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3503d56cc7
Allocate the time namespace page among VVAR pages. Provide __arch_get_timens_vdso_data() helper for VDSO code to get the code-relative position of VVARs on that special page. If a task belongs to a time namespace then the VVAR page which contains the system wide VDSO data is replaced with a namespace specific page which has the same layout as the VVAR page. That page has vdso_data->seq set to 1 to enforce the slow path and vdso_data->clock_mode set to VCLOCK_TIMENS to enforce the time namespace handling path. The extra check in the case that vdso_data->seq is odd, e.g. a concurrent update of the VDSO data is in progress, is not really affecting regular tasks which are not part of a time namespace as the task is spin waiting for the update to finish and vdso_data->seq to become even again. If a time namespace task hits that code path, it invokes the corresponding time getter function which retrieves the real VVAR page, reads host time and then adds the offset for the requested clock which is stored in the special VVAR page. The time-namespace page isn't allocated on !CONFIG_TIME_NAMESPACE, but vma is the same size, which simplifies criu/vdso migration between different kernel configs. Signed-off-by: Andrei Vagin <avagin@gmail.com> Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com> Reviewed-by: Dmitry Safonov <dima@arista.com> Cc: Mark Rutland <mark.rutland@arm.com> Link: https://lore.kernel.org/r/20200624083321.144975-4-avagin@gmail.com Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
32 lines
631 B
C
32 lines
631 B
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (C) 2012 ARM Limited
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*/
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#ifndef __ASM_VDSO_H
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#define __ASM_VDSO_H
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/*
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* Default link address for the vDSO.
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* Since we randomise the VDSO mapping, there's little point in trying
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* to prelink this.
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*/
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#define VDSO_LBASE 0x0
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#define __VVAR_PAGES 2
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#ifndef __ASSEMBLY__
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#include <generated/vdso-offsets.h>
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#ifdef CONFIG_COMPAT_VDSO
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#include <generated/vdso32-offsets.h>
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#endif
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#define VDSO_SYMBOL(base, name) \
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({ \
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(void *)(vdso_offset_##name - VDSO_LBASE + (unsigned long)(base)); \
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})
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#endif /* !__ASSEMBLY__ */
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#endif /* __ASM_VDSO_H */
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