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bpf: verifier: Allocate idmap scratch in verifier env

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func_states_equal makes a very short lived allocation for idmap,
probably because it's too large to fit on the stack. However the
function is called quite often, leading to a lot of alloc / free
churn. Replace the temporary allocation with dedicated scratch
space in struct bpf_verifier_env.

Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Edward Cree <ecree.xilinx@gmail.com>
Link: https://lore.kernel.org/bpf/20210429134656.122225-4-lmb@cloudflare.com
This commit is contained in:
Lorenz Bauer 2021-04-29 14:46:56 +01:00 committed by Alexei Starovoitov
parent 06ab6a5055
commit c9e73e3d2b
2 changed files with 23 additions and 31 deletions
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8
include/linux/bpf_verifier.h
View File

@ -215,6 +215,13 @@ struct bpf_idx_pair {
u32 idx;
};
struct bpf_id_pair {
u32 old;
u32 cur;
};
/* Maximum number of register states that can exist at once */
#define BPF_ID_MAP_SIZE (MAX_BPF_REG + MAX_BPF_STACK / BPF_REG_SIZE)
#define MAX_CALL_FRAMES 8
struct bpf_verifier_state {
/* call stack tracking */
@ -418,6 +425,7 @@ struct bpf_verifier_env {
const struct bpf_line_info *prev_linfo;
struct bpf_verifier_log log;
struct bpf_subprog_info subprog_info[BPF_MAX_SUBPROGS + 1];
struct bpf_id_pair idmap_scratch[BPF_ID_MAP_SIZE];
struct {
int *insn_state;
int *insn_stack;

46
kernel/bpf/verifier.c
View File

@ -9748,13 +9748,6 @@ static bool range_within(struct bpf_reg_state *old,
old->s32_max_value >= cur->s32_max_value;
}
/* Maximum number of register states that can exist at once */
#define ID_MAP_SIZE (MAX_BPF_REG + MAX_BPF_STACK / BPF_REG_SIZE)
struct idpair {
u32 old;
u32 cur;
};
/* If in the old state two registers had the same id, then they need to have
* the same id in the new state as well. But that id could be different from
* the old state, so we need to track the mapping from old to new ids.
@ -9765,11 +9758,11 @@ struct idpair {
* So we look through our idmap to see if this old id has been seen before. If
* so, we require the new id to match; otherwise, we add the id pair to the map.
*/
static bool check_ids(u32 old_id, u32 cur_id, struct idpair *idmap)
static bool check_ids(u32 old_id, u32 cur_id, struct bpf_id_pair *idmap)
{
unsigned int i;
for (i = 0; i < ID_MAP_SIZE; i++) {
for (i = 0; i < BPF_ID_MAP_SIZE; i++) {
if (!idmap[i].old) {
/* Reached an empty slot; haven't seen this id before */
idmap[i].old = old_id;
@ -9882,7 +9875,7 @@ next:
/* Returns true if (rold safe implies rcur safe) */
static bool regsafe(struct bpf_reg_state *rold, struct bpf_reg_state *rcur,
struct idpair *idmap)
struct bpf_id_pair *idmap)
{
bool equal;
@ -10000,7 +9993,7 @@ static bool regsafe(struct bpf_reg_state *rold, struct bpf_reg_state *rcur,
static bool stacksafe(struct bpf_func_state *old,
struct bpf_func_state *cur,
struct idpair *idmap)
struct bpf_id_pair *idmap)
{
int i, spi;
@ -10097,32 +10090,23 @@ static bool refsafe(struct bpf_func_state *old, struct bpf_func_state *cur)
* whereas register type in current state is meaningful, it means that
* the current state will reach 'bpf_exit' instruction safely
*/
static bool func_states_equal(struct bpf_func_state *old,
static bool func_states_equal(struct bpf_verifier_env *env, struct bpf_func_state *old,
struct bpf_func_state *cur)
{
struct idpair *idmap;
bool ret = false;
int i;
idmap = kcalloc(ID_MAP_SIZE, sizeof(struct idpair), GFP_KERNEL);
/* If we failed to allocate the idmap, just say it's not safe */
if (!idmap)
memset(env->idmap_scratch, 0, sizeof(env->idmap_scratch));
for (i = 0; i < MAX_BPF_REG; i++)
if (!regsafe(&old->regs[i], &cur->regs[i], env->idmap_scratch))
return false;
if (!stacksafe(old, cur, env->idmap_scratch))
return false;
for (i = 0; i < MAX_BPF_REG; i++) {
if (!regsafe(&old->regs[i], &cur->regs[i], idmap))
goto out_free;
}
if (!stacksafe(old, cur, idmap))
goto out_free;
if (!refsafe(old, cur))
goto out_free;
ret = true;
out_free:
kfree(idmap);
return ret;
return false;
return true;
}
static bool states_equal(struct bpf_verifier_env *env,
@ -10149,7 +10133,7 @@ static bool states_equal(struct bpf_verifier_env *env,
for (i = 0; i <= old->curframe; i++) {
if (old->frame[i]->callsite != cur->frame[i]->callsite)
return false;
if (!func_states_equal(old->frame[i], cur->frame[i]))
if (!func_states_equal(env, old->frame[i], cur->frame[i]))
return false;
}
return true;