2015-10-21 11:54:38 +03:00
/*
* 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 && defined(CONFIG_64BIT)
/* Building 32-bit VDSO for the 64-bit kernel. Fake a 32-bit Kconfig. */
# undef CONFIG_64BIT
# define CONFIG_32BIT 1
# ifndef __ASSEMBLY__
# include <asm-generic/atomic64.h>
# endif
# endif
# ifndef __ASSEMBLY__
# include <asm/asm.h>
# include <asm/page.h>
# include <asm/vdso.h>
static inline unsigned long get_vdso_base ( void )
{
unsigned long addr ;
/*
* We can ' t use cpu_has_mips_r6 since it needs the cpu_data [ ]
* kernel symbol .
*/
# ifdef CONFIG_CPU_MIPSR6
/*
* lapc < symbol > is an alias to addiupc reg , < symbol > - .
*
* We can ' t use addiupc because there is no label - label
* support for the addiupc reloc
*/
__asm__ ( " lapc %0, _start \n "
: " =r " ( addr ) : : ) ;
# else
/*
* Get the base load address of the VDSO . We have to avoid generating
* relocations and references to the GOT because ld . so does not peform
* relocations on the VDSO . We use the current offset from the VDSO base
* and perform a PC - relative branch which gives the absolute address in
* ra , and take the difference . The assembler chokes on
* " li %0, _start - . " , so embed the offset as a word and branch over
* it .
*
*/
__asm__ (
" .set push \n "
" .set noreorder \n "
" bal 1f \n "
" nop \n "
" .word _start - . \n "
" 1: lw %0, 0($31) \n "
" " STR ( PTR_ADDU ) " %0, $31, %0 \n "
" .set pop \n "
: " =r " ( addr )
:
: " $31 " ) ;
# endif /* CONFIG_CPU_MIPSR6 */
return addr ;
}
static inline const union mips_vdso_data * get_vdso_data ( void )
{
return ( const union mips_vdso_data * ) ( get_vdso_base ( ) - PAGE_SIZE ) ;
}
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 11:57:44 +03:00
# ifdef CONFIG_CLKSRC_MIPS_GIC
static inline void __iomem * get_gic ( const union mips_vdso_data * data )
{
return ( void __iomem * ) data - PAGE_SIZE ;
}
# endif /* CONFIG_CLKSRC_MIPS_GIC */
2015-10-21 11:54:38 +03:00
# endif /* __ASSEMBLY__ */
