For struct_ops progs, whether a particular prog uses private stack
depends on prog->aux->priv_stack_requested setting before actual
insn-level verification for that prog. One particular implementation
is to piggyback on struct_ops->check_member(). The next patch has
an example for this. The struct_ops->check_member() sets
prog->aux->priv_stack_requested to be true which enables private stack
usage.
The struct_ops prog follows the same rule as kprobe/tracing progs after
function bpf_enable_priv_stack(). For example, even a struct_ops prog
requests private stack, it could still use normal kernel stack if
the stack size is small (< 64 bytes).
Similar to tracing progs, nested same cpu same prog run will be skipped.
A field (recursion_detected()) is added to bpf_prog_aux structure.
If bpf_prog->aux->recursion_detected is implemented by the struct_ops
subsystem and nested same cpu/prog happens, the function will be
triggered to report an error, collect related info, etc.
Acked-by: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Yonghong Song <yonghong.song@xxxxxxxxx>
---
include/linux/bpf.h | 2 ++
include/linux/bpf_verifier.h | 1 +
kernel/bpf/trampoline.c | 4 ++++
kernel/bpf/verifier.c | 7 ++++++-
4 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 9cfb8f55d691..ae50826f9ace 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1525,9 +1525,11 @@ struct bpf_prog_aux {
bool exception_boundary;
bool is_extended; /* true if extended by freplace program */
bool jits_use_priv_stack;
+ bool priv_stack_requested;
u64 prog_array_member_cnt; /* counts how many times as member of prog_array */
struct mutex ext_mutex; /* mutex for is_extended and prog_array_member_cnt */
struct bpf_arena *arena;
+ void (*recursion_detected)(struct bpf_prog *prog); /* callback if recursion is detected */
/* BTF_KIND_FUNC_PROTO for valid attach_btf_id */
const struct btf_type *attach_func_proto;
/* function name for valid attach_btf_id */
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 456fd2265345..f013988d2e7f 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -895,6 +895,7 @@ static inline bool bpf_prog_check_recur(const struct bpf_prog *prog)
case BPF_PROG_TYPE_TRACING:
return prog->expected_attach_type != BPF_TRACE_ITER;
case BPF_PROG_TYPE_STRUCT_OPS:
+ return prog->aux->jits_use_priv_stack;
case BPF_PROG_TYPE_LSM:
return false;
default:
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 9f36c049f4c2..a8d188b31da5 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -899,6 +899,8 @@ static u64 notrace __bpf_prog_enter_recur(struct bpf_prog *prog, struct bpf_tram
if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
bpf_prog_inc_misses_counter(prog);
+ if (prog->aux->recursion_detected)
+ prog->aux->recursion_detected(prog);
return 0;
}
return bpf_prog_start_time();
@@ -975,6 +977,8 @@ u64 notrace __bpf_prog_enter_sleepable_recur(struct bpf_prog *prog,
if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
bpf_prog_inc_misses_counter(prog);
+ if (prog->aux->recursion_detected)
+ prog->aux->recursion_detected(prog);
return 0;
}
return bpf_prog_start_time();
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 8a7576233814..cf69caf67d61 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -6054,7 +6054,7 @@ static enum priv_stack_mode bpf_enable_priv_stack(struct bpf_prog *prog)
case BPF_PROG_TYPE_TRACING:
case BPF_PROG_TYPE_LSM:
case BPF_PROG_TYPE_STRUCT_OPS:
- if (bpf_prog_check_recur(prog))
+ if (prog->aux->priv_stack_requested || bpf_prog_check_recur(prog))
return PRIV_STACK_ADAPTIVE;
fallthrough;
default:
@@ -22000,6 +22000,11 @@ static int check_struct_ops_btf_id(struct bpf_verifier_env *env)
}
}
+ if (prog->aux->priv_stack_requested && !bpf_jit_supports_private_stack()) {
+ verbose(env, "Private stack not supported by jit\n");
+ return -EACCES;
+ }
+
/* btf_ctx_access() used this to provide argument type info */
prog->aux->ctx_arg_info =
st_ops_desc->arg_info[member_idx].info;
--
2.43.5
