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SubjectRe: [PATCH v4 7/8] powerpc/vdso32: implement clock_getres entirely
Hi,

On 2019-12-02 07:57, Christophe Leroy wrote:
> clock_getres returns hrtimer_res for all clocks but coarse ones
> for which it returns KTIME_LOW_RES.
>
> return EINVAL for unknown clocks.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> ---
> arch/powerpc/kernel/asm-offsets.c | 3 +++
> arch/powerpc/kernel/vdso32/gettimeofday.S | 19 +++++++++++--------
> 2 files changed, 14 insertions(+), 8 deletions(-)
>
> diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
> index 0013197d89a6..90e53d432f2e 100644
> --- a/arch/powerpc/kernel/asm-offsets.c
> +++ b/arch/powerpc/kernel/asm-offsets.c
> @@ -413,7 +413,10 @@ int main(void)
> DEFINE(CLOCK_MONOTONIC, CLOCK_MONOTONIC);
> DEFINE(CLOCK_REALTIME_COARSE, CLOCK_REALTIME_COARSE);
> DEFINE(CLOCK_MONOTONIC_COARSE, CLOCK_MONOTONIC_COARSE);
> + DEFINE(CLOCK_MAX, CLOCK_TAI);
> DEFINE(NSEC_PER_SEC, NSEC_PER_SEC);
> + DEFINE(EINVAL, EINVAL);
> + DEFINE(KTIME_LOW_RES, KTIME_LOW_RES);
>
> #ifdef CONFIG_BUG
> DEFINE(BUG_ENTRY_SIZE, sizeof(struct bug_entry));
> diff --git a/arch/powerpc/kernel/vdso32/gettimeofday.S b/arch/powerpc/kernel/vdso32/gettimeofday.S
> index 9aafacea9c4a..20ae38f3a5a3 100644
> --- a/arch/powerpc/kernel/vdso32/gettimeofday.S
> +++ b/arch/powerpc/kernel/vdso32/gettimeofday.S
> @@ -196,17 +196,20 @@ V_FUNCTION_END(__kernel_clock_gettime)
> V_FUNCTION_BEGIN(__kernel_clock_getres)
> .cfi_startproc
> /* Check for supported clock IDs */
> - cmpwi cr0,r3,CLOCK_REALTIME
> - cmpwi cr1,r3,CLOCK_MONOTONIC
> - cror cr0*4+eq,cr0*4+eq,cr1*4+eq
> - bne cr0,99f
> + cmplwi cr0, r3, CLOCK_MAX
> + cmpwi cr1, r3, CLOCK_REALTIME_COARSE
> + cmpwi cr7, r3, CLOCK_MONOTONIC_COARSE
> + bgt cr0, 99f
> + LOAD_REG_IMMEDIATE(r5, KTIME_LOW_RES)
> + beq cr1, 1f
> + beq cr7, 1f
>
> mflr r12
> .cfi_register lr,r12
> get_datapage r3, r0
> lwz r5, CLOCK_HRTIMER_RES(r3)
> mtlr r12
> - li r3,0
> +1: li r3,0
> cmpli cr0,r4,0
> crclr cr0*4+so
> beqlr
> @@ -215,11 +218,11 @@ V_FUNCTION_BEGIN(__kernel_clock_getres)
> blr
>
> /*
> - * syscall fallback
> + * invalid clock
> */
> 99:
> - li r0,__NR_clock_getres
> - sc
> + li r3, EINVAL
> + crset so
> blr
> .cfi_endproc
> V_FUNCTION_END(__kernel_clock_getres)

Removing the syscall fallback looks wrong, and broke access to
per-processes clocks. With this change a few glibc tests now fail.

This can be reproduced by the simple code below:

| #include <errno.h>
| #include <stdio.h>
| #include <string.h>
| #include <sys/types.h>
| #include <time.h>
| #include <unistd.h>
|
| int main()
| {
| struct timespec res;
| clockid_t ci;
| int e;
|
| e = clock_getcpuclockid(getpid(), &ci);
| if (e) {
| printf("clock_getcpuclockid returned %d\n", e);
| return e;
| }
| e = clock_getres (ci, &res);
| printf("clock_getres returned %d\n", e);
| if (e) {
| printf(" errno: %d, %s\n", errno, strerror(errno));
| }
|
| return e;
| }

Without this patch or with -m64, it returns:

| clock_getres returned 0

With this patch with -m32 it returns:

| clock_getres returned -1
| errno: 22, Invalid argument

Regards,
Aurelien

--
Aurelien Jarno GPG: 4096R/1DDD8C9B
aurelien@aurel32.net http://www.aurel32.net

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