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Message-ID: <Yo9SiJssne1oJgIq@FVFF77S0Q05N>
Date: Thu, 26 May 2022 11:12:24 +0100
From: Mark Rutland <mark.rutland@....com>
To: Xu Kuohai <xukuohai@...wei.com>
Cc: bpf@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
linux-kselftest@...r.kernel.org,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Steven Rostedt <rostedt@...dmis.org>,
Ingo Molnar <mingo@...hat.com>,
Daniel Borkmann <daniel@...earbox.net>,
Alexei Starovoitov <ast@...nel.org>,
Zi Shen Lim <zlim.lnx@...il.com>,
Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <kafai@...com>,
Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
John Fastabend <john.fastabend@...il.com>,
KP Singh <kpsingh@...nel.org>,
"David S . Miller" <davem@...emloft.net>,
Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
David Ahern <dsahern@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
hpa@...or.com, Shuah Khan <shuah@...nel.org>,
Jakub Kicinski <kuba@...nel.org>,
Jesper Dangaard Brouer <hawk@...nel.org>,
Pasha Tatashin <pasha.tatashin@...een.com>,
Ard Biesheuvel <ardb@...nel.org>,
Daniel Kiss <daniel.kiss@....com>,
Steven Price <steven.price@....com>,
Sudeep Holla <sudeep.holla@....com>,
Marc Zyngier <maz@...nel.org>,
Peter Collingbourne <pcc@...gle.com>,
Mark Brown <broonie@...nel.org>,
Delyan Kratunov <delyank@...com>,
Kumar Kartikeya Dwivedi <memxor@...il.com>
Subject: Re: [PATCH bpf-next v5 3/6] bpf: Remove is_valid_bpf_tramp_flags()
On Thu, May 26, 2022 at 05:45:25PM +0800, Xu Kuohai wrote:
> On 5/25/2022 9:45 PM, Mark Rutland wrote:
> > On Wed, May 18, 2022 at 09:16:35AM -0400, Xu Kuohai wrote:
> >> BPF_TRAM_F_XXX flags are not used by user code and are almost constant
> >> at compile time, so run time validation is a bit overkill. Remove
> >> is_valid_bpf_tramp_flags() and add some usage comments.
> >>
> >> Signed-off-by: Xu Kuohai <xukuohai@...wei.com>
> >> Acked-by: Song Liu <songliubraving@...com>
> >
> > Am I right in thinking this is independent of the arm64-specific bits, and
> > could be taken on its own now?
> >
>
> Currenly is_valid_bpf_tramp_flags() is defined in x86 and called before
> bpf trampoline is constructed. The check logic is irrelevant to the
> architecture code. So we also need to call this function on arm64. But
> as Alexei pointed out, the check is not requried, so it's better to
> remove it before adding bpf trampoline to arm64.
Cool. So this patch could be merged now, even if the rest of the series needs
more work?
Thanks,
Mark.
> >> ---
> >> arch/x86/net/bpf_jit_comp.c | 20 --------------------
> >> kernel/bpf/bpf_struct_ops.c | 3 +++
> >> kernel/bpf/trampoline.c | 3 +++
> >> 3 files changed, 6 insertions(+), 20 deletions(-)
> >>
> >> diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
> >> index a2b6d197c226..7698ef3b4821 100644
> >> --- a/arch/x86/net/bpf_jit_comp.c
> >> +++ b/arch/x86/net/bpf_jit_comp.c
> >> @@ -1922,23 +1922,6 @@ static int invoke_bpf_mod_ret(const struct btf_func_model *m, u8 **pprog,
> >> return 0;
> >> }
> >>
> >> -static bool is_valid_bpf_tramp_flags(unsigned int flags)
> >> -{
> >> - if ((flags & BPF_TRAMP_F_RESTORE_REGS) &&
> >> - (flags & BPF_TRAMP_F_SKIP_FRAME))
> >> - return false;
> >> -
> >> - /*
> >> - * BPF_TRAMP_F_RET_FENTRY_RET is only used by bpf_struct_ops,
> >> - * and it must be used alone.
> >> - */
> >> - if ((flags & BPF_TRAMP_F_RET_FENTRY_RET) &&
> >> - (flags & ~BPF_TRAMP_F_RET_FENTRY_RET))
> >> - return false;
> >> -
> >> - return true;
> >> -}
> >> -
> >> /* Example:
> >> * __be16 eth_type_trans(struct sk_buff *skb, struct net_device *dev);
> >> * its 'struct btf_func_model' will be nr_args=2
> >> @@ -2017,9 +2000,6 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
> >> if (nr_args > 6)
> >> return -ENOTSUPP;
> >>
> >> - if (!is_valid_bpf_tramp_flags(flags))
> >> - return -EINVAL;
> >> -
> >> /* Generated trampoline stack layout:
> >> *
> >> * RBP + 8 [ return address ]
> >> diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
> >> index d9a3c9207240..0572cc5aeb28 100644
> >> --- a/kernel/bpf/bpf_struct_ops.c
> >> +++ b/kernel/bpf/bpf_struct_ops.c
> >> @@ -341,6 +341,9 @@ int bpf_struct_ops_prepare_trampoline(struct bpf_tramp_links *tlinks,
> >>
> >> tlinks[BPF_TRAMP_FENTRY].links[0] = link;
> >> tlinks[BPF_TRAMP_FENTRY].nr_links = 1;
> >> + /* BPF_TRAMP_F_RET_FENTRY_RET is only used by bpf_struct_ops,
> >> + * and it must be used alone.
> >> + */
> >> flags = model->ret_size > 0 ? BPF_TRAMP_F_RET_FENTRY_RET : 0;
> >> return arch_prepare_bpf_trampoline(NULL, image, image_end,
> >> model, flags, tlinks, NULL);
> >> diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
> >> index 93c7675f0c9e..bd3f2e673874 100644
> >> --- a/kernel/bpf/trampoline.c
> >> +++ b/kernel/bpf/trampoline.c
> >> @@ -358,6 +358,9 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr)
> >>
> >> if (tlinks[BPF_TRAMP_FEXIT].nr_links ||
> >> tlinks[BPF_TRAMP_MODIFY_RETURN].nr_links)
> >> + /* NOTE: BPF_TRAMP_F_RESTORE_REGS and BPF_TRAMP_F_SKIP_FRAME
> >> + * should not be set together.
> >> + */
> >> flags = BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_SKIP_FRAME;
> >>
> >> if (ip_arg)
> >> --
> >> 2.30.2
> >>
> > .
>
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