x86_64 redzone

[Samuel Thibault]

Hi,

We are using newlib embedded in a small kernel that runs on x86_64.  We
have a problem with the red zone because the interrupts just use the
current stack.  I hence had to compile newlib with -mno-red-zone and
use the patch below.  Could there be a newlib --no-red-zone option or
something similar that would do this?

Samuel

Index: newlib/libc/machine/x86_64/memcpy.S
===================================================================
RCS file: /cvs/src/src/newlib/libc/machine/x86_64/memcpy.S,v
retrieving revision 1.1
diff -u -p -r1.1 memcpy.S
--- newlib/libc/machine/x86_64/memcpy.S	28 Aug 2007 21:56:49 -0000	1.1
+++ newlib/libc/machine/x86_64/memcpy.S	8 Nov 2007 16:32:44 -0000
@@ -30,10 +30,18 @@ quadword_aligned:
   cmpq    $256, rdx
   jb      quadword_copy
 
+#if 1
+  subq    $32, rsp
+  movq    rax, 24 (rsp)
+  movq    r12, 16 (rsp)
+  movq    r13, 8  (rsp)
+  movq    r14, 0  (rsp)
+#else
   movq    rax, -8  (rsp)
   movq    r12, -16 (rsp)
   movq    r13, -24 (rsp)
   movq    r14, -32 (rsp)
+#endif
 
   movq    rdx, rcx                /* Copy 128 bytes at a time with minimum cache polution */
   shrq    $7, rcx
@@ -89,10 +97,18 @@ loop:
   movq    rdx, rcx
   andq    $127, rcx
   rep     movsb
+#if 1
+  movq    24 (rsp), rax
+  movq    16 (rsp), r12
+  movq    8  (rsp), r13
+  movq    0  (rsp), r14
+  addq    $32, rsp
+#else
   movq    -8  (rsp), rax
   movq    -16 (rsp), r12
   movq    -24 (rsp), r13
   movq    -32 (rsp), r14
+#endif
   ret