[PATCH 4/6] linux: Use 32-bit time_t for itimerval
Alistair Francis
alistair23@gmail.com
Mon Feb 10 18:04:00 GMT 2020
On Tue, Feb 4, 2020 at 6:49 AM Lukasz Majewski <lukma@denx.de> wrote:
>
> Hi Alistair,
>
> Maybe it would be good to rewrite the subject line to also reflect the
> introduction of __[gs]etitimer64 ?
>
> > The Linux kernel expects itimerval to use a 32-bit time_t, even on
> > archs with a 64-bit time_t (like RV32). To address this let's convert
> > itimerval to/from 32-bit and 64-bit to ensure the kernel always gets
> > a 32-bit time_t.
> >
> > This means that all 32-bit architectures with a 64-bit time_t will be
> > able to use this generic implementation.
> >
> > This code is based on similar code in alpha, but adjusted to pass the
> > 32-bit time_t to the kernel.
> >
> > We can't directly call the __getitimer/__setitimer functions as they
> > expect a struct itimerval but we need to pass in a struct itimerval32.
>
> Please update this patch series to also include information about
> build/run testing.
>
> For example:
>
> Build-tests:
> ./src/scripts/build-many-glibcs.py glibcs
Sorry Lukasz, I somehow lost your response in my v2. I have updated my
v3 with your comments here.
>
>
> > ---
> > include/time.h | 12 +++
> > .../linux/generic/wordsize-32/getitimer.c | 54 +++++++++++++
> > .../linux/generic/wordsize-32/setitimer.c | 77
> > +++++++++++++++++++ .../linux/generic/wordsize-32/tv32-compat.h |
> > 35 +++++++++ 4 files changed, 178 insertions(+)
> > create mode 100644
> > sysdeps/unix/sysv/linux/generic/wordsize-32/getitimer.c create mode
>
> The same issue as pointed out in patch 6/6. The path
> sysdeps/unix/sysv/linux/generic/wordsize-32 is NOT searched by ARMv7
> (ARM32) for files to be built.
>
> I've removed getitimer, getrusage and setitimer from
> ./sysdeps/unix/syscalls.list, so they are NOT auto generated wrappers
> anymore, but this doesn't help.
>
> It seems like for RV32 some extra paths are added...
>
> I've dug to the @sysnames@ variable set in configure in the source of glibc.
> I'm wondering how RV32 modifies it (and how it differs from ARM32)?
This has been addressed in v2.
>
>
> > 100644 sysdeps/unix/sysv/linux/generic/wordsize-32/setitimer.c create
> > mode 100644 sysdeps/unix/sysv/linux/generic/wordsize-32/tv32-compat.h
> >
> > diff --git a/include/time.h b/include/time.h
> > index 898ff0fb2d..e1d80b4190 100644
> > --- a/include/time.h
> > +++ b/include/time.h
> > @@ -6,6 +6,7 @@
> > # include <bits/types/locale_t.h>
> > # include <stdbool.h>
> > # include <time/mktime-internal.h>
> > +# include <sys/time.h>
> > # include <endian.h>
> > # include <time-clockid.h>
> >
> > @@ -118,6 +119,17 @@ struct __itimerval64
> > };
> > #endif
> >
> > +#if __TIMESIZE == 64
> > +# define __getitimer64 __getitimer
> > +# define __setitimer64 __setitimer
> > +#else
> > +extern int __getitimer64 (enum __itimer_which __which,
> > + struct __itimerval64 *__value);
>
> Please add here:
> libc_hidden_proto (__getitimer64)
Fixed in v3
>
> > +extern int __setitimer64 (enum __itimer_which __which,
> > + const struct __itimerval64 *__restrict
> > __new,
> > + struct __itimerval64 *__restrict __old);
>
> Please add here:
> libc_hidden_proto (__setitimer64)
Fixed in v3
>
> > +#endif
> > +
> > #if __TIMESIZE == 64
> > # define __ctime64 ctime
> > #else
> > diff --git a/sysdeps/unix/sysv/linux/generic/wordsize-32/getitimer.c
> > b/sysdeps/unix/sysv/linux/generic/wordsize-32/getitimer.c new file
> > mode 100644 index 0000000000..28a3e31126
> > --- /dev/null
> > +++ b/sysdeps/unix/sysv/linux/generic/wordsize-32/getitimer.c
> > @@ -0,0 +1,54 @@
> > +/* getitimer -- Get the state of an interval timer. Linux/tv32
> > version.
> > + Copyright (C) 2020 Free Software Foundation, Inc.
> > + This file is part of the GNU C Library.
> > +
> > + The GNU C Library is free software; you can redistribute it and/or
> > + modify it under the terms of the GNU Lesser General Public
> > + License as published by the Free Software Foundation; either
> > + version 2.1 of the License, or (at your option) any later version.
> > +
> > + The GNU C Library is distributed in the hope that it will be
> > useful,
> > + but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> > + Lesser General Public License for more details.
> > +
> > + You should have received a copy of the GNU Lesser General Public
> > + License along with the GNU C Library; if not, see
> > + <http://www.gnu.org/licenses/>. */
> > +
> > +#include <time.h>
> > +#include <sys/time.h>
> > +#include <sysdep.h>
> > +#include <tv32-compat.h>
> > +
> > +int
> > +__getitimer64 (__itimer_which_t which, struct __itimerval64
> > *curr_value) +{
> > + struct __itimerval32 curr_value_32;
> > + if (INLINE_SYSCALL_CALL (getitimer, which, &curr_value_32) == -1)
> > + return -1;
> > +
> > + /* Write all fields of 'curr_value' regardless of overflow. */
> > + curr_value->it_interval
> > + = valid_timeval32_to_timeval64 (curr_value_32.it_interval);
> > + curr_value->it_value
> > + = valid_timeval32_to_timeval64 (curr_value_32.it_value);
> > + return 0;
> > +}
> > +
> > +
> > +#if __TIMESIZE != 64
>
> Please add here:
> libc_hidden_def (__gettimer64)
Fixed in v3
>
> Rationale:
>
> Before we introduce the Y2038 support (with -D_TIME_BITS=64) the
> __gettimer64 shall be hidden (to avoid resolving it via PLT).
>
> > +int
> > +__getitimer (__itimer_which_t which, struct itimerval *curr_value)
> > +{
> > + struct __itimerval64 val64;
> > +
> > + val64.it_interval
> > + = valid_timeval_to_timeval64 (curr_value->it_interval);
> > + val64.it_value
> > + = valid_timeval_to_timeval64 (curr_value->it_value);
> > +
> > + return __getitimer64 (which, &val64);
> > +}
>
> Ok. As we expect 32 bit values - there is no need for checking (and 64
> <-> 32 conversions will be OK).
>
> > +#endif
> > +weak_alias (__getitimer, getitimer)
> > diff --git a/sysdeps/unix/sysv/linux/generic/wordsize-32/setitimer.c
> > b/sysdeps/unix/sysv/linux/generic/wordsize-32/setitimer.c new file
> > mode 100644 index 0000000000..fabc7f2c0c
> > --- /dev/null
> > +++ b/sysdeps/unix/sysv/linux/generic/wordsize-32/setitimer.c
> > @@ -0,0 +1,77 @@
> > +/* setitimer -- Set the state of an interval timer. Linux/tv32
> > version.
> > + Copyright (C) 2020 Free Software Foundation, Inc.
> > + This file is part of the GNU C Library.
> > +
> > + The GNU C Library is free software; you can redistribute it and/or
> > + modify it under the terms of the GNU Lesser General Public
> > + License as published by the Free Software Foundation; either
> > + version 2.1 of the License, or (at your option) any later version.
> > +
> > + The GNU C Library is distributed in the hope that it will be
> > useful,
> > + but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> > + Lesser General Public License for more details.
> > +
> > + You should have received a copy of the GNU Lesser General Public
> > + License along with the GNU C Library; if not, see
> > + <http://www.gnu.org/licenses/>. */
> > +
> > +#include <time.h>
> > +#include <sys/time.h>
> > +#include <sysdep.h>
> > +#include <tv32-compat.h>
> > +
> > +int
> > +__setitimer64 (__itimer_which_t which,
> > + const struct __itimerval64 *restrict new_value,
> > + struct __itimerval64 *restrict old_value)
> > +{
> > + struct __itimerval32 new_value_32;
> > + new_value_32.it_interval
> > + = valid_timeval64_to_timeval32 (new_value->it_interval);
> > + new_value_32.it_value
> > + = valid_timeval64_to_timeval32 (new_value->it_value);
> > +
> > + if (old_value == NULL)
> > + return INLINE_SYSCALL_CALL (setitimer, which, &new_value_32,
> > NULL); +
>
> The above code is correct of course.
>
> However, I've used another approach for timerfd_settime (IMHO a bit
> more concise):
> https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/timerfd_settime.c;h=164b4e860acb6a365a3890f30e2eac364a518c22;hb=eae22432723b877354291aca4dbbfde5891dad59#l49
>
> > + struct __itimerval32 old_value_32;
> > + if (INLINE_SYSCALL_CALL (setitimer, which, &new_value_32,
> > &old_value_32) == -1)
> > + return -1;
> > +
> > + /* Write all fields of 'old_value' regardless of overflow. */
> > + old_value->it_interval
> > + = valid_timeval32_to_timeval64 (old_value_32.it_interval);
> > + old_value->it_value
> > + = valid_timeval32_to_timeval64 (old_value_32.it_value);
> > + return 0;
> > +}
> > +
> > +#if __TIMESIZE != 64
>
> Please add here:
> libc_hidden_def (__settimer64)
Fixed in v3
>
> > +int
> > +__setitimer (__itimer_which_t which,
> > + const struct itimerval *restrict new_value,
> > + struct itimerval *restrict old_value)
> > +{
> > + int ret;
> > + struct __itimerval64 new64, old64;
> > +
> > + new64.it_interval
> > + = valid_timeval_to_timeval64 (new_value->it_interval);
> > + new64.it_value
> > + = valid_timeval_to_timeval64 (new_value->it_value);
> > +
> > + ret = __setitimer64 (which, &new64, &old64);
>
> I think that here we shall also consider the NULL pointer for old_value
> (as stated in http://man7.org/linux/man-pages/man2/setitimer.2.html)
>
> ret = __setitimer64 (which, &new64, old_value ? &old64 : NULL);
>
> > +
> > + if (ret != 0)
> > + return ret;
> > +
> > + old_value->it_interval
> > + = valid_timeval64_to_timeval (old64.it_interval);
> > + old_value->it_value
> > + = valid_timeval64_to_timeval (old64.it_value);
> > +
>
> Maybe it would be better to change this code to:
>
> if (ret == 0 && old_value)
> {
> old_value->it_interval
> = valid_timeval64_to_timeval (old64.it_interval);
> old_value->it_value
> = valid_timeval64_to_timeval (old64.it_value);
> }
>
> return ret
Fixed in v3
>
> Please find the timerfd_settime as a reference:
> https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/timerfd_settime.c;h=164b4e860acb6a365a3890f30e2eac364a518c22;hb=eae22432723b877354291aca4dbbfde5891dad59#l77
>
> > + return ret;
> > +}
> > +#endif
> > +weak_alias (__setitimer, setitimer)
> > diff --git
> > a/sysdeps/unix/sysv/linux/generic/wordsize-32/tv32-compat.h
> > b/sysdeps/unix/sysv/linux/generic/wordsize-32/tv32-compat.h new file
> > mode 100644 index 0000000000..4eb6f216ea --- /dev/null
> > +++ b/sysdeps/unix/sysv/linux/generic/wordsize-32/tv32-compat.h
> > @@ -0,0 +1,35 @@
> > +/* Compatibility definitions for `struct timeval' with 32-bit time_t.
> > + Copyright (C) 2020 Free Software Foundation, Inc.
> > + This file is part of the GNU C Library.
> > +
> > + The GNU C Library is free software; you can redistribute it and/or
> > + modify it under the terms of the GNU Lesser General Public
> > + License as published by the Free Software Foundation; either
> > + version 2.1 of the License, or (at your option) any later version.
> > +
> > + The GNU C Library is distributed in the hope that it will be
> > useful,
> > + but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> > + Lesser General Public License for more details.
> > +
> > + You should have received a copy of the GNU Lesser General Public
> > + License along with the GNU C Library; if not, see
> > + <http://www.gnu.org/licenses/>. */
> > +
> > +#ifndef _TV32_COMPAT_H
> > +#define _TV32_COMPAT_H 1
> > +
> > +#include <features.h>
> > +
> > +#include <bits/types.h>
> > +#include <bits/types/time_t.h>
> > +#include <bits/types/struct_timeval.h>
> > +
> > +/* Structures containing 'struct timeval' with 32-bit time_t. */
> > +struct __itimerval32
> > +{
> > + struct __timeval32 it_interval;
> > + struct __timeval32 it_value;
> > +};
>
> I do guess that here (with the introduction of tv32-compat.h) we do
> follow what is done for alpha port?
Alpha always uses a 32-bit value, while in the generic case we use a
long (so the wordsize).
Alistair
>
> > +
> > +#endif /* tv32-compat.h */
>
>
>
>
> 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
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