/* 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_seal_endbr()).
 */
#define IBT_NOSEAL(fname)                \
    ".pushsection .discard.ibt_endbr_noseal\n\t"    \
    _ASM_PTR fname "\n\t"                \
    ".popsection\n\t"

static __always_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 __always_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(bool disable);
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(bool disable) { 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 */