Add sysdeps/unix/syscall-template.S; build syscall stubs with deps and -g pointing to it.

1 files changed, 88 insertions, 0 deletions

diff --git a/sysdeps/unix/syscall-template.S b/sysdeps/unix/syscall-template.S
new file mode 100644
index 0000000000..66319f158b
--- /dev/null
+++ b/sysdeps/unix/syscall-template.S
@@ -0,0 +1,88 @@
+/* Assembly code template for system call stubs.
+   Copyright (C) 2009 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, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+/* The real guts of this work are in the macros defined in the
+   machine- and kernel-specific sysdep.h header file.  When we
+   are defining a cancellable system call, the sysdep-cancel.h
+   versions of those macros are what we really use.
+
+   Each system call's object is built by a rule in sysd-syscalls
+   generated by make-syscalls.sh that #include's this file after
+   defining a few macros:
+	SYSCALL_NAME		syscall name
+	SYSCALL_NARGS		number of arguments this call takes
+	SYSCALL_SYMBOL		primary symbol name
+	SYSCALL_CANCELLABLE	1 if the call is a cancelation point
+	SYSCALL_NOERRNO		1 to define a no-errno version (see below)
+	SYSCALL_ERRVAL		1 to define an error-value version (see below)
+
+   We used to simply pipe the correct three lines below through cpp into
+   the assembler.  The main reason to have this file instead is so that
+   stub objects can be assembled with -g and get source line information
+   that leads a user back to a source file and these fine comments.  The
+   average user otherwise has a hard time knowing which "syscall-like"
+   functions in libc are plain stubs and which have nontrivial C wrappers.
+   Some versions of the "plain" stub generation macros are more than a few
+   instructions long and the untrained eye might not distinguish them from
+   some compiled code that inexplicably lacks source line information.  */
+
+#if SYSCALL_CANCELLABLE
+# include <sysdep-cancel.h>
+#else
+# include <sysdep.h>
+#endif
+
+#define T_PSEUDO(SYMBOL, NAME, N)		PSEUDO (SYMBOL, NAME, N)
+#define T_PSEUDO_NOERRNO(SYMBOL, NAME, N)	PSEUDO_NOERRNO (SYMBOL, NAME, N)
+#define T_PSEUDO_ERRVAL(SYMBOL, NAME, N)	PSEUDO_ERRVAL (SYMBOL, NAME, N)
+#define T_PSEUDO_END(SYMBOL)			PSEUDO_END (SYMBOL)
+#define T_PSEUDO_END_NOERRNO(SYMBOL)		PSEUDO_END_NOERRNO (SYMBOL)
+#define T_PSEUDO_END_ERRVAL(SYMBOL)		PSEUDO_END_ERRVAL (SYMBOL)
+
+#if SYSCALL_NOERRNO
+
+/* This kind of system call stub never returns an error.
+   We return the return value register to the caller unexamined.  */
+
+T_PSEUDO_NOERRNO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS)
+	ret_NOERRNO
+T_PSEUDO_END_NOERRNO (SYSCALL_SYMBOL)
+
+#elif SYSCALL_ERRVAL
+
+/* This kind of system call stub returns the errno code as its return
+   value, or zero for success.  We may massage the kernel's return value
+   to meet that ABI, but we never set errno here.  */
+
+T_PSEUDO_ERRVAL (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS)
+	ret_ERRVAL
+T_PSEUDO_END_ERRVAL (SYSCALL_SYMBOL)
+
+#else
+
+/* This is a "normal" system call stub: if there is an error,
+   it returns -1 and sets errno.  */
+
+T_PSEUDO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS)
+	ret
+T_PSEUDO_END (SYSCALL_SYMBOL)
+
+#endif
+
+libc_hidden_def (SYSCALL_SYMBOL)