From: Andrii Nakryiko <andrii@kernel.org>
To: <bpf@vger.kernel.org>, <ast@kernel.org>, <daniel@iogearbox.net>,
<martin.lau@kernel.org>
Cc: <andrii@kernel.org>, <kernel-team@meta.com>
Subject: [PATCH v5 bpf-next 19/23] bpf: generalize is_scalar_branch_taken() logic
Date: Fri, 27 Oct 2023 11:13:42 -0700 [thread overview]
Message-ID: <20231027181346.4019398-20-andrii@kernel.org> (raw)
In-Reply-To: <20231027181346.4019398-1-andrii@kernel.org>
Generalize is_branch_taken logic for SCALAR_VALUE register to handle
cases when both registers are not constants. Previously supported
<range> vs <scalar> cases are a natural subset of more generic <range>
vs <range> set of cases.
Generalized logic relies on straightforward segment intersection checks.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
kernel/bpf/verifier.c | 104 ++++++++++++++++++++++++++----------------
1 file changed, 64 insertions(+), 40 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 4c974296127b..f18a8247e5e2 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -14189,82 +14189,105 @@ static int is_scalar_branch_taken(struct bpf_reg_state *reg1, struct bpf_reg_sta
u8 opcode, bool is_jmp32)
{
struct tnum t1 = is_jmp32 ? tnum_subreg(reg1->var_off) : reg1->var_off;
+ struct tnum t2 = is_jmp32 ? tnum_subreg(reg2->var_off) : reg2->var_off;
u64 umin1 = is_jmp32 ? (u64)reg1->u32_min_value : reg1->umin_value;
u64 umax1 = is_jmp32 ? (u64)reg1->u32_max_value : reg1->umax_value;
s64 smin1 = is_jmp32 ? (s64)reg1->s32_min_value : reg1->smin_value;
s64 smax1 = is_jmp32 ? (s64)reg1->s32_max_value : reg1->smax_value;
- u64 val = is_jmp32 ? (u32)tnum_subreg(reg2->var_off).value : reg2->var_off.value;
- s64 sval = is_jmp32 ? (s32)val : (s64)val;
+ u64 umin2 = is_jmp32 ? (u64)reg2->u32_min_value : reg2->umin_value;
+ u64 umax2 = is_jmp32 ? (u64)reg2->u32_max_value : reg2->umax_value;
+ s64 smin2 = is_jmp32 ? (s64)reg2->s32_min_value : reg2->smin_value;
+ s64 smax2 = is_jmp32 ? (s64)reg2->s32_max_value : reg2->smax_value;
switch (opcode) {
case BPF_JEQ:
- if (tnum_is_const(t1))
- return !!tnum_equals_const(t1, val);
- else if (val < umin1 || val > umax1)
+ /* const tnums */
+ if (tnum_is_const(t1) && tnum_is_const(t2))
+ return t1.value == t2.value;
+ /* const ranges */
+ if (umin1 == umax1 && umin2 == umax2)
+ return umin1 == umin2;
+ if (smin1 == smax1 && smin2 == smax2)
+ return umin1 == umin2;
+ /* non-overlapping ranges */
+ if (umin1 > umax2 || umax1 < umin2)
return 0;
- else if (sval < smin1 || sval > smax1)
+ if (smin1 > smax2 || smax1 < smin2)
return 0;
break;
case BPF_JNE:
- if (tnum_is_const(t1))
- return !tnum_equals_const(t1, val);
- else if (val < umin1 || val > umax1)
+ /* const tnums */
+ if (tnum_is_const(t1) && tnum_is_const(t2))
+ return t1.value != t2.value;
+ /* const ranges */
+ if (umin1 == umax1 && umin2 == umax2)
+ return umin1 != umin2;
+ if (smin1 == smax1 && smin2 == smax2)
+ return umin1 != umin2;
+ /* non-overlapping ranges */
+ if (umin1 > umax2 || umax1 < umin2)
return 1;
- else if (sval < smin1 || sval > smax1)
+ if (smin1 > smax2 || smax1 < smin2)
return 1;
break;
case BPF_JSET:
- if ((~t1.mask & t1.value) & val)
+ if (!is_reg_const(reg2, is_jmp32)) {
+ swap(reg1, reg2);
+ swap(t1, t2);
+ }
+ if (!is_reg_const(reg2, is_jmp32))
+ return -1;
+ if ((~t1.mask & t1.value) & t2.value)
return 1;
- if (!((t1.mask | t1.value) & val))
+ if (!((t1.mask | t1.value) & t2.value))
return 0;
break;
case BPF_JGT:
- if (umin1 > val )
+ if (umin1 > umax2)
return 1;
- else if (umax1 <= val)
+ else if (umax1 <= umin2)
return 0;
break;
case BPF_JSGT:
- if (smin1 > sval)
+ if (smin1 > smax2)
return 1;
- else if (smax1 <= sval)
+ else if (smax1 <= smin2)
return 0;
break;
case BPF_JLT:
- if (umax1 < val)
+ if (umax1 < umin2)
return 1;
- else if (umin1 >= val)
+ else if (umin1 >= umax2)
return 0;
break;
case BPF_JSLT:
- if (smax1 < sval)
+ if (smax1 < smin2)
return 1;
- else if (smin1 >= sval)
+ else if (smin1 >= smax2)
return 0;
break;
case BPF_JGE:
- if (umin1 >= val)
+ if (umin1 >= umax2)
return 1;
- else if (umax1 < val)
+ else if (umax1 < umin2)
return 0;
break;
case BPF_JSGE:
- if (smin1 >= sval)
+ if (smin1 >= smax2)
return 1;
- else if (smax1 < sval)
+ else if (smax1 < smin2)
return 0;
break;
case BPF_JLE:
- if (umax1 <= val)
+ if (umax1 <= umin2)
return 1;
- else if (umin1 > val)
+ else if (umin1 > umax2)
return 0;
break;
case BPF_JSLE:
- if (smax1 <= sval)
+ if (smax1 <= smin2)
return 1;
- else if (smin1 > sval)
+ else if (smin1 > smax2)
return 0;
break;
}
@@ -14343,28 +14366,28 @@ 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)
{
- u64 val;
-
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 = reg_const_value(reg2, is_jmp32);
+ if (__is_pointer_value(false, reg1) || __is_pointer_value(false, reg2)) {
+ u64 val;
+
+ /* arrange that reg2 is a scalar, and reg1 is a pointer */
+ if (!is_reg_const(reg2, is_jmp32)) {
+ opcode = flip_opcode(opcode);
+ swap(reg1, reg2);
+ }
+ /* and ensure that reg2 is a constant */
+ if (!is_reg_const(reg2, is_jmp32))
+ return -1;
- if (__is_pointer_value(false, reg1)) {
if (!reg_not_null(reg1))
return -1;
/* If pointer is valid tests against zero will fail so we can
* use this to direct branch taken.
*/
+ val = reg_const_value(reg2, is_jmp32);
if (val != 0)
return -1;
@@ -14378,6 +14401,7 @@ static int is_branch_taken(struct bpf_reg_state *reg1, struct bpf_reg_state *reg
}
}
+ /* now deal with two scalars, but not necessarily constants */
return is_scalar_branch_taken(reg1, reg2, opcode, is_jmp32);
}
--
2.34.1
next prev parent reply other threads:[~2023-10-27 18:16 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
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 ` Andrii Nakryiko [this message]
2023-10-31 2:12 ` [PATCH v5 bpf-next 19/23] bpf: generalize is_scalar_branch_taken() logic 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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