qemu

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/*
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 * x86-64 linux replacement vdso.
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 *
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 * Copyright 2023 Linaro, Ltd.
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 *
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 * SPDX-License-Identifier: GPL-2.0-or-later
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 */
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#include <asm/unistd.h>
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.macro endf name
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	.globl	\name
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	.type	\name, @function
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	.size	\name, . - \name
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.endm
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.macro weakalias name
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\name	= __vdso_\name
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	.weak	\name
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.endm
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.macro vdso_syscall name, nr
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__vdso_\name:
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	mov	$\nr, %eax
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	syscall
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	ret
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endf	__vdso_\name
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weakalias \name
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.endm
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	.cfi_startproc
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vdso_syscall clock_gettime, __NR_clock_gettime
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vdso_syscall clock_getres, __NR_clock_getres
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vdso_syscall gettimeofday, __NR_gettimeofday
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vdso_syscall time, __NR_time
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__vdso_getcpu:
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	/*
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         * There is no syscall number for this allocated on x64.
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	 * We can handle this several ways:
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         *
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	 * (1) Invent a syscall number for use within qemu.
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         *     It should be easy enough to pick a number that
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         *     is well out of the way of the kernel numbers.
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         *
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         * (2) Force the emulated cpu to support the rdtscp insn,
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	 *     and initialize the TSC_AUX value the appropriate value.
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         *
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	 * (3) Pretend that we're always running on cpu 0.
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         *
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	 * This last is the one that's implemented here, with the
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	 * tiny bit of extra code to support rdtscp in place.
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         */
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	xor	%ecx, %ecx		/* rdtscp w/ tsc_aux = 0 */
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	/* if (cpu != NULL) *cpu = (ecx & 0xfff); */
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	test	%rdi, %rdi
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	jz	1f
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	mov	%ecx, %eax
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	and	$0xfff, %eax
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	mov	%eax, (%rdi)
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	/* if (node != NULL) *node = (ecx >> 12); */
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1:	test	%rsi, %rsi
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	jz	2f
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	shr	$12, %ecx
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	mov	%ecx, (%rsi)
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2:	xor	%eax, %eax
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	ret
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endf	__vdso_getcpu
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weakalias getcpu
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	.cfi_endproc
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/* TODO: Add elf note for LINUX_VERSION_CODE */
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