From 5febf432df1cfa5b25d99b54c32103fafbdd0eb9 Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Sun, 16 Aug 2026 15:32:33 +0200 Subject: kbuild: rust: keep Rust objects out of Clang LTO with inline helpers Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit `objtool` errors such as: vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a: can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd The reason is that in such builds, the Clang invocation that compiles the combined Rust plus helpers bitcode emits LLVM bitcode (again) -- the final code generation happens in the linker's LTO step, which the `-mllvm` trap options passed to Clang do not reach. This, in turn, means that unreachable traps are missing, and the impossible paths do not merely fallthrough to the next symbol, but past the end of their own section, since LTO builds place each function in its own section. Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always emits machine code directly, with the traps in place. Assisted-by: LLM Cc: Gary Guo Cc: Boqun Feng Cc: Alice Ryhl Cc: Matthew Maurer Cc: Josh Poimboeuf Cc: Peter Zijlstra Cc: stable@vger.kernel.org Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust") Acked-by: Gary Guo Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org Signed-off-by: Miguel Ojeda --- lib/test_static_keys.c | 240 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 240 insertions(+) create mode 100644 lib/test_static_keys.c (limited to 'lib/test_static_keys.c') diff --git a/lib/test_static_keys.c b/lib/test_static_keys.c new file mode 100644 index 000000000..00c715f30 --- /dev/null +++ b/lib/test_static_keys.c @@ -0,0 +1,240 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Kernel module for testing static keys. + * + * Copyright 2015 Akamai Technologies Inc. All Rights Reserved + * + * Authors: + * Jason Baron + */ + +#include +#include + +/* old keys */ +struct static_key old_true_key = STATIC_KEY_INIT_TRUE; +struct static_key old_false_key = STATIC_KEY_INIT_FALSE; + +/* new api */ +DEFINE_STATIC_KEY_TRUE(true_key); +DEFINE_STATIC_KEY_FALSE(false_key); + +/* external */ +extern struct static_key base_old_true_key; +extern struct static_key base_inv_old_true_key; +extern struct static_key base_old_false_key; +extern struct static_key base_inv_old_false_key; + +/* new api */ +extern struct static_key_true base_true_key; +extern struct static_key_true base_inv_true_key; +extern struct static_key_false base_false_key; +extern struct static_key_false base_inv_false_key; + + +struct test_key { + bool init_state; + struct static_key *key; + bool (*test_key)(void); +}; + +#define test_key_func(key, branch) \ +static bool key ## _ ## branch(void) \ +{ \ + return branch(&key); \ +} + +static void invert_key(struct static_key *key) +{ + if (static_key_enabled(key)) + static_key_disable(key); + else + static_key_enable(key); +} + +static void invert_keys(struct test_key *keys, int size) +{ + struct static_key *previous = NULL; + int i; + + for (i = 0; i < size; i++) { + if (previous != keys[i].key) { + invert_key(keys[i].key); + previous = keys[i].key; + } + } +} + +static int verify_keys(struct test_key *keys, int size, bool invert) +{ + int i; + bool ret, init; + + for (i = 0; i < size; i++) { + ret = static_key_enabled(keys[i].key); + init = keys[i].init_state; + if (ret != (invert ? !init : init)) + return -EINVAL; + ret = keys[i].test_key(); + if (static_key_enabled(keys[i].key)) { + if (!ret) + return -EINVAL; + } else { + if (ret) + return -EINVAL; + } + } + return 0; +} + +test_key_func(old_true_key, static_key_true) +test_key_func(old_false_key, static_key_false) +test_key_func(true_key, static_branch_likely) +test_key_func(true_key, static_branch_unlikely) +test_key_func(false_key, static_branch_likely) +test_key_func(false_key, static_branch_unlikely) +test_key_func(base_old_true_key, static_key_true) +test_key_func(base_inv_old_true_key, static_key_true) +test_key_func(base_old_false_key, static_key_false) +test_key_func(base_inv_old_false_key, static_key_false) +test_key_func(base_true_key, static_branch_likely) +test_key_func(base_true_key, static_branch_unlikely) +test_key_func(base_inv_true_key, static_branch_likely) +test_key_func(base_inv_true_key, static_branch_unlikely) +test_key_func(base_false_key, static_branch_likely) +test_key_func(base_false_key, static_branch_unlikely) +test_key_func(base_inv_false_key, static_branch_likely) +test_key_func(base_inv_false_key, static_branch_unlikely) + +static int __init test_static_key_init(void) +{ + int ret; + int size; + + struct test_key static_key_tests[] = { + /* internal keys - old keys */ + { + .init_state = true, + .key = &old_true_key, + .test_key = &old_true_key_static_key_true, + }, + { + .init_state = false, + .key = &old_false_key, + .test_key = &old_false_key_static_key_false, + }, + /* internal keys - new keys */ + { + .init_state = true, + .key = &true_key.key, + .test_key = &true_key_static_branch_likely, + }, + { + .init_state = true, + .key = &true_key.key, + .test_key = &true_key_static_branch_unlikely, + }, + { + .init_state = false, + .key = &false_key.key, + .test_key = &false_key_static_branch_likely, + }, + { + .init_state = false, + .key = &false_key.key, + .test_key = &false_key_static_branch_unlikely, + }, + /* external keys - old keys */ + { + .init_state = true, + .key = &base_old_true_key, + .test_key = &base_old_true_key_static_key_true, + }, + { + .init_state = false, + .key = &base_inv_old_true_key, + .test_key = &base_inv_old_true_key_static_key_true, + }, + { + .init_state = false, + .key = &base_old_false_key, + .test_key = &base_old_false_key_static_key_false, + }, + { + .init_state = true, + .key = &base_inv_old_false_key, + .test_key = &base_inv_old_false_key_static_key_false, + }, + /* external keys - new keys */ + { + .init_state = true, + .key = &base_true_key.key, + .test_key = &base_true_key_static_branch_likely, + }, + { + .init_state = true, + .key = &base_true_key.key, + .test_key = &base_true_key_static_branch_unlikely, + }, + { + .init_state = false, + .key = &base_inv_true_key.key, + .test_key = &base_inv_true_key_static_branch_likely, + }, + { + .init_state = false, + .key = &base_inv_true_key.key, + .test_key = &base_inv_true_key_static_branch_unlikely, + }, + { + .init_state = false, + .key = &base_false_key.key, + .test_key = &base_false_key_static_branch_likely, + }, + { + .init_state = false, + .key = &base_false_key.key, + .test_key = &base_false_key_static_branch_unlikely, + }, + { + .init_state = true, + .key = &base_inv_false_key.key, + .test_key = &base_inv_false_key_static_branch_likely, + }, + { + .init_state = true, + .key = &base_inv_false_key.key, + .test_key = &base_inv_false_key_static_branch_unlikely, + }, + }; + + size = ARRAY_SIZE(static_key_tests); + + ret = verify_keys(static_key_tests, size, false); + if (ret) + goto out; + + invert_keys(static_key_tests, size); + ret = verify_keys(static_key_tests, size, true); + if (ret) + goto out; + + invert_keys(static_key_tests, size); + ret = verify_keys(static_key_tests, size, false); + if (ret) + goto out; + return 0; +out: + return ret; +} + +static void __exit test_static_key_exit(void) +{ +} + +module_init(test_static_key_init); +module_exit(test_static_key_exit); + +MODULE_AUTHOR("Jason Baron "); +MODULE_DESCRIPTION("Kernel module for testing static keys"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1