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:
- When the timebase is used, make it always return true.
- When the RTC clock is used, make it always return false.

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 <christophe.le...@csgroup.eu>
---
v11:
- Changed of __arch_get_hw_counter() to adapt to 4c5a116ada95
("vdso/treewide: Add vdso_data pointer argument to __arch_get_hw_counter()")

v10:
- Added a comment to explain the reason for the two stack frames.
- Moved back the .cfi_register next to mflr

v9:
- No more modification of __get_datapage(). Offset is added after.
- Adding a second stack frame because the PPC VDSO ABI doesn't force
the caller to set one.

v8:
- New, splitted out of last patch of the series

Signed-off-by: Christophe Leroy <christophe.le...@csgroup.eu>
---
 arch/powerpc/include/asm/clocksource.h       |   7 +
 arch/powerpc/include/asm/vdso/clocksource.h  |   7 +
 arch/powerpc/include/asm/vdso/gettimeofday.h | 186 +++++++++++++++++++
 arch/powerpc/kernel/vdso32/vgettimeofday.c   |  29 +++
 arch/powerpc/kernel/vdso64/vgettimeofday.c   |  29 +++
 5 files changed, 258 insertions(+)
 create mode 100644 arch/powerpc/include/asm/clocksource.h
 create mode 100644 arch/powerpc/include/asm/vdso/clocksource.h
 create mode 100644 arch/powerpc/include/asm/vdso/gettimeofday.h
 create mode 100644 arch/powerpc/kernel/vdso32/vgettimeofday.c
 create mode 100644 arch/powerpc/kernel/vdso64/vgettimeofday.c

diff --git a/arch/powerpc/include/asm/clocksource.h 
b/arch/powerpc/include/asm/clocksource.h
new file mode 100644
index 000000000000..482185566b0c
--- /dev/null
+++ b/arch/powerpc/include/asm/clocksource.h
@@ -0,0 +1,7 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_CLOCKSOURCE_H
+#define _ASM_CLOCKSOURCE_H
+
+#include <asm/vdso/clocksource.h>
+
+#endif
diff --git a/arch/powerpc/include/asm/vdso/clocksource.h 
b/arch/powerpc/include/asm/vdso/clocksource.h
new file mode 100644
index 000000000000..ec5d672d2569
--- /dev/null
+++ b/arch/powerpc/include/asm/vdso/clocksource.h
@@ -0,0 +1,7 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_VDSOCLOCKSOURCE_H
+#define __ASM_VDSOCLOCKSOURCE_H
+
+#define VDSO_ARCH_CLOCKMODES   VDSO_CLOCKMODE_ARCHTIMER
+
+#endif
diff --git a/arch/powerpc/include/asm/vdso/gettimeofday.h 
b/arch/powerpc/include/asm/vdso/gettimeofday.h
new file mode 100644
index 000000000000..dce9d5051259
--- /dev/null
+++ b/arch/powerpc/include/asm/vdso/gettimeofday.h
@@ -0,0 +1,186 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_VDSO_GETTIMEOFDAY_H
+#define __ASM_VDSO_GETTIMEOFDAY_H
+
+#include <asm/ptrace.h>
+
+#ifdef __ASSEMBLY__
+
+/*
+ * 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, -STACK_FRAME_OVERHEAD(r1)
+       mflr            r0
+  .cfi_register lr, r0
+       PPC_STLU        r1, -STACK_FRAME_OVERHEAD(r1)
+       PPC_STL         r0, STACK_FRAME_OVERHEAD + PPC_LR_STKOFF(r1)
+       get_datapage    r5, r0
+       addi            r5, r5, VDSO_DATA_OFFSET
+       bl              \funct
+       PPC_LL          r0, STACK_FRAME_OVERHEAD + PPC_LR_STKOFF(r1)
+       cmpwi           r3, 0
+       mtlr            r0
+  .cfi_restore lr
+       addi            r1, r1, 2 * STACK_FRAME_OVERHEAD
+       crclr           so
+       beqlr+
+       crset           so
+       neg             r3, r3
+       blr
+  .cfi_endproc
+.endm
+
+.macro cvdso_call_time funct
+  .cfi_startproc
+       PPC_STLU        r1, -STACK_FRAME_OVERHEAD(r1)
+       mflr            r0
+  .cfi_register lr, r0
+       PPC_STLU        r1, -STACK_FRAME_OVERHEAD(r1)
+       PPC_STL         r0, STACK_FRAME_OVERHEAD + PPC_LR_STKOFF(r1)
+       get_datapage    r4, r0
+       addi            r4, r4, VDSO_DATA_OFFSET
+       bl              \funct
+       PPC_LL          r0, STACK_FRAME_OVERHEAD + PPC_LR_STKOFF(r1)
+       crclr           so
+       mtlr            r0
+  .cfi_restore lr
+       addi            r1, r1, 2 * STACK_FRAME_OVERHEAD
+       blr
+  .cfi_endproc
+.endm
+
+#else
+
+#include <asm/time.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 !__USE_RTC();
+}
+#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_VDSO_GETTIMEOFDAY_H */
diff --git a/arch/powerpc/kernel/vdso32/vgettimeofday.c 
b/arch/powerpc/kernel/vdso32/vgettimeofday.c
new file mode 100644
index 000000000000..0b9ab4c22ef2
--- /dev/null
+++ b/arch/powerpc/kernel/vdso32/vgettimeofday.c
@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Powerpc userspace implementations of gettimeofday() and similar.
+ */
+#include <linux/time.h>
+#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);
+}
diff --git a/arch/powerpc/kernel/vdso64/vgettimeofday.c 
b/arch/powerpc/kernel/vdso64/vgettimeofday.c
new file mode 100644
index 000000000000..5b5500058344
--- /dev/null
+++ b/arch/powerpc/kernel/vdso64/vgettimeofday.c
@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Powerpc userspace implementations of gettimeofday() and similar.
+ */
+#include <linux/time.h>
+#include <linux/types.h>
+
+int __c_kernel_clock_gettime(clockid_t clock, struct __kernel_timespec *ts,
+                            const struct vdso_data *vd)
+{
+       return __cvdso_clock_gettime_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 __kernel_timespec *res,
+                           const struct vdso_data *vd)
+{
+       return __cvdso_clock_getres_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);
+}
-- 
2.25.0

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