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bpf: Introduce bpf_per_cpu_ptr()

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Add bpf_per_cpu_ptr() to help bpf programs access percpu vars.
bpf_per_cpu_ptr() has the same semantic as per_cpu_ptr() in the kernel
except that it may return NULL. This happens when the cpu parameter is
out of range. So the caller must check the returned value.

Signed-off-by: Hao Luo <haoluo@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200929235049.2533242-5-haoluo@google.com
This commit is contained in:
Hao Luo
2020-09-29 16:50:47 -07:00
committed by Alexei Starovoitov
parent 2c2f6abeff
commit eaa6bcb71e
8 changed files with 132 additions and 13 deletions
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64
kernel/bpf/verifier.c
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@@ -238,6 +238,8 @@ struct bpf_call_arg_meta {
u64 msize_max_value;
int ref_obj_id;
int func_id;
u32 btf_id;
u32 ret_btf_id;
};
struct btf *btf_vmlinux;
@@ -517,6 +519,7 @@ static const char * const reg_type_str[] = {
[PTR_TO_XDP_SOCK] = "xdp_sock",
[PTR_TO_BTF_ID] = "ptr_",
[PTR_TO_BTF_ID_OR_NULL] = "ptr_or_null_",
[PTR_TO_PERCPU_BTF_ID] = "percpu_ptr_",
[PTR_TO_MEM] = "mem",
[PTR_TO_MEM_OR_NULL] = "mem_or_null",
[PTR_TO_RDONLY_BUF] = "rdonly_buf",
@@ -583,7 +586,9 @@ static void print_verifier_state(struct bpf_verifier_env *env,
/* reg->off should be 0 for SCALAR_VALUE */
verbose(env, "%lld", reg->var_off.value + reg->off);
} else {
if (t == PTR_TO_BTF_ID || t == PTR_TO_BTF_ID_OR_NULL)
if (t == PTR_TO_BTF_ID ||
t == PTR_TO_BTF_ID_OR_NULL ||
t == PTR_TO_PERCPU_BTF_ID)
verbose(env, "%s", kernel_type_name(reg->btf_id));
verbose(env, "(id=%d", reg->id);
if (reg_type_may_be_refcounted_or_null(t))
@@ -2204,6 +2209,7 @@ static bool is_spillable_regtype(enum bpf_reg_type type)
case PTR_TO_RDONLY_BUF_OR_NULL:
case PTR_TO_RDWR_BUF:
case PTR_TO_RDWR_BUF_OR_NULL:
case PTR_TO_PERCPU_BTF_ID:
return true;
default:
return false;
@@ -4017,6 +4023,7 @@ static const struct bpf_reg_types alloc_mem_types = { .types = { PTR_TO_MEM } };
static const struct bpf_reg_types const_map_ptr_types = { .types = { CONST_PTR_TO_MAP } };
static const struct bpf_reg_types btf_ptr_types = { .types = { PTR_TO_BTF_ID } };
static const struct bpf_reg_types spin_lock_types = { .types = { PTR_TO_MAP_VALUE } };
static const struct bpf_reg_types percpu_btf_ptr_types = { .types = { PTR_TO_PERCPU_BTF_ID } };
static const struct bpf_reg_types *compatible_reg_types[__BPF_ARG_TYPE_MAX] = {
[ARG_PTR_TO_MAP_KEY] = &map_key_value_types,
@@ -4042,6 +4049,7 @@ static const struct bpf_reg_types *compatible_reg_types[__BPF_ARG_TYPE_MAX] = {
[ARG_PTR_TO_ALLOC_MEM_OR_NULL] = &alloc_mem_types,
[ARG_PTR_TO_INT] = &int_ptr_types,
[ARG_PTR_TO_LONG] = &int_ptr_types,
[ARG_PTR_TO_PERCPU_BTF_ID] = &percpu_btf_ptr_types,
};
static int check_reg_type(struct bpf_verifier_env *env, u32 regno,
@@ -4205,6 +4213,12 @@ skip_type_check:
err = check_helper_mem_access(env, regno,
meta->map_ptr->value_size, false,
meta);
} else if (arg_type == ARG_PTR_TO_PERCPU_BTF_ID) {
if (!reg->btf_id) {
verbose(env, "Helper has invalid btf_id in R%d\n", regno);
return -EACCES;
}
meta->ret_btf_id = reg->btf_id;
} else if (arg_type == ARG_PTR_TO_SPIN_LOCK) {
if (meta->func_id == BPF_FUNC_spin_lock) {
if (process_spin_lock(env, regno, true))
@@ -5114,6 +5128,30 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn
regs[BPF_REG_0].type = PTR_TO_MEM_OR_NULL;
regs[BPF_REG_0].id = ++env->id_gen;
regs[BPF_REG_0].mem_size = meta.mem_size;
} else if (fn->ret_type == RET_PTR_TO_MEM_OR_BTF_ID_OR_NULL) {
const struct btf_type *t;
mark_reg_known_zero(env, regs, BPF_REG_0);
t = btf_type_skip_modifiers(btf_vmlinux, meta.ret_btf_id, NULL);
if (!btf_type_is_struct(t)) {
u32 tsize;
const struct btf_type *ret;
const char *tname;
/* resolve the type size of ksym. */
ret = btf_resolve_size(btf_vmlinux, t, &tsize);
if (IS_ERR(ret)) {
tname = btf_name_by_offset(btf_vmlinux, t->name_off);
verbose(env, "unable to resolve the size of type '%s': %ld\n",
tname, PTR_ERR(ret));
return -EINVAL;
}
regs[BPF_REG_0].type = PTR_TO_MEM_OR_NULL;
regs[BPF_REG_0].mem_size = tsize;
} else {
regs[BPF_REG_0].type = PTR_TO_BTF_ID_OR_NULL;
regs[BPF_REG_0].btf_id = meta.ret_btf_id;
}
} else if (fn->ret_type == RET_PTR_TO_BTF_ID_OR_NULL) {
int ret_btf_id;
@@ -7523,6 +7561,7 @@ static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn)
dst_reg->mem_size = aux->btf_var.mem_size;
break;
case PTR_TO_BTF_ID:
case PTR_TO_PERCPU_BTF_ID:
dst_reg->btf_id = aux->btf_var.btf_id;
break;
default:
@@ -9449,10 +9488,14 @@ static int check_pseudo_btf_id(struct bpf_verifier_env *env,
struct bpf_insn *insn,
struct bpf_insn_aux_data *aux)
{
u32 type, id = insn->imm;
u32 datasec_id, type, id = insn->imm;
const struct btf_var_secinfo *vsi;
const struct btf_type *datasec;
const struct btf_type *t;
const char *sym_name;
bool percpu = false;
u64 addr;
int i;
if (!btf_vmlinux) {
verbose(env, "kernel is missing BTF, make sure CONFIG_DEBUG_INFO_BTF=y is specified in Kconfig.\n");
@@ -9484,12 +9527,27 @@ static int check_pseudo_btf_id(struct bpf_verifier_env *env,
return -ENOENT;
}
datasec_id = btf_find_by_name_kind(btf_vmlinux, ".data..percpu",
BTF_KIND_DATASEC);
if (datasec_id > 0) {
datasec = btf_type_by_id(btf_vmlinux, datasec_id);
for_each_vsi(i, datasec, vsi) {
if (vsi->type == id) {
percpu = true;
break;
}
}
}
insn[0].imm = (u32)addr;
insn[1].imm = addr >> 32;
type = t->type;
t = btf_type_skip_modifiers(btf_vmlinux, type, NULL);
if (!btf_type_is_struct(t)) {
if (percpu) {
aux->btf_var.reg_type = PTR_TO_PERCPU_BTF_ID;
aux->btf_var.btf_id = type;
} else if (!btf_type_is_struct(t)) {
const struct btf_type *ret;
const char *tname;
u32 tsize;