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charset=UTF-8 Date: Wed, 08 Jan 2025 21:46:19 +0100 Message-Id: To: "Eduard Zingerman" , Cc: "Alexei Starovoitov" , "Daniel Borkmann" , "John Fastabend" , "Andrii Nakryiko" , "Martin KaFai Lau" , "Song Liu" , "Yonghong Song" , "KP Singh" , "Stanislav Fomichev" , "Hao Luo" , "Jiri Olsa" , Subject: Re: [PATCH bpf v3 2/2] selftests/bpf: Test r0 and ref lifetime after BPF-BPF call with abnormal return From: "Arthur Fabre" X-Mailer: aerc 0.17.0 References: <20250106171709.2832649-1-afabre@cloudflare.com> <20250106171709.2832649-3-afabre@cloudflare.com> In-Reply-To: On Mon Jan 6, 2025 at 9:34 PM CET, Eduard Zingerman wrote: > On Mon, 2025-01-06 at 18:15 +0100, Arthur Fabre wrote: [...] > > +#define TEST(NAME, CALLEE) \ > > + SEC("socket") \ > > + __description("r0: " #NAME) \ > > + __failure __msg("math between ctx pointer and register with unbounded= min value") \ > > + __naked int check_abnormal_ret_r0_##NAME(void) \ > > + { \ > > + asm volatile(" \ > > + r6 =3D r1; \ > > + r2 =3D r10; \ > > + r2 +=3D -8; \ > > + call " #CALLEE "; \ > > + r6 +=3D r0; \ > > + r0 =3D 0; \ > > + exit; \ > > + " : \ > > + : \ > > + : __clobber_all); \ > > + } \ > > + \ > > + SEC("socket") \ > > + __description("ref: " #NAME) \ > > + __failure __msg("math between ctx pointer and register with unbounded= min value") \ > > + __naked int check_abnormal_ret_ref_##NAME(void) \ > > + { \ > > + asm volatile(" \ > > + r6 =3D r1; \ > > + r7 =3D r10; \ > > + r7 +=3D -8; \ > > + r2 =3D r7; \ > > + call " #CALLEE "; \ > > + r0 =3D *(u64*)(r7 + 0); \ > > + r6 +=3D r0; \ > > + exit; \ > > + " : \ > > + : \ > > + : __clobber_all); \ > > + } > > Nit: I think having both cases is an overkill, as both effectively > test if branching occur. Fair enough, I can drop the reference tests. > [...] > > > +struct { > > + __uint(type, BPF_MAP_TYPE_PROG_ARRAY); > > + __uint(max_entries, 1); > > + __uint(key_size, sizeof(int)); > > + __array(values, void(void)); > > +} map_prog SEC(".maps") =3D { > > + .values =3D { > > + [0] =3D (void *)&dummy_prog, > > + }, > > +}; > > + > > +static __noinline __used > > +int callee_tail_call(struct __sk_buff *skb, __u64 *foo) > > +{ > > + bpf_tail_call(skb, &map_prog, 0); > > + *foo =3D 1; > > + return 0; > > +} > > Nit: I'd also add a test where invalid action is taken > after bpf_tail_call inside the callee, > just to make sure that both branches are explored. Good idea, I'll add that in and resend. Thanks for the feedback! > > > + > > +SEC("socket") > > +__description("r0 not set by tail_call") > > +__failure __msg("R0 !read_ok") > > +int check_abnormal_ret_tail_call_fail(struct __sk_buff *skb) > > +{ > > + return bpf_tail_call(skb, &map_prog, 0); > > +} > > + > > +char _license[] SEC("license") =3D "GPL";