[U-Boot-Users] Alignment of bss section in hello world standalone application on ARM

[Christian Eggers]

Hello,

some builds of the example hello_world application causes a data abort in 
app_startup().
This seems to be caused by an unligned memory access to __bss_start 
(stubs.c):

 
 173 extern unsigned long __bss_start, _end;
 174
 175 void app_startup(char **argv)
 176 {
 177         unsigned long * cp = &__bss_start;
 178 
 179         /* Zero out BSS */
 180         while (cp < &_end) {
 181                 *cp++ = 0;
 182         }
 183 
 189 }

There's no explicit linker script for ARM platform. The implicit default 
script seems not to
aling __bss_start to a multiple of 4 (required for unsigned long access). 
(gcc-3.3.5)

Solution 1:
The data type could be changed to "unsigned char". This may drop some 
performance,
if really large amounts of uninitialised data used.

Unfortunately I don't know whether this will work on all platforms.

Solution 2:
Create a suitable linker file. I've attached a slightly modified "default" 
script generated
ld --verbose. Perhaps this file might be more complex then necessary or 
may not run
on different gcc versions. Unfortunately I'dont know how to create a more 
"minimalistic"
file.

regards

-- 
Christian Eggers
Dipl. Ing. (FH)
Development Software
Mobile Communication Networks, EMA

KATHREIN-Werke KG
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E-Mail: christian.eggers at kathrein.de
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