[PATCH v5 bpf-next 15/23] bpf: unify 32-bit and 64-bit is_branch_taken logic

Andrii Nakryiko
2023-10-27T18:17:00Z

Combine 32-bit and 64-bit is_branch_taken logic for SCALAR_VALUE
registers. It makes it easier to see parallels between two domains
(32-bit and 64-bit), and makes subsequent refactoring more
straightforward.

No functional changes.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
kernel/bpf/verifier.c | 154 ++++++++++--------------------------------
1 file changed, 36 insertions(+), 118 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index fedd6d0e76e5..b911d1111fad 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -14185,166 +14185,86 @@ static u64 reg_const_value(struct bpf_reg_state *reg, bool subreg32)
/*
* <reg1> <op> <reg2>, currently assuming reg2 is a constant
*/
-static int is_branch32_taken(struct bpf_reg_state *reg1, struct bpf_reg_state *reg2, u8 opcode)
+static int is_scalar_branch_taken(struct bpf_reg_state *reg1, struct bpf_reg_state *reg2,
+ u8 opcode, bool is_jmp32)
{
- struct tnum subreg = tnum_subreg(reg1->var_off);
- u32 val = (u32)tnum_subreg(reg2->var_off).value;
- s32 sval = (s32)val;
+ struct tnum t1 = is_jmp32 ? tnum_subreg(reg1->var_off) : reg1->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;

switch (opcode) {
case BPF_JEQ:
- if (tnum_is_const(subreg))
- return !!tnum_equals_const(subreg, val);
- else if (val < reg1->u32_min_value || val > reg1->u32_max_value)
+ if (tnum_is_const(t1))
+ return !!tnum_equals_const(t1, val);
+ else if (val < umin1 || val > umax1)
return 0;
- else if (sval < reg1->s32_min_value || sval > reg1->s32_max_value)
+ else if (sval < smin1 || sval > smax1)
return 0;
break;
case BPF_JNE:
- if (tnum_is_const(subreg))
- return !tnum_equals_const(subreg, val);
- else if (val < reg1->u32_min_value || val > reg1->u32_max_value)
+ if (tnum_is_const(t1))
+ return !tnum_equals_const(t1, val);
+ else if (val < umin1 || val > umax1)
return 1;
- else if (sval < reg1->s32_min_value || sval > reg1->s32_max_value)
+ else if (sval < smin1 || sval > smax1)
return 1;
break;
case BPF_JSET:
- if ((~subreg.mask & subreg.value) & val)
+ if ((~t1.mask & t1.value) & val)
return 1;
- if (!((subreg.mask | subreg.value) & val))
+ if (!((t1.mask | t1.value) & val))
return 0;
break;
case BPF_JGT:
- if (reg1->u32_min_value > val)
+ if (umin1 > val )
return 1;
- else if (reg1->u32_max_value <= val)
+ else if (umax1 <= val)
return 0;
break;
case BPF_JSGT:
- if (reg1->s32_min_value > sval)
+ if (smin1 > sval)
return 1;
- else if (reg1->s32_max_value <= sval)
+ else if (smax1 <= sval)
return 0;
break;
case BPF_JLT:
- if (reg1->u32_max_value < val)
+ if (umax1 < val)
return 1;
- else if (reg1->u32_min_value >= val)
+ else if (umin1 >= val)
return 0;
break;
case BPF_JSLT:
- if (reg1->s32_max_value < sval)
+ if (smax1 < sval)
return 1;
- else if (reg1->s32_min_value >= sval)
+ else if (smin1 >= sval)
return 0;
break;
case BPF_JGE:
- if (reg1->u32_min_value >= val)
+ if (umin1 >= val)
return 1;
- else if (reg1->u32_max_value < val)
+ else if (umax1 < val)
return 0;
break;
case BPF_JSGE:
- if (reg1->s32_min_value >= sval)
+ if (smin1 >= sval)
return 1;
- else if (reg1->s32_max_value < sval)
+ else if (smax1 < sval)
return 0;
break;
case BPF_JLE:
- if (reg1->u32_max_value <= val)
+ if (umax1 <= val)
return 1;
- else if (reg1->u32_min_value > val)
+ else if (umin1 > val)
return 0;
break;
case BPF_JSLE:
- if (reg1->s32_max_value <= sval)
+ if (smax1 <= sval)
return 1;
- else if (reg1->s32_min_value > sval)
- return 0;
- break;
- }
-
- return -1;
-}
-
-
-/*
- * <reg1> <op> <reg2>, currently assuming reg2 is a constant
- */
-static int is_branch64_taken(struct bpf_reg_state *reg1, struct bpf_reg_state *reg2, u8 opcode)
-{
- u64 val = reg2->var_off.value;
- s64 sval = (s64)val;
-
- switch (opcode) {
- case BPF_JEQ:
- if (tnum_is_const(reg1->var_off))
- return !!tnum_equals_const(reg1->var_off, val);
- else if (val < reg1->umin_value || val > reg1->umax_value)
- return 0;
- else if (sval < reg1->smin_value || sval > reg1->smax_value)
- return 0;
- break;
- case BPF_JNE:
- if (tnum_is_const(reg1->var_off))
- return !tnum_equals_const(reg1->var_off, val);
- else if (val < reg1->umin_value || val > reg1->umax_value)
- return 1;
- else if (sval < reg1->smin_value || sval > reg1->smax_value)
- return 1;
- break;
- case BPF_JSET:
- if ((~reg1->var_off.mask & reg1->var_off.value) & val)
- return 1;
- if (!((reg1->var_off.mask | reg1->var_off.value) & val))
- return 0;
- break;
- case BPF_JGT:
- if (reg1->umin_value > val)
- return 1;
- else if (reg1->umax_value <= val)
- return 0;
- break;
- case BPF_JSGT:
- if (reg1->smin_value > sval)
- return 1;
- else if (reg1->smax_value <= sval)
- return 0;
- break;
- case BPF_JLT:
- if (reg1->umax_value < val)
- return 1;
- else if (reg1->umin_value >= val)
- return 0;
- break;
- case BPF_JSLT:
- if (reg1->smax_value < sval)
- return 1;
- else if (reg1->smin_value >= sval)
- return 0;
- break;
- case BPF_JGE:
- if (reg1->umin_value >= val)
- return 1;
- else if (reg1->umax_value < val)
- return 0;
- break;
- case BPF_JSGE:
- if (reg1->smin_value >= sval)
- return 1;
- else if (reg1->smax_value < sval)
- return 0;
- break;
- case BPF_JLE:
- if (reg1->umax_value <= val)
- return 1;
- else if (reg1->umin_value > val)
- return 0;
- break;
- case BPF_JSLE:
- if (reg1->smax_value <= sval)
- return 1;
- else if (reg1->smin_value > sval)
+ else if (smin1 > sval)
return 0;
break;
}
@@ -14458,9 +14378,7 @@ static int is_branch_taken(struct bpf_reg_state *reg1, struct bpf_reg_state *reg
}
}

- if (is_jmp32)
- return is_branch32_taken(reg1, reg2, opcode);
- return is_branch64_taken(reg1, reg2, opcode);
+ return is_scalar_branch_taken(reg1, reg2, opcode, is_jmp32);
}

/* Adjusts the register min/max values in the case that the dst_reg is the
--
2.34.1