From mboxrd@z Thu Jan  1 00:00:00 1970
From: Daniel Mack <daniel@caiaq.de>
Date: Fri, 28 Nov 2008 22:04:15 +0100
Subject: [U-Boot] gd_t/bd_t on ARM
Message-ID: <20081128210415.GD14044@buzzloop.caiaq.de>
List-Id: <u-boot.lists.denx.de>
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To: u-boot@lists.denx.de

Hi,

I'm hunting weird behaviours with the gd_t global data pointer on my
PXA300 board board. The pointer gets set up fine in lib_arm/boot.c and
gd->bd is filled in my board specific code. However, after the tftp
download is finished, the content of these structures have been
destroyed and overwritten with garbage.

I suspect a stack corruption to be the culprit, an overflow or overlap,
as it seems to happen randomly, after a while and some function calls.
Any hints about that?

Also, I wonder why the pointer to this struct is not placed *after*
U-Boot's own code as shown in the patch below. This works fine for me
now. Any oppinion on that?

Thanks and best regards,
Daniel


diff --git a/lib_arm/board.c b/lib_arm/board.c
index 4ba1f5e..90ad5f7 100644
--- a/lib_arm/board.c
+++ b/lib_arm/board.c
@@ -282,12 +282,12 @@ void start_armboot (void)
 #endif
 
        /* Pointer is writable since we allocated a register for it */
-       gd = (gd_t*)(_armboot_start - CONFIG_SYS_MALLOC_LEN - sizeof(gd_t));
+       gd = (gd_t*) _bss_end;
        /* compiler optimization barrier needed for GCC >= 3.4 */
        __asm__ __volatile__("": : :"memory");
 
        memset ((void*)gd, 0, sizeof (gd_t));
-       gd->bd = (bd_t*)((char*)gd - sizeof(bd_t));
+       gd->bd = (bd_t*)((char*)gd + sizeof(gd_t));
        memset (gd->bd, 0, sizeof (bd_t));
 
        gd->flags |= GD_FLG_RELOC;