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bpf: Factor out check_atomic_rmw()

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Currently, check_atomic() only handles atomic read-modify-write (RMW)
instructions.  Since we are planning to introduce other types of atomic
instructions (i.e., atomic load/store), extract the existing RMW
handling logic into its own function named check_atomic_rmw().

Remove the @insn_idx parameter as it is not really necessary.  Use
'env->insn_idx' instead, as in other places in verifier.c.

Signed-off-by: Peilin Ye <yepeilin@google.com>
Link: https://lore.kernel.org/r/6323ac8e73a10a1c8ee547c77ed68cf8eb6b90e1.1740978603.git.yepeilin@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Peilin Ye 2025-03-03 05:37:19 +00:00 committed by Alexei Starovoitov
parent 66faaea94e
commit 2626ffe9f3
1 changed files with 29 additions and 24 deletions
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53
kernel/bpf/verifier.c
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@ -7616,28 +7616,12 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
static int save_aux_ptr_type(struct bpf_verifier_env *env, enum bpf_reg_type type,
bool allow_trust_mismatch);
static int check_atomic(struct bpf_verifier_env *env, int insn_idx, struct bpf_insn *insn)
static int check_atomic_rmw(struct bpf_verifier_env *env,
struct bpf_insn *insn)
{
int load_reg;
int err;
switch (insn->imm) {
case BPF_ADD:
case BPF_ADD | BPF_FETCH:
case BPF_AND:
case BPF_AND | BPF_FETCH:
case BPF_OR:
case BPF_OR | BPF_FETCH:
case BPF_XOR:
case BPF_XOR | BPF_FETCH:
case BPF_XCHG:
case BPF_CMPXCHG:
break;
default:
verbose(env, "BPF_ATOMIC uses invalid atomic opcode %02x\n", insn->imm);
return -EINVAL;
}
if (BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) {
verbose(env, "invalid atomic operand size\n");
return -EINVAL;
@ -7699,12 +7683,12 @@ static int check_atomic(struct bpf_verifier_env *env, int insn_idx, struct bpf_i
/* Check whether we can read the memory, with second call for fetch
* case to simulate the register fill.
*/
err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off,
err = check_mem_access(env, env->insn_idx, insn->dst_reg, insn->off,
BPF_SIZE(insn->code), BPF_READ, -1, true, false);
if (!err && load_reg >= 0)
err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off,
BPF_SIZE(insn->code), BPF_READ, load_reg,
true, false);
err = check_mem_access(env, env->insn_idx, insn->dst_reg,
insn->off, BPF_SIZE(insn->code),
BPF_READ, load_reg, true, false);
if (err)
return err;
@ -7714,13 +7698,34 @@ static int check_atomic(struct bpf_verifier_env *env, int insn_idx, struct bpf_i
return err;
}
/* Check whether we can write into the same memory. */
err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off,
err = check_mem_access(env, env->insn_idx, insn->dst_reg, insn->off,
BPF_SIZE(insn->code), BPF_WRITE, -1, true, false);
if (err)
return err;
return 0;
}
static int check_atomic(struct bpf_verifier_env *env, struct bpf_insn *insn)
{
switch (insn->imm) {
case BPF_ADD:
case BPF_ADD | BPF_FETCH:
case BPF_AND:
case BPF_AND | BPF_FETCH:
case BPF_OR:
case BPF_OR | BPF_FETCH:
case BPF_XOR:
case BPF_XOR | BPF_FETCH:
case BPF_XCHG:
case BPF_CMPXCHG:
return check_atomic_rmw(env, insn);
default:
verbose(env, "BPF_ATOMIC uses invalid atomic opcode %02x\n",
insn->imm);
return -EINVAL;
}
}
/* When register 'regno' is used to read the stack (either directly or through
* a helper function) make sure that it's within stack boundary and, depending
* on the access type and privileges, that all elements of the stack are
@ -19224,7 +19229,7 @@ static int do_check(struct bpf_verifier_env *env)
enum bpf_reg_type dst_reg_type;
if (BPF_MODE(insn->code) == BPF_ATOMIC) {
err = check_atomic(env, env->insn_idx, insn);
err = check_atomic(env, insn);
if (err)
return err;
env->insn_idx++;