| 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
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| 2 | #ifndef _ASM_STATIC_CALL_H |
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| 3 | #define _ASM_STATIC_CALL_H |
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| 4 | |
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| 5 | #include <asm/text-patching.h> |
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| 6 | |
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| 7 | /* |
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| 8 | * For CONFIG_HAVE_STATIC_CALL_INLINE, this is a temporary trampoline which |
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| 9 | * uses the current value of the key->func pointer to do an indirect jump to |
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| 10 | * the function. This trampoline is only used during boot, before the call |
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| 11 | * sites get patched by static_call_update(). The name of this trampoline has |
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| 12 | * a magical aspect: objtool uses it to find static call sites so it can create |
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| 13 | * the .static_call_sites section. |
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| 14 | * |
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| 15 | * For CONFIG_HAVE_STATIC_CALL, this is a permanent trampoline which |
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| 16 | * does a direct jump to the function. The direct jump gets patched by |
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| 17 | * static_call_update(). |
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| 18 | * |
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| 19 | * Having the trampoline in a special section forces GCC to emit a JMP.d32 when |
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| 20 | * it does tail-call optimization on the call; since you cannot compute the |
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| 21 | * relative displacement across sections. |
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| 22 | */ |
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| 23 | |
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| 24 | /* |
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| 25 | * The trampoline is 8 bytes and of the general form: |
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| 26 | * |
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| 27 | * jmp.d32 \func |
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| 28 | * ud1 %esp, %ecx |
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| 29 | * |
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| 30 | * That trailing #UD provides both a speculation stop and serves as a unique |
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| 31 | * 3 byte signature identifying static call trampolines. Also see tramp_ud[] |
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| 32 | * and __static_call_fixup(). |
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| 33 | */ |
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| 34 | #define __ARCH_DEFINE_STATIC_CALL_TRAMP(name, insns) \ |
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| 35 | asm(".pushsection .static_call.text, \"ax\" \n" \ |
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| 36 | ".align 4 \n" \ |
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| 37 | ".globl " STATIC_CALL_TRAMP_STR(name) " \n" \ |
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| 38 | STATIC_CALL_TRAMP_STR(name) ": \n" \ |
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| 39 | ANNOTATE_NOENDBR \ |
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| 40 | insns " \n" \ |
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| 41 | ".byte 0x0f, 0xb9, 0xcc \n" \ |
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| 42 | ".type " STATIC_CALL_TRAMP_STR(name) ", @function \n" \ |
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| 43 | ".size " STATIC_CALL_TRAMP_STR(name) ", . - " STATIC_CALL_TRAMP_STR(name) " \n" \ |
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| 44 | ".popsection \n") |
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| 45 | |
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| 46 | #define ARCH_DEFINE_STATIC_CALL_TRAMP(name, func) \ |
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| 47 | __ARCH_DEFINE_STATIC_CALL_TRAMP(name, ".byte 0xe9; .long " #func " - (. + 4)") |
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| 48 | |
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| 49 | #ifdef CONFIG_RETHUNK |
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| 50 | #define ARCH_DEFINE_STATIC_CALL_NULL_TRAMP(name) \ |
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| 51 | __ARCH_DEFINE_STATIC_CALL_TRAMP(name, "jmp __x86_return_thunk") |
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| 52 | #else |
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| 53 | #define ARCH_DEFINE_STATIC_CALL_NULL_TRAMP(name) \ |
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| 54 | __ARCH_DEFINE_STATIC_CALL_TRAMP(name, "ret; int3; nop; nop; nop") |
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| 55 | #endif |
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| 56 | |
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| 57 | #define ARCH_DEFINE_STATIC_CALL_RET0_TRAMP(name) \ |
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| 58 | ARCH_DEFINE_STATIC_CALL_TRAMP(name, __static_call_return0) |
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| 59 | |
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| 60 | #define ARCH_ADD_TRAMP_KEY(name) \ |
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| 61 | asm(".pushsection .static_call_tramp_key, \"a\" \n" \ |
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| 62 | ".long " STATIC_CALL_TRAMP_STR(name) " - . \n" \ |
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| 63 | ".long " STATIC_CALL_KEY_STR(name) " - . \n" \ |
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| 64 | ".popsection \n") |
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| 65 | |
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| 66 | extern bool __static_call_fixup(void *tramp, u8 op, void *dest); |
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| 67 | |
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| 68 | #endif /* _ASM_STATIC_CALL_H */ |
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| 69 | |
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