On Thu, Mar 02, 2023 at 08:14:46PM -0800, Alexei Starovoitov wrote: > From: Alexei Starovoitov <ast@xxxxxxxxxx> > > bpf_rcu_read_lock/unlock() are only available in clang compiled kernels. Lack > of such key mechanism makes it impossible for sleepable bpf programs to use RCU > pointers. > > Allow bpf_rcu_read_lock/unlock() in GCC compiled kernels (though GCC doesn't > support btf_type_tag yet) and allowlist certain field dereferences in important > data structures like tast_struct, cgroup, socket that are used by sleepable > programs either as RCU pointer or full trusted pointer (which is valid outside > of RCU CS). Use BTF_TYPE_SAFE_RCU and BTF_TYPE_SAFE_TRUSTED macros for such > tagging. They will be removed once GCC supports btf_type_tag. > > With that refactor check_ptr_to_btf_access(). Make it strict in enforcing > PTR_TRUSTED and PTR_UNTRUSTED while deprecating old PTR_TO_BTF_ID without > modifier flags. There is a chance that this strict enforcement might break > existing programs (especially on GCC compiled kernels), but this cleanup has to > start sooner than later. Note PTR_TO_CTX access still yields old deprecated > PTR_TO_BTF_ID. Once it's converted to strict PTR_TRUSTED or PTR_UNTRUSTED the > kfuncs and helpers will be able to default to KF_TRUSTED_ARGS. KF_RCU will > remain as a weaker version of KF_TRUSTED_ARGS where obj refcnt could be 0. > > Adjust rcu_read_lock selftest to run on gcc and clang compiled kernels. > > Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx> Acked-by: David Vernet <void@xxxxxxxxxxxxx>
