From: Eduard Zingerman <eddyz87@gmail.com>
To: Andrii Nakryiko <andrii@kernel.org>,
bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net,
martin.lau@kernel.org
Cc: kernel-team@meta.com
Subject: Re: [PATCH v5 bpf-next 14/23] bpf: generalize is_branch_taken to handle all conditional jumps in one place
Date: Tue, 31 Oct 2023 17:38:29 +0200 [thread overview]
Message-ID: <8a9da941cc2aefba27da706e4e9b2d11aedfc86f.camel@gmail.com> (raw)
In-Reply-To: <20231027181346.4019398-15-andrii@kernel.org>
On Fri, 2023-10-27 at 11:13 -0700, Andrii Nakryiko wrote:
> > Make is_branch_taken() a single entry point for branch pruning decision
> > making, handling both pointer vs pointer, pointer vs scalar, and scalar
> > vs scalar cases in one place. This also nicely cleans up check_cond_jmp_op().
> >
> > Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
> > ---
> > kernel/bpf/verifier.c | 49 ++++++++++++++++++++++---------------------
> > 1 file changed, 25 insertions(+), 24 deletions(-)
> >
> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index 25b5234ebda3..fedd6d0e76e5 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -14169,6 +14169,19 @@ static void find_good_pkt_pointers(struct bpf_verifier_state *vstate,
> > }));
> > }
> >
> > +/* check if register is a constant scalar value */
> > +static bool is_reg_const(struct bpf_reg_state *reg, bool subreg32)
> > +{
> > + return reg->type == SCALAR_VALUE &&
> > + tnum_is_const(subreg32 ? tnum_subreg(reg->var_off) : reg->var_off);
> > +}
> > +
> > +/* assuming is_reg_const() is true, return constant value of a register */
> > +static u64 reg_const_value(struct bpf_reg_state *reg, bool subreg32)
> > +{
> > + return subreg32 ? tnum_subreg(reg->var_off).value : reg->var_off.value;
> > +}
> > +
> > /*
> > * <reg1> <op> <reg2>, currently assuming reg2 is a constant
> > */
> > @@ -14410,12 +14423,20 @@ static int is_pkt_ptr_branch_taken(struct bpf_reg_state *dst_reg,
> > static int is_branch_taken(struct bpf_reg_state *reg1, struct bpf_reg_state *reg2,
> > u8 opcode, bool is_jmp32)
> > {
> > - struct tnum reg2_tnum = is_jmp32 ? tnum_subreg(reg2->var_off) : reg2->var_off;
> > u64 val;
> >
> > - if (!tnum_is_const(reg2_tnum))
> > + if (reg_is_pkt_pointer_any(reg1) && reg_is_pkt_pointer_any(reg2) && !is_jmp32)
> > + return is_pkt_ptr_branch_taken(reg1, reg2, opcode);
> > +
> > + /* try to make sure reg2 is a constant SCALAR_VALUE */
> > + if (!is_reg_const(reg2, is_jmp32)) {
> > + opcode = flip_opcode(opcode);
> > + swap(reg1, reg2);
> > + }
> > + /* for now we expect reg2 to be a constant to make any useful decisions */
> > + if (!is_reg_const(reg2, is_jmp32))
> > return -1;
> > - val = reg2_tnum.value;
> > + val = reg_const_value(reg2, is_jmp32);
> >
> > if (__is_pointer_value(false, reg1)) {
> > if (!reg_not_null(reg1))
> > @@ -14896,27 +14917,7 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env,
> > }
> >
> > is_jmp32 = BPF_CLASS(insn->code) == BPF_JMP32;
> > -
> > - if (BPF_SRC(insn->code) == BPF_K) {
> > - pred = is_branch_taken(dst_reg, src_reg, opcode, is_jmp32);
> > - } else if (src_reg->type == SCALAR_VALUE &&
> > - is_jmp32 && tnum_is_const(tnum_subreg(src_reg->var_off))) {
> > - pred = is_branch_taken(dst_reg, src_reg, opcode, is_jmp32);
> > - } else if (src_reg->type == SCALAR_VALUE &&
> > - !is_jmp32 && tnum_is_const(src_reg->var_off)) {
> > - pred = is_branch_taken(dst_reg, src_reg, opcode, is_jmp32);
> > - } else if (dst_reg->type == SCALAR_VALUE &&
> > - is_jmp32 && tnum_is_const(tnum_subreg(dst_reg->var_off))) {
> > - pred = is_branch_taken(src_reg, dst_reg, flip_opcode(opcode), is_jmp32);
> > - } else if (dst_reg->type == SCALAR_VALUE &&
> > - !is_jmp32 && tnum_is_const(dst_reg->var_off)) {
> > - pred = is_branch_taken(src_reg, dst_reg, flip_opcode(opcode), is_jmp32);
> > - } else if (reg_is_pkt_pointer_any(dst_reg) &&
> > - reg_is_pkt_pointer_any(src_reg) &&
> > - !is_jmp32) {
> > - pred = is_pkt_ptr_branch_taken(dst_reg, src_reg, opcode);
> > - }
> > -
> > + pred = is_branch_taken(dst_reg, src_reg, opcode, is_jmp32);
> > if (pred >= 0) {
> > /* If we get here with a dst_reg pointer type it is because
> > * above is_branch_taken() special cased the 0 comparison.
next prev parent reply other threads:[~2023-10-31 15:38 UTC|newest]
Thread overview: 77+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-27 18:13 [PATCH v5 bpf-next 00/23] BPF register bounds logic and testing improvements Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 01/23] selftests/bpf: fix RELEASE=1 build for tc_opts Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 02/23] selftests/bpf: satisfy compiler by having explicit return in btf test Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 03/23] bpf: derive smin/smax from umin/max bounds Andrii Nakryiko
2023-10-31 15:37 ` Eduard Zingerman
2023-10-31 17:30 ` Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 04/23] bpf: derive smin32/smax32 from umin32/umax32 bounds Andrii Nakryiko
2023-10-31 15:37 ` Eduard Zingerman
2023-10-27 18:13 ` [PATCH v5 bpf-next 05/23] bpf: derive subreg bounds from full bounds when upper 32 bits are constant Andrii Nakryiko
2023-10-31 15:37 ` Eduard Zingerman
2023-10-27 18:13 ` [PATCH v5 bpf-next 06/23] bpf: add special smin32/smax32 derivation from 64-bit bounds Andrii Nakryiko
2023-10-31 15:37 ` Eduard Zingerman
2023-10-31 17:39 ` Andrii Nakryiko
2023-10-31 18:41 ` Alexei Starovoitov
2023-10-31 18:49 ` Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 07/23] bpf: improve deduction of 64-bit bounds from 32-bit bounds Andrii Nakryiko
2023-10-31 15:37 ` Eduard Zingerman
2023-10-31 20:26 ` Alexei Starovoitov
2023-10-31 20:33 ` Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 08/23] bpf: try harder to deduce register bounds from different numeric domains Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 09/23] bpf: drop knowledge-losing __reg_combine_{32,64}_into_{64,32} logic Andrii Nakryiko
2023-10-31 15:38 ` Eduard Zingerman
2023-10-27 18:13 ` [PATCH v5 bpf-next 10/23] selftests/bpf: BPF register range bounds tester Andrii Nakryiko
2023-11-08 22:08 ` Eduard Zingerman
2023-11-08 23:23 ` Andrii Nakryiko
2023-11-09 0:30 ` Eduard Zingerman
2023-10-27 18:13 ` [PATCH v5 bpf-next 11/23] bpf: rename is_branch_taken reg arguments to prepare for the second one Andrii Nakryiko
2023-10-30 19:39 ` Alexei Starovoitov
2023-10-31 5:19 ` Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 12/23] bpf: generalize is_branch_taken() to work with two registers Andrii Nakryiko
2023-10-31 15:38 ` Eduard Zingerman
2023-10-31 17:41 ` Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 13/23] bpf: move is_branch_taken() down Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 14/23] bpf: generalize is_branch_taken to handle all conditional jumps in one place Andrii Nakryiko
2023-10-31 15:38 ` Eduard Zingerman [this message]
2023-10-27 18:13 ` [PATCH v5 bpf-next 15/23] bpf: unify 32-bit and 64-bit is_branch_taken logic Andrii Nakryiko
2023-10-30 19:52 ` Alexei Starovoitov
2023-10-31 5:28 ` Andrii Nakryiko
2023-10-31 17:35 ` Eduard Zingerman
2023-10-27 18:13 ` [PATCH v5 bpf-next 16/23] bpf: prepare reg_set_min_max for second set of registers Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 17/23] bpf: generalize reg_set_min_max() to handle two sets of two registers Andrii Nakryiko
2023-10-31 2:02 ` Alexei Starovoitov
2023-10-31 6:03 ` Andrii Nakryiko
2023-10-31 16:23 ` Alexei Starovoitov
2023-10-31 17:50 ` Andrii Nakryiko
2023-10-31 17:56 ` Andrii Nakryiko
2023-10-31 18:04 ` Alexei Starovoitov
2023-10-31 18:06 ` Andrii Nakryiko
2023-10-31 18:14 ` Eduard Zingerman
2023-10-27 18:13 ` [PATCH v5 bpf-next 18/23] bpf: generalize reg_set_min_max() to handle non-const register comparisons Andrii Nakryiko
2023-10-31 23:25 ` Eduard Zingerman
2023-11-01 16:35 ` Andrii Nakryiko
2023-11-01 17:12 ` Eduard Zingerman
2023-10-27 18:13 ` [PATCH v5 bpf-next 19/23] bpf: generalize is_scalar_branch_taken() logic Andrii Nakryiko
2023-10-31 2:12 ` Alexei Starovoitov
2023-10-31 6:12 ` Andrii Nakryiko
2023-10-31 16:34 ` Alexei Starovoitov
2023-10-31 18:01 ` Andrii Nakryiko
2023-10-31 20:53 ` Andrii Nakryiko
2023-10-31 20:55 ` Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 20/23] bpf: enhance BPF_JEQ/BPF_JNE is_branch_taken logic Andrii Nakryiko
2023-10-31 2:20 ` Alexei Starovoitov
2023-10-31 6:16 ` Andrii Nakryiko
2023-10-31 16:36 ` Alexei Starovoitov
2023-10-31 18:04 ` Andrii Nakryiko
2023-10-31 18:06 ` Alexei Starovoitov
2023-10-27 18:13 ` [PATCH v5 bpf-next 21/23] selftests/bpf: adjust OP_EQ/OP_NE handling to use subranges for branch taken Andrii Nakryiko
2023-11-08 18:22 ` Eduard Zingerman
2023-11-08 19:59 ` Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 22/23] selftests/bpf: add range x range test to reg_bounds Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 23/23] selftests/bpf: add iter test requiring range x range logic Andrii Nakryiko
2023-10-30 17:55 ` [PATCH v5 bpf-next 00/23] BPF register bounds logic and testing improvements Alexei Starovoitov
2023-10-31 5:19 ` Andrii Nakryiko
2023-11-01 12:37 ` Paul Chaignon
2023-11-01 17:13 ` Andrii Nakryiko
2023-11-07 6:37 ` Harishankar Vishwanathan
2023-11-07 16:38 ` Paul Chaignon
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