[PATCH 1/2] Add nocancel version of pread64()

[Leandro Pereira <Leandro dot Pereira at microsoft dot com>]

This is in preparation for changes in the dynamic linker so that pread() is used instead of lseek()+read().

2019-08-05  Leandro Pereira  <leandro.pereira@microsoft.com>

	* sysdeps/generic/not-cancel.h: New macro.
	* sysdeps/unix/sysv/linux/not-cancel.h: New macro.
	* sysdeps/unix/sysv/linux/pread64_nocancel.c: Implement nocancel
	version of pread64.
	* sysdeps/unix/sysv/linux/Versions (GLIBC_PRIVATE): Add
	__pread64_nocancel.
	* sysdeps/unix/sysv/linux/Makefile: Reference pread64_nocancel.c.

---
 sysdeps/generic/not-cancel.h               |  2 ++
 sysdeps/unix/sysv/linux/Makefile           |  4 +--
 sysdeps/unix/sysv/linux/Versions           |  1 +
 sysdeps/unix/sysv/linux/not-cancel.h       |  4 +++
 sysdeps/unix/sysv/linux/pread64_nocancel.c | 32 ++++++++++++++++++++++
 5 files changed, 41 insertions(+), 2 deletions(-)
 create mode 100644 sysdeps/unix/sysv/linux/pread64_nocancel.c

diff --git a/sysdeps/generic/not-cancel.h b/sysdeps/generic/not-cancel.h
index f3d862651e..724c3e5e71 100644
--- a/sysdeps/generic/not-cancel.h
+++ b/sysdeps/generic/not-cancel.h
@@ -41,6 +41,8 @@
   (void) __close (fd)
 #define __read_nocancel(fd, buf, n) \
   __read (fd, buf, n)
+#define __pread64_nocancel(fd, buf, count, offset) \
+  __pread64 (fd, buf, count, offset)
 #define __write_nocancel(fd, buf, n) \
   __write (fd, buf, n)
 #define __writev_nocancel_nostatus(fd, iov, n) \
diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index 1ab6bcbfc8..a7980a60f6 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -212,8 +212,8 @@ sysdep_routines += xstatconv internal_statvfs internal_statvfs64 \
 		   close_nocancel fcntl_nocancel nanosleep_nocancel \
 		   open_nocancel open64_nocancel \
 		   openat_nocancel openat64_nocancel \
-		   pause_nocancel read_nocancel waitpid_nocancel \
-		   write_nocancel statx_cp
+		   pause_nocancel read_nocancel pread64_nocancel \
+		   waitpid_nocancel write_nocancel statx_cp
 
 sysdep_headers += bits/fcntl-linux.h
 
diff --git a/sysdeps/unix/sysv/linux/Versions b/sysdeps/unix/sysv/linux/Versions
index 1ca102a9e2..d385085c61 100644
--- a/sysdeps/unix/sysv/linux/Versions
+++ b/sysdeps/unix/sysv/linux/Versions
@@ -182,6 +182,7 @@ libc {
     __syscall_rt_sigqueueinfo;
     __open_nocancel;
     __read_nocancel;
+    __pread64_nocancel;
     __close_nocancel;
     __sigtimedwait;
     # functions used by nscd
diff --git a/sysdeps/unix/sysv/linux/not-cancel.h b/sysdeps/unix/sysv/linux/not-cancel.h
index 16cc31cba5..bf7d80125a 100644
--- a/sysdeps/unix/sysv/linux/not-cancel.h
+++ b/sysdeps/unix/sysv/linux/not-cancel.h
@@ -43,6 +43,9 @@ __typeof (openat64) __openat64_nocancel;
 /* Non cancellable read syscall.  */
 __typeof (__read) __read_nocancel;
 
+/* Non cancellable pread syscall (LFS version).  */
+__typeof (__pread64) __pread64_nocancel;
+
 /* Uncancelable write.  */
 __typeof (__write) __write_nocancel;
 
@@ -84,6 +87,7 @@ hidden_proto (__open64_nocancel)
 hidden_proto (__openat_nocancel)
 hidden_proto (__openat64_nocancel)
 hidden_proto (__read_nocancel)
+hidden_proto (__pread64_nocancel)
 hidden_proto (__write_nocancel)
 hidden_proto (__close_nocancel)
 hidden_proto (__waitpid_nocancel)
diff --git a/sysdeps/unix/sysv/linux/pread64_nocancel.c b/sysdeps/unix/sysv/linux/pread64_nocancel.c
new file mode 100644
index 0000000000..dab61260e5
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/pread64_nocancel.c
@@ -0,0 +1,32 @@
+/* Linux pread64() syscall implementation -- non-cancellable.
+   Copyright (C) 2019 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 <unistd.h>
+#include <sysdep-cancel.h>
+#include <not-cancel.h>
+
+#ifndef __NR_pread64
+# define __NR_pread64 __NR_pread
+#endif
+
+ssize_t
+__pread64_nocancel (int fd, void *buf, size_t count, off64_t offset)
+{
+  return INLINE_SYSCALL_CALL (pread64, fd, buf, count, SYSCALL_LL64_PRW (offset));
+}
+hidden_def (__pread64_nocancel)
-- 
2.21.0