Patch: Linux PPC64 libffi -vs- long double return

[Tom Tromey]

This patch fixes a bug found when running libgcj on a Linux PPC64
machine.

The problem is that the return value processing for 'double' would
actually write 2 double values, potentially smashing the stack.  The
fix is to add some special handling for 'long double', as is done in
the Darwin port.

I've also included a patch to a test case which shows this failure.

Tested on Linux PPC64.

Ok?

Tom

:ADDPATCH libffi:

Index: ChangeLog
from  Tom Tromey  <tromey@redhat.com>

	* testsuite/libffi.call/float1.c (value_type): New typedef.
	(CANARY): New define.
	(main): Check for result buffer overflow.
	* src/powerpc/linux64.S: Handle linux64 long double returns.
	* src/powerpc/ffi.c (FLAG_RETURNS_128BITS): New constant.
	(ffi_prep_cif_machdep): Handle linux64 long double returns.

Index: src/powerpc/ffi.c
===================================================================
RCS file: /cvs/gcc/gcc/libffi/src/powerpc/ffi.c,v
retrieving revision 1.15
diff -u -r1.15 ffi.c
--- src/powerpc/ffi.c 25 Aug 2005 00:54:54 -0000 1.15
+++ src/powerpc/ffi.c 26 Sep 2005 16:08:18 -0000
@@ -39,6 +39,7 @@
   FLAG_RETURNS_NOTHING  = 1 << (31-30), /* These go in cr7 */
   FLAG_RETURNS_FP       = 1 << (31-29),
   FLAG_RETURNS_64BITS   = 1 << (31-28),
+  FLAG_RETURNS_128BITS  = 1 << (31-27),
 
   FLAG_ARG_NEEDS_COPY   = 1 << (31- 7),
   FLAG_FP_ARGUMENTS     = 1 << (31- 6), /* cr1.eq; specified by ABI */
@@ -543,6 +544,12 @@
       /* else fall through.  */
 #if FFI_TYPE_LONGDOUBLE != FFI_TYPE_DOUBLE
     case FFI_TYPE_LONGDOUBLE:
+      if (type == FFI_TYPE_LONGDOUBLE && cif->abi == FFI_LINUX64)
+	{
+	  flags |= FLAG_RETURNS_128BITS;
+	  flags |= FLAG_RETURNS_FP;
+	  break;
+	}
 #endif
       intarg_count++;
       flags |= FLAG_RETVAL_REFERENCE;
Index: src/powerpc/linux64.S
===================================================================
RCS file: /cvs/gcc/gcc/libffi/src/powerpc/linux64.S,v
retrieving revision 1.7
diff -u -r1.7 linux64.S
--- src/powerpc/linux64.S 2 Sep 2004 21:07:21 -0000 1.7
+++ src/powerpc/linux64.S 26 Sep 2005 16:08:18 -0000
@@ -120,9 +120,13 @@
 	blr
 
 .Lfp_return_value:
+	bt	27, .Lfd_return_value
 	bf	28, .Lfloat_return_value
 	stfd	%f1, 0(%r30)
-	stfd	%f2, 8(%r30)	/* It might be a long double */
+	b	.Ldone_return_value
+.Lfd_return_value:
+	stfd	%f1, 0(%r30)
+	stfd	%f2, 8(%r30)
 	b	.Ldone_return_value
 .Lfloat_return_value:
 	stfs	%f1, 0(%r30)
Index: testsuite/libffi.call/float1.c
===================================================================
RCS file: /cvs/gcc/gcc/libffi/testsuite/libffi.call/float1.c,v
retrieving revision 1.1
diff -u -r1.1 float1.c
--- testsuite/libffi.call/float1.c 4 Sep 2003 14:47:48 -0000 1.1
+++ testsuite/libffi.call/float1.c 26 Sep 2005 16:08:18 -0000
@@ -8,6 +8,14 @@
 #include "ffitest.h"
 #include "float.h"
 
+typedef union
+{
+  double d;
+  unsigned char c[sizeof (double)];
+} value_type;
+
+#define CANARY 0xba
+
 static double dblit(float f)
 {
   return f/3.0;
@@ -19,8 +27,8 @@
   ffi_type *args[MAX_ARGS];
   void *values[MAX_ARGS];
   float f;
-  double d;
-
+  value_type result[2];
+  int i;
 
   args[0] = &ffi_type_float;
   values[0] = &f;
@@ -31,11 +39,19 @@
   
   f = 3.14159;
   
-  ffi_call(&cif, FFI_FN(dblit), &d, values);
+  /* Put a canary in the return array.  This is a regression test for
+     a buffer overrun.  */
+  memset(result[1].c, CANARY, sizeof (double));
+
+  ffi_call(&cif, FFI_FN(dblit), &result[0].d, values);
   
   /* These are not always the same!! Check for a reasonable delta */
  
-  CHECK(d - dblit(f) < DBL_EPSILON);
+  CHECK(result[0].d - dblit(f) < DBL_EPSILON);
+
+  /* Check the canary.  */
+  for (i = 0; i < sizeof (double); ++i)
+    CHECK(result[1].c[i] == CANARY);
 
   exit(0);