From: Tim 'mithro' Ansell <mithro@mithis.com>
Date: Mon, 25 Sep 2017 19:28:27 +0000 (+1000)
Subject: or1k: Use EXCEPTION_STACK_SIZE of 256bytes.
X-Git-Tag: 24jan2021_ls180~1802^2~3
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=b1b6a741702a7ca1bf5b021f7f8504784a26aa19;p=litex.git

or1k: Use EXCEPTION_STACK_SIZE of 256bytes.

or1k defines a 128 byte "red zone" after the stack that can not be
touched by the exception handler.

We also need 128 bytes to store the 32 registers.
---

diff --git a/litex/soc/software/libbase/crt0-or1k.S b/litex/soc/software/libbase/crt0-or1k.S
index 5db4142a..ff77910d 100644
--- a/litex/soc/software/libbase/crt0-or1k.S
+++ b/litex/soc/software/libbase/crt0-or1k.S
@@ -19,7 +19,18 @@
 
 #include <spr-defs.h>
 
-#define EXCEPTION_STACK_SIZE (4*32)
+/*
+ * OR1K Architecture has a 128 byte "red zone" after the stack that can not be
+ * touched by exception handlers. GCC uses this red zone for locals and
+ * temps without needing to change the stack pointer.
+ */
+#define OR1K_RED_ZONE_SIZE	128
+
+/*
+ * We need 4 bytes (32 bits) * 32 registers space on the stack to save all the
+ * registers.
+ */
+#define EXCEPTION_STACK_SIZE	((4*32) + OR1K_RED_ZONE_SIZE)
 
 #define HANDLE_EXCEPTION                    ; \
     l.addi  r1, r1, -EXCEPTION_STACK_SIZE   ; \