4bff8cb545
Convert s390 to generic vDSO. There are a few special things on s390: - vDSO can be called without a stack frame - glibc did this in the past. So we need to allocate a stackframe on our own. - The former assembly code used stcke to get the TOD clock and applied time steering to it. We need to do the same in the new code. This is done in the architecture specific __arch_get_hw_counter function. The steering information is stored in an architecure specific area in the vDSO data. - CPUCLOCK_VIRT is now handled with a syscall fallback, which might be slower/less accurate than the old implementation. The getcpu() function stays as an assembly function because there is no generic implementation and the code is just a few lines. Performance number from my system do 100 mio gettimeofday() calls: Plain syscall: 8.6s Generic VDSO: 1.3s old ASM VDSO: 1s So it's a bit slower but still much faster than syscalls. Signed-off-by: Sven Schnelle <svens@linux.ibm.com> Reviewed-by: Heiko Carstens <hca@linux.ibm.com> Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
39 lines
1.0 KiB
ArmAsm
39 lines
1.0 KiB
ArmAsm
/* SPDX-License-Identifier: GPL-2.0 */
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#include <asm/vdso.h>
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#include <asm/unistd.h>
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#include <asm/asm-offsets.h>
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#include <asm/dwarf.h>
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#include <asm/ptrace.h>
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#define WRAPPER_FRAME_SIZE (STACK_FRAME_OVERHEAD+8)
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/*
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* Older glibc version called vdso without allocating a stackframe. This wrapper
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* is just used to allocate a stackframe. See
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* https://sourceware.org/git/?p=glibc.git;a=commit;h=478593e6374f3818da39332260dc453cb19cfa1e
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* for details.
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*/
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.macro vdso_func func
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.globl __kernel_\func
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.type __kernel_\func,@function
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.align 8
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__kernel_\func:
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CFI_STARTPROC
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aghi %r15,-WRAPPER_FRAME_SIZE
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CFI_DEF_CFA_OFFSET (STACK_FRAME_OVERHEAD + WRAPPER_FRAME_SIZE)
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CFI_VAL_OFFSET 15, -STACK_FRAME_OVERHEAD
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stg %r14,STACK_FRAME_OVERHEAD(%r15)
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brasl %r14,__s390_vdso_\func
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lg %r14,STACK_FRAME_OVERHEAD(%r15)
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aghi %r15,WRAPPER_FRAME_SIZE
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CFI_DEF_CFA_OFFSET STACK_FRAME_OVERHEAD
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CFI_RESTORE 15
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br %r14
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CFI_ENDPROC
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.size __kernel_\func,.-__kernel_\func
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.endm
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vdso_func gettimeofday
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vdso_func clock_getres
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vdso_func clock_gettime
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