On 11/8/22 8:56 AM, Alexei Starovoitov wrote:
On 11/7/22 11:41 PM, Yonghong Song wrote:
Add two kfunc's bpf_rcu_read_lock() and bpf_rcu_read_unlock(). These
two kfunc's
can be used for all program types. A new kfunc hook type
BTF_KFUNC_HOOK_GENERIC
is added which corresponds to prog type BPF_PROG_TYPE_UNSPEC,
indicating the
kfunc intends to be used for all prog types.
The kfunc bpf_rcu_read_lock() is tagged with new flag KF_RCU_LOCK and
bpf_rcu_read_unlock() with new flag KF_RCU_UNLOCK. These two new flags
are used by the verifier to identify these two helpers.
Signed-off-by: Yonghong Song <yhs@xxxxxx>
---
include/linux/bpf.h | 3 +++
include/linux/btf.h | 2 ++
kernel/bpf/btf.c | 8 ++++++++
kernel/bpf/helpers.c | 25 ++++++++++++++++++++++++-
4 files changed, 37 insertions(+), 1 deletion(-)
For new kfuncs, I added KF_RCU_LOCK and KF_RCU_UNLOCK flags to
indicate a helper could be bpf_rcu_read_lock/unlock(). This could
be a waste for kfunc flag space as the flag is used to identify
one helper. Alternatively, we might identify kfunc based on
btf_id. Any suggestions are welcome.
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 5011cb50abf1..b4bbcafd1c9b 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2118,6 +2118,9 @@ bool bpf_prog_has_kfunc_call(const struct
bpf_prog *prog);
const struct btf_func_model *
bpf_jit_find_kfunc_model(const struct bpf_prog *prog,
const struct bpf_insn *insn);
+void bpf_rcu_read_lock(void);
+void bpf_rcu_read_unlock(void);
+
struct bpf_core_ctx {
struct bpf_verifier_log *log;
const struct btf *btf;
diff --git a/include/linux/btf.h b/include/linux/btf.h
index d80345fa566b..8783ca7e6079 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -51,6 +51,8 @@
#define KF_TRUSTED_ARGS (1 << 4) /* kfunc only takes trusted pointer
arguments */
#define KF_SLEEPABLE (1 << 5) /* kfunc may sleep */
#define KF_DESTRUCTIVE (1 << 6) /* kfunc performs destructive
actions */
+#define KF_RCU_LOCK (1 << 7) /* kfunc does rcu_read_lock() */
+#define KF_RCU_UNLOCK (1 << 8) /* kfunc does rcu_read_unlock() */
Please don't use KF flags for these. It's not going to scale.
Compare btf_id instead.
Will do. Kumar has a suggestion like:
https://lore.kernel.org/bpf/20221107230950.7117-17-memxor@xxxxxxxxx
which I will explore.
