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bpf: unify 32-bit and 64-bit is_branch_taken logic
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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.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231102033759.2541186-16-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Andrii Nakryiko authored and Alexei Starovoitov committed Nov 10, 2023
1 parent b74c2a8 commit 4d34588
Showing 1 changed file with 59 additions and 141 deletions.
200 changes: 59 additions & 141 deletions kernel/bpf/verifier.c
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Original file line number Diff line number Diff line change
Expand Up @@ -14204,166 +14204,86 @@ 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 uval = is_jmp32 ? (u32)tnum_subreg(reg2->var_off).value : reg2->var_off.value;
s64 sval = is_jmp32 ? (s32)uval : (s64)uval;

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, uval);
else if (uval < umin1 || uval > 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, uval);
else if (uval < umin1 || uval > 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) & uval)
return 1;
if (!((subreg.mask | subreg.value) & val))
if (!((t1.mask | t1.value) & uval))
return 0;
break;
case BPF_JGT:
if (reg1->u32_min_value > val)
if (umin1 > uval )
return 1;
else if (reg1->u32_max_value <= val)
else if (umax1 <= uval)
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 < uval)
return 1;
else if (reg1->u32_min_value >= val)
else if (umin1 >= uval)
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 >= uval)
return 1;
else if (reg1->u32_max_value < val)
else if (umax1 < uval)
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 <= uval)
return 1;
else if (reg1->u32_min_value > val)
else if (umin1 > uval)
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;
}
Expand Down Expand Up @@ -14477,9 +14397,7 @@ 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
Expand All @@ -14489,15 +14407,15 @@ static int is_branch_taken(struct bpf_reg_state *reg1, struct bpf_reg_state *reg
*/
static void reg_set_min_max(struct bpf_reg_state *true_reg,
struct bpf_reg_state *false_reg,
u64 val, u32 val32,
u64 uval, u32 uval32,
u8 opcode, bool is_jmp32)
{
struct tnum false_32off = tnum_subreg(false_reg->var_off);
struct tnum false_64off = false_reg->var_off;
struct tnum true_32off = tnum_subreg(true_reg->var_off);
struct tnum true_64off = true_reg->var_off;
s64 sval = (s64)val;
s32 sval32 = (s32)val32;
s64 sval = (s64)uval;
s32 sval32 = (s32)uval32;

/* If the dst_reg is a pointer, we can't learn anything about its
* variable offset from the compare (unless src_reg were a pointer into
Expand All @@ -14520,49 +14438,49 @@ static void reg_set_min_max(struct bpf_reg_state *true_reg,
*/
case BPF_JEQ:
if (is_jmp32) {
__mark_reg32_known(true_reg, val32);
__mark_reg32_known(true_reg, uval32);
true_32off = tnum_subreg(true_reg->var_off);
} else {
___mark_reg_known(true_reg, val);
___mark_reg_known(true_reg, uval);
true_64off = true_reg->var_off;
}
break;
case BPF_JNE:
if (is_jmp32) {
__mark_reg32_known(false_reg, val32);
__mark_reg32_known(false_reg, uval32);
false_32off = tnum_subreg(false_reg->var_off);
} else {
___mark_reg_known(false_reg, val);
___mark_reg_known(false_reg, uval);
false_64off = false_reg->var_off;
}
break;
case BPF_JSET:
if (is_jmp32) {
false_32off = tnum_and(false_32off, tnum_const(~val32));
if (is_power_of_2(val32))
false_32off = tnum_and(false_32off, tnum_const(~uval32));
if (is_power_of_2(uval32))
true_32off = tnum_or(true_32off,
tnum_const(val32));
tnum_const(uval32));
} else {
false_64off = tnum_and(false_64off, tnum_const(~val));
if (is_power_of_2(val))
false_64off = tnum_and(false_64off, tnum_const(~uval));
if (is_power_of_2(uval))
true_64off = tnum_or(true_64off,
tnum_const(val));
tnum_const(uval));
}
break;
case BPF_JGE:
case BPF_JGT:
{
if (is_jmp32) {
u32 false_umax = opcode == BPF_JGT ? val32 : val32 - 1;
u32 true_umin = opcode == BPF_JGT ? val32 + 1 : val32;
u32 false_umax = opcode == BPF_JGT ? uval32 : uval32 - 1;
u32 true_umin = opcode == BPF_JGT ? uval32 + 1 : uval32;

false_reg->u32_max_value = min(false_reg->u32_max_value,
false_umax);
true_reg->u32_min_value = max(true_reg->u32_min_value,
true_umin);
} else {
u64 false_umax = opcode == BPF_JGT ? val : val - 1;
u64 true_umin = opcode == BPF_JGT ? val + 1 : val;
u64 false_umax = opcode == BPF_JGT ? uval : uval - 1;
u64 true_umin = opcode == BPF_JGT ? uval + 1 : uval;

false_reg->umax_value = min(false_reg->umax_value, false_umax);
true_reg->umin_value = max(true_reg->umin_value, true_umin);
Expand Down Expand Up @@ -14591,16 +14509,16 @@ static void reg_set_min_max(struct bpf_reg_state *true_reg,
case BPF_JLT:
{
if (is_jmp32) {
u32 false_umin = opcode == BPF_JLT ? val32 : val32 + 1;
u32 true_umax = opcode == BPF_JLT ? val32 - 1 : val32;
u32 false_umin = opcode == BPF_JLT ? uval32 : uval32 + 1;
u32 true_umax = opcode == BPF_JLT ? uval32 - 1 : uval32;

false_reg->u32_min_value = max(false_reg->u32_min_value,
false_umin);
true_reg->u32_max_value = min(true_reg->u32_max_value,
true_umax);
} else {
u64 false_umin = opcode == BPF_JLT ? val : val + 1;
u64 true_umax = opcode == BPF_JLT ? val - 1 : val;
u64 false_umin = opcode == BPF_JLT ? uval : uval + 1;
u64 true_umax = opcode == BPF_JLT ? uval - 1 : uval;

false_reg->umin_value = max(false_reg->umin_value, false_umin);
true_reg->umax_value = min(true_reg->umax_value, true_umax);
Expand Down Expand Up @@ -14649,15 +14567,15 @@ static void reg_set_min_max(struct bpf_reg_state *true_reg,
*/
static void reg_set_min_max_inv(struct bpf_reg_state *true_reg,
struct bpf_reg_state *false_reg,
u64 val, u32 val32,
u64 uval, u32 uval32,
u8 opcode, bool is_jmp32)
{
opcode = flip_opcode(opcode);
/* This uses zero as "not present in table"; luckily the zero opcode,
* BPF_JA, can't get here.
*/
if (opcode)
reg_set_min_max(true_reg, false_reg, val, val32, opcode, is_jmp32);
reg_set_min_max(true_reg, false_reg, uval, uval32, opcode, is_jmp32);
}

/* Regs are known to be equal, so intersect their min/max/var_off */
Expand Down

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