Re: [PATCH v2 6/6] linux: Use long time_t for wait4/getrusage

[Lukasz Majewski <lukma at denx dot de>]

Hi Alistair,

> The Linux kernel expects rusage to use a 32-bit time_t, even on archs
> with a 64-bit time_t (like RV32). To address this let's convert
> rusage to/from 32-bit and 64-bit to ensure the kernel always gets
> a 32-bit time_t.
> 
> While we are converting these functions let's also convert them to be
> the y2038 safe versions. This means there is a *64 function that is
> called by a backwards compatible wrapper.
> ---
>  include/sys/resource.h                | 10 +++++
>  sysdeps/unix/sysv/linux/getrusage.c   | 53
> +++++++++++++++++++++++++++ sysdeps/unix/sysv/linux/tv32-compat.h |
> 47 ++++++++++++++++++++++++ sysdeps/unix/sysv/linux/wait4.c       |
> 40 ++++++++++++++++++-- 4 files changed, 146 insertions(+), 4
> deletions(-) create mode 100644 sysdeps/unix/sysv/linux/getrusage.c
> 
> diff --git a/include/sys/resource.h b/include/sys/resource.h
> index 9d604dfe3e..8e115b4df8 100644
> --- a/include/sys/resource.h
> +++ b/include/sys/resource.h
> @@ -134,5 +134,15 @@ extern int __getrusage (enum __rusage_who __who,
> struct rusage *__usage) extern int __setrlimit (enum
> __rlimit_resource __resource, const struct rlimit *__rlimits);
>  libc_hidden_proto (__setrlimit);
> +
> +#if __TIMESIZE == 64
> +# define __getrusage64 __getrusage
> +# define __wait464 __wait4
> +#else
> +extern int __getrusage64 (enum __rusage_who who, struct __rusage64
> *usage); +libc_hidden_proto (__getrusage64)
> +pid_t __wait464 (pid_t pid, int *stat_loc, int options, struct
> __rusage64 *usage); +libc_hidden_proto (__wait464)
> +#endif
>  #endif
>  #endif
> diff --git a/sysdeps/unix/sysv/linux/getrusage.c
> b/sysdeps/unix/sysv/linux/getrusage.c new file mode 100644
> index 0000000000..f8bcd3f9d0
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/getrusage.c
> @@ -0,0 +1,53 @@
> +/* getrusage -- get the rusage struct.  Linux 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 <sys/time.h>
> +#include <sys/resource.h>
> +#include <sysdep.h>
> +#include <tv32-compat.h>
> +
> +int
> +__getrusage64 (enum __rusage_who who, struct __rusage64 *usage)
> +{
> +  struct __rusage32 usage32;
> +  if (INLINE_SYSCALL_CALL (getrusage, who, &usage32) == -1)
> +    return -1;
> +
> +  rusage32_to_rusage64 (&usage32, usage);
> +  return 0;
> +}
> +
> +#if __TIMESIZE != 64
> +libc_hidden_def (__getrusage64)
> +int
> +__getrusage (enum __rusage_who who, struct rusage *usage)
> +{
> +  int ret ;
> +  struct __rusage64 usage64;
> +
> +  ret = __getrusage64 (who, &usage64);
> +
> +  if (ret != 0)
> +    return ret;
> +
> +  rusage64_to_rusage (&usage64, usage);
> +
> +  return ret;
> +}
> +#endif
> +weak_alias (__getrusage, getrusage)
> diff --git a/sysdeps/unix/sysv/linux/tv32-compat.h
> b/sysdeps/unix/sysv/linux/tv32-compat.h index 4eb6f216ea..c2231f042f
> 100644 --- a/sysdeps/unix/sysv/linux/tv32-compat.h
> +++ b/sysdeps/unix/sysv/linux/tv32-compat.h
> @@ -24,6 +24,7 @@
>  #include <bits/types.h>
>  #include <bits/types/time_t.h>
>  #include <bits/types/struct_timeval.h>
> +#include <sys/resource.h>
>  
>  /* Structures containing 'struct timeval' with 32-bit time_t.  */
>  struct __itimerval32
> @@ -32,4 +33,50 @@ struct __itimerval32
>    struct __timeval32 it_value;
>  };
>  
> +struct __rusage32
> +{
> +  struct __timeval32 ru_utime;	/* user time used */
> +  struct __timeval32 ru_stime;	/* system time used */
> +  long ru_maxrss;		/* maximum resident set size */
> +  long ru_ixrss;		/* integral shared memory size */
> +  long ru_idrss;		/* integral unshared data size */
> +  long ru_isrss;		/* integral unshared stack size */
> +  long ru_minflt;		/* page reclaims */
> +  long ru_majflt;		/* page faults */
> +  long ru_nswap;		/* swaps */
> +  long ru_inblock;		/* block input operations */
> +  long ru_oublock;		/* block output operations */
> +  long ru_msgsnd;		/* messages sent */
> +  long ru_msgrcv;		/* messages received */
> +  long ru_nsignals;		/* signals received */
> +  long ru_nvcsw;		/* voluntary context switches */
> +  long ru_nivcsw;		/* involuntary " */
> +};
> +
> +static inline void
> +rusage32_to_rusage64 (const struct __rusage32 *restrict r32,
> +                    struct __rusage64 *restrict r64)
> +{
> +  /* Make sure the entire output structure is cleared, including
> +     padding and reserved fields.  */
> +  memset (r64, 0, sizeof *r64);
> +
> +  r64->ru_utime    = valid_timeval32_to_timeval64 (r32->ru_utime);
> +  r64->ru_stime    = valid_timeval32_to_timeval64 (r32->ru_stime);
> +  r64->ru_maxrss   = r32->ru_maxrss;
> +  r64->ru_ixrss    = r32->ru_ixrss;
> +  r64->ru_idrss    = r32->ru_idrss;
> +  r64->ru_isrss    = r32->ru_isrss;
> +  r64->ru_minflt   = r32->ru_minflt;
> +  r64->ru_majflt   = r32->ru_majflt;
> +  r64->ru_nswap    = r32->ru_nswap;
> +  r64->ru_inblock  = r32->ru_inblock;
> +  r64->ru_oublock  = r32->ru_oublock;
> +  r64->ru_msgsnd   = r32->ru_msgsnd;
> +  r64->ru_msgrcv   = r32->ru_msgrcv;
> +  r64->ru_nsignals = r32->ru_nsignals;
> +  r64->ru_nvcsw    = r32->ru_nvcsw;
> +  r64->ru_nivcsw   = r32->ru_nivcsw;
> +}
> +
>  #endif /* tv32-compat.h */
> diff --git a/sysdeps/unix/sysv/linux/wait4.c
> b/sysdeps/unix/sysv/linux/wait4.c index 3a8bed1169..73f1c24269 100644
> --- a/sysdeps/unix/sysv/linux/wait4.c
> +++ b/sysdeps/unix/sysv/linux/wait4.c
> @@ -19,12 +19,22 @@
>  #include <sys/wait.h>
>  #include <sys/resource.h>
>  #include <sysdep-cancel.h>
> +#include <tv32-compat.h>
>  
>  pid_t
> -__wait4 (pid_t pid, int *stat_loc, int options, struct rusage *usage)
> +__wait464 (pid_t pid, int *stat_loc, int options, struct __rusage64

Just some consideration regarding naming convention - maybe it would be
more readable to have __wait4_time64 ? Frankly speaking - the __wait464
seems a bit confusing for me.

> *usage) {
> +  struct __rusage32 usage32;
>  #ifdef __NR_wait4
> -  return SYSCALL_CANCEL (wait4, pid, stat_loc, options, usage);
> +  pid_t ret = SYSCALL_CANCEL (wait4, pid, stat_loc, options,
> &usage32); +
> +  if (ret != 0)
> +    return ret;
> +
> +  if (usage != NULL)
> +      rusage32_to_rusage64 (&usage32, usage);
> +
> +  return ret;
>  #elif defined (__ASSUME_WAITID_PID0_P_PGID)
>    idtype_t idtype = P_PID;
>  
> @@ -41,7 +51,7 @@ __wait4 (pid_t pid, int *stat_loc, int options,
> struct rusage *usage) options |= WEXITED;
>  
>    siginfo_t infop;
> -  if (SYSCALL_CANCEL (waitid, idtype, pid, &infop, options, usage) <
> 0)
> +  if (SYSCALL_CANCEL (waitid, idtype, pid, &infop, options,
> &usage32) < 0) return -1;
>  
>    if (stat_loc)
> @@ -70,8 +80,11 @@ __wait4 (pid_t pid, int *stat_loc, int options,
> struct rusage *usage) }
>      }
>  
> +  if (usage != NULL)
> +      rusage32_to_rusage64 (&usage32, usage);
> +
>    return infop.si_pid;
> -# else
> +#else
>  /* Linux waitid prior kernel 5.4 does not support waiting for the
> current process.  It is possible to emulate wait4 it by calling
> getpgid for PID 0, however, it would require an additional syscall
> and it is inherent @@ -81,5 +94,24 @@ __wait4 (pid_t pid, int
> *stat_loc, int options, struct rusage *usage) # error "The kernel ABI
> does not provide a way to implement wait4" #endif
>  }
> +libc_hidden_def (__wait464)
> +
> +#if __TIMESIZE != 64
> +pid_t
> +__wait4 (pid_t pid, int *stat_loc, int options, struct rusage *usage)
> +{
> +  pid_t ret ;
> +  struct __rusage64 usage64;
> +
> +  ret = __wait464 (pid, stat_loc, options, &usage64);
> +
> +  if (ret != 0)
> +    return ret;
> +
> +  rusage64_to_rusage (&usage64, usage);
> +
> +  return ret;
> +}
>  libc_hidden_def (__wait4);
> +#endif
>  weak_alias (__wait4, wait4)




Best regards,

Lukasz Majewski

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