commit b31d4355ae817aa3caf9414f842cc07465bca028

Author: Florian Weimer <fweimer@redhat.com>

Date:   Wed Oct 7 16:39:50 2020 +0200

    elf: Implement _dl_write

    The generic version is parallel to _dl_writev.  It cannot use

    _dl_writev directly because the errno value needs to be obtained

    under a lock.

    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

Backport adjusted for different INTERNAL_SYSCALL_CALL definition

downstream.

diff --git a/elf/Makefile b/elf/Makefile

index ef655630d50b07aa..e2078f6bc325b7e0 100644

--- a/elf/Makefile

+++ b/elf/Makefile

@@ -34,7 +34,7 @@ dl-routines	= $(addprefix dl-,load lookup object reloc deps \

 				  version profile tls origin scope \

 				  execstack open close trampoline \

 				  exception sort-maps lookup-direct \

-				  call-libc-early-init)

+				  call-libc-early-init write)

 ifeq (yes,$(use-ldconfig))

 dl-routines += dl-cache

 endif

diff --git a/elf/dl-write.c b/elf/dl-write.c

new file mode 100644

index 0000000000000000..7350aff0035d4fbc

--- /dev/null

+++ b/elf/dl-write.c

@@ -0,0 +1,56 @@

+/* Implementation of the _dl_write function.  Generic 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

+   <https://www.gnu.org/licenses/>.  */

+

+#include <errno.h>

+#include <ldsodefs.h>

+#include <libc-lock.h>

+#include <sys/uio.h>

+

+ssize_t

+_dl_write (int fd, const void *buffer, size_t length)

+{

+  struct iovec iov = { .iov_base = (void *) buffer, .iov_len = length };

+  ssize_t ret;

+

+#if RTLD_PRIVATE_ERRNO

+  /* We have to take this lock just to be sure we don't clobber the private

+     errno when it's being used by another thread that cares about it.

+     Yet we must be sure not to try calling the lock functions before

+     the thread library is fully initialized.  */

+  if (__glibc_unlikely (_dl_starting_up))

+    {

+      ret = __writev (fd, &iov, 1);

+      if (ret < 0)

+        ret = -errno;

+    }

+  else

+    {

+      __rtld_lock_lock_recursive (GL(dl_load_lock));

+      __writev (fd, &iov, 1);

+      if (ret < 0)

+        ret = -errno;

+      __rtld_lock_unlock_recursive (GL(dl_load_lock));

+    }

+#else

+  ret = __writev (fd, &iov, 1);

+  if (ret < 0)

+    ret = -errno;

+#endif

+

+  return ret;

+}

diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h

index 37f1915b0c75a020..4aa28b0229e0b339 100644

--- a/sysdeps/generic/ldsodefs.h

+++ b/sysdeps/generic/ldsodefs.h

@@ -754,6 +754,12 @@ _dl_dprintf (int fd, const char *fmt, ...)

 }

 #endif

+/* Write LENGTH bytes at BUFFER to FD, like write.  Returns the number

+   of bytes written on success, or a negative error constant on

+   failure.  */

+ssize_t _dl_write (int fd, const void *buffer, size_t length)

+  attribute_hidden;

+

 /* Write a message on the specified descriptor standard output.  The

    parameters are interpreted as for a `printf' call.  */

 #define _dl_printf(fmt, args...) \

diff --git a/sysdeps/unix/sysv/linux/dl-write.c b/sysdeps/unix/sysv/linux/dl-write.c

new file mode 100644

index 0000000000000000..2c670a8059077076

--- /dev/null

+++ b/sysdeps/unix/sysv/linux/dl-write.c

@@ -0,0 +1,31 @@

+/* Implementation of the _dl_write function.  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

+   <https://www.gnu.org/licenses/>.  */

+

+#include <sysdep.h>

+#include <unistd.h>

+#include <ldsodefs.h>

+

+ssize_t

+_dl_write (int fd, const void *buffer, size_t length)

+{

+  INTERNAL_SYSCALL_DECL (err);

+  long int r = INTERNAL_SYSCALL_CALL (write, err, fd, buffer, length);

+  if (INTERNAL_SYSCALL_ERROR_P (r, err))

+    r = - INTERNAL_SYSCALL_ERRNO (r, err);

+  return r;

+}