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- /* SPDX-License-Identifier: GPL-2.0 */
- #ifndef _ASM_X86_IBT_H
- #define _ASM_X86_IBT_H
- #include <linux/types.h>
- /*
- * The rules for enabling IBT are:
- *
- * - CC_HAS_IBT: the toolchain supports it
- * - X86_KERNEL_IBT: it is selected in Kconfig
- * - !__DISABLE_EXPORTS: this is regular kernel code
- *
- * Esp. that latter one is a bit non-obvious, but some code like compressed,
- * purgatory, realmode etc.. is built with custom CFLAGS that do not include
- * -fcf-protection=branch and things will go *bang*.
- *
- * When all the above are satisfied, HAS_KERNEL_IBT will be 1, otherwise 0.
- */
- #if defined(CONFIG_X86_KERNEL_IBT) && !defined(__DISABLE_EXPORTS)
- #define HAS_KERNEL_IBT 1
- #ifndef __ASSEMBLY__
- #ifdef CONFIG_X86_64
- #define ASM_ENDBR "endbr64\n\t"
- #else
- #define ASM_ENDBR "endbr32\n\t"
- #endif
- #define __noendbr __attribute__((nocf_check))
- /*
- * Create a dummy function pointer reference to prevent objtool from marking
- * the function as needing to be "sealed" (i.e. ENDBR converted to NOP by
- * apply_ibt_endbr()).
- */
- #define IBT_NOSEAL(fname) \
- ".pushsection .discard.ibt_endbr_noseal\n\t" \
- _ASM_PTR fname "\n\t" \
- ".popsection\n\t"
- static inline __attribute_const__ u32 gen_endbr(void)
- {
- u32 endbr;
- /*
- * Generate ENDBR64 in a way that is sure to not result in
- * an ENDBR64 instruction as immediate.
- */
- asm ( "mov $~0xfa1e0ff3, %[endbr]\n\t"
- "not %[endbr]\n\t"
- : [endbr] "=&r" (endbr) );
- return endbr;
- }
- static inline __attribute_const__ u32 gen_endbr_poison(void)
- {
- /*
- * 4 byte NOP that isn't NOP4 (in fact it is OSP NOP3), such that it
- * will be unique to (former) ENDBR sites.
- */
- return 0x001f0f66; /* osp nopl (%rax) */
- }
- static inline bool is_endbr(u32 val)
- {
- if (val == gen_endbr_poison())
- return true;
- val &= ~0x01000000U; /* ENDBR32 -> ENDBR64 */
- return val == gen_endbr();
- }
- extern __noendbr u64 ibt_save(void);
- extern __noendbr void ibt_restore(u64 save);
- #else /* __ASSEMBLY__ */
- #ifdef CONFIG_X86_64
- #define ENDBR endbr64
- #else
- #define ENDBR endbr32
- #endif
- #endif /* __ASSEMBLY__ */
- #else /* !IBT */
- #define HAS_KERNEL_IBT 0
- #ifndef __ASSEMBLY__
- #define ASM_ENDBR
- #define IBT_NOSEAL(name)
- #define __noendbr
- static inline bool is_endbr(u32 val) { return false; }
- static inline u64 ibt_save(void) { return 0; }
- static inline void ibt_restore(u64 save) { }
- #else /* __ASSEMBLY__ */
- #define ENDBR
- #endif /* __ASSEMBLY__ */
- #endif /* CONFIG_X86_KERNEL_IBT */
- #define ENDBR_INSN_SIZE (4*HAS_KERNEL_IBT)
- #endif /* _ASM_X86_IBT_H */
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