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, 193 insertions, 0 deletions

diff --git a/libc/sysdeps/linux/xtensa/pread_write.c b/libc/sysdeps/linux/xtensa/pread_write.c
new file mode 100644
index 000000000..9e8813210
--- /dev/null
+++ b/libc/sysdeps/linux/xtensa/pread_write.c
@@ -0,0 +1,193 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Copyright (C) 2000-2006 Erik Andersen <andersen@uclibc.org>
+ *
+ * Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
+ */
+/*
+ * Based in part on the files
+ *		./sysdeps/unix/sysv/linux/pwrite.c,
+ *		./sysdeps/unix/sysv/linux/pread.c,
+ *		sysdeps/posix/pread.c
+ *		sysdeps/posix/pwrite.c
+ * from GNU libc 2.2.5, but reworked considerably...
+ */
+
+#include <sys/syscall.h>
+#include <unistd.h>
+#include <stdint.h>
+#include <endian.h>
+
+extern __typeof(pread) __libc_pread;
+extern __typeof(pwrite) __libc_pwrite;
+#ifdef __UCLIBC_HAS_LFS__
+extern __typeof(pread64) __libc_pread64;
+extern __typeof(pwrite64) __libc_pwrite64;
+#endif
+
+#include <bits/kernel_types.h>
+
+#ifdef __NR_pread
+
+# define __NR___syscall_pread __NR_pread
+/* On Xtensa, 64-bit values are aligned in even/odd register pairs.  */
+static inline _syscall6(ssize_t, __syscall_pread, int, fd, void *, buf,
+		size_t, count, int, pad, off_t, offset_hi, off_t, offset_lo);
+
+ssize_t __libc_pread(int fd, void *buf, size_t count, off_t offset)
+{
+	return __syscall_pread(fd, buf, count, 0, __LONG_LONG_PAIR(offset >> 31, offset));
+}
+weak_alias(__libc_pread,pread)
+
+# ifdef __UCLIBC_HAS_LFS__
+ssize_t __libc_pread64(int fd, void *buf, size_t count, off64_t offset)
+{
+    uint32_t low = offset & 0xffffffff;
+    uint32_t high = offset >> 32;
+	return __syscall_pread(fd, buf, count, 0, __LONG_LONG_PAIR(high, low));
+}
+weak_alias(__libc_pread64,pread64)
+# endif /* __UCLIBC_HAS_LFS__  */
+
+#endif /* __NR_pread */
+
+#ifdef __NR_pwrite
+
+# define __NR___syscall_pwrite __NR_pwrite
+/* On Xtensa, 64-bit values are aligned in even/odd register pairs.  */
+static inline _syscall6(ssize_t, __syscall_pwrite, int, fd, const void *, buf,
+		size_t, count, int, pad, off_t, offset_hi, off_t, offset_lo);
+
+ssize_t __libc_pwrite(int fd, const void *buf, size_t count, off_t offset)
+{
+	return __syscall_pwrite(fd, buf, count, 0, __LONG_LONG_PAIR(offset >> 31, offset));
+}
+weak_alias(__libc_pwrite,pwrite)
+
+# ifdef __UCLIBC_HAS_LFS__
+ssize_t __libc_pwrite64(int fd, const void *buf, size_t count, off64_t offset)
+{
+    uint32_t low = offset & 0xffffffff;
+    uint32_t high = offset >> 32;
+	return __syscall_pwrite(fd, buf, count, 0, __LONG_LONG_PAIR(high, low));
+}
+weak_alias(__libc_pwrite64,pwrite64)
+# endif /* __UCLIBC_HAS_LFS__  */
+#endif /* __NR_pwrite */
+
+#if ! defined __NR_pread || ! defined __NR_pwrite
+libc_hidden_proto(read)
+libc_hidden_proto(write)
+libc_hidden_proto(lseek)
+
+static ssize_t __fake_pread_write(int fd, void *buf,
+		size_t count, off_t offset, int do_pwrite)
+{
+	int save_errno;
+	ssize_t result;
+	off_t old_offset;
+
+	/* Since we must not change the file pointer preserve the
+	 * value so that we can restore it later.  */
+	if ((old_offset=lseek(fd, 0, SEEK_CUR)) == (off_t) -1)
+		return -1;
+
+	/* Set to wanted position.  */
+	if (lseek(fd, offset, SEEK_SET) == (off_t) -1)
+		return -1;
+
+	if (do_pwrite == 1) {
+		/* Write the data.  */
+		result = write(fd, buf, count);
+	} else {
+		/* Read the data.  */
+		result = read(fd, buf, count);
+	}
+
+	/* Now we have to restore the position.  If this fails we
+	 * have to return this as an error.  */
+	save_errno = errno;
+	if (lseek(fd, old_offset, SEEK_SET) == (off_t) -1)
+	{
+		if (result == -1)
+			__set_errno(save_errno);
+		return -1;
+	}
+	__set_errno(save_errno);
+	return(result);
+}
+
+# ifdef __UCLIBC_HAS_LFS__
+libc_hidden_proto(lseek64)
+
+static ssize_t __fake_pread_write64(int fd, void *buf,
+		size_t count, off64_t offset, int do_pwrite)
+{
+	int save_errno;
+	ssize_t result;
+	off64_t old_offset;
+
+	/* Since we must not change the file pointer preserve the
+	 * value so that we can restore it later.  */
+	if ((old_offset=lseek64(fd, 0, SEEK_CUR)) == (off64_t) -1)
+		return -1;
+
+	/* Set to wanted position.  */
+	if (lseek64(fd, offset, SEEK_SET) == (off64_t) -1)
+		return -1;
+
+	if (do_pwrite == 1) {
+		/* Write the data.  */
+		result = write(fd, buf, count);
+	} else {
+		/* Read the data.  */
+		result = read(fd, buf, count);
+	}
+
+	/* Now we have to restore the position. */
+	save_errno = errno;
+	if (lseek64(fd, old_offset, SEEK_SET) == (off64_t) -1) {
+		if (result == -1)
+			__set_errno (save_errno);
+		return -1;
+	}
+	__set_errno (save_errno);
+	return result;
+}
+# endif /* __UCLIBC_HAS_LFS__  */
+#endif /*  ! defined __NR_pread || ! defined __NR_pwrite */
+
+#ifndef __NR_pread
+ssize_t __libc_pread(int fd, void *buf, size_t count, off_t offset)
+{
+	return __fake_pread_write(fd, buf, count, offset, 0);
+}
+weak_alias(__libc_pread,pread)
+
+# ifdef __UCLIBC_HAS_LFS__
+ssize_t __libc_pread64(int fd, void *buf, size_t count, off64_t offset)
+{
+	return __fake_pread_write64(fd, buf, count, offset, 0);
+}
+weak_alias(__libc_pread64,pread64)
+# endif /* __UCLIBC_HAS_LFS__  */
+#endif /* ! __NR_pread */
+
+#ifndef __NR_pwrite
+ssize_t __libc_pwrite(int fd, const void *buf, size_t count, off_t offset)
+{
+	/* we won't actually be modifying the buffer,
+	 *just cast it to get rid of warnings */
+	return __fake_pread_write(fd, (void*)buf, count, offset, 1);
+}
+weak_alias(__libc_pwrite,pwrite)
+
+# ifdef __UCLIBC_HAS_LFS__
+ssize_t __libc_pwrite64(int fd, const void *buf, size_t count, off64_t offset)
+{
+	return __fake_pread_write64(fd, (void*)buf, count, offset, 1);
+}
+weak_alias(__libc_pwrite64,pwrite64)
+# endif /* __UCLIBC_HAS_LFS__  */
+#endif /* ! __NR_pwrite */