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bpf: Add bpf_spill_size()

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A utility function counting the number of STACK_SPILL slots in a
bpf_stat_state instance. For use by SCEV widening logic.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://patch.msgid.link/20261009-scev-minimal-rebase-v3-30-bcba9bc53ac9@gmail.com
This commit is contained in:
Eduard Zingerman 2026-10-09 03:47:48 -07:00 committed by Alexei Starovoitov
parent 4c3a56544b
commit 1291ad5906
No known key found for this signature in database
2 changed files with 10 additions and 4 deletions
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9
include/linux/bpf_verifier.h
View File

@ -1420,6 +1420,15 @@ static inline bool bpf_is_spilled_reg(const struct bpf_stack_state *stack)
return stack->slot_type[BPF_REG_SIZE - 1] == STACK_SPILL;
}
static inline int bpf_spill_size(const struct bpf_stack_state *stack)
{
int i, spill_size = 0;
for (i = BPF_REG_SIZE - 1; i >= 0 && stack->slot_type[i] == STACK_SPILL; i--)
spill_size++;
return spill_size;
}
static inline bool bpf_is_spilled_scalar_reg(const struct bpf_stack_state *stack)
{
return bpf_is_spilled_reg(stack) && stack->spilled_ptr.type == SCALAR_VALUE;

5
kernel/bpf/verifier.c
View File

@ -4247,10 +4247,7 @@ static int check_stack_read_fixed_off(struct bpf_verifier_env *env,
bpf_diag_mod_begin(env, &state->regs[dst_regno], reg, BPF_DIAG_MOD_WRITE);
if (bpf_is_spilled_reg(ss)) {
u8 spill_size = 1;
for (i = BPF_REG_SIZE - 1; i > 0 && stype[i - 1] == STACK_SPILL; i--)
spill_size++;
u8 spill_size = bpf_spill_size(ss);
if (size != BPF_REG_SIZE || spill_size != BPF_REG_SIZE) {
if (reg->type != SCALAR_VALUE) {