Jean
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next prev parent reply other threads:[~2022-07-08 8:29 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-25 16:12 [PATCH bpf-next v6 0/4] bpf trampoline for arm64 Xu Kuohai
2022-06-25 16:12 ` [PATCH bpf-next v6 1/4] bpf: Remove is_valid_bpf_tramp_flags() Xu Kuohai
2022-06-25 16:12 ` [PATCH bpf-next v6 2/4] arm64: Add LDR (literal) instruction Xu Kuohai
2022-07-05 16:39 ` Will Deacon
2022-07-06 1:43 ` Xu Kuohai
2022-06-25 16:12 ` [PATCH bpf-next v6 3/4] bpf, arm64: Impelment bpf_arch_text_poke() for arm64 Xu Kuohai
2022-07-07 16:41 ` Jean-Philippe Brucker
2022-07-08 2:41 ` Xu Kuohai
2022-07-08 8:25 ` Jean-Philippe Brucker [this message]
2022-06-25 16:12 ` [PATCH bpf-next v6 4/4] bpf, arm64: bpf trampoline " Xu Kuohai
2022-07-07 16:37 ` Jean-Philippe Brucker
2022-07-08 4:35 ` Xu Kuohai
2022-07-08 8:24 ` Jean-Philippe Brucker
2022-07-08 9:08 ` Xu Kuohai
2022-06-30 21:12 ` [PATCH bpf-next v6 0/4] " Daniel Borkmann
2022-07-05 16:00 ` Will Deacon
2022-07-05 18:34 ` KP Singh
2022-07-07 3:35 ` Xu Kuohai
2022-07-06 16:08 ` Jean-Philippe Brucker
2022-07-06 16:11 ` Will Deacon
2022-07-07 2:56 ` Xu Kuohai
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