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Fri, 05 Jun 2026 16:22:40 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Fri, 05 Jun 2026 16:22:39 -0700 Message-Id: Cc: , "Bastien Curutchet" , "Thomas Petazzoni" , , , , , Subject: Re: [PATCH bpf-next v2 4/8] bpf, x86: refactor BPF_ST management in do_jit From: "Alexei Starovoitov" To: =?utf-8?b?QWxleGlzIExvdGhvcsOpIChlQlBGIEZvdW5kYXRpb24p?= , "Alexei Starovoitov" , "Daniel Borkmann" , "Andrii Nakryiko" , "Martin KaFai Lau" , "Eduard Zingerman" , "Kumar Kartikeya Dwivedi" , "Song Liu" , "Yonghong Song" , "Jiri Olsa" , "John Fastabend" , "Thomas Gleixner" , "Ingo Molnar" , "Borislav Petkov" , "Dave Hansen" , , "H. Peter Anvin" , "Shuah Khan" , "Maxime Coquelin" , "Alexandre Torgue" , "Ihor Solodrai" X-Mailer: aerc References: <20260604-kasan-v2-0-c066e627fda8@bootlin.com> <20260604-kasan-v2-4-c066e627fda8@bootlin.com> In-Reply-To: <20260604-kasan-v2-4-c066e627fda8@bootlin.com> On Thu Jun 4, 2026 at 1:22 PM PDT, Alexis Lothor=C3=A9 (eBPF Foundation) wr= ote: > In order to prepare for KASAN checks insertion before every > memory-related load or store, group all BPF_ST instructions that indeed > access memory in a single block of fall-through cases to allow > instrumenting those in one call, rather than having to instrument all > cases individually. > > Signed-off-by: Alexis Lothor=C3=A9 (eBPF Foundation) > --- > arch/x86/net/bpf_jit_comp.c | 53 ++++++++++++++++++++++++++-------------= ------ > 1 file changed, 31 insertions(+), 22 deletions(-) > > diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c > index 0981791014eb..943a0f315cf2 100644 > --- a/arch/x86/net/bpf_jit_comp.c > +++ b/arch/x86/net/bpf_jit_comp.c > @@ -2300,41 +2300,50 @@ static int do_jit(struct bpf_verifier_env *env, s= truct bpf_prog *bpf_prog, int * > EMIT_LFENCE(); > break; > =20 > - /* ST: *(u8*)(dst_reg + off) =3D imm */ > case BPF_ST | BPF_MEM | BPF_B: > - if (is_ereg(dst_reg)) > - EMIT2(0x41, 0xC6); > - else > - EMIT1(0xC6); > - goto st; > case BPF_ST | BPF_MEM | BPF_H: > - if (is_ereg(dst_reg)) > - EMIT3(0x66, 0x41, 0xC7); > - else > - EMIT2(0x66, 0xC7); > - goto st; > case BPF_ST | BPF_MEM | BPF_W: > - if (is_ereg(dst_reg)) > - EMIT2(0x41, 0xC7); > - else > - EMIT1(0xC7); > - goto st; > case BPF_ST | BPF_MEM | BPF_DW: > - if (dst_reg =3D=3D BPF_REG_PARAMS && insn->off =3D=3D -8) { > - /* Arg 6: store immediate in r9 register */ > - emit_mov_imm64(&prog, X86_REG_R9, imm32 >> 31, (u32)imm32); > + switch (BPF_SIZE(insn->code)) { > + case BPF_B: > + if (is_ereg(dst_reg)) > + EMIT2(0x41, 0xC6); > + else > + EMIT1(0xC6); > + break; > + case BPF_H: > + if (is_ereg(dst_reg)) > + EMIT3(0x66, 0x41, 0xC7); > + else > + EMIT2(0x66, 0xC7); > + break; > + case BPF_W: > + if (is_ereg(dst_reg)) > + EMIT2(0x41, 0xC7); > + else > + EMIT1(0xC7); > + break; > + case BPF_DW: > + if (dst_reg =3D=3D BPF_REG_PARAMS && > + insn->off =3D=3D -8) { > + /* Arg 6: store immediate in r9 register */ > + emit_mov_imm64(&prog, X86_REG_R9, > + imm32 >> 31, (u32)imm32); > + break; > + } > + EMIT2(add_1mod(0x48, dst_reg), 0xC7); maybe it's an opportunity to cover this into separate helper function? When indent reaches 4 tabs it's about time.