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authorRoland McGrath <roland@redhat.com>2009-08-23 17:43:21 -0700
committerRoland McGrath <roland@redhat.com>2009-08-24 11:40:15 -0700
commit036e46b655557f9a17784e502f694a80abfd68dc (patch)
tree13d443cd242f9e7a26465894b8d0d24442cfd0e1 /sysdeps/unix/syscall-template.S
parent7b943af6cf2bfd4b94be271877a10128c32d03da (diff)
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Add sysdeps/unix/syscall-template.S; build syscall stubs with deps and -g pointing to it.
Diffstat (limited to 'sysdeps/unix/syscall-template.S')
-rw-r--r--sysdeps/unix/syscall-template.S88
1 files changed, 88 insertions, 0 deletions
diff --git a/sysdeps/unix/syscall-template.S b/sysdeps/unix/syscall-template.S
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+/* 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)