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torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/arch/x86/entry/entry.S
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/* SPDX-License-Identifier: GPL-2.0 */

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/*

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 * Common place for both 32- and 64-bit entry routines.

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 */

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#include <linux/export.h>

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#include <linux/kvm_types.h>

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#include <linux/linkage.h>

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#include <linux/objtool.h>

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#include <asm/msr-index.h>

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#include <asm/unwind_hints.h>

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#include <asm/segment.h>

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#include <asm/cache.h>

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#include <asm/cpufeatures.h>

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#include <asm/nospec-branch.h>

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#include "calling.h"

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.pushsection .noinstr.text, "ax"

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/* Clobbers AX, CX, DX */

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SYM_FUNC_START(write_ibpb)

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	ANNOTATE_NOENDBR

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	movl	$MSR_IA32_PRED_CMD, %ecx

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	movl	_ASM_RIP(x86_pred_cmd), %eax

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	xorl	%edx, %edx

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	wrmsr

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	/* Make sure IBPB clears return stack preductions too. */

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	FILL_RETURN_BUFFER %rax, RSB_CLEAR_LOOPS, X86_BUG_IBPB_NO_RET

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	RET

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SYM_FUNC_END(write_ibpb)

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EXPORT_SYMBOL_FOR_KVM(write_ibpb);

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SYM_FUNC_START(__WARN_trap)

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	ANNOTATE_NOENDBR

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	ANNOTATE_REACHABLE

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	ud1 (%edx), %_ASM_ARG1

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	RET

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SYM_FUNC_END(__WARN_trap)

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EXPORT_SYMBOL(__WARN_trap)

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.popsection

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/*

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 * Define the VERW operand that is disguised as entry code so that

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 * it can be referenced with KPTI enabled. This ensures VERW can be

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 * used late in exit-to-user path after page tables are switched.

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 */

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.pushsection .entry.text, "ax"

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.align L1_CACHE_BYTES, 0xcc

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SYM_CODE_START_NOALIGN(x86_verw_sel)

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	UNWIND_HINT_UNDEFINED

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	ANNOTATE_NOENDBR

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	.word __KERNEL_DS

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.align L1_CACHE_BYTES, 0xcc

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SYM_CODE_END(x86_verw_sel);

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EXPORT_SYMBOL_FOR_KVM(x86_verw_sel);

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.popsection

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THUNK warn_thunk_thunk, __warn_thunk

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/*

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 * Clang's implementation of TLS stack cookies requires the variable in

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 * question to be a TLS variable. If the variable happens to be defined as an

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 * ordinary variable with external linkage in the same compilation unit (which

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 * amounts to the whole of vmlinux with LTO enabled), Clang will drop the

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 * segment register prefix from the references, resulting in broken code. Work

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 * around this by avoiding the symbol used in -mstack-protector-guard-symbol=

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 * entirely in the C code, and use an alias emitted by the linker script

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 * instead.

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 */

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#if defined(CONFIG_STACKPROTECTOR) && defined(CONFIG_SMP)

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EXPORT_SYMBOL(__ref_stack_chk_guard);

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#endif

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