[PATCH 4/8] ppc: Use libc_ifunc macro for time, gettimeofday.
Stefan Liebler
stli@linux.vnet.ibm.com
Fri Jul 29 15:38:00 GMT 2016
This is an update due to the comments from Paul.
On 06/23/2016 01:55 PM, Stefan Liebler wrote:
> This patch uses the libc_ifunc macro to create already existing ifunc functions
> time and gettimeofday on power. This way, the libc_hidden_def macro can be used
> instead of inline assemblies.
> On ppc32, the __GI_* symbols do not target the ifunc symbol and thus the
> redirection construct has to be applied here.
>
> ChangeLog:
>
> * sysdeps/unix/sysv/linux/powerpc/gettimeofday.c (__gettimeofday):
> Use libc_ifunc and libc_hidden_def macro. Redirect ifunced function in
> header and create a copy of the prototype for using as ifunc function
> for ppc32 and add appropiate aliases to the real symbol names.
> * sysdeps/unix/sysv/linux/powerpc/time.c (time): Likewise.
> ---
> sysdeps/unix/sysv/linux/powerpc/gettimeofday.c | 64 ++++++++++++++-----------
> sysdeps/unix/sysv/linux/powerpc/time.c | 66 +++++++++++++-------------
> 2 files changed, 69 insertions(+), 61 deletions(-)
>
> diff --git a/sysdeps/unix/sysv/linux/powerpc/gettimeofday.c b/sysdeps/unix/sysv/linux/powerpc/gettimeofday.c
> index 25a4e7c..366364c 100644
> --- a/sysdeps/unix/sysv/linux/powerpc/gettimeofday.c
> +++ b/sysdeps/unix/sysv/linux/powerpc/gettimeofday.c
> @@ -15,6 +15,9 @@
> License along with the GNU C Library; if not, see
> <http://www.gnu.org/licenses/>. */
>
> +#if defined SHARED && !defined __powerpc64__
> +# define __gettimeofday __redirect___gettimeofday
> +#endif
>
> #include <sys/time.h>
>
> @@ -24,30 +27,17 @@
> # include <libc-vdso.h>
> # include <dl-machine.h>
>
> -void *gettimeofday_ifunc (void) __asm__ ("__gettimeofday");
> +# ifndef __powerpc64__
> +# undef __gettimeofday
>
> -static int
> -__gettimeofday_syscall (struct timeval *tv, struct timezone *tz)
> -{
> - return INLINE_SYSCALL (gettimeofday, 2, tv, tz);
> -}
> +extern __typeof (__redirect___gettimeofday) __libc___gettimeofday;
> +# define __gettimeofday __libc___gettimeofday
>
> -void *
> -gettimeofday_ifunc (void)
> +int
> +__gettimeofday_vsyscall (struct timeval *tv, struct timezone *tz)
> {
> - PREPARE_VERSION (linux2615, "LINUX_2.6.15", 123718565);
> -
> - /* If the vDSO is not available we fall back syscall. */
> - void *vdso_gettimeofday = _dl_vdso_vsym ("__kernel_gettimeofday", &linux2615);
> - return (vdso_gettimeofday ? VDSO_IFUNC_RET (vdso_gettimeofday)
> - : (void*)__gettimeofday_syscall);
> + return INLINE_VSYSCALL (gettimeofday, 2, tv, tz);
> }
> -asm (".type __gettimeofday, %gnu_indirect_function");
> -
> -/* This is doing "libc_hidden_def (__gettimeofday)" but the compiler won't
> - let us do it in C because it doesn't know we're defining __gettimeofday
> - here in this file. */
> -asm (".globl __GI___gettimeofday");
>
> /* __GI___gettimeofday is defined as hidden and for ppc32 it enables the
> compiler make a local call (symbol@local) for internal GLIBC usage. It
> @@ -55,16 +45,29 @@ asm (".globl __GI___gettimeofday");
> For ppc64 a call to a function in another translation unit might use a
> different toc pointer thus disallowing direct branchess and making internal
> ifuncs calls safe. */
> -#ifdef __powerpc64__
> -asm ("__GI___gettimeofday = __gettimeofday");
> -#else
> -int
> -__gettimeofday_vsyscall (struct timeval *tv, struct timezone *tz)
> +# undef libc_hidden_def
> +# define libc_hidden_def(name) \
> + __hidden_ver1 (__gettimeofday_vsyscall, __GI___gettimeofday, \
> + __gettimeofday_vsyscall);
> +
> +# endif
> +
> +static int
> +__gettimeofday_syscall (struct timeval *tv, struct timezone *tz)
> {
> - return INLINE_VSYSCALL (gettimeofday, 2, tv, tz);
> + return INLINE_SYSCALL (gettimeofday, 2, tv, tz);
> }
> -asm ("__GI___gettimeofday = __gettimeofday_vsyscall");
> -#endif
> +
> +# define INIT_ARCH() \
> + PREPARE_VERSION (linux2615, "LINUX_2.6.15", 123718565); \
> + void *vdso_gettimeofday = _dl_vdso_vsym ("__kernel_gettimeofday", &linux2615);
> +
> +/* If the vDSO is not available we fall back syscall. */
> +libc_ifunc (__gettimeofday,
> + vdso_gettimeofday
> + ? VDSO_IFUNC_RET (vdso_gettimeofday)
> + : (void *) __gettimeofday_syscall);
> +libc_hidden_def (__gettimeofday)
>
> #else
>
> @@ -81,3 +84,8 @@ libc_hidden_def (__gettimeofday)
> #endif
> weak_alias (__gettimeofday, gettimeofday)
> libc_hidden_weak (gettimeofday)
> +
> +#if defined SHARED && !defined __powerpc64__
> +# undef __gettimeofday
> +strong_alias (__libc___gettimeofday, __gettimeofday)
> +#endif
> diff --git a/sysdeps/unix/sysv/linux/powerpc/time.c b/sysdeps/unix/sysv/linux/powerpc/time.c
> index 7973419..200f4a7 100644
> --- a/sysdeps/unix/sysv/linux/powerpc/time.c
> +++ b/sysdeps/unix/sysv/linux/powerpc/time.c
> @@ -17,6 +17,9 @@
> <http://www.gnu.org/licenses/>. */
>
> #ifdef SHARED
> +# ifndef __powerpc64__
> +# define time __redirect_time
> +# endif
>
> # include <time.h>
> # include <sysdep.h>
> @@ -24,7 +27,27 @@
> # include <libc-vdso.h>
> # include <dl-machine.h>
>
> -void *time_ifunc (void) asm ("time");
> +# ifndef __powerpc64__
> +# undef time
> +extern __typeof (__redirect_time) time;
> +
> +time_t
> +__time_vsyscall (time_t *t)
> +{
> + return INLINE_VSYSCALL (time, 1, t);
> +}
> +
> +/* __GI_time is defined as hidden and for ppc32 it enables the
> + compiler make a local call (symbol@local) for internal GLIBC usage. It
> + means the PLT won't be used and the ifunc resolver will be called directly.
> + For ppc64 a call to a function in another translation unit might use a
> + different toc pointer thus disallowing direct branchess and making internal
> + ifuncs calls safe. */
> +# undef libc_hidden_def
> +# define libc_hidden_def(name) \
> + __hidden_ver1 (__time_vsyscall, __GI_time, __time_vsyscall);
> +
> +# endif /* !__powerpc64__ */
>
> static time_t
> time_syscall (time_t *t)
> @@ -42,42 +65,19 @@ time_syscall (time_t *t)
> return result;
> }
>
> -void *
> -time_ifunc (void)
> -{
> - PREPARE_VERSION (linux2615, "LINUX_2.6.15", 123718565);
> -
> - /* If the vDSO is not available we fall back to the syscall. */
> +# define INIT_ARCH() \
> + PREPARE_VERSION (linux2615, "LINUX_2.6.15", 123718565); \
> void *vdso_time = _dl_vdso_vsym ("__kernel_time", &linux2615);
> - return (vdso_time ? VDSO_IFUNC_RET (vdso_time)
> - : (void*)time_syscall);
> -}
> -asm (".type time, %gnu_indirect_function");
>
> -/* This is doing "libc_hidden_def (time)" but the compiler won't
> - * let us do it in C because it doesn't know we're defining time
> - * here in this file. */
> -asm (".globl __GI_time");
> -
> -/* __GI_time is defined as hidden and for ppc32 it enables the
> - compiler make a local call (symbol@local) for internal GLIBC usage. It
> - means the PLT won't be used and the ifunc resolver will be called directly.
> - For ppc64 a call to a function in another translation unit might use a
> - different toc pointer thus disallowing direct branchess and making internal
> - ifuncs calls safe. */
> -#ifdef __powerpc64__
> -asm ("__GI_time = time");
> -#else
> -time_t
> -__time_vsyscall (time_t *t)
> -{
> - return INLINE_VSYSCALL (time, 1, t);
> -}
> -asm ("__GI_time = __time_vsyscall");
> -#endif
> +/* If the vDSO is not available we fall back to the syscall. */
> +libc_ifunc (time,
> + vdso_time
> + ? VDSO_IFUNC_RET (vdso_time)
> + : (void *) time_syscall);
> +libc_hidden_def (time)
>
> #else
>
> #include <sysdeps/posix/time.c>
>
> -#endif
> +#endif /* !SHARED */
>
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