147 lines
2.5 KiB
C
147 lines
2.5 KiB
C
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/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_X86_CFI_H
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#define _ASM_X86_CFI_H
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/*
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* Clang Control Flow Integrity (CFI) support.
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*
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* Copyright (C) 2022 Google LLC
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*/
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#include <linux/bug.h>
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#include <asm/ibt.h>
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/*
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* An overview of the various calling conventions...
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*
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* Traditional:
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*
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* foo:
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* ... code here ...
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* ret
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*
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* direct caller:
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* call foo
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*
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* indirect caller:
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* lea foo(%rip), %r11
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* ...
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* call *%r11
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*
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*
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* IBT:
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*
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* foo:
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* endbr64
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* ... code here ...
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* ret
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*
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* direct caller:
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* call foo / call foo+4
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*
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* indirect caller:
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* lea foo(%rip), %r11
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* ...
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* call *%r11
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*
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*
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* kCFI:
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*
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* __cfi_foo:
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* movl $0x12345678, %eax
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* # 11 nops when CONFIG_CALL_PADDING
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* foo:
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* endbr64 # when IBT
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* ... code here ...
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* ret
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*
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* direct call:
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* call foo # / call foo+4 when IBT
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*
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* indirect call:
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* lea foo(%rip), %r11
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* ...
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* movl $(-0x12345678), %r10d
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* addl -4(%r11), %r10d # -15 when CONFIG_CALL_PADDING
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* jz 1f
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* ud2
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* 1:call *%r11
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*
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*
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* FineIBT (builds as kCFI + CALL_PADDING + IBT + RETPOLINE and runtime patches into):
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*
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* __cfi_foo:
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* endbr64
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* subl 0x12345678, %r10d
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* jz foo
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* ud2
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* nop
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* foo:
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* osp nop3 # was endbr64
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* ... code here ...
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* ret
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*
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* direct caller:
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* call foo / call foo+4
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*
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* indirect caller:
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* lea foo(%rip), %r11
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* ...
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* movl $0x12345678, %r10d
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* subl $16, %r11
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* nop4
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* call *%r11
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*
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*/
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enum cfi_mode {
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CFI_DEFAULT, /* FineIBT if hardware has IBT, otherwise kCFI */
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CFI_OFF, /* Taditional / IBT depending on .config */
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CFI_KCFI, /* Optionally CALL_PADDING, IBT, RETPOLINE */
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CFI_FINEIBT, /* see arch/x86/kernel/alternative.c */
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};
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extern enum cfi_mode cfi_mode;
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struct pt_regs;
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#ifdef CONFIG_CFI_CLANG
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enum bug_trap_type handle_cfi_failure(struct pt_regs *regs);
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#define __bpfcall
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extern u32 cfi_bpf_hash;
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extern u32 cfi_bpf_subprog_hash;
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static inline int cfi_get_offset(void)
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{
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switch (cfi_mode) {
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case CFI_FINEIBT:
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return 16;
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case CFI_KCFI:
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if (IS_ENABLED(CONFIG_CALL_PADDING))
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return 16;
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return 5;
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default:
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return 0;
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}
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}
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#define cfi_get_offset cfi_get_offset
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extern u32 cfi_get_func_hash(void *func);
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#else
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static inline enum bug_trap_type handle_cfi_failure(struct pt_regs *regs)
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{
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return BUG_TRAP_TYPE_NONE;
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}
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#define cfi_bpf_hash 0U
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#define cfi_bpf_subprog_hash 0U
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static inline u32 cfi_get_func_hash(void *func)
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{
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return 0;
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}
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#endif /* CONFIG_CFI_CLANG */
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#if HAS_KERNEL_IBT == 1
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#define CFI_NOSEAL(x) asm(IBT_NOSEAL(__stringify(x)))
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#endif
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#endif /* _ASM_X86_CFI_H */
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