mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-11-24 15:40:56 +07:00
a7f4df4e21
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>
106 lines
2.7 KiB
ArmAsm
106 lines
2.7 KiB
ArmAsm
/*
|
|
* Copyright (C) 2015 Imagination Technologies
|
|
* Author: Alex Smith <alex.smith@imgtec.com>
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify it
|
|
* under the terms of the GNU General Public License as published by the
|
|
* Free Software Foundation; either version 2 of the License, or (at your
|
|
* option) any later version.
|
|
*/
|
|
|
|
#include <asm/sgidefs.h>
|
|
|
|
#if _MIPS_SIM == _MIPS_SIM_ABI64
|
|
OUTPUT_FORMAT("elf64-tradlittlemips", "elf64-tradbigmips", "elf64-tradlittlemips")
|
|
#elif _MIPS_SIM == _MIPS_SIM_NABI32
|
|
OUTPUT_FORMAT("elf32-ntradlittlemips", "elf32-ntradbigmips", "elf32-ntradlittlemips")
|
|
#else
|
|
OUTPUT_FORMAT("elf32-tradlittlemips", "elf32-tradbigmips", "elf32-tradlittlemips")
|
|
#endif
|
|
|
|
OUTPUT_ARCH(mips)
|
|
|
|
SECTIONS
|
|
{
|
|
PROVIDE(_start = .);
|
|
. = SIZEOF_HEADERS;
|
|
|
|
/*
|
|
* In order to retain compatibility with older toolchains we provide the
|
|
* ABI flags section ourself. Newer assemblers will automatically
|
|
* generate .MIPS.abiflags sections so we discard such input sections,
|
|
* and then manually define our own section here. genvdso will patch
|
|
* this section to have the correct name/type.
|
|
*/
|
|
.mips_abiflags : { *(.mips_abiflags) } :text :abiflags
|
|
|
|
.reginfo : { *(.reginfo) } :text :reginfo
|
|
|
|
.hash : { *(.hash) } :text
|
|
.gnu.hash : { *(.gnu.hash) }
|
|
.dynsym : { *(.dynsym) }
|
|
.dynstr : { *(.dynstr) }
|
|
.gnu.version : { *(.gnu.version) }
|
|
.gnu.version_d : { *(.gnu.version_d) }
|
|
.gnu.version_r : { *(.gnu.version_r) }
|
|
|
|
.note : { *(.note.*) } :text :note
|
|
|
|
.text : { *(.text*) } :text
|
|
PROVIDE (__etext = .);
|
|
PROVIDE (_etext = .);
|
|
PROVIDE (etext = .);
|
|
|
|
.eh_frame_hdr : { *(.eh_frame_hdr) } :text :eh_frame_hdr
|
|
.eh_frame : { KEEP (*(.eh_frame)) } :text
|
|
|
|
.dynamic : { *(.dynamic) } :text :dynamic
|
|
|
|
.rodata : { *(.rodata*) } :text
|
|
|
|
_end = .;
|
|
PROVIDE(end = .);
|
|
|
|
/DISCARD/ : {
|
|
*(.MIPS.abiflags)
|
|
*(.gnu.attributes)
|
|
*(.note.GNU-stack)
|
|
*(.data .data.* .gnu.linkonce.d.* .sdata*)
|
|
*(.bss .sbss .dynbss .dynsbss)
|
|
}
|
|
}
|
|
|
|
PHDRS
|
|
{
|
|
/*
|
|
* Provide a PT_MIPS_ABIFLAGS header to assign the ABI flags section
|
|
* to. We can specify the header type directly here so no modification
|
|
* is needed later on.
|
|
*/
|
|
abiflags 0x70000003;
|
|
|
|
/*
|
|
* The ABI flags header must exist directly after the PT_INTERP header,
|
|
* so we must explicitly place the PT_MIPS_REGINFO header after it to
|
|
* stop the linker putting one in at the start.
|
|
*/
|
|
reginfo 0x70000000;
|
|
|
|
text PT_LOAD FLAGS(5) FILEHDR PHDRS; /* PF_R|PF_X */
|
|
dynamic PT_DYNAMIC FLAGS(4); /* PF_R */
|
|
note PT_NOTE FLAGS(4); /* PF_R */
|
|
eh_frame_hdr PT_GNU_EH_FRAME;
|
|
}
|
|
|
|
VERSION
|
|
{
|
|
LINUX_2.6 {
|
|
#ifndef DISABLE_MIPS_VDSO
|
|
global:
|
|
__vdso_clock_gettime;
|
|
__vdso_gettimeofday;
|
|
#endif
|
|
local: *;
|
|
};
|
|
}
|