Commit ce7d8056 authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
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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: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201126131006.2431205-6-mpe@ellerman.id.au
parent 1f1676bb

arch/powerpc/include/asm/clocksource.h

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/* SPDX-License-Identifier: GPL-2.0 */

#ifndef _ASM_POWERPC_CLOCKSOURCE_H

#define _ASM_POWERPC_CLOCKSOURCE_H



#include <asm/vdso/clocksource.h>



#endif /* _ASM_POWERPC_CLOCKSOURCE_H */

arch/powerpc/include/asm/ppc_asm.h

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Original line number Diff line number Diff line
@@ -251,6 +251,8 @@ n: 


#define _GLOBAL_TOC(name) _GLOBAL(name)



#define DOTSYM(a)	a



#endif



/*

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

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/* SPDX-License-Identifier: GPL-2.0 */

#ifndef _ASM_POWERPC_VDSO_CLOCKSOURCE_H

#define _ASM_POWERPC_VDSO_CLOCKSOURCE_H



#define VDSO_ARCH_CLOCKMODES	VDSO_CLOCKMODE_ARCHTIMER



#endif

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

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/* SPDX-License-Identifier: GPL-2.0 */

#ifndef _ASM_POWERPC_VDSO_GETTIMEOFDAY_H

#define _ASM_POWERPC_VDSO_GETTIMEOFDAY_H



#ifdef __ASSEMBLY__



#include <asm/ppc_asm.h>



/*

 * The macros sets two stack frames, one for the caller and one for the callee

 * because there are no requirement for the caller to set a stack frame when

 * calling VDSO so it may have omitted to set one, especially on PPC64

 */



.macro cvdso_call funct

  .cfi_startproc

	PPC_STLU	r1, -PPC_MIN_STKFRM(r1)

	mflr		r0

  .cfi_register lr, r0

	PPC_STLU	r1, -PPC_MIN_STKFRM(r1)

	PPC_STL		r0, PPC_MIN_STKFRM + PPC_LR_STKOFF(r1)

	get_datapage	r5, r0

	addi		r5, r5, VDSO_DATA_OFFSET

	bl		DOTSYM(\funct)

	PPC_LL		r0, PPC_MIN_STKFRM + PPC_LR_STKOFF(r1)

	cmpwi		r3, 0

	mtlr		r0

  .cfi_restore lr

	addi		r1, r1, 2 * PPC_MIN_STKFRM

	crclr		so

	beqlr+

	crset		so

	neg		r3, r3

	blr

  .cfi_endproc

.endm



.macro cvdso_call_time funct

  .cfi_startproc

	PPC_STLU	r1, -PPC_MIN_STKFRM(r1)

	mflr		r0

  .cfi_register lr, r0

	PPC_STLU	r1, -PPC_MIN_STKFRM(r1)

	PPC_STL		r0, PPC_MIN_STKFRM + PPC_LR_STKOFF(r1)

	get_datapage	r4, r0

	addi		r4, r4, VDSO_DATA_OFFSET

	bl		DOTSYM(\funct)

	PPC_LL		r0, PPC_MIN_STKFRM + PPC_LR_STKOFF(r1)

	crclr		so

	mtlr		r0

  .cfi_restore lr

	addi		r1, r1, 2 * PPC_MIN_STKFRM

	blr

  .cfi_endproc

.endm



#else



#include <asm/vdso/timebase.h>

#include <asm/barrier.h>

#include <asm/unistd.h>

#include <uapi/linux/time.h>



#define VDSO_HAS_CLOCK_GETRES		1



#define VDSO_HAS_TIME			1



static __always_inline int do_syscall_2(const unsigned long _r0, const unsigned long _r3,

					const unsigned long _r4)

{

	register long r0 asm("r0") = _r0;

	register unsigned long r3 asm("r3") = _r3;

	register unsigned long r4 asm("r4") = _r4;

	register int ret asm ("r3");



	asm volatile(

		"       sc\n"

		"	bns+	1f\n"

		"	neg	%0, %0\n"

		"1:\n"

	: "=r" (ret), "+r" (r4), "+r" (r0)

	: "r" (r3)

	: "memory", "r5", "r6", "r7", "r8", "r9", "r10", "r11", "r12", "cr0", "ctr");



	return ret;

}



static __always_inline

int gettimeofday_fallback(struct __kernel_old_timeval *_tv, struct timezone *_tz)

{

	return do_syscall_2(__NR_gettimeofday, (unsigned long)_tv, (unsigned long)_tz);

}



static __always_inline

int clock_gettime_fallback(clockid_t _clkid, struct __kernel_timespec *_ts)

{

	return do_syscall_2(__NR_clock_gettime, _clkid, (unsigned long)_ts);

}



static __always_inline

int clock_getres_fallback(clockid_t _clkid, struct __kernel_timespec *_ts)

{

	return do_syscall_2(__NR_clock_getres, _clkid, (unsigned long)_ts);

}



#ifdef CONFIG_VDSO32



#define BUILD_VDSO32		1



static __always_inline

int clock_gettime32_fallback(clockid_t _clkid, struct old_timespec32 *_ts)

{

	return do_syscall_2(__NR_clock_gettime, _clkid, (unsigned long)_ts);

}



static __always_inline

int clock_getres32_fallback(clockid_t _clkid, struct old_timespec32 *_ts)

{

	return do_syscall_2(__NR_clock_getres, _clkid, (unsigned long)_ts);

}

#endif



static __always_inline u64 __arch_get_hw_counter(s32 clock_mode,

						 const struct vdso_data *vd)

{

	return get_tb();

}



const struct vdso_data *__arch_get_vdso_data(void);



static inline bool vdso_clocksource_ok(const struct vdso_data *vd)

{

	return true;

}

#define vdso_clocksource_ok vdso_clocksource_ok



/*

 * powerpc specific delta calculation.

 *

 * This variant removes the masking of the subtraction because the

 * clocksource mask of all VDSO capable clocksources on powerpc is U64_MAX

 * which would result in a pointless operation. The compiler cannot

 * optimize it away as the mask comes from the vdso data and is not compile

 * time constant.

 */

static __always_inline u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult)

{

	return (cycles - last) * mult;

}

#define vdso_calc_delta vdso_calc_delta



#ifndef __powerpc64__

static __always_inline u64 vdso_shift_ns(u64 ns, unsigned long shift)

{

	u32 hi = ns >> 32;

	u32 lo = ns;



	lo >>= shift;

	lo |= hi << (32 - shift);

	hi >>= shift;



	if (likely(hi == 0))

		return lo;



	return ((u64)hi << 32) | lo;

}

#define vdso_shift_ns vdso_shift_ns

#endif



#ifdef __powerpc64__

int __c_kernel_clock_gettime(clockid_t clock, struct __kernel_timespec *ts,

			     const struct vdso_data *vd);

int __c_kernel_clock_getres(clockid_t clock_id, struct __kernel_timespec *res,

			    const struct vdso_data *vd);

#else

int __c_kernel_clock_gettime(clockid_t clock, struct old_timespec32 *ts,

			     const struct vdso_data *vd);

int __c_kernel_clock_getres(clockid_t clock_id, struct old_timespec32 *res,

			    const struct vdso_data *vd);

#endif

int __c_kernel_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz,

			    const struct vdso_data *vd);

__kernel_old_time_t __c_kernel_time(__kernel_old_time_t *time,

				    const struct vdso_data *vd);

#endif /* __ASSEMBLY__ */



#endif /* _ASM_POWERPC_VDSO_GETTIMEOFDAY_H */

arch/powerpc/kernel/vdso32/vgettimeofday.c

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// SPDX-License-Identifier: GPL-2.0

/*

 * Powerpc userspace implementations of gettimeofday() and similar.

 */

#include <linux/types.h>



int __c_kernel_clock_gettime(clockid_t clock, struct old_timespec32 *ts,

			     const struct vdso_data *vd)

{

	return __cvdso_clock_gettime32_data(vd, clock, ts);

}



int __c_kernel_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz,

			    const struct vdso_data *vd)

{

	return __cvdso_gettimeofday_data(vd, tv, tz);

}



int __c_kernel_clock_getres(clockid_t clock_id, struct old_timespec32 *res,

			    const struct vdso_data *vd)

{

	return __cvdso_clock_getres_time32_data(vd, clock_id, res);

}



__kernel_old_time_t __c_kernel_time(__kernel_old_time_t *time, const struct vdso_data *vd)

{

	return __cvdso_time_data(vd, time);

}

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