| 1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768 |
- /* 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 */
|
