2019-05-27 00:55:01 -06:00
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/* SPDX-License-Identifier: GPL-2.0-or-later */
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2010-02-18 17:13:04 -07:00
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/*
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2015-10-21 02:54:38 -06:00
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* Copyright (C) 2015 Imagination Technologies
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* Author: Alex Smith <alex.smith@imgtec.com>
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2010-02-18 17:13:04 -07:00
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*/
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#ifndef __ASM_VDSO_H
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#define __ASM_VDSO_H
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2015-10-21 02:54:38 -06:00
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#include <linux/mm_types.h>
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2019-06-21 03:52:46 -06:00
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#include <vdso/datapage.h>
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2010-02-18 17:13:04 -07:00
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MIPS: VDSO: Add implementations of gettimeofday() and clock_gettime()
Add user-mode implementations of gettimeofday() and clock_gettime() to
the VDSO. This is currently usable with 2 clocksources: the CP0 count
register, which is accessible to user-mode via RDHWR on R2 and later
cores, or the MIPS Global Interrupt Controller (GIC) timer, which
provides a "user-mode visible" section containing a mirror of its
counter registers. This section must be mapped into user memory, which
is done below the VDSO data page.
When a supported clocksource is not in use, the VDSO functions will
return -ENOSYS, which causes libc to fall back on the standard syscall
path.
When support for neither of these clocksources is compiled into the
kernel at all, the VDSO still provides clock_gettime(), as the coarse
realtime/monotonic clocks can still be implemented. However,
gettimeofday() is not provided in this case as nothing can be done
without a suitable clocksource. This causes the symbol lookup to fail
in libc and it will then always use the standard syscall path.
This patch includes a workaround for a bug in QEMU which results in
RDHWR on the CP0 count register always returning a constant (incorrect)
value. A fix for this has been submitted, and the workaround can be
removed after the fix has been in stable releases for a reasonable
amount of time.
A simple performance test which calls gettimeofday() 1000 times in a
loop and calculates the average execution time gives the following
results on a Malta + I6400 (running at 20MHz):
- Syscall: ~31000 ns
- VDSO (GIC): ~15000 ns
- VDSO (CP0): ~9500 ns
[markos.chandras@imgtec.com:
- Minor code re-arrangements in order for mappings to be made
in the order they appear to the process' address space.
- Move do_{monotonic, realtime} outside of the MIPS_CLOCK_VSYSCALL ifdef
- Use gic_get_usm_range so we can do the GIC mapping in the
arch/mips/kernel/vdso instead of the GIC irqchip driver]
Signed-off-by: Alex Smith <alex.smith@imgtec.com>
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/11338/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
2015-10-21 02:57:44 -06:00
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#include <asm/barrier.h>
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2015-10-21 02:54:38 -06:00
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/**
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* struct mips_vdso_image - Details of a VDSO image.
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* @data: Pointer to VDSO image data (page-aligned).
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* @size: Size of the VDSO image data (page-aligned).
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* @off_sigreturn: Offset of the sigreturn() trampoline.
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* @off_rt_sigreturn: Offset of the rt_sigreturn() trampoline.
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* @mapping: Special mapping structure.
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*
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* This structure contains details of a VDSO image, including the image data
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* and offsets of certain symbols required by the kernel. It is generated as
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* part of the VDSO build process, aside from the mapping page array, which is
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* populated at runtime.
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*/
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struct mips_vdso_image {
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void *data;
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unsigned long size;
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unsigned long off_sigreturn;
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unsigned long off_rt_sigreturn;
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struct vm_special_mapping mapping;
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};
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/*
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* The following structures are auto-generated as part of the build for each
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* ABI by genvdso, see arch/mips/vdso/Makefile.
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*/
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extern struct mips_vdso_image vdso_image;
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#ifdef CONFIG_MIPS32_O32
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extern struct mips_vdso_image vdso_image_o32;
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#endif
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#ifdef CONFIG_MIPS32_N32
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extern struct mips_vdso_image vdso_image_n32;
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#endif
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union mips_vdso_data {
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struct vdso_data data[CS_BASES];
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u8 page[PAGE_SIZE];
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};
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#endif /* __ASM_VDSO_H */
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