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bpf: Simplify mark_stack_slot_obj_read() and callers

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Rename mark_stack_slot_obj_read() as mark_stack_slots_scratched() and
directly call it from functions processing iter, dynptr and irq_flag.
Commit 6762e3a0bc ("bpf: simplify liveness to use (callsite, depth)
keyed func_instances") has removed the dynamic liveness component in
mark_stack_slot_obj_read(). The function effectively only marks stack
slots as scratched and always succeed. Therefore, return void, drop the
unused bpf_reg_state argument and rename it to
mark_stack_slots_scratched() to reflect what it does now.

In addition, to prepare for unifying dynptr handling, dynptr_get_spi()
will be moved out of mark_dynptr_read(). As mark_dynptr_read() would join
mark_iter_read() as a thin wrapper of mark_stack_slots_scratched(), just
open code these helpers.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Amery Hung <ameryhung@gmail.com>
Link: https://lore.kernel.org/r/20260529014936.2811085-2-ameryhung@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Amery Hung 2026-05-28 18:49:24 -07:00 committed by Alexei Starovoitov
parent 868d43cf8f
commit bab08d1f70
1 changed files with 21 additions and 48 deletions
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69
kernel/bpf/verifier.c
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@ -3006,50 +3006,13 @@ static int sort_subprogs_topo(struct bpf_verifier_env *env)
return ret;
}
static int mark_stack_slot_obj_read(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
int spi, int nr_slots)
static void mark_stack_slots_scratched(struct bpf_verifier_env *env,
int spi, int nr_slots)
{
int i;
for (i = 0; i < nr_slots; i++)
mark_stack_slot_scratched(env, spi - i);
return 0;
}
static int mark_dynptr_read(struct bpf_verifier_env *env, struct bpf_reg_state *reg)
{
int spi;
/* For CONST_PTR_TO_DYNPTR, it must have already been done by
* check_reg_arg in check_helper_call and mark_btf_func_reg_size in
* check_kfunc_call.
*/
if (reg->type == CONST_PTR_TO_DYNPTR)
return 0;
spi = dynptr_get_spi(env, reg);
if (spi < 0)
return spi;
/* Caller ensures dynptr is valid and initialized, which means spi is in
* bounds and spi is the first dynptr slot. Simply mark stack slot as
* read.
*/
return mark_stack_slot_obj_read(env, reg, spi, BPF_DYNPTR_NR_SLOTS);
}
static int mark_iter_read(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
int spi, int nr_slots)
{
return mark_stack_slot_obj_read(env, reg, spi, nr_slots);
}
static int mark_irq_flag_read(struct bpf_verifier_env *env, struct bpf_reg_state *reg)
{
int spi;
spi = irq_flag_get_spi(env, reg);
if (spi < 0)
return spi;
return mark_stack_slot_obj_read(env, reg, spi, 1);
}
/* This function is supposed to be used by the following 32-bit optimization
@ -7261,7 +7224,7 @@ static int process_kptr_func(struct bpf_verifier_env *env, int regno,
static int process_dynptr_func(struct bpf_verifier_env *env, struct bpf_reg_state *reg, argno_t argno, int insn_idx,
enum bpf_arg_type arg_type, int clone_ref_obj_id)
{
int err;
int spi, err = 0;
if (reg->type != PTR_TO_STACK && reg->type != CONST_PTR_TO_DYNPTR) {
verbose(env,
@ -7323,7 +7286,17 @@ static int process_dynptr_func(struct bpf_verifier_env *env, struct bpf_reg_stat
return -EINVAL;
}
err = mark_dynptr_read(env, reg);
if (reg->type != CONST_PTR_TO_DYNPTR) {
spi = dynptr_get_spi(env, reg);
if (spi < 0)
return spi;
/*
* For CONST_PTR_TO_DYNPTR, reg is already scratched by check_reg_arg
* in check_helper_call and mark_btf_func_reg_size in check_kfunc_call.
*/
mark_stack_slots_scratched(env, spi, BPF_DYNPTR_NR_SLOTS);
}
}
return err;
}
@ -7433,9 +7406,7 @@ static int process_iter_arg(struct bpf_verifier_env *env, struct bpf_reg_state *
if (spi < 0)
return spi;
err = mark_iter_read(env, reg, spi, nr_slots);
if (err)
return err;
mark_stack_slots_scratched(env, spi, nr_slots);
/* remember meta->iter info for process_iter_next_call() */
meta->iter.spi = spi;
@ -11399,7 +11370,7 @@ static int process_kf_arg_ptr_to_btf_id(struct bpf_verifier_env *env,
static int process_irq_flag(struct bpf_verifier_env *env, struct bpf_reg_state *reg, argno_t argno,
struct bpf_kfunc_call_arg_meta *meta)
{
int err, kfunc_class = IRQ_NATIVE_KFUNC;
int err, spi, kfunc_class = IRQ_NATIVE_KFUNC;
bool irq_save;
if (meta->func_id == special_kfunc_list[KF_bpf_local_irq_save] ||
@ -11440,9 +11411,11 @@ static int process_irq_flag(struct bpf_verifier_env *env, struct bpf_reg_state *
return err;
}
err = mark_irq_flag_read(env, reg);
if (err)
return err;
spi = irq_flag_get_spi(env, reg);
if (spi < 0)
return spi;
mark_stack_slots_scratched(env, spi, 1);
err = unmark_stack_slot_irq_flag(env, reg, kfunc_class);
if (err)