[RFC PATCH 4/6] bpf: Add a bpf program function argument constraint for PMU map

kaixu xia
2015-07-17T10:45:24Z

For the pmu that contains the pointer to struct perf_event,
add the corresponding bpf program function argument constraint
'ARG_PTR_TO_MAP_PERF_EVENT_VALUE'.

Signed-off-by: kaixu xia <xiakaixu@huawei.com>
---
include/linux/bpf.h | 1 +
kernel/bpf/verifier.c | 9 +++++++++
2 files changed, 10 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index f593199..31a93fc 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -56,6 +56,7 @@ enum bpf_arg_type {
ARG_CONST_MAP_PTR, /* const argument used as pointer to bpf_map */
ARG_PTR_TO_MAP_KEY, /* pointer to stack used as map key */
ARG_PTR_TO_MAP_VALUE, /* pointer to stack used as map value */
+ ARG_PTR_TO_MAP_PERF_EVENT_VALUE, /* pointer to stack used as map pmu value */

/* the following constraints used to prototype bpf_memcmp() and other
* functions that access data on eBPF program stack
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 039d866..a04223b 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -132,6 +132,7 @@ enum bpf_reg_type {
PTR_TO_CTX, /* reg points to bpf_context */
CONST_PTR_TO_MAP, /* reg points to struct bpf_map */
PTR_TO_MAP_VALUE, /* reg points to map element value */
+ PTR_TO_PTR_PERF_EVENT, /* reg points to map element pmu value */
PTR_TO_MAP_VALUE_OR_NULL,/* points to map elem value or NULL */
FRAME_PTR, /* reg == frame_pointer */
PTR_TO_STACK, /* reg == frame_pointer + imm */
@@ -769,6 +770,8 @@ static int check_func_arg(struct verifier_env *env, u32 regno,
if (arg_type == ARG_PTR_TO_STACK || arg_type == ARG_PTR_TO_MAP_KEY ||
arg_type == ARG_PTR_TO_MAP_VALUE) {
expected_type = PTR_TO_STACK;
+ } else if (arg_type == ARG_PTR_TO_MAP_PERF_EVENT_VALUE) {
+ expected_type = PTR_TO_PTR_PERF_EVENT;
} else if (arg_type == ARG_CONST_STACK_SIZE) {
expected_type = CONST_IMM;
} else if (arg_type == ARG_CONST_MAP_PTR) {
@@ -817,6 +820,9 @@ static int check_func_arg(struct verifier_env *env, u32 regno,
}
err = check_stack_boundary(env, regno, (*mapp)->value_size);

+ } else if (arg_type == ARG_PTR_TO_MAP_PERF_EVENT_VALUE) {
+ /* check for ARG_PTR_TO_MAP_PERF_EVENT_VALUE has been done before*/
+
} else if (arg_type == ARG_CONST_STACK_SIZE) {
/* bpf_xxx(..., buf, len) call will access 'len' bytes
* from stack pointer 'buf'. Check it
@@ -902,6 +908,9 @@ static int check_call(struct verifier_env *env, int func_id)
return -EINVAL;
}
regs[BPF_REG_0].map_ptr = map;
+
+ if (map->flags & BPF_MAP_FLAG_PERF_EVENT)
+ regs[BPF_REG_0].type = PTR_TO_PTR_PERF_EVENT;
} else {
verbose("unknown return type %d of func %d\n",
fn->ret_type, func_id);
--
1.7.10.4