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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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