ARM EABI mcount

[Daniel Jacobowitz <drow at false dot org>]

I've committed this patch, from Paul Brook.  He wrote:

 - Define a new __gnu_mcount_nc entry point, with an ABI that doesn't
 require the compiler to generate crufty old APCS frames. I'm choosing
 to define a new entry point to preserve backwards compatibility, and
 to allow for different variants as necessary.  The "nc" comes from the
 fact that we do not need to pass mcount the location of a counter.
 Further justification can be found in this thread:
 http://gcc.gnu.org/ml/gcc-patches/2005-05/msg01001.html

 - Rewrite the the old _mcount implementation to not rely on particular
 compiler behavior when building glibc itself.

There'll be a corresponding GCC patch at some point to call
__gnu_mcount_nc.

-- 
Daniel Jacobowitz
CodeSourcery

2008-04-11  Paul Brook  <paul@codesourcery.com>
	    Sandra Loosemore  <sandra@codesourcery.com>

	* sysdeps/arm/eabi/machine-gmon.h: New file.
	* sysdeps/arm/eabi/Versions: Add __gnu_mcount_nc.

Index: sysdeps/arm/eabi/machine-gmon.h
===================================================================
--- sysdeps/arm/eabi/machine-gmon.h	(revision 0)
+++ sysdeps/arm/eabi/machine-gmon.h	(revision 5885)
@@ -0,0 +1,99 @@
+/* Machine-dependent definitions for profiling support.  ARM EABI version.
+   Copyright (C) 2008 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.  */
+
+/* GCC for the ARM cannot compile __builtin_return_address(N) for N != 0, 
+   so we must use an assembly stub.  */
+
+#include <sysdep.h>
+static void mcount_internal (u_long frompc, u_long selfpc) __attribute_used__;
+
+#define _MCOUNT_DECL(frompc, selfpc) \
+static void mcount_internal (u_long frompc, u_long selfpc)
+
+/* Use an assembly stub with a special ABI.  The calling lr has been
+   pushed to the stack (which will be misaligned).  We should preserve
+   all registers except ip and pop a word off the stack.
+
+   NOTE: This assumes mcount_internal does not clobber any non-core
+   (coprocessor) registers.  Currently this is true, but may require
+   additional attention in the future.
+
+   The calling sequence looks something like:
+func:
+   push {lr}
+   bl __gnu_mount_nc
+   <function body>
+ */
+
+
+#define MCOUNT								\
+void __attribute__((__naked__)) __gnu_mcount_nc(void)			\
+{									\
+    asm ("push {r0, r1, r2, r3, lr}\n\t"				\
+	 "bic r1, lr, #1\n\t"						\
+	 "ldr r0, [sp, #20]\n\t"					\
+	 "bl mcount_internal\n\t"					\
+	 "pop {r0, r1, r2, r3, ip, lr}\n\t"				\
+	 "bx ip");							\
+}									\
+OLD_MCOUNT
+
+/* Provide old mcount for backwards compatibility.  This requires
+   code be compiled with APCS frame pointers.  */
+
+#ifndef NO_UNDERSCORES
+/* The asm symbols for C functions are `_function'.
+   The canonical name for the counter function is `mcount', no _.  */
+void _mcount (void) asm ("mcount");
+#else
+/* The canonical name for the function is `_mcount' in both C and asm,
+   but some old asm code might assume it's `mcount'.  */
+void _mcount (void);
+weak_alias (_mcount, mcount)
+#endif
+
+#ifdef __thumb2__
+
+#define OLD_MCOUNT							\
+void __attribute__((__naked__)) _mcount (void)				\
+{									\
+  __asm__("push		{r0, r1, r2, r3, fp, lr};"			\
+	  "movs		r0, fp;"					\
+	  "ittt		ne;"						\
+	  "ldrne	r0, [r0, #-4];"					\
+	  "movsne	r1, lr;"					\
+	  "blne		mcount_internal;"				\
+	  "pop		{r0, r1, r2, r3, fp, pc}");			\
+}
+
+#else
+
+#define OLD_MCOUNT							\
+void __attribute__((__naked__)) _mcount (void)				\
+{									\
+  __asm__("stmdb	sp!, {r0, r1, r2, r3, fp, lr};"			\
+	  "movs		fp, fp;"					\
+	  "ldrne	r0, [fp, #-4];"					\
+	  "movnes	r1, lr;"					\
+	  "blne		mcount_internal;"				\
+	  "ldmia	sp!, {r0, r1, r2, r3, fp, lr};"			\
+	  "bx		lr");						\
+}
+
+#endif
Index: sysdeps/arm/eabi/Versions
===================================================================
--- sysdeps/arm/eabi/Versions	(revision 5760)
+++ sysdeps/arm/eabi/Versions	(revision 5885)
@@ -14,4 +14,7 @@
     # Helper routines
     __gnu_Unwind_Find_exidx;
   }
+  GLIBC_2.8 {
+    __gnu_mcount_nc;
+  }
 }