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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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56d20861c0
Call Frame Information is used by gdb for back-traces and inserting breakpoints on function return for the "finish" command. This failed when inside __kernel_clock_gettime. More concerning than difficulty debugging is that CFI is also used by stack frame unwinding code to implement exceptions. If you have an app that needs to handle asynchronous exceptions for some reason, and you are unlucky enough to get one inside the VDSO time functions, your app will crash. What's wrong: There is control flow in __kernel_clock_gettime that reaches label 99 without saving lr in r12. CFI info however is interpreted by the unwinder without reference to control flow: It's a simple matter of "Execute all the CFI opcodes up to the current address". That means the unwinder thinks r12 contains the return address at label 99. Disabuse it of that notion by resetting CFI for the return address at label 99. Note that the ".cfi_restore lr" could have gone anywhere from the "mtlr r12" a few instructions earlier to the instruction at label 99. I put the CFI as late as possible, because in general that's best practice (and if possible grouped with other CFI in order to reduce the number of CFI opcodes executed when unwinding). Using r12 as the return address is perfectly fine after the "mtlr r12" since r12 on that code path still contains the return address. __get_datapage also has a CFI error. That function temporarily saves lr in r0, and reflects that fact with ".cfi_register lr,r0". A later use of r0 means the CFI at that point isn't correct, as r0 no longer contains the return address. Fix that too. Signed-off-by: Alan Modra <amodra@gmail.com> Tested-by: Reza Arbab <arbab@linux.ibm.com> Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
291 lines
6.9 KiB
ArmAsm
291 lines
6.9 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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lis r7,1000000@ha /* load up USEC_PER_SEC */
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addi r7,r7,1000000@l
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bl V_LOCAL_FUNC(__do_get_tspec) /* get sec/us from tb & kernel */
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std r4,TVAL64_TV_SEC(r11) /* store sec in tv */
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std r5,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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cmpwi cr5,r3,CLOCK_REALTIME_COARSE
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cmpwi cr6,r3,CLOCK_MONOTONIC_COARSE
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cror cr5*4+eq,cr5*4+eq,cr6*4+eq
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cror cr0*4+eq,cr0*4+eq,cr5*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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lis r7,NSEC_PER_SEC@h /* want nanoseconds */
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ori r7,r7,NSEC_PER_SEC@l
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beq cr5,70f
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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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b 78f
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/*
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* For coarse clocks we get data directly from the vdso data page, so
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* we don't need to call __do_get_tspec, but we still need to do the
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* counter trick.
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*/
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70: ld r8,CFG_TB_UPDATE_COUNT(r3)
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andi. r0,r8,1 /* pending update ? loop */
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bne- 70b
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add r3,r3,r0 /* r0 is already 0 */
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/*
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* CLOCK_REALTIME_COARSE, below values are needed for MONOTONIC_COARSE
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* too
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*/
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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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bne cr6,75f
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/* CLOCK_MONOTONIC_COARSE */
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lwa r6,WTOM_CLOCK_SEC(r3)
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lwa r9,WTOM_CLOCK_NSEC(r3)
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/* check if counter has updated */
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or r0,r6,r9
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75: or r0,r0,r4
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or r0,r0,r5
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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- 70b
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/* Counter has not updated, so continue calculating proper values for
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* sec and nsec if monotonic coarse, or just return with the proper
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* values for realtime.
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*/
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bne cr6,80f
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/* Add wall->monotonic offset and check for overflow or underflow */
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78: 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 79f
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subf r5,r7,r5
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addi r4,r4,1
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79: 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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.cfi_restore lr
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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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cmpldi 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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* Exact prototype of time()
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*
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* time_t time(time *t);
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*
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*/
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V_FUNCTION_BEGIN(__kernel_time)
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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 t */
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bl V_LOCAL_FUNC(__get_datapage)
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ld r4,STAMP_XTIME+TSPC64_TV_SEC(r3)
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cmpldi r11,0 /* check if t is NULL */
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beq 2f
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std r4,0(r11) /* store result at *t */
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2: mtlr r12
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crclr cr0*4+so
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mr r3,r4
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blr
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.cfi_endproc
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V_FUNCTION_END(__kernel_time)
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/*
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* This is the core of clock_gettime() and gettimeofday(),
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* it returns the current time in r4 (seconds) and r5.
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* On entry, r7 gives the resolution of r5, either USEC_PER_SEC
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* or NSEC_PER_SEC, giving r5 in microseconds or nanoseconds.
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* It expects the datapage ptr in r3 and doesn't clobber it.
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* It clobbers r0, r6 and r9.
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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(r6)
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ld r9,CFG_TB_ORIG_STAMP(r3)
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subf r6,r9,r6
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/* Scale result */
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ld r5,CFG_TB_TO_XS(r3)
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sldi r6,r6,12 /* compute time since stamp_xtime */
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mulhdu r6,r6,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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lwz r5,STAMP_SEC_FRAC(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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add r6,r6,r5 /* add on fractional seconds of xtime */
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mulhwu r5,r6,r7 /* compute micro or nanoseconds and */
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srdi r6,r6,32 /* seconds since stamp_xtime */
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clrldi r5,r5,32
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add r4,r4,r6
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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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