Re: [PATCH 3/6] linux: Implement mremap in C

[Adhemerval Zanella via Libc-alpha <libc-alpha@sourceware.org>]

On 25/11/2021 21:26, Stafford Horne wrote:
> On Mon, Nov 22, 2021 at 03:54:34PM -0300, Adhemerval Zanella wrote:
>> Variadic function calls in syscalls.list does not work for all ABIs
>> (for instance where the argument are passed on the stack instead of
>> registers) and might have underlying issues depending of the variadic
>> type (for instance if a 64-bit argument is used).
>>
>> Checked on x86_64-linux-gnu.
>> ---
>>  sysdeps/unix/sysv/linux/Makefile      |  1 +
>>  sysdeps/unix/sysv/linux/mremap.c      | 41 +++++++++++++++++++++++++++
>>  sysdeps/unix/sysv/linux/syscalls.list |  1 -
>>  3 files changed, 42 insertions(+), 1 deletion(-)
>>  create mode 100644 sysdeps/unix/sysv/linux/mremap.c
>>
>> diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
>> index aa10754b98..1dd6ec9ef9 100644
>> --- a/sysdeps/unix/sysv/linux/Makefile
>> +++ b/sysdeps/unix/sysv/linux/Makefile
>> @@ -68,6 +68,7 @@ sysdep_routines += adjtimex clone umount umount2 readahead sysctl \
>>  		   closefrom_fallback \
>>  		   clone3 clone-internal \
>>  		   fanotify_mark \
>> +		   mremap \
>>  
>>  CFLAGS-gethostid.c = -fexceptions
>>  CFLAGS-tee.c = -fexceptions -fasynchronous-unwind-tables
>> diff --git a/sysdeps/unix/sysv/linux/mremap.c b/sysdeps/unix/sysv/linux/mremap.c
>> new file mode 100644
>> index 0000000000..83b4e95338
>> --- /dev/null
>> +++ b/sysdeps/unix/sysv/linux/mremap.c
>> @@ -0,0 +1,41 @@
>> +/* Remap a virtual memory address.  Linux specific syscall.
>> +   Copyright (C) 2020 Free Software Foundation, Inc.
>> +   This file is part of the GNU C Library.
> 
> 2021

Ack.

> 
>> +
>> +   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
>> +   <https://www.gnu.org/licenses/>.  */
>> +
>> +#include <sys/mman.h>
>> +#include <sysdep.h>
>> +#include <stdarg.h>
>> +#include <stddef.h>
>> +
>> +void *
>> +__mremap (void *addr, size_t old_len, size_t new_len, int flags, ...)
>> +{
>> +  va_list va;
>> +  void *new_addr = NULL;
>> +
>> +  if (flags & MREMAP_FIXED)
>> +    {
>> +      va_start (va, flags);
>> +      new_addr = va_arg (va, void *);
>> +      va_end (va);
>> +    }
>> +
>> +  return (void *) INLINE_SYSCALL_CALL (mremap, addr, old_len, new_len, flags,
>> +				       new_addr);
>> +}
>> +libc_hidden_def (__mremap)
>> +weak_alias (__mremap, mremap)
>> diff --git a/sysdeps/unix/sysv/linux/syscalls.list b/sysdeps/unix/sysv/linux/syscalls.list
>> index 29899eb264..2acd7551d3 100644
>> --- a/sysdeps/unix/sysv/linux/syscalls.list
>> +++ b/sysdeps/unix/sysv/linux/syscalls.list
>> @@ -35,7 +35,6 @@ mincore		-	mincore		i:aUV	mincore
>>  mlock		-	mlock		i:bU	mlock
>>  mlockall	-	mlockall	i:i	mlockall
>>  mount		EXTRA	mount		i:sssUp	__mount	mount
>> -mremap		EXTRA	mremap		b:aUUip	__mremap	mremap
>>  munlock		-	munlock		i:aU	munlock
>>  munlockall	-	munlockall	i:	munlockall
>>  nfsservctl	EXTRA	nfsservctl	i:ipp	__compat_nfsservctl	nfsservctl@GLIBC_2.0:GLIBC_2.28
>> -- 
>> 2.32.0
>>
> 
> This looks OK to me.
> 
> Note, I guess this syscall would be broken in or1k at the moment as it passes
> variadic args on the stack.  However,  I didn't see any test failures due to
> this.

I think it would be for MREMAP_FIXED and the there is no failures because we
don't use the flag neither internally nor on any test.