From: Lorenz Bauer lmb@cloudflare.com
commit c9e73e3d2b1eb1ea7ff068e05007eec3bd8ef1c9 upstream.
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 [OP: adjusted context for 4.19] Signed-off-by: Ovidiu Panait ovidiu.panait@windriver.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/linux/bpf_verifier.h | 8 ++++++++ kernel/bpf/verifier.c | 42 +++++++++++++----------------------------- 2 files changed, 21 insertions(+), 29 deletions(-)
--- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -127,6 +127,13 @@ struct bpf_func_state { struct bpf_stack_state *stack; };
+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 */ @@ -213,6 +220,7 @@ struct bpf_verifier_env { struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */ 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]; u32 subprog_cnt; };
--- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4783,13 +4783,6 @@ static bool range_within(struct bpf_reg_ old->smax_value >= cur->smax_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. @@ -4800,11 +4793,11 @@ 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; @@ -4821,7 +4814,7 @@ static bool check_ids(u32 old_id, u32 cu
/* 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;
@@ -4925,7 +4918,7 @@ static bool regsafe(struct bpf_reg_state
static bool stacksafe(struct bpf_func_state *old, struct bpf_func_state *cur, - struct idpair *idmap) + struct bpf_id_pair *idmap) { int i, spi;
@@ -5011,29 +5004,20 @@ static bool stacksafe(struct bpf_func_st * 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) - return false; + 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;
- for (i = 0; i < MAX_BPF_REG; i++) { - if (!regsafe(&old->regs[i], &cur->regs[i], idmap)) - goto out_free; - } + if (!stacksafe(old, cur, env->idmap_scratch)) + return false;
- if (!stacksafe(old, cur, idmap)) - goto out_free; - ret = true; -out_free: - kfree(idmap); - return ret; + return true; }
static bool states_equal(struct bpf_verifier_env *env, @@ -5057,7 +5041,7 @@ static bool states_equal(struct bpf_veri 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;