linux-kernel - [tip: x86/core] x86/ibt: Ensure module init/exit points have references

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Date:   Wed, 09 Mar 2022 07:54:50 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: x86/core] x86/ibt: Ensure module init/exit points have references

The following commit has been merged into the x86/core branch of tip:

Commit-ID:     43d8f5801147a9d3998261d491e2d9a3de6e05eb
Gitweb:        https://git.kernel.org/tip/43d8f5801147a9d3998261d491e2d9a3de6e05eb
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Tue, 08 Mar 2022 16:30:44 +01:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Tue, 08 Mar 2022 23:53:35 +01:00

x86/ibt: Ensure module init/exit points have references

Since the references to the module init/exit points only have external
references, a module LTO run will consider them 'unused' and seal
them, leading to an immediate fail on module load.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Josh Poimboeuf <jpoimboe@...hat.com>
Link: https://lore.kernel.org/r/20220308154319.113767246@infradead.org
---
 include/linux/cfi.h | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/include/linux/cfi.h b/include/linux/cfi.h
index 879744a..c6dfc1e 100644
--- a/include/linux/cfi.h
+++ b/include/linux/cfi.h
@@ -34,8 +34,17 @@ static inline void cfi_module_remove(struct module *mod, unsigned long base_addr
 
 #else /* !CONFIG_CFI_CLANG */
 
-#define __CFI_ADDRESSABLE(fn, __attr)
+#ifdef CONFIG_X86_KERNEL_IBT
+
+#define __CFI_ADDRESSABLE(fn, __attr) \
+	const void *__cfi_jt_ ## fn __visible __attr = (void *)&fn
+
+#endif /* CONFIG_X86_KERNEL_IBT */
 
 #endif /* CONFIG_CFI_CLANG */
 
+#ifndef __CFI_ADDRESSABLE
+#define __CFI_ADDRESSABLE(fn, __attr)
+#endif
+
 #endif /* _LINUX_CFI_H */