/* 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 */