4.19-stable review patch. If anyone has any objections, please let me know.
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From: Paolo Abeni pabeni@redhat.com
[ Upstream commit 283c16a2dfd332bf5610c874f7b9f9c8b601ce53 ]
This header define a bunch of helpers that allow avoiding the retpoline overhead when calling builtin functions via function pointers. It boils down to explicitly comparing the function pointers to known builtin functions and eventually invoke directly the latter.
The macros defined here implement the boilerplate for the above schema and will be used by the next patches.
rfc -> v1: - use branch prediction hint, as suggested by Eric v1 -> v2: - list explicitly the builtin function names in INDIRECT_CALL_*(), as suggested by Ed Cree
Suggested-by: Eric Dumazet edumazet@google.com Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: David S. Miller davem@davemloft.net Stable-dep-of: 86a7e0b69bd5 ("net: prevent rewrite of msg_name in sock_sendmsg()") Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/indirect_call_wrapper.h | 51 +++++++++++++++++++++++++++ 1 file changed, 51 insertions(+) create mode 100644 include/linux/indirect_call_wrapper.h
diff --git a/include/linux/indirect_call_wrapper.h b/include/linux/indirect_call_wrapper.h new file mode 100644 index 0000000000000..7c8b7f4948af5 --- /dev/null +++ b/include/linux/indirect_call_wrapper.h @@ -0,0 +1,51 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_INDIRECT_CALL_WRAPPER_H +#define _LINUX_INDIRECT_CALL_WRAPPER_H + +#ifdef CONFIG_RETPOLINE + +/* + * INDIRECT_CALL_$NR - wrapper for indirect calls with $NR known builtin + * @f: function pointer + * @f$NR: builtin functions names, up to $NR of them + * @__VA_ARGS__: arguments for @f + * + * Avoid retpoline overhead for known builtin, checking @f vs each of them and + * eventually invoking directly the builtin function. The functions are check + * in the given order. Fallback to the indirect call. + */ +#define INDIRECT_CALL_1(f, f1, ...) \ + ({ \ + likely(f == f1) ? f1(__VA_ARGS__) : f(__VA_ARGS__); \ + }) +#define INDIRECT_CALL_2(f, f2, f1, ...) \ + ({ \ + likely(f == f2) ? f2(__VA_ARGS__) : \ + INDIRECT_CALL_1(f, f1, __VA_ARGS__); \ + }) + +#define INDIRECT_CALLABLE_DECLARE(f) f +#define INDIRECT_CALLABLE_SCOPE + +#else +#define INDIRECT_CALL_1(f, name, ...) f(__VA_ARGS__) +#define INDIRECT_CALL_2(f, name, ...) f(__VA_ARGS__) +#define INDIRECT_CALLABLE_DECLARE(f) +#define INDIRECT_CALLABLE_SCOPE static +#endif + +/* + * We can use INDIRECT_CALL_$NR for ipv6 related functions only if ipv6 is + * builtin, this macro simplify dealing with indirect calls with only ipv4/ipv6 + * alternatives + */ +#if IS_BUILTIN(CONFIG_IPV6) +#define INDIRECT_CALL_INET(f, f2, f1, ...) \ + INDIRECT_CALL_2(f, f2, f1, __VA_ARGS__) +#elif IS_ENABLED(CONFIG_INET) +#define INDIRECT_CALL_INET(f, f2, f1, ...) INDIRECT_CALL_1(f, f1, __VA_ARGS__) +#else +#define INDIRECT_CALL_INET(f, f2, f1, ...) f(__VA_ARGS__) +#endif + +#endif