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([2620:10d:c090:500::7:1c5e]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-141387ac9b1sm2272210c88.2.2026.08.13.15.20.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 Aug 2026 15:20:58 -0700 (PDT) Message-ID: <7d608380ec448046a6783c96583cd493ca639a15.camel@gmail.com> Subject: Re: [PATCH bpf-next 2/2] selftests/bpf: Cover mixed arena and map-value atomics From: Eduard Zingerman To: Yiyang Chen , Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrii Nakryiko , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Ihor Solodrai , Shuah Khan Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Date: Thu, 13 Aug 2026 15:20:56 -0700 In-Reply-To: <20260813-bpf-next-038-mixed-atomic-v1-v1-2-e79aadb46a8a@mails.tsinghua.edu.cn> References: <20260813-bpf-next-038-mixed-atomic-v1-v1-0-e79aadb46a8a@mails.tsinghua.edu.cn> <20260813-bpf-next-038-mixed-atomic-v1-v1-2-e79aadb46a8a@mails.tsinghua.edu.cn> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.60.1 (3.60.1-1.fc44) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Thu, 2026-08-13 at 12:01 +0000, Yiyang Chen wrote: > Add a verifier test with one atomic RMW instruction reached through > PTR_TO_ARENA and PTR_TO_MAP_VALUE paths. The verifier must reject the > shared instruction with the existing incompatible-pointer diagnostic. >=20 > Signed-off-by: Yiyang Chen > --- > tools/testing/selftests/bpf/progs/verifier_arena.c | 44 ++++++++++++++++= ++++++ > 1 file changed, 44 insertions(+) >=20 > diff --git a/tools/testing/selftests/bpf/progs/verifier_arena.c b/tools/t= esting/selftests/bpf/progs/verifier_arena.c > index b241bbcf54a8a..2e43da188194b 100644 > --- a/tools/testing/selftests/bpf/progs/verifier_arena.c > +++ b/tools/testing/selftests/bpf/progs/verifier_arena.c > @@ -25,6 +25,15 @@ struct { > __ulong(map_extra, ARENA_VM_START); /* start of mmap() region */ > } arena SEC(".maps"); > =20 > +struct { > + __uint(type, BPF_MAP_TYPE_ARRAY); > + __uint(max_entries, 1); > + __type(key, __u32); > + __type(value, __u64); > +} atomic_map SEC(".maps"); Please use existing arena map. > + > +static __u64 arena_atomic_target SEC(".addr_space.1"); The bot is right, verifier_arena tests are failing. Did you test this patch before sending? > SEC("socket") > __success __retval(0) > int basic_alloc1_nosleep(void *ctx) > @@ -637,6 +646,41 @@ int non_arena_ptr_add_to_arena_ptr(void *ctx) > =20 > #endif > =20 > +SEC("socket") > +__description("arena and map value atomic at the same instruction") > +__failure __msg("same insn cannot be used with different pointers") > +__arch_x86_64 > +__load_if_JITed() > +__naked void mixed_arena_map_value_atomic(void) > +{ > + asm volatile (" \ > + r1 =3D 0; \ > + *(u32 *)(r10 - 4) =3D r1; \ > + r2 =3D r10; \ > + r2 +=3D -4; \ > + r1 =3D %[atomic_map] ll; \ > + call %[bpf_map_lookup_elem]; \ > + if r0 =3D=3D 0 goto 1f; \ > + r6 =3D r0; \ > + r7 =3D %[arena_atomic_target] ll; \ > + .byte 0xbf; .byte 0x77; .short 1; .long 1; \ Please use __imm_insn, see examples in the test suite. > + call %[bpf_get_prandom_u32]; \ > + if w0 !=3D 0 goto 2f; \ > + r8 =3D r6; \ > + goto 3f; \ > +2: r8 =3D r7; \ > +3: r9 =3D 1; \ > + lock *(u64 *)(r8 + 0) +=3D r9; \ > +1: r0 =3D 0; \ > + exit; \ > +" : > + : __imm_addr(atomic_map), > + __imm_addr(arena_atomic_target), You can conjure an arena pointer as in non_arena_ptr_add_to_arena_ptr() w/o the need for the variable. > + __imm(bpf_map_lookup_elem), > + __imm(bpf_get_prandom_u32) > + : __clobber_all); > +} > + > static __noinline > u32 __arena *check_arena_arg_nonglobal(u32 __arena *arg) > { pw-bot: cr.