/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_STATIC_CALL_H
#define _ASM_STATIC_CALL_H

#include <asm/text-patching.h>

/*
 * For CONFIG_HAVE_STATIC_CALL_INLINE, this is a temporary trampoline which
 * uses the current value of the key->func pointer to do an indirect jump to
 * the function.  This trampoline is only used during boot, before the call
 * sites get patched by static_call_update().  The name of this trampoline has
 * a magical aspect: objtool uses it to find static call sites so it can create
 * the .static_call_sites section.
 *
 * For CONFIG_HAVE_STATIC_CALL, this is a permanent trampoline which
 * does a direct jump to the function.  The direct jump gets patched by
 * static_call_update().
 *
 * Having the trampoline in a special section forces GCC to emit a JMP.d32 when
 * it does tail-call optimization on the call; since you cannot compute the
 * relative displacement across sections.
 */

/*
 * The trampoline is 8 bytes and of the general form:
 *
 *   jmp.d32 \func
 *   ud1 %esp, %ecx
 *
 * That trailing #UD provides both a speculation stop and serves as a unique
 * 3 byte signature identifying static call trampolines. Also see tramp_ud[]
 * and __static_call_fixup().
 */
#define __ARCH_DEFINE_STATIC_CALL_TRAMP(name, insns)            \
    asm(".pushsection .static_call.text, \"ax\"        \n"    \
        ".align 4                        \n"    \
        ".globl " STATIC_CALL_TRAMP_STR(name) "        \n"    \
        STATIC_CALL_TRAMP_STR(name) ":            \n"    \
        ANNOTATE_NOENDBR                        \
        insns "                        \n"    \
        ".byte 0x0f, 0xb9, 0xcc                \n"    \
        ".type " STATIC_CALL_TRAMP_STR(name) ", @function    \n"    \
        ".size " STATIC_CALL_TRAMP_STR(name) ", . - " STATIC_CALL_TRAMP_STR(name) " \n" \
        ".popsection                    \n")

#define ARCH_DEFINE_STATIC_CALL_TRAMP(name, func)            \
    __ARCH_DEFINE_STATIC_CALL_TRAMP(name, ".byte 0xe9; .long " #func " - (. + 4)")

#ifdef CONFIG_RETHUNK
#define ARCH_DEFINE_STATIC_CALL_NULL_TRAMP(name)            \
    __ARCH_DEFINE_STATIC_CALL_TRAMP(name, "jmp __x86_return_thunk")
#else
#define ARCH_DEFINE_STATIC_CALL_NULL_TRAMP(name)            \
    __ARCH_DEFINE_STATIC_CALL_TRAMP(name, "ret; int3; nop; nop; nop")
#endif

#define ARCH_DEFINE_STATIC_CALL_RET0_TRAMP(name)            \
    ARCH_DEFINE_STATIC_CALL_TRAMP(name, __static_call_return0)

#define ARCH_ADD_TRAMP_KEY(name)                    \
    asm(".pushsection .static_call_tramp_key, \"a\"        \n"    \
        ".long " STATIC_CALL_TRAMP_STR(name) " - .        \n"    \
        ".long " STATIC_CALL_KEY_STR(name) " - .        \n"    \
        ".popsection                    \n")

extern bool __static_call_fixup(void *tramp, u8 op, void *dest);

#endif /* _ASM_STATIC_CALL_H */