597bc5c00b
Currently the clock_gettime implementation in the VDSO produces a result with microsecond resolution for the cases that are handled without a system call, i.e. CLOCK_REALTIME and CLOCK_MONOTONIC. The nanoseconds field of the result is obtained by computing a microseconds value and multiplying by 1000. This changes the code in the VDSO to do the computation for clock_gettime with nanosecond resolution. That means that the resolution of the result will ultimately depend on the timebase frequency. Because the timestamp in the VDSO datapage (stamp_xsec, the real time corresponding to the timebase count in tb_orig_stamp) is in units of 2^-20 seconds, it doesn't have sufficient resolution for computing a result with nanosecond resolution. Therefore this adds a copy of xtime to the VDSO datapage and updates it in update_gtod() along with the other time-related fields. Signed-off-by: Paul Mackerras <paulus@samba.org>
267 lines
6.4 KiB
ArmAsm
267 lines
6.4 KiB
ArmAsm
/*
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* Userland implementation of gettimeofday() for 64 bits processes in a
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* ppc64 kernel for use in the vDSO
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*
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* Copyright (C) 2004 Benjamin Herrenschmuidt (benh@kernel.crashing.org),
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* IBM Corp.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <asm/processor.h>
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#include <asm/ppc_asm.h>
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#include <asm/vdso.h>
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#include <asm/asm-offsets.h>
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#include <asm/unistd.h>
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.text
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/*
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* Exact prototype of gettimeofday
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*
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* int __kernel_gettimeofday(struct timeval *tv, struct timezone *tz);
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*
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*/
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V_FUNCTION_BEGIN(__kernel_gettimeofday)
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.cfi_startproc
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mflr r12
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.cfi_register lr,r12
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mr r11,r3 /* r11 holds tv */
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mr r10,r4 /* r10 holds tz */
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bl V_LOCAL_FUNC(__get_datapage) /* get data page */
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cmpldi r11,0 /* check if tv is NULL */
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beq 2f
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bl V_LOCAL_FUNC(__do_get_xsec) /* get xsec from tb & kernel */
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lis r7,15 /* r7 = 1000000 = USEC_PER_SEC */
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ori r7,r7,16960
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rldicl r5,r4,44,20 /* r5 = sec = xsec / XSEC_PER_SEC */
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rldicr r6,r5,20,43 /* r6 = sec * XSEC_PER_SEC */
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std r5,TVAL64_TV_SEC(r11) /* store sec in tv */
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subf r0,r6,r4 /* r0 = xsec = (xsec - r6) */
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mulld r0,r0,r7 /* usec = (xsec * USEC_PER_SEC) /
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* XSEC_PER_SEC
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*/
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rldicl r0,r0,44,20
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std r0,TVAL64_TV_USEC(r11) /* store usec in tv */
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2: cmpldi r10,0 /* check if tz is NULL */
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beq 1f
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lwz r4,CFG_TZ_MINUTEWEST(r3)/* fill tz */
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lwz r5,CFG_TZ_DSTTIME(r3)
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stw r4,TZONE_TZ_MINWEST(r10)
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stw r5,TZONE_TZ_DSTTIME(r10)
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1: mtlr r12
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crclr cr0*4+so
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li r3,0 /* always success */
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blr
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.cfi_endproc
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V_FUNCTION_END(__kernel_gettimeofday)
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/*
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* Exact prototype of clock_gettime()
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*
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* int __kernel_clock_gettime(clockid_t clock_id, struct timespec *tp);
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*
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*/
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V_FUNCTION_BEGIN(__kernel_clock_gettime)
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.cfi_startproc
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/* Check for supported clock IDs */
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cmpwi cr0,r3,CLOCK_REALTIME
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cmpwi cr1,r3,CLOCK_MONOTONIC
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cror cr0*4+eq,cr0*4+eq,cr1*4+eq
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bne cr0,99f
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mflr r12 /* r12 saves lr */
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.cfi_register lr,r12
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mr r11,r4 /* r11 saves tp */
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bl V_LOCAL_FUNC(__get_datapage) /* get data page */
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50: bl V_LOCAL_FUNC(__do_get_tspec) /* get time from tb & kernel */
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bne cr1,80f /* if not monotonic, all done */
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/*
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* CLOCK_MONOTONIC
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*/
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/* now we must fixup using wall to monotonic. We need to snapshot
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* that value and do the counter trick again. Fortunately, we still
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* have the counter value in r8 that was returned by __do_get_tspec.
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* At this point, r4,r5 contain our sec/nsec values.
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*/
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lwa r6,WTOM_CLOCK_SEC(r3)
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lwa r9,WTOM_CLOCK_NSEC(r3)
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/* We now have our result in r6,r9. We create a fake dependency
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* on that result and re-check the counter
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*/
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or r0,r6,r9
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xor r0,r0,r0
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add r3,r3,r0
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ld r0,CFG_TB_UPDATE_COUNT(r3)
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cmpld cr0,r0,r8 /* check if updated */
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bne- 50b
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/* Add wall->monotonic offset and check for overflow or underflow.
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*/
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add r4,r4,r6
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add r5,r5,r9
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cmpd cr0,r5,r7
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cmpdi cr1,r5,0
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blt 1f
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subf r5,r7,r5
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addi r4,r4,1
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1: bge cr1,80f
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addi r4,r4,-1
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add r5,r5,r7
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80: std r4,TSPC64_TV_SEC(r11)
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std r5,TSPC64_TV_NSEC(r11)
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mtlr r12
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crclr cr0*4+so
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li r3,0
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blr
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/*
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* syscall fallback
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*/
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99:
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li r0,__NR_clock_gettime
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sc
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blr
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.cfi_endproc
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V_FUNCTION_END(__kernel_clock_gettime)
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/*
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* Exact prototype of clock_getres()
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*
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* int __kernel_clock_getres(clockid_t clock_id, struct timespec *res);
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*
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*/
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V_FUNCTION_BEGIN(__kernel_clock_getres)
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.cfi_startproc
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/* Check for supported clock IDs */
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cmpwi cr0,r3,CLOCK_REALTIME
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cmpwi cr1,r3,CLOCK_MONOTONIC
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cror cr0*4+eq,cr0*4+eq,cr1*4+eq
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bne cr0,99f
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li r3,0
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cmpli cr0,r4,0
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crclr cr0*4+so
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beqlr
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lis r5,CLOCK_REALTIME_RES@h
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ori r5,r5,CLOCK_REALTIME_RES@l
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std r3,TSPC64_TV_SEC(r4)
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std r5,TSPC64_TV_NSEC(r4)
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blr
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/*
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* syscall fallback
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*/
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99:
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li r0,__NR_clock_getres
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sc
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blr
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.cfi_endproc
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V_FUNCTION_END(__kernel_clock_getres)
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/*
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* This is the core of gettimeofday(), it returns the xsec
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* value in r4 and expects the datapage ptr (non clobbered)
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* in r3. clobbers r0,r4,r5,r6,r7,r8
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* When returning, r8 contains the counter value that can be reused
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*/
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V_FUNCTION_BEGIN(__do_get_xsec)
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.cfi_startproc
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/* check for update count & load values */
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1: ld r8,CFG_TB_UPDATE_COUNT(r3)
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andi. r0,r8,1 /* pending update ? loop */
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bne- 1b
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xor r0,r8,r8 /* create dependency */
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add r3,r3,r0
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/* Get TB & offset it. We use the MFTB macro which will generate
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* workaround code for Cell.
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*/
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MFTB(r7)
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ld r9,CFG_TB_ORIG_STAMP(r3)
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subf r7,r9,r7
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/* Scale result */
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ld r5,CFG_TB_TO_XS(r3)
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mulhdu r7,r7,r5
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/* Add stamp since epoch */
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ld r6,CFG_STAMP_XSEC(r3)
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add r4,r6,r7
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xor r0,r4,r4
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add r3,r3,r0
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ld r0,CFG_TB_UPDATE_COUNT(r3)
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cmpld cr0,r0,r8 /* check if updated */
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bne- 1b
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blr
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.cfi_endproc
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V_FUNCTION_END(__do_get_xsec)
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/*
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* This is the core of clock_gettime(), it returns the current
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* time in seconds and nanoseconds in r4 and r5.
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* It expects the datapage ptr in r3 and doesn't clobber it.
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* It clobbers r0 and r6 and returns NSEC_PER_SEC in r7.
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* On return, r8 contains the counter value that can be reused.
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* This clobbers cr0 but not any other cr field.
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*/
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V_FUNCTION_BEGIN(__do_get_tspec)
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.cfi_startproc
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/* check for update count & load values */
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1: ld r8,CFG_TB_UPDATE_COUNT(r3)
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andi. r0,r8,1 /* pending update ? loop */
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bne- 1b
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xor r0,r8,r8 /* create dependency */
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add r3,r3,r0
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/* Get TB & offset it. We use the MFTB macro which will generate
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* workaround code for Cell.
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*/
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MFTB(r7)
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ld r9,CFG_TB_ORIG_STAMP(r3)
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subf r7,r9,r7
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/* Scale result */
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ld r5,CFG_TB_TO_XS(r3)
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sldi r7,r7,12 /* compute time since stamp_xtime */
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mulhdu r6,r7,r5 /* in units of 2^-32 seconds */
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/* Add stamp since epoch */
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ld r4,STAMP_XTIME+TSPC64_TV_SEC(r3)
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ld r5,STAMP_XTIME+TSPC64_TV_NSEC(r3)
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or r0,r4,r5
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or r0,r0,r6
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xor r0,r0,r0
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add r3,r3,r0
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ld r0,CFG_TB_UPDATE_COUNT(r3)
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cmpld r0,r8 /* check if updated */
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bne- 1b /* reload if so */
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/* convert to seconds & nanoseconds and add to stamp */
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lis r7,NSEC_PER_SEC@h
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ori r7,r7,NSEC_PER_SEC@l
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mulhwu r0,r6,r7 /* compute nanoseconds and */
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srdi r6,r6,32 /* seconds since stamp_xtime */
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clrldi r0,r0,32
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add r5,r5,r0 /* add nanoseconds together */
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cmpd r5,r7 /* overflow? */
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add r4,r4,r6
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bltlr /* all done if no overflow */
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subf r5,r7,r5 /* if overflow, adjust */
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addi r4,r4,1
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blr
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.cfi_endproc
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V_FUNCTION_END(__do_get_tspec)
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