Chris Zankel writes:

The following patches add support for the Xtensa processor architecture
to uClibc. They are based on a recent SVN checkout (12/05/2007).

The first patch (attached to this post) adds Xtensa support to various
shared configuration and make files. The following patches then include
the Xtensa specific files and directories.

I welcome any feedback and would appreciate it if you could include the
patches into the mainline tree. I am certainly committed to maintain the port. 

Bob Wilson was kind enough to review the patches.

Some notes about the architecture: Xtensa is a configurable and
extensible processor architecture developed by Tensilica. For more
information, please visit: www.linux-xtensa.org.

1 files changed, 160 insertions, 0 deletions

diff --git a/libc/sysdeps/linux/xtensa/sysdep.h b/libc/sysdeps/linux/xtensa/sysdep.h
new file mode 100644
index 000000000..5708a8114
--- /dev/null
+++ b/libc/sysdeps/linux/xtensa/sysdep.h
@@ -0,0 +1,160 @@
+/* Assembler macros for Xtensa processors.
+   Copyright (C) 2001, 2007 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., 51 Franklin Street - Fifth Floor,
+   Boston, MA 02110-1301, USA.  */
+
+#ifdef __ASSEMBLER__
+
+#define ALIGNARG(log2) 1 << log2
+#define ASM_TYPE_DIRECTIVE(name, typearg) .type name, typearg
+#define ASM_SIZE_DIRECTIVE(name) .size name, . - name
+
+#ifdef __STDC__
+#define C_LABEL(name)	name :
+#else
+#define C_LABEL(name)	name/**/:
+#endif
+
+#define	ENTRY(name)							\
+  ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME(name);				\
+  ASM_TYPE_DIRECTIVE (C_SYMBOL_NAME(name), @function);			\
+  .align ALIGNARG(2);							\
+  LITERAL_POSITION;							\
+  C_LABEL(name)								\
+  entry sp, FRAMESIZE;							\
+  CALL_MCOUNT
+
+#undef END
+#define END(name) ASM_SIZE_DIRECTIVE(name)
+
+/* Define a macro for this directive so it can be removed in a few places.  */
+#define LITERAL_POSITION .literal_position
+
+#undef JUMPTARGET
+#ifdef PIC
+/* The "@PLT" suffix is currently a no-op for non-shared linking, but
+   it doesn't hurt to use it conditionally for PIC code in case that
+   changes someday.  */
+#define JUMPTARGET(name) name##@PLT
+#else
+#define JUMPTARGET(name) name
+#endif
+
+#define FRAMESIZE 16
+#define CALL_MCOUNT		/* Do nothing.  */
+
+
+/* Linux uses a negative return value to indicate syscall errors,
+   unlike most Unices, which use the condition codes' carry flag.
+
+   Since version 2.1 the return value of a system call might be
+   negative even if the call succeeded.  E.g., the `lseek' system call
+   might return a large offset.  Therefore we must not anymore test
+   for < 0, but test for a real error by making sure the value in a2
+   is a real error number.  Linus said he will make sure the no syscall
+   returns a value in -1 .. -4095 as a valid result so we can safely
+   test with -4095.  */
+
+/* We don't want the label for the error handler to be global when we define
+   it here.  */
+#define SYSCALL_ERROR_LABEL 0f
+
+#undef  PSEUDO
+#define	PSEUDO(name, syscall_name, args)				      \
+  .text;								      \
+  ENTRY (name)								      \
+	DO_CALL	(syscall_name, args);					      \
+	movi	a4, -4095;						      \
+	bgeu	a2, a4, SYSCALL_ERROR_LABEL;				      \
+  .Lpseudo_end:
+
+#undef	PSEUDO_END
+#define	PSEUDO_END(name)						      \
+  SYSCALL_ERROR_HANDLER							      \
+  END (name)
+
+#undef	PSEUDO_NOERRNO
+#define	PSEUDO_NOERRNO(name, syscall_name, args)			      \
+  .text;								      \
+  ENTRY (name)								      \
+	DO_CALL	(syscall_name, args)
+
+#undef	PSEUDO_END_NOERRNO
+#define	PSEUDO_END_NOERRNO(name)					      \
+  END (name)
+
+#undef	ret_NOERRNO
+#define ret_NOERRNO retw
+
+/* The function has to return the error code.  */
+#undef	PSEUDO_ERRVAL
+#define	PSEUDO_ERRVAL(name, syscall_name, args)				      \
+  .text;								      \
+  ENTRY (name)								      \
+	DO_CALL	(syscall_name, args);					      \
+	neg	a2, a2
+
+#undef	PSEUDO_END_ERRVAL
+#define	PSEUDO_END_ERRVAL(name)						      \
+  END (name)
+
+#define ret_ERRVAL retw
+
+#if RTLD_PRIVATE_ERRNO
+# define SYSCALL_ERROR_HANDLER						      \
+0:	movi	a4, rtld_errno;						      \
+	neg	a2, a2;							      \
+	s32i	a2, a4, 0;						      \
+	movi	a2, -1;							      \
+	j	.Lpseudo_end;
+
+#elif defined _LIBC_REENTRANT
+
+# if USE___THREAD
+#  ifndef NOT_IN_libc
+#   define SYSCALL_ERROR_ERRNO __libc_errno
+#  else
+#   define SYSCALL_ERROR_ERRNO errno
+#  endif
+#  define SYSCALL_ERROR_HANDLER						      \
+0:	rur	a4, THREADPTR;						      \
+	movi	a3, SYSCALL_ERROR_ERRNO@TPOFF;				      \
+	neg	a2, a2;							      \
+	add	a4, a4, a3;						      \
+	s32i	a2, a4, 0;						      \
+	movi	a2, -1;							      \
+	j	.Lpseudo_end;
+# else /* !USE___THREAD */
+#  define SYSCALL_ERROR_HANDLER						      \
+0:	neg	a2, a2;							      \
+	mov	a6, a2;							      \
+	movi	a4, __errno_location@PLT;				      \
+	callx4	a4;						              \
+	s32i	a2, a6, 0;						      \
+	movi	a2, -1;							      \
+	j	.Lpseudo_end;
+# endif /* !USE___THREAD */
+#else /* !_LIBC_REENTRANT */
+#define SYSCALL_ERROR_HANDLER						      \
+0:	movi	a4, errno;						      \
+	neg	a2, a2;							      \
+	s32i	a2, a4, 0;						      \
+	movi	a2, -1;							      \
+	j	.Lpseudo_end;
+#endif /* _LIBC_REENTRANT */
+
+#endif	/* __ASSEMBLER__ */