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, 106 insertions, 0 deletions

diff --git a/ldso/ldso/xtensa/dl-startup.h b/ldso/ldso/xtensa/dl-startup.h
new file mode 100644
index 000000000..2fd012846
--- /dev/null
+++ b/ldso/ldso/xtensa/dl-startup.h
@@ -0,0 +1,106 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Xtensa ELF code used by dl-startup.c.
+ *
+ * Copyright (C) 2007 Tensilica Inc.
+ *
+ * Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
+ * Parts taken from glibc/sysdeps/xtensa/dl-machine.h. 
+ */
+
+__asm__ (
+    "	.text\n"
+    "	.align  4\n"
+    "	.global _start\n"
+    "	.type   _start, @function\n"
+    "_start:\n"
+    "	# Compute load offset in a2: the GOT has not yet been relocated\n"
+    "	# but the entries for local symbols contain the relative offsets\n"
+    "	# and we can explicitly add the load offset in this code.\n"
+    "	_call0  0f\n"
+    "	.align  4\n"
+    "0:	movi    a3, _start+3\n"
+    "	sub     a2, a0, a3\n"
+    "	# Make sure a0 is cleared to mark the top of stack.\n"
+    "	movi    a0, 0\n"
+    "	# user_entry_point = _dl_start(pointer to argument block)\n"
+    "	movi    a4, _dl_start\n"
+    "	mov     a6, sp\n"
+    "	add     a4, a4, a2\n"
+    "	callx4  a4\n"
+    "	# Save user_entry_point so we can jump to it.\n"
+    "	mov     a3, a6\n"
+    "	l32i    a7, sp, 0   # load argc\n"
+    "	# Load _dl_skip_args into a4.\n"
+    "	movi    a4, _dl_skip_args\n"
+    "	l32i    a4, a4, 0\n"
+    "	bnez    a4, .Lfixup_stack\n"
+    ".Lfixup_stack_ret:\n"
+    "	# Pass finalizer (_dl_fini) in a2 to the user entry point.\n"
+    "	movi    a2, _dl_fini\n"
+    "	# Jump to user's entry point (_start).\n"
+    "	jx      a3\n"
+    ".Lfixup_stack:\n"
+    "	# argc -= _dl_skip_args (with argc @ sp+0)\n"
+    "	sub     a7, a7, a4\n"
+    "	s32i    a7, sp, 0\n"
+    "	# Shift everything by _dl_skip_args.\n"
+    "	addi    a5, sp, 4   # a5 = destination ptr = argv\n"
+    "	add     a4, a5, a4  # a4 = source ptr = argv + _dl_skip_args\n"
+    "	# Shift argv.\n"
+    "1:	l32i    a6, a4, 0\n"
+    "	addi    a4, a4, 4\n"
+    "	s32i    a6, a5, 0\n"
+    "	addi    a5, a5, 4\n"
+    "	bnez    a6, 1b\n"
+    "	# Shift envp.\n"
+    "2:	l32i    a6, a4, 0\n"
+    "	addi    a4, a4, 4\n"
+    "	s32i    a6, a5, 0\n"
+    "	addi    a5, a5, 4\n"
+    "	bnez    a6, 2b\n"
+    "	# Shift auxiliary table.\n"
+    "3:	l32i    a6, a4, 0\n"
+    "	l32i    a8, a4, 4\n"
+    "	addi    a4, a4, 8\n"
+    "	s32i    a6, a5, 0\n"
+    "	s32i    a8, a5, 4\n"
+    "	addi    a5, a5, 8\n"
+    "	bnez    a6, 3b\n"
+    "	j      .Lfixup_stack_ret");
+
+/* Get a pointer to the argv value.  */
+#define GET_ARGV(ARGVP, ARGS) ARGVP = (((unsigned long *) ARGS) + 1)
+
+/* Function calls are not safe until the GOT relocations have been done.  */
+#define NO_FUNCS_BEFORE_BOOTSTRAP
+
+#define PERFORM_BOOTSTRAP_GOT(tpnt) \
+do { \
+	xtensa_got_location *got_loc; \
+	unsigned long l_addr = tpnt->loadaddr; \
+	Elf32_Word relative_count; \
+	unsigned long rel_addr; \
+	int x; \
+\
+	got_loc = (xtensa_got_location *) \
+		(tpnt->dynamic_info[DT_XTENSA (GOT_LOC_OFF)] + l_addr); \
+\
+	for (x = 0; x < tpnt->dynamic_info[DT_XTENSA (GOT_LOC_SZ)]; x++) { \
+		Elf32_Addr got_start, got_end; \
+		got_start = got_loc[x].offset & ~(PAGE_SIZE - 1); \
+		got_end = ((got_loc[x].offset + got_loc[x].length + PAGE_SIZE - 1) \
+				   & ~(PAGE_SIZE - 1)); \
+		_dl_mprotect ((void *)(got_start + l_addr), got_end - got_start, \
+					  PROT_READ | PROT_WRITE | PROT_EXEC); \
+	} \
+\
+	/* The following is a stripped down version of the code following \
+	   the invocation of PERFORM_BOOTSTRAP_GOT in dl-startup.c.	 That \
+	   code is skipped when PERFORM_BOOTSTRAP_GOT is defined, so it has \
+	   to be done here instead.	 */ \
+	relative_count = tpnt->dynamic_info[DT_RELCONT_IDX]; \
+	rel_addr = tpnt->dynamic_info[DT_RELOC_TABLE_ADDR]; \
+	if (rel_addr) \
+	  elf_machine_relative(load_addr, rel_addr, relative_count); \
+} while (0)