[04/18] linux: Only use 64-bit syscall if required for ppoll

Message ID 20210617115104.1359598-5-adhemerval.zanella@linaro.org
State New
Headers show
Series
  • More y2038 fixes
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Commit Message

Adhemerval Zanella via Libc-alpha June 17, 2021, 11:50 a.m.
For !__ASSUME_TIME64_SYSCALLS there is no need to issue a 64-bit syscall
if the provided timeout fits in a 32-bit one.  The 64-bit usage should
be rare since the timeout is a relative one.  This also avoids the need
to use supports_time64() (which breaks the usage case of live migration
like CRIU or similar).

Checked on i686-linux-gnu on a 4.15 kernel and on a 5.11 kernel
(with and without --enable-kernel=5.1) and on x86_64-linux-gnu.
---
 sysdeps/unix/sysv/linux/Makefile    |  9 +++++++
 sysdeps/unix/sysv/linux/ppoll.c     | 41 +++++++++++------------------
 sysdeps/unix/sysv/linux/tst-ppoll.c | 15 +++++++++++
 3 files changed, 40 insertions(+), 25 deletions(-)

-- 
2.30.2

Comments

Lukasz Majewski June 21, 2021, 7:42 a.m. | #1
On Thu, 17 Jun 2021 08:50:50 -0300
Adhemerval Zanella <adhemerval.zanella@linaro.org> wrote:

> For !__ASSUME_TIME64_SYSCALLS there is no need to issue a 64-bit

> syscall if the provided timeout fits in a 32-bit one.  The 64-bit

> usage should be rare since the timeout is a relative one.  This also

> avoids the need to use supports_time64() (which breaks the usage case

> of live migration like CRIU or similar).

> 

> Checked on i686-linux-gnu on a 4.15 kernel and on a 5.11 kernel

> (with and without --enable-kernel=5.1) and on x86_64-linux-gnu.

> ---

>  sysdeps/unix/sysv/linux/Makefile    |  9 +++++++

>  sysdeps/unix/sysv/linux/ppoll.c     | 41

> +++++++++++------------------ sysdeps/unix/sysv/linux/tst-ppoll.c |

> 15 +++++++++++ 3 files changed, 40 insertions(+), 25 deletions(-)

> 

> diff --git a/sysdeps/unix/sysv/linux/Makefile

> b/sysdeps/unix/sysv/linux/Makefile index 294c366e3b..c36ea0e494 100644

> --- a/sysdeps/unix/sysv/linux/Makefile

> +++ b/sysdeps/unix/sysv/linux/Makefile

> @@ -137,6 +137,15 @@ tests-time64 += \

>  

>  CFLAGS-tst-sigcontext-get_pc.c = -fasynchronous-unwind-tables

>  

> +ifeq (yes,$(build-shared))

> +librt = $(common-objpfx)rt/librt.so

> +else

> +librt = $(common-objpfx)rt/librt.a

> +endif

> +

> +$(objpfx)tst-ppoll: $(librt)

> +$(objpfx)tst-ppoll-time64: $(librt)

> +

>  # Generate the list of SYS_* macros for the system calls (__NR_*

>  # macros).  The file syscall-names.list contains all possible system

>  # call names, and the generated header file produces SYS_* macros for

> diff --git a/sysdeps/unix/sysv/linux/ppoll.c

> b/sysdeps/unix/sysv/linux/ppoll.c index 624f14f517..e1ad316e2e 100644

> --- a/sysdeps/unix/sysv/linux/ppoll.c

> +++ b/sysdeps/unix/sysv/linux/ppoll.c

> @@ -21,9 +21,6 @@

>  #include <time.h>

>  #include <sys/poll.h>

>  #include <sysdep-cancel.h>

> -#include <kernel-features.h>

> -#include <time64-support.h>

> -

>  

>  int

>  __ppoll64 (struct pollfd *fds, nfds_t nfds, const struct

> __timespec64 *timeout, @@ -38,40 +35,34 @@ __ppoll64 (struct pollfd

> *fds, nfds_t nfds, const struct __timespec64 *timeout, timeout =

> &tval; }

>  

> -  int ret;

> -

> -  if (supports_time64 ())

> -    {

>  #ifndef __NR_ppoll_time64

>  # define __NR_ppoll_time64 __NR_ppoll

>  #endif

> +

> +#ifdef __ASSUME_TIME64_SYSCALLS

> +  return SYSCALL_CANCEL (ppoll_time64, fds, nfds, timeout, sigmask,

> +			 __NSIG_BYTES);

> +#else

> +  bool is32bit = timeout != NULL

> +		 ? in_time_t_range (timeout->tv_sec) : true;

> +  int ret;

> +  if (!is32bit)

> +    {

>        ret = SYSCALL_CANCEL (ppoll_time64, fds, nfds, timeout,

> sigmask, __NSIG_BYTES);

> -

>        if (ret == 0 || errno != ENOSYS)

>  	return ret;

> -

> -      mark_time64_unsupported ();

> +      __set_errno (EOVERFLOW);

> +      return -1;

>      }

>  

> -#ifndef __ASSUME_TIME64_SYSCALLS

>    struct timespec ts32;

> -  if (timeout)

> -    {

> -      if (! in_time_t_range (timeout->tv_sec))

> -        {

> -          __set_errno (EOVERFLOW);

> -          return -1;

> -        }

> -

> -      ts32 = valid_timespec64_to_timespec (*timeout);

> -    }

> +  if (timeout != NULL)

> +    ts32 = valid_timespec64_to_timespec (*timeout);

>  

> -  ret = SYSCALL_CANCEL (ppoll, fds, nfds, timeout ? &ts32 : NULL,

> sigmask,

> -			__NSIG_BYTES);

> +  return SYSCALL_CANCEL (ppoll, fds, nfds, timeout ? &ts32 : NULL,

> sigmask,

> +			 __NSIG_BYTES);

>  #endif

> -

> -  return ret;

>  }

>  

>  #if __TIMESIZE != 64

> diff --git a/sysdeps/unix/sysv/linux/tst-ppoll.c

> b/sysdeps/unix/sysv/linux/tst-ppoll.c index 9fe6ad07ce..e21e2fcc72

> 100644 --- a/sysdeps/unix/sysv/linux/tst-ppoll.c

> +++ b/sysdeps/unix/sysv/linux/tst-ppoll.c

> @@ -19,9 +19,11 @@

>  #include <time.h>

>  #include <poll.h>

>  #include <errno.h>

> +#include <intprops.h>

>  #include <support/check.h>

>  #include <support/xtime.h>

>  #include <support/timespec.h>

> +#include <support/support.h>

>  #include <stdbool.h>

>  

>  static int test_ppoll_timeout (bool zero_tmo)

> @@ -41,6 +43,16 @@ static int test_ppoll_timeout (bool zero_tmo)

>    return 0;

>  }

>  

> +static void

> +test_ppoll_large_timeout (void)

> +{

> +  support_create_timer (0, 100000000, false, NULL);

> +  struct timespec ts = { TYPE_MAXIMUM (time_t), 0 };

> +  struct pollfd fds = { -1, 0, 0 };

> +  TEST_COMPARE (ppoll (&fds, 1, &ts, 0), -1);

> +  TEST_VERIFY (errno == EINTR || errno == EOVERFLOW);

> +}

> +

>  static int

>  do_test (void)

>  {

> @@ -50,6 +62,9 @@ do_test (void)

>    /* Check if ppoll exits after specified timeout.  */

>    test_ppoll_timeout (false);

>  

> +  /* Check if ppoll with large timeout.  */

> +  test_ppoll_large_timeout ();

> +

>    return 0;

>  }

>  


Reviewed-by: Lukasz Majewski <lukma@denx.de>



Best regards,

Lukasz Majewski

--

DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de

Patch

diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index 294c366e3b..c36ea0e494 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -137,6 +137,15 @@  tests-time64 += \
 
 CFLAGS-tst-sigcontext-get_pc.c = -fasynchronous-unwind-tables
 
+ifeq (yes,$(build-shared))
+librt = $(common-objpfx)rt/librt.so
+else
+librt = $(common-objpfx)rt/librt.a
+endif
+
+$(objpfx)tst-ppoll: $(librt)
+$(objpfx)tst-ppoll-time64: $(librt)
+
 # Generate the list of SYS_* macros for the system calls (__NR_*
 # macros).  The file syscall-names.list contains all possible system
 # call names, and the generated header file produces SYS_* macros for
diff --git a/sysdeps/unix/sysv/linux/ppoll.c b/sysdeps/unix/sysv/linux/ppoll.c
index 624f14f517..e1ad316e2e 100644
--- a/sysdeps/unix/sysv/linux/ppoll.c
+++ b/sysdeps/unix/sysv/linux/ppoll.c
@@ -21,9 +21,6 @@ 
 #include <time.h>
 #include <sys/poll.h>
 #include <sysdep-cancel.h>
-#include <kernel-features.h>
-#include <time64-support.h>
-
 
 int
 __ppoll64 (struct pollfd *fds, nfds_t nfds, const struct __timespec64 *timeout,
@@ -38,40 +35,34 @@  __ppoll64 (struct pollfd *fds, nfds_t nfds, const struct __timespec64 *timeout,
       timeout = &tval;
     }
 
-  int ret;
-
-  if (supports_time64 ())
-    {
 #ifndef __NR_ppoll_time64
 # define __NR_ppoll_time64 __NR_ppoll
 #endif
+
+#ifdef __ASSUME_TIME64_SYSCALLS
+  return SYSCALL_CANCEL (ppoll_time64, fds, nfds, timeout, sigmask,
+			 __NSIG_BYTES);
+#else
+  bool is32bit = timeout != NULL
+		 ? in_time_t_range (timeout->tv_sec) : true;
+  int ret;
+  if (!is32bit)
+    {
       ret = SYSCALL_CANCEL (ppoll_time64, fds, nfds, timeout, sigmask,
 			    __NSIG_BYTES);
-
       if (ret == 0 || errno != ENOSYS)
 	return ret;
-
-      mark_time64_unsupported ();
+      __set_errno (EOVERFLOW);
+      return -1;
     }
 
-#ifndef __ASSUME_TIME64_SYSCALLS
   struct timespec ts32;
-  if (timeout)
-    {
-      if (! in_time_t_range (timeout->tv_sec))
-        {
-          __set_errno (EOVERFLOW);
-          return -1;
-        }
-
-      ts32 = valid_timespec64_to_timespec (*timeout);
-    }
+  if (timeout != NULL)
+    ts32 = valid_timespec64_to_timespec (*timeout);
 
-  ret = SYSCALL_CANCEL (ppoll, fds, nfds, timeout ? &ts32 : NULL, sigmask,
-			__NSIG_BYTES);
+  return SYSCALL_CANCEL (ppoll, fds, nfds, timeout ? &ts32 : NULL, sigmask,
+			 __NSIG_BYTES);
 #endif
-
-  return ret;
 }
 
 #if __TIMESIZE != 64
diff --git a/sysdeps/unix/sysv/linux/tst-ppoll.c b/sysdeps/unix/sysv/linux/tst-ppoll.c
index 9fe6ad07ce..e21e2fcc72 100644
--- a/sysdeps/unix/sysv/linux/tst-ppoll.c
+++ b/sysdeps/unix/sysv/linux/tst-ppoll.c
@@ -19,9 +19,11 @@ 
 #include <time.h>
 #include <poll.h>
 #include <errno.h>
+#include <intprops.h>
 #include <support/check.h>
 #include <support/xtime.h>
 #include <support/timespec.h>
+#include <support/support.h>
 #include <stdbool.h>
 
 static int test_ppoll_timeout (bool zero_tmo)
@@ -41,6 +43,16 @@  static int test_ppoll_timeout (bool zero_tmo)
   return 0;
 }
 
+static void
+test_ppoll_large_timeout (void)
+{
+  support_create_timer (0, 100000000, false, NULL);
+  struct timespec ts = { TYPE_MAXIMUM (time_t), 0 };
+  struct pollfd fds = { -1, 0, 0 };
+  TEST_COMPARE (ppoll (&fds, 1, &ts, 0), -1);
+  TEST_VERIFY (errno == EINTR || errno == EOVERFLOW);
+}
+
 static int
 do_test (void)
 {
@@ -50,6 +62,9 @@  do_test (void)
   /* Check if ppoll exits after specified timeout.  */
   test_ppoll_timeout (false);
 
+  /* Check if ppoll with large timeout.  */
+  test_ppoll_large_timeout ();
+
   return 0;
 }