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powerpc/vdso: Prepare for switching VDSO to generic C implementation.
Prepare for switching VDSO to generic C implementation in following patch. Here, we: - Prepare the helpers to call the C VDSO functions - Prepare the required callbacks for the C VDSO functions - Prepare the clocksource.h files to define VDSO_ARCH_CLOCKMODES - Add the C trampolines to the generic C VDSO functions powerpc is a bit special for VDSO as well as system calls in the way that it requires setting CR SO bit which cannot be done in C. Therefore, entry/exit needs to be performed in ASM. Implementing __arch_get_vdso_data() would clobber the link register, requiring the caller to save it. As the ASM calling function already has to set a stack frame and saves the link register before calling the C vdso function, retriving the vdso data pointer there is lighter. Implement __arch_vdso_capable() and always return true. Provide vdso_shift_ns(), as the generic x >> s gives the following bad result: 18: 35 25 ff e0 addic. r9,r5,-32 1c: 41 80 00 10 blt 2c <shift+0x14> 20: 7c 64 4c 30 srw r4,r3,r9 24: 38 60 00 00 li r3,0 ... 2c: 54 69 08 3c rlwinm r9,r3,1,0,30 30: 21 45 00 1f subfic r10,r5,31 34: 7c 84 2c 30 srw r4,r4,r5 38: 7d 29 50 30 slw r9,r9,r10 3c: 7c 63 2c 30 srw r3,r3,r5 40: 7d 24 23 78 or r4,r9,r4 In our case the shift is always <= 32. In addition, the upper 32 bits of the result are likely nul. Lets GCC know it, it also optimises the following calculations. With the patch, we get: 0: 21 25 00 20 subfic r9,r5,32 4: 7c 69 48 30 slw r9,r3,r9 8: 7c 84 2c 30 srw r4,r4,r5 c: 7d 24 23 78 or r4,r9,r4 10: 7c 63 2c 30 srw r3,r3,r5 Signed-off-by: Christophe Leroy <[email protected]> Signed-off-by: Michael Ellerman <[email protected]> Link: https://lore.kernel.org/r/[email protected]
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‎arch/powerpc/include/asm/clocksource.h

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/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_POWERPC_CLOCKSOURCE_H
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#define _ASM_POWERPC_CLOCKSOURCE_H
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#include <asm/vdso/clocksource.h>
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#endif /* _ASM_POWERPC_CLOCKSOURCE_H */

‎arch/powerpc/include/asm/ppc_asm.h

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@@ -251,6 +251,8 @@ GLUE(.,name):
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#define _GLOBAL_TOC(name) _GLOBAL(name)
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#define DOTSYM(a) a
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#endif
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/*

‎arch/powerpc/include/asm/vdso/clocksource.h

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/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_POWERPC_VDSO_CLOCKSOURCE_H
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#define _ASM_POWERPC_VDSO_CLOCKSOURCE_H
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#define VDSO_ARCH_CLOCKMODES VDSO_CLOCKMODE_ARCHTIMER
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#endif

‎arch/powerpc/include/asm/vdso/gettimeofday.h

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/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_POWERPC_VDSO_GETTIMEOFDAY_H
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#define _ASM_POWERPC_VDSO_GETTIMEOFDAY_H
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#ifdef __ASSEMBLY__
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#include <asm/ppc_asm.h>
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/*
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* The macros sets two stack frames, one for the caller and one for the callee
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* because there are no requirement for the caller to set a stack frame when
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* calling VDSO so it may have omitted to set one, especially on PPC64
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*/
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.macro cvdso_call funct
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.cfi_startproc
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PPC_STLU r1, -PPC_MIN_STKFRM(r1)
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mflr r0
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.cfi_register lr, r0
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PPC_STLU r1, -PPC_MIN_STKFRM(r1)
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PPC_STL r0, PPC_MIN_STKFRM + PPC_LR_STKOFF(r1)
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get_datapage r5, r0
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addi r5, r5, VDSO_DATA_OFFSET
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bl DOTSYM(\funct)
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PPC_LL r0, PPC_MIN_STKFRM + PPC_LR_STKOFF(r1)
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cmpwi r3, 0
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mtlr r0
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.cfi_restore lr
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addi r1, r1, 2 * PPC_MIN_STKFRM
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crclr so
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beqlr+
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crset so
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neg r3, r3
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blr
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.cfi_endproc
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.endm
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.macro cvdso_call_time funct
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.cfi_startproc
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PPC_STLU r1, -PPC_MIN_STKFRM(r1)
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mflr r0
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.cfi_register lr, r0
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PPC_STLU r1, -PPC_MIN_STKFRM(r1)
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PPC_STL r0, PPC_MIN_STKFRM + PPC_LR_STKOFF(r1)
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get_datapage r4, r0
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addi r4, r4, VDSO_DATA_OFFSET
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bl DOTSYM(\funct)
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PPC_LL r0, PPC_MIN_STKFRM + PPC_LR_STKOFF(r1)
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crclr so
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mtlr r0
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.cfi_restore lr
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addi r1, r1, 2 * PPC_MIN_STKFRM
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blr
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.cfi_endproc
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.endm
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#else
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#include <asm/vdso/timebase.h>
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#include <asm/barrier.h>
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#include <asm/unistd.h>
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#include <uapi/linux/time.h>
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#define VDSO_HAS_CLOCK_GETRES 1
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#define VDSO_HAS_TIME 1
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static __always_inline int do_syscall_2(const unsigned long _r0, const unsigned long _r3,
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const unsigned long _r4)
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{
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register long r0 asm("r0") = _r0;
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register unsigned long r3 asm("r3") = _r3;
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register unsigned long r4 asm("r4") = _r4;
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register int ret asm ("r3");
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asm volatile(
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" sc\n"
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" bns+ 1f\n"
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" neg %0, %0\n"
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"1:\n"
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: "=r" (ret), "+r" (r4), "+r" (r0)
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: "r" (r3)
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: "memory", "r5", "r6", "r7", "r8", "r9", "r10", "r11", "r12", "cr0", "ctr");
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return ret;
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}
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static __always_inline
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int gettimeofday_fallback(struct __kernel_old_timeval *_tv, struct timezone *_tz)
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{
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return do_syscall_2(__NR_gettimeofday, (unsigned long)_tv, (unsigned long)_tz);
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}
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static __always_inline
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int clock_gettime_fallback(clockid_t _clkid, struct __kernel_timespec *_ts)
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{
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return do_syscall_2(__NR_clock_gettime, _clkid, (unsigned long)_ts);
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}
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static __always_inline
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int clock_getres_fallback(clockid_t _clkid, struct __kernel_timespec *_ts)
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{
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return do_syscall_2(__NR_clock_getres, _clkid, (unsigned long)_ts);
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}
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#ifdef CONFIG_VDSO32
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#define BUILD_VDSO32 1
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static __always_inline
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int clock_gettime32_fallback(clockid_t _clkid, struct old_timespec32 *_ts)
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{
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return do_syscall_2(__NR_clock_gettime, _clkid, (unsigned long)_ts);
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}
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static __always_inline
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int clock_getres32_fallback(clockid_t _clkid, struct old_timespec32 *_ts)
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{
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return do_syscall_2(__NR_clock_getres, _clkid, (unsigned long)_ts);
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}
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#endif
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static __always_inline u64 __arch_get_hw_counter(s32 clock_mode,
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const struct vdso_data *vd)
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{
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return get_tb();
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}
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const struct vdso_data *__arch_get_vdso_data(void);
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static inline bool vdso_clocksource_ok(const struct vdso_data *vd)
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{
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return true;
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}
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#define vdso_clocksource_ok vdso_clocksource_ok
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/*
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* powerpc specific delta calculation.
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*
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* This variant removes the masking of the subtraction because the
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* clocksource mask of all VDSO capable clocksources on powerpc is U64_MAX
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* which would result in a pointless operation. The compiler cannot
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* optimize it away as the mask comes from the vdso data and is not compile
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* time constant.
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*/
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static __always_inline u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult)
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{
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return (cycles - last) * mult;
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}
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#define vdso_calc_delta vdso_calc_delta
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#ifndef __powerpc64__
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static __always_inline u64 vdso_shift_ns(u64 ns, unsigned long shift)
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{
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u32 hi = ns >> 32;
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u32 lo = ns;
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lo >>= shift;
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lo |= hi << (32 - shift);
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hi >>= shift;
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if (likely(hi == 0))
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return lo;
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return ((u64)hi << 32) | lo;
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}
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#define vdso_shift_ns vdso_shift_ns
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#endif
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#ifdef __powerpc64__
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int __c_kernel_clock_gettime(clockid_t clock, struct __kernel_timespec *ts,
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const struct vdso_data *vd);
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int __c_kernel_clock_getres(clockid_t clock_id, struct __kernel_timespec *res,
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const struct vdso_data *vd);
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#else
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int __c_kernel_clock_gettime(clockid_t clock, struct old_timespec32 *ts,
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const struct vdso_data *vd);
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int __c_kernel_clock_getres(clockid_t clock_id, struct old_timespec32 *res,
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const struct vdso_data *vd);
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#endif
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int __c_kernel_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz,
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const struct vdso_data *vd);
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__kernel_old_time_t __c_kernel_time(__kernel_old_time_t *time,
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const struct vdso_data *vd);
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#endif /* __ASSEMBLY__ */
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#endif /* _ASM_POWERPC_VDSO_GETTIMEOFDAY_H */

‎arch/powerpc/kernel/vdso32/vgettimeofday.c

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// SPDX-License-Identifier: GPL-2.0
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/*
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* Powerpc userspace implementations of gettimeofday() and similar.
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*/
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#include <linux/types.h>
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int __c_kernel_clock_gettime(clockid_t clock, struct old_timespec32 *ts,
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const struct vdso_data *vd)
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{
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return __cvdso_clock_gettime32_data(vd, clock, ts);
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}
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int __c_kernel_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz,
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const struct vdso_data *vd)
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{
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return __cvdso_gettimeofday_data(vd, tv, tz);
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}
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int __c_kernel_clock_getres(clockid_t clock_id, struct old_timespec32 *res,
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const struct vdso_data *vd)
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{
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return __cvdso_clock_getres_time32_data(vd, clock_id, res);
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}
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__kernel_old_time_t __c_kernel_time(__kernel_old_time_t *time, const struct vdso_data *vd)
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{
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return __cvdso_time_data(vd, time);
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}

‎arch/powerpc/kernel/vdso64/vgettimeofday.c

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// SPDX-License-Identifier: GPL-2.0
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/*
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* Powerpc userspace implementations of gettimeofday() and similar.
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*/
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#include <linux/time.h>
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#include <linux/types.h>
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int __c_kernel_clock_gettime(clockid_t clock, struct __kernel_timespec *ts,
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const struct vdso_data *vd)
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{
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return __cvdso_clock_gettime_data(vd, clock, ts);
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}
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int __c_kernel_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz,
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const struct vdso_data *vd)
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{
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return __cvdso_gettimeofday_data(vd, tv, tz);
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}
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int __c_kernel_clock_getres(clockid_t clock_id, struct __kernel_timespec *res,
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const struct vdso_data *vd)
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{
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return __cvdso_clock_getres_data(vd, clock_id, res);
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}
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__kernel_old_time_t __c_kernel_time(__kernel_old_time_t *time, const struct vdso_data *vd)
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{
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return __cvdso_time_data(vd, time);
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}

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