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bpf: Add helper macro bpf_for_each_reg_in_vstate

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For a lot of use cases in future patches, we will want to modify the
state of registers part of some same 'group' (e.g. same ref_obj_id). It
won't just be limited to releasing reference state, but setting a type
flag dynamically based on certain actions, etc.

Hence, we need a way to easily pass a callback to the function that
iterates over all registers in current bpf_verifier_state in all frames
upto (and including) the curframe.

While in C++ we would be able to easily use a lambda to pass state and
the callback together, sadly we aren't using C++ in the kernel. The next
best thing to avoid defining a function for each case seems like
statement expressions in GNU C. The kernel already uses them heavily,
hence they can passed to the macro in the style of a lambda. The
statement expression will then be substituted in the for loop bodies.

Variables __state and __reg are set to current bpf_func_state and reg
for each invocation of the expression inside the passed in verifier
state.

Then, convert mark_ptr_or_null_regs, clear_all_pkt_pointers,
release_reference, find_good_pkt_pointers, find_equal_scalars to
use bpf_for_each_reg_in_vstate.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20220904204145.3089-16-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Kumar Kartikeya Dwivedi 2022-09-04 22:41:28 +02:00 committed by Alexei Starovoitov
parent cc48755808
commit b239da3420
2 changed files with 50 additions and 108 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
include/linux/bpf_verifier.h
View File

@ -348,6 +348,27 @@ struct bpf_verifier_state {
iter < frame->allocated_stack / BPF_REG_SIZE; \
iter++, reg = bpf_get_spilled_reg(iter, frame))
/* Invoke __expr over regsiters in __vst, setting __state and __reg */
#define bpf_for_each_reg_in_vstate(__vst, __state, __reg, __expr) \
({ \
struct bpf_verifier_state *___vstate = __vst; \
int ___i, ___j; \
for (___i = 0; ___i <= ___vstate->curframe; ___i++) { \
struct bpf_reg_state *___regs; \
__state = ___vstate->frame[___i]; \
___regs = __state->regs; \
for (___j = 0; ___j < MAX_BPF_REG; ___j++) { \
__reg = &___regs[___j]; \
(void)(__expr); \
} \
bpf_for_each_spilled_reg(___j, __state, __reg) { \
if (!__reg) \
continue; \
(void)(__expr); \
} \
} \
})
/* linked list of verifier states used to prune search */
struct bpf_verifier_state_list {
struct bpf_verifier_state state;

133
kernel/bpf/verifier.c
View File

@ -6513,31 +6513,15 @@ static int check_func_proto(const struct bpf_func_proto *fn, int func_id)
/* Packet data might have moved, any old PTR_TO_PACKET[_META,_END]
* are now invalid, so turn them into unknown SCALAR_VALUE.
*/
static void __clear_all_pkt_pointers(struct bpf_verifier_env *env,
struct bpf_func_state *state)
{
struct bpf_reg_state *regs = state->regs, *reg;
int i;
for (i = 0; i < MAX_BPF_REG; i++)
if (reg_is_pkt_pointer_any(&regs[i]))
mark_reg_unknown(env, regs, i);
bpf_for_each_spilled_reg(i, state, reg) {
if (!reg)
continue;
if (reg_is_pkt_pointer_any(reg))
__mark_reg_unknown(env, reg);
}
}
static void clear_all_pkt_pointers(struct bpf_verifier_env *env)
{
struct bpf_verifier_state *vstate = env->cur_state;
int i;
struct bpf_func_state *state;
struct bpf_reg_state *reg;
for (i = 0; i <= vstate->curframe; i++)
__clear_all_pkt_pointers(env, vstate->frame[i]);
bpf_for_each_reg_in_vstate(env->cur_state, state, reg, ({
if (reg_is_pkt_pointer_any(reg))
__mark_reg_unknown(env, reg);
}));
}
enum {
@ -6566,41 +6550,24 @@ static void mark_pkt_end(struct bpf_verifier_state *vstate, int regn, bool range
reg->range = AT_PKT_END;
}
static void release_reg_references(struct bpf_verifier_env *env,
struct bpf_func_state *state,
int ref_obj_id)
{
struct bpf_reg_state *regs = state->regs, *reg;
int i;
for (i = 0; i < MAX_BPF_REG; i++)
if (regs[i].ref_obj_id == ref_obj_id)
mark_reg_unknown(env, regs, i);
bpf_for_each_spilled_reg(i, state, reg) {
if (!reg)
continue;
if (reg->ref_obj_id == ref_obj_id)
__mark_reg_unknown(env, reg);
}
}
/* The pointer with the specified id has released its reference to kernel
* resources. Identify all copies of the same pointer and clear the reference.
*/
static int release_reference(struct bpf_verifier_env *env,
int ref_obj_id)
{
struct bpf_verifier_state *vstate = env->cur_state;
struct bpf_func_state *state;
struct bpf_reg_state *reg;
int err;
int i;
err = release_reference_state(cur_func(env), ref_obj_id);
if (err)
return err;
for (i = 0; i <= vstate->curframe; i++)
release_reg_references(env, vstate->frame[i], ref_obj_id);
bpf_for_each_reg_in_vstate(env->cur_state, state, reg, ({
if (reg->ref_obj_id == ref_obj_id)
__mark_reg_unknown(env, reg);
}));
return 0;
}
@ -9335,34 +9302,14 @@ static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn)
return 0;
}
static void __find_good_pkt_pointers(struct bpf_func_state *state,
struct bpf_reg_state *dst_reg,
enum bpf_reg_type type, int new_range)
{
struct bpf_reg_state *reg;
int i;
for (i = 0; i < MAX_BPF_REG; i++) {
reg = &state->regs[i];
if (reg->type == type && reg->id == dst_reg->id)
/* keep the maximum range already checked */
reg->range = max(reg->range, new_range);
}
bpf_for_each_spilled_reg(i, state, reg) {
if (!reg)
continue;
if (reg->type == type && reg->id == dst_reg->id)
reg->range = max(reg->range, new_range);
}
}
static void find_good_pkt_pointers(struct bpf_verifier_state *vstate,
struct bpf_reg_state *dst_reg,
enum bpf_reg_type type,
bool range_right_open)
{
int new_range, i;
struct bpf_func_state *state;
struct bpf_reg_state *reg;
int new_range;
if (dst_reg->off < 0 ||
(dst_reg->off == 0 && range_right_open))
@ -9427,9 +9374,11 @@ static void find_good_pkt_pointers(struct bpf_verifier_state *vstate,
* the range won't allow anything.
* dst_reg->off is known < MAX_PACKET_OFF, therefore it fits in a u16.
*/
for (i = 0; i <= vstate->curframe; i++)
__find_good_pkt_pointers(vstate->frame[i], dst_reg, type,
new_range);
bpf_for_each_reg_in_vstate(vstate, state, reg, ({
if (reg->type == type && reg->id == dst_reg->id)
/* keep the maximum range already checked */
reg->range = max(reg->range, new_range);
}));
}
static int is_branch32_taken(struct bpf_reg_state *reg, u32 val, u8 opcode)
@ -9918,7 +9867,7 @@ static void mark_ptr_or_null_reg(struct bpf_func_state *state,
if (!reg_may_point_to_spin_lock(reg)) {
/* For not-NULL ptr, reg->ref_obj_id will be reset
* in release_reg_references().
* in release_reference().
*
* reg->id is still used by spin_lock ptr. Other
* than spin_lock ptr type, reg->id can be reset.
@ -9928,22 +9877,6 @@ static void mark_ptr_or_null_reg(struct bpf_func_state *state,
}
}
static void __mark_ptr_or_null_regs(struct bpf_func_state *state, u32 id,
bool is_null)
{
struct bpf_reg_state *reg;
int i;
for (i = 0; i < MAX_BPF_REG; i++)
mark_ptr_or_null_reg(state, &state->regs[i], id, is_null);
bpf_for_each_spilled_reg(i, state, reg) {
if (!reg)
continue;
mark_ptr_or_null_reg(state, reg, id, is_null);
}
}
/* The logic is similar to find_good_pkt_pointers(), both could eventually
* be folded together at some point.
*/
@ -9951,10 +9884,9 @@ static void mark_ptr_or_null_regs(struct bpf_verifier_state *vstate, u32 regno,
bool is_null)
{
struct bpf_func_state *state = vstate->frame[vstate->curframe];
struct bpf_reg_state *regs = state->regs;
struct bpf_reg_state *regs = state->regs, *reg;
u32 ref_obj_id = regs[regno].ref_obj_id;
u32 id = regs[regno].id;
int i;
if (ref_obj_id && ref_obj_id == id && is_null)
/* regs[regno] is in the " == NULL" branch.
@ -9963,8 +9895,9 @@ static void mark_ptr_or_null_regs(struct bpf_verifier_state *vstate, u32 regno,
*/
WARN_ON_ONCE(release_reference_state(state, id));
for (i = 0; i <= vstate->curframe; i++)
__mark_ptr_or_null_regs(vstate->frame[i], id, is_null);
bpf_for_each_reg_in_vstate(vstate, state, reg, ({
mark_ptr_or_null_reg(state, reg, id, is_null);
}));
}
static bool try_match_pkt_pointers(const struct bpf_insn *insn,
@ -10077,23 +10010,11 @@ static void find_equal_scalars(struct bpf_verifier_state *vstate,
{
struct bpf_func_state *state;
struct bpf_reg_state *reg;
int i, j;
for (i = 0; i <= vstate->curframe; i++) {
state = vstate->frame[i];
for (j = 0; j < MAX_BPF_REG; j++) {
reg = &state->regs[j];
bpf_for_each_reg_in_vstate(vstate, state, reg, ({
if (reg->type == SCALAR_VALUE && reg->id == known_reg->id)
*reg = *known_reg;
}
bpf_for_each_spilled_reg(j, state, reg) {
if (!reg)
continue;
if (reg->type == SCALAR_VALUE && reg->id == known_reg->id)
*reg = *known_reg;
}
}
}));
}
static int check_cond_jmp_op(struct bpf_verifier_env *env,