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bpf: move is_branch_taken() down

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Move is_branch_taken() slightly down. In subsequent patched we'll need
both flip_opcode() and is_pkt_ptr_branch_taken() for is_branch_taken(),
but instead of sprinkling forward declarations around, it makes more
sense to move is_branch_taken() lower below is_pkt_ptr_branch_taken(),
and also keep it closer to very tightly related reg_set_min_max(), as
they are two critical parts of the same SCALAR range tracking logic.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231102033759.2541186-14-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrii Nakryiko 2023-11-01 20:37:55 -07:00 committed by Alexei Starovoitov
parent c31534267c
commit c697289efe
1 changed files with 42 additions and 42 deletions
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84
kernel/bpf/verifier.c
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@ -14358,48 +14358,6 @@ static int is_branch64_taken(struct bpf_reg_state *reg1, struct bpf_reg_state *r
return -1;
}
/* compute branch direction of the expression "if (<reg1> opcode <reg2>) goto target;"
* and return:
* 1 - branch will be taken and "goto target" will be executed
* 0 - branch will not be taken and fall-through to next insn
* -1 - unknown. Example: "if (reg1 < 5)" is unknown when register value
* range [0,10]
*/
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))
return -1;
val = reg2_tnum.value;
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.
*/
if (val != 0)
return -1;
switch (opcode) {
case BPF_JEQ:
return 0;
case BPF_JNE:
return 1;
default:
return -1;
}
}
if (is_jmp32)
return is_branch32_taken(reg1, reg2, opcode);
return is_branch64_taken(reg1, reg2, opcode);
}
static int flip_opcode(u32 opcode)
{
/* How can we transform "a <op> b" into "b <op> a"? */
@ -14461,6 +14419,48 @@ static int is_pkt_ptr_branch_taken(struct bpf_reg_state *dst_reg,
return -1;
}
/* compute branch direction of the expression "if (<reg1> opcode <reg2>) goto target;"
* and return:
* 1 - branch will be taken and "goto target" will be executed
* 0 - branch will not be taken and fall-through to next insn
* -1 - unknown. Example: "if (reg1 < 5)" is unknown when register value
* range [0,10]
*/
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))
return -1;
val = reg2_tnum.value;
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.
*/
if (val != 0)
return -1;
switch (opcode) {
case BPF_JEQ:
return 0;
case BPF_JNE:
return 1;
default:
return -1;
}
}
if (is_jmp32)
return is_branch32_taken(reg1, reg2, opcode);
return is_branch64_taken(reg1, reg2, opcode);
}
/* Adjusts the register min/max values in the case that the dst_reg is the
* variable register that we are working on, and src_reg is a constant or we're
* simply doing a BPF_K check.