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author | Christophe Leroy <christophe.leroy@csgroup.eu> | 2020-11-27 00:10:03 +1100 |
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committer | Michael Ellerman <mpe@ellerman.id.au> | 2020-12-04 01:01:10 +1100 |
commit | ce7d8056e38b770f070fc4499c577322b6ccb9c7 (patch) | |
tree | f02c93e953ba4c907e33ac6d08936519d2858934 /arch/powerpc/kernel/vdso32 | |
parent | 1f1676bb2dd52c1054db8476d6387e6dcf62a1ba (diff) | |
download | linux-ce7d8056e38b770f070fc4499c577322b6ccb9c7.tar.gz linux-ce7d8056e38b770f070fc4499c577322b6ccb9c7.tar.bz2 linux-ce7d8056e38b770f070fc4499c577322b6ccb9c7.zip |
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 <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201126131006.2431205-6-mpe@ellerman.id.au
Diffstat (limited to 'arch/powerpc/kernel/vdso32')
-rw-r--r-- | arch/powerpc/kernel/vdso32/vgettimeofday.c | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/vdso32/vgettimeofday.c b/arch/powerpc/kernel/vdso32/vgettimeofday.c new file mode 100644 index 000000000000..0d4bc217529e --- /dev/null +++ b/arch/powerpc/kernel/vdso32/vgettimeofday.c @@ -0,0 +1,28 @@ +// 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); +} |