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

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

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.
+
+   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