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, 140 insertions, 0 deletions

diff --git a/libc/sysdeps/linux/xtensa/bits/syscalls.h b/libc/sysdeps/linux/xtensa/bits/syscalls.h
new file mode 100644
index 000000000..76bcf404f
--- /dev/null
+++ b/libc/sysdeps/linux/xtensa/bits/syscalls.h
@@ -0,0 +1,140 @@
+#ifndef _BITS_SYSCALLS_H
+#define _BITS_SYSCALLS_H
+#ifndef _SYSCALL_H
+# error "Never use <bits/syscalls.h> directly; include <sys/syscall.h> instead."
+#endif
+
+/*
+   Some of the sneaky macros in the code were taken from 
+   glibc .../sysdeps/unix/sysv/linux/xtensa/sysdep.h
+*/
+
+#define SYS_ify(syscall_name)	__NR_##syscall_name
+
+#ifdef __ASSEMBLER__
+
+/* The register layout upon entering the function is:
+
+   return addr	stack ptr	arg0, arg1, arg2, arg3, arg4, arg5
+   -----------	---------	----------------------------------
+   a0		a1		a2,   a3,   a4,   a5,   a6,   a7
+
+   (Of course a function with say 3 arguments does not have entries for
+   arguments 4, 5, and 6.)
+
+   Linux takes system-call arguments in registers.  The ABI and Xtensa
+   software conventions require the system-call number in a2.  We move any
+   argument that was in a2 to a7, and a7 to a8 if we have all 6 arguments.
+   Note that for improved efficiency, we do NOT shift all parameters down
+   one register to maintain the original order.
+
+   syscall number		arg0, arg1, arg2, arg3, arg4, arg5
+   --------------		----------------------------------
+   a2				a6,   a3,   a4,   a5,   a8,   a9
+
+   Upon return, a2 and a3 are clobbered; all other registers are preserved.  */
+
+#undef  DO_CALL
+#define DO_CALL(syscall_name, nargs)					      \
+	DO_ARGS_##nargs							      \
+	movi	a2, SYS_ify (syscall_name);				      \
+	syscall
+
+#define DO_ARGS_0
+#define DO_ARGS_1	mov a6, a2;
+#define DO_ARGS_2	mov a6, a2;
+#define DO_ARGS_3	mov a6, a2;
+#define DO_ARGS_4	mov a6, a2;
+#define DO_ARGS_5	mov a8, a6; mov a6, a2;
+#define DO_ARGS_6	mov a9, a7; mov a8, a6; mov a6, a2;
+
+#else /* not __ASSEMBLER__ */
+
+#include <errno.h>
+
+#define STR(s) #s
+#define LD_ARG(n,ar)	register int _a##n asm (STR(a##n)) = (int) (ar)
+
+#define LD_ARGS_0()
+#define LD_ARGS_1(a0)			LD_ARG(6,a0)
+#define LD_ARGS_2(a0,a1)		LD_ARGS_1(a0); LD_ARG(3,a1)
+#define LD_ARGS_3(a0,a1,a2)		LD_ARGS_2(a0,a1); LD_ARG(4,a2)
+#define LD_ARGS_4(a0,a1,a2,a3)		LD_ARGS_3(a0,a1,a2); LD_ARG(5,a3)
+#define LD_ARGS_5(a0,a1,a2,a3,a4)	LD_ARGS_4(a0,a1,a2,a3); LD_ARG(8,a4)
+#define LD_ARGS_6(a0,a1,a2,a3,a4,a5)	LD_ARGS_5(a0,a1,a2,a3,a4); LD_ARG(9,a5)
+
+#define ASM_ARGS_0			"r"(_a2)
+#define ASM_ARGS_1			ASM_ARGS_0, "r"(_a6)
+#define ASM_ARGS_2			ASM_ARGS_1, "r"(_a3)
+#define ASM_ARGS_3			ASM_ARGS_2, "r"(_a4)
+#define ASM_ARGS_4			ASM_ARGS_3, "r"(_a5)
+#define ASM_ARGS_5			ASM_ARGS_4, "r"(_a8)
+#define ASM_ARGS_6			ASM_ARGS_5, "r"(_a9)
+
+/* Define a macro which expands into the inline wrapper code for a system
+   call.  */
+
+#undef INLINE_SYSCALL
+#define INLINE_SYSCALL(name, nr, args...)				      \
+  ({ unsigned long resultvar = INTERNAL_SYSCALL (name, , nr, args);	      \
+     if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (resultvar, ), 0))	      \
+       {								      \
+         __set_errno (INTERNAL_SYSCALL_ERRNO (resultvar, ));		      \
+        resultvar = (unsigned long) -1;					      \
+       }								      \
+   (long) resultvar; })
+
+#undef INTERNAL_SYSCALL_DECL
+#define INTERNAL_SYSCALL_DECL(err) do { } while (0)
+
+#define INTERNAL_SYSCALL_NCS(name, err, nr, args...)			      \
+  ({ LD_ARG(2, name);							      \
+     LD_ARGS_##nr(args);						      \
+     asm volatile ("syscall\n" 						      \
+	 	   : "=a" (_a2)						      \
+	 	   : ASM_ARGS_##nr					      \
+	 	   : "memory");						      \
+     (long) _a2; })
+
+#undef INTERNAL_SYSCALL
+#define INTERNAL_SYSCALL(name, err, nr, args...)			      \
+  INTERNAL_SYSCALL_NCS (__NR_##name, err, nr, ##args)
+
+#undef INTERNAL_SYSCALL_ERROR_P
+#define INTERNAL_SYSCALL_ERROR_P(val, err)				      \
+  ((unsigned long) (val) >= -4095L)
+
+#undef INTERNAL_SYSCALL_ERRNO
+#define INTERNAL_SYSCALL_ERRNO(val, err)	(-(val))
+
+#define _syscall0(args...)		SYSCALL_FUNC (0, args)
+#define _syscall1(args...)		SYSCALL_FUNC (1, args)
+#define _syscall2(args...)		SYSCALL_FUNC (2, args)
+#define _syscall3(args...)		SYSCALL_FUNC (3, args)
+#define _syscall4(args...)		SYSCALL_FUNC (4, args)
+#define _syscall5(args...)		SYSCALL_FUNC (5, args)
+#define _syscall6(args...)		SYSCALL_FUNC (6, args)
+
+#define C_DECL_ARGS_0()			void
+#define C_DECL_ARGS_1(t, v)		t v
+#define C_DECL_ARGS_2(t, v, args...)	t v, C_DECL_ARGS_1(args)
+#define C_DECL_ARGS_3(t, v, args...)	t v, C_DECL_ARGS_2(args)
+#define C_DECL_ARGS_4(t, v, args...)	t v, C_DECL_ARGS_3(args)
+#define C_DECL_ARGS_5(t, v, args...)	t v, C_DECL_ARGS_4(args)
+#define C_DECL_ARGS_6(t, v, args...)	t v, C_DECL_ARGS_5(args)
+
+#define C_ARGS_0()	
+#define C_ARGS_1(t, v)			v
+#define C_ARGS_2(t, v, args...)		v, C_ARGS_1 (args)
+#define C_ARGS_3(t, v, args...)		v, C_ARGS_2 (args)
+#define C_ARGS_4(t, v, args...)		v, C_ARGS_3 (args)
+#define C_ARGS_5(t, v, args...)		v, C_ARGS_4 (args)
+#define C_ARGS_6(t, v, args...)		v, C_ARGS_5 (args)
+
+#define SYSCALL_FUNC(nargs, type, name, args...)			      \
+type name (C_DECL_ARGS_##nargs (args)) {				      \
+	return (type) INLINE_SYSCALL (name, nargs, C_ARGS_##nargs (args));    \
+}
+
+#endif /* not __ASSEMBLER__ */
+#endif /* _BITS_SYSCALLS_H */