V2 [PATCH] Add a C wrapper for prctl [BZ #25896]

["H.J. Lu" <hjl.tools@gmail.com>]

On Thu, Apr 30, 2020 at 09:26:18AM +0200, Florian Weimer wrote:
> * H. J. Lu via Libc-alpha:
> 
> > Add a C wrapper to pass arguments in
> >
> > /* Control process execution.  */
> > extern int prctl (int __option, ...) __THROW;
> >
> > to prctl syscall:
> >
> > extern int prctl (int, unsigned long int, unsigned long int,
> > 		  unsigned long int, unsigned long int);
> > ---
> >  include/sys/prctl.h                   |  2 ++
> >  sysdeps/unix/sysv/linux/Makefile      |  2 +-
> >  sysdeps/unix/sysv/linux/prctl.c       | 38 +++++++++++++++++++++++++++
> >  sysdeps/unix/sysv/linux/syscalls.list |  1 -
> >  4 files changed, 41 insertions(+), 2 deletions(-)
> >  create mode 100644 sysdeps/unix/sysv/linux/prctl.c
> >
> > diff --git a/include/sys/prctl.h b/include/sys/prctl.h
> > index 0920ed642b..1a74d83879 100644
> > --- a/include/sys/prctl.h
> > +++ b/include/sys/prctl.h
> > @@ -4,6 +4,8 @@
> >  # ifndef _ISOMAC
> >  
> >  extern int __prctl (int __option, ...);
> > +libc_hidden_proto (__prctl)
> > +libc_hidden_proto (prctl)
> 
> I see we have some internal callers of prctl.  I will clean this up
> later.
> 
> 
> Please add a comment that this over-reads arguments for some option
> values, something like:
> 
> /* Unconditionally read all potential arguments.  This may pass
>    garbage values to the kernel, but avoids the need for teaching
>    glibc the argument counts of individual options (including ones
>    that are added to the kernel in the future).  */
> 
> Rest looks fine.  Generated code is quite a bit worse, but I don't
> think this matter here.

Here is the updated patch.  I added the assembly version for x86.  Other
arches can do

#include <sysdeps/unix/sysv/linux/x86/prctl.S>

if they are similar.

OK for master?

Thanks.

H.J.
---
Add a C wrapper to pass arguments in

/* Control process execution.  */
extern int prctl (int __option, ...) __THROW;

to prctl syscall:

extern int prctl (int, unsigned long int, unsigned long int,
		  unsigned long int, unsigned long int);

On Linux/x86, since the prctl syscall interface:

extern int prctl (int, unsigned long int, unsigned long int,
		  unsigned long int, unsigned long int);

and the glibc prctl interface:

extern int prctl (int option, ...);

pass the arguments identically, the assembly verion:

PSEUDO (__prctl, prctl, 5)
	ret
PSEUDO_END (__prctl)

is used.
---
 include/sys/prctl.h                        |  2 +
 sysdeps/unix/sysv/linux/Makefile           |  2 +-
 sysdeps/unix/sysv/linux/prctl.c            | 43 ++++++++++++++++++++++
 sysdeps/unix/sysv/linux/syscalls.list      |  1 -
 sysdeps/unix/sysv/linux/x86/prctl.S        | 38 +++++++++++++++++++
 sysdeps/unix/sysv/linux/x86_64/x32/prctl.S | 28 ++++++++++++++
 6 files changed, 112 insertions(+), 2 deletions(-)
 create mode 100644 sysdeps/unix/sysv/linux/prctl.c
 create mode 100644 sysdeps/unix/sysv/linux/x86/prctl.S
 create mode 100644 sysdeps/unix/sysv/linux/x86_64/x32/prctl.S

diff --git a/include/sys/prctl.h b/include/sys/prctl.h
index 0920ed642b..1a74d83879 100644
--- a/include/sys/prctl.h
+++ b/include/sys/prctl.h
@@ -4,6 +4,8 @@
 # ifndef _ISOMAC
 
 extern int __prctl (int __option, ...);
+libc_hidden_proto (__prctl)
+libc_hidden_proto (prctl)
 
 # endif /* !_ISOMAC */
 #endif
diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index db78eeadd1..0326f92c40 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -59,7 +59,7 @@ sysdep_routines += adjtimex clone umount umount2 readahead sysctl \
 		   eventfd eventfd_read eventfd_write prlimit \
 		   personality epoll_wait tee vmsplice splice \
 		   open_by_handle_at mlock2 pkey_mprotect pkey_set pkey_get \
-		   timerfd_gettime timerfd_settime \
+		   timerfd_gettime timerfd_settime prctl \
 		   process_vm_readv process_vm_writev
 
 CFLAGS-gethostid.c = -fexceptions
diff --git a/sysdeps/unix/sysv/linux/prctl.c b/sysdeps/unix/sysv/linux/prctl.c
new file mode 100644
index 0000000000..49049fd85f
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/prctl.c
@@ -0,0 +1,43 @@
+/* prctl - 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 <sysdep.h>
+#include <stdarg.h>
+#include <sys/prctl.h>
+
+/* Unconditionally read all potential arguments.  This may pass
+   garbage values to the kernel, but avoids the need for teaching
+   glibc the argument counts of individual options (including ones
+   that are added to the kernel in the future).  */
+
+int
+__prctl (int option, ...)
+{
+  va_list arg;
+  va_start (arg, option);
+  unsigned long int arg2 = va_arg (arg, unsigned long int);
+  unsigned long int arg3 = va_arg (arg, unsigned long int);
+  unsigned long int arg4 = va_arg (arg, unsigned long int);
+  unsigned long int arg5 = va_arg (arg, unsigned long int);
+  va_end (arg);
+  return INLINE_SYSCALL_CALL (prctl, option, arg2, arg3, arg4, arg5);
+}
+
+libc_hidden_def (__prctl)
+weak_alias (__prctl, prctl)
+hidden_weak (prctl)
diff --git a/sysdeps/unix/sysv/linux/syscalls.list b/sysdeps/unix/sysv/linux/syscalls.list
index ced77d49fa..1d8893d1b8 100644
--- a/sysdeps/unix/sysv/linux/syscalls.list
+++ b/sysdeps/unix/sysv/linux/syscalls.list
@@ -43,7 +43,6 @@ nfsservctl	EXTRA	nfsservctl	i:ipp	__compat_nfsservctl	nfsservctl@GLIBC_2.0:GLIBC
 pipe		-	pipe		i:f	__pipe		pipe
 pipe2		-	pipe2		i:fi	__pipe2		pipe2
 pivot_root	EXTRA	pivot_root	i:ss	pivot_root
-prctl		EXTRA	prctl		i:iiiii	__prctl		prctl
 query_module	EXTRA	query_module	i:sipip	__compat_query_module	query_module@GLIBC_2.0:GLIBC_2.23
 quotactl	EXTRA	quotactl	i:isip	quotactl
 remap_file_pages -	remap_file_pages i:pUiUi	__remap_file_pages remap_file_pages
diff --git a/sysdeps/unix/sysv/linux/x86/prctl.S b/sysdeps/unix/sysv/linux/x86/prctl.S
new file mode 100644
index 0000000000..99bb62ad39
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86/prctl.S
@@ -0,0 +1,38 @@
+/* prctl - Linux specific syscall.  Linux/x86 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>
+
+/* On Linux/x86, the prctl syscall interface:
+
+   extern int prctl (int, unsigned long int, unsigned long int,
+		     unsigned long int, unsigned long int);
+
+   and the glibc prctl interface:
+
+   extern int prctl (int option, ...);
+
+   pass the arguments identically.  */
+
+PSEUDO (__prctl, prctl, 5)
+	ret
+PSEUDO_END (__prctl)
+
+hidden_def (__prctl)
+weak_alias (__prctl, prctl)
+hidden_weak (prctl)
diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/prctl.S b/sysdeps/unix/sysv/linux/x86_64/x32/prctl.S
new file mode 100644
index 0000000000..5acf5406a8
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86_64/x32/prctl.S
@@ -0,0 +1,28 @@
+/* prctl - Linux specific syscall.  Linux/x32 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>
+
+/* On Linux/x32, we need to zero-extend from 32 bits to 64 bits for the
+   last 4 arguments.  */
+
+#undef DOARGS_5
+#define DOARGS_5 \
+  movl %esi, %esi; movl %edx, %edx; movl %ecx, %r10d; movl %r8d, %r8d;
+
+#include <sysdeps/unix/sysv/linux/x86/prctl.S>
-- 
2.26.2