From: Martin KaFai Lau <martin.lau@linux.dev>
To: Paul Chaignon <paul.chaignon@gmail.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Eduard Zingerman <eddyz87@gmail.com>,
Amery Hung <ameryhung@gmail.com>,
bpf@vger.kernel.org
Subject: Re: [PATCH bpf-next v6 5/5] selftests/bpf: Test direct packet access on non-linear skbs
Date: Tue, 7 Oct 2025 11:01:32 -0700 [thread overview]
Message-ID: <62e288f3-9917-4218-84f7-01e2eb27130c@linux.dev> (raw)
In-Reply-To: <302cd8554710d04986925df1737c787c09b5ff65.1759843268.git.paul.chaignon@gmail.com>
On 10/7/25 6:38 AM, Paul Chaignon wrote:
> +#define access_test_non_linear(name, type, desc, retval, linear_sz, off) \
> + SEC(type) \
> + __description("direct packet access: " #name " (non-linear, " type ", " desc ")") \
> + __success __retval(retval) \
> + __linear_size(linear_sz) \
> + __naked void access_non_linear_##name(void) \
> + { \
> + asm volatile (" \
> + r2 = *(u32*)(r1 + %[skb_data]); \
> + r3 = *(u32*)(r1 + %[skb_data_end]); \
> + r0 = r2; \
> + r0 += %[offset]; \
> + if r0 > r3 goto l0_%=; \
> + r0 = *(u8*)(r0 - 1); \
> + r0 = 0; \
> + exit; \
> + l0_%=: r0 = 1; \
> + exit; \
> + " : \
> + : __imm_const(skb_data, offsetof(struct __sk_buff, data)), \
> + __imm_const(skb_data_end, offsetof(struct __sk_buff, data_end)), \
> + __imm_const(offset, off) \
> + : __clobber_all); \
> + }
> +
> +access_test_non_linear(test31, "tc", "too short eth", 1, ETH_HLEN, 22);
> +access_test_non_linear(test32, "tc", "too short 1", 1, 1, 22);
> +access_test_non_linear(test33, "tc", "long enough", 0, 22, 22);
> +access_test_non_linear(test34, "cgroup_skb/ingress", "too short eth", 1, ETH_HLEN, 8);
> +access_test_non_linear(test35, "cgroup_skb/ingress", "too short 1", 1, 1, 8);
> +access_test_non_linear(test36, "cgroup_skb/ingress", "long enough", 0, 22, 8);
> +
> +SEC("tc")
> +__description("direct packet access: test36 (non-linear, linearized)")
> +__success __retval(0)
> +__linear_size(ETH_HLEN)
> +__naked void access_non_linear_linearized(void)
> +{
> + asm volatile (" \
> + r6 = r1; \
> + r2 = 22; \
> + call %[bpf_skb_pull_data]; \
> + r2 = *(u32*)(r6 + %[skb_data]); \
> + r3 = *(u32*)(r6 + %[skb_data_end]); \
> + r0 = r2; \
> + r0 += 22; \
> + if r0 > r3 goto l0_%=; \
> + r0 = *(u8*)(r0 - 1); \
> + exit; \
> +l0_%=: r0 = 1; \
> + exit; \
> +" :
> + : __imm(bpf_skb_pull_data),
> + __imm_const(skb_data, offsetof(struct __sk_buff, data)),
> + __imm_const(skb_data_end, offsetof(struct __sk_buff, data_end))
> + : __clobber_all);
> +}
Does it have to be in asm?
next prev parent reply other threads:[~2025-10-07 18:01 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-07 13:36 [PATCH bpf-next v6 0/5] Support non-linear skbs for BPF_PROG_TEST_RUN Paul Chaignon
2025-10-07 13:37 ` [PATCH bpf-next v6 1/5] bpf: Refactor cleanup of bpf_prog_test_run_skb Paul Chaignon
2025-10-07 13:37 ` [PATCH bpf-next v6 2/5] bpf: Reorder bpf_prog_test_run_skb initialization Paul Chaignon
2025-10-07 13:38 ` [PATCH bpf-next v6 3/5] bpf: Craft non-linear skbs in BPF_PROG_TEST_RUN Paul Chaignon
2025-10-07 17:59 ` Martin KaFai Lau
2025-10-09 13:32 ` Paul Chaignon
2025-10-07 13:38 ` [PATCH bpf-next v6 4/5] selftests/bpf: Support non-linear flag in test loader Paul Chaignon
2025-10-07 13:38 ` [PATCH bpf-next v6 5/5] selftests/bpf: Test direct packet access on non-linear skbs Paul Chaignon
2025-10-07 18:01 ` Martin KaFai Lau [this message]
2025-10-09 13:44 ` Paul Chaignon
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