Hi,
I'm working on nRF52822 device with gcc4.9.3 compiler under eclipse environnement (with gnuarm toolchain plugin).
I have some problems with data initialisation. To check what is wrong I made this simple example:
volatile uint32_t test_data=0x12345678;
volatile uint32_t test_bss = 0;
int main(void) {
printf("test data %08X\n", (int)test_data);
test_data = 0;
printf("test bss %d\n", (int)test_bss);
test_bss = 1;
}
On the first launch, the console shows:
test data 12345678
test bss 980
Then I generate a reset to restart my test, the console shows:
test data 00000000
test bss 1
So
a) the "test_data" value is well initialized on the first time, but not on the following ones.
b) the "test_bss" value is never initialized.
Note, my linker options are -T "D:\Eclipse\eclipse64-mars\workbench.arm\nRF52\nRF52_AA.ld" -Xlinker --gc-sections -Wl,-Map,"nRF52.map" --specs=rdimon.specs
I use rdimon library to have the SWO console.
If I try to debug the code, in the statup routine form "gcc_startup_nrf52.s" file, some values (addresses) are not correct.
Reset_Handler:
ldr r1, =__etext ; <= value correspond to the end of text section
ldr r2, =__data_start__ ; <= value correspond to the start of the RAM (0x20000000)
ldr r3, =__bss_start__ ; !! value = 0x8000 doesn't correspond to the start of bss section !!
...
So the initialization of data is not done here. I guess that it's done inside crt0 routine.
Then to initialize the bss section I've compiled with -D__STARTUP_CLEAR_BSS to be sure the the following code will be added.
#ifdef __STARTUP_CLEAR_BSS
ldr r1, =__bss_start__ ; !! value still set to 0x8000
ldr r2, =__bss_end__ ; !! value = 0x8000 doesn't correspond to the end of bss section !!
movs r0, 0
subs r2, r1
ble .L_loop3_done
.L_loop3:
subs r2, #4
str r0, [r1, r2]
bgt .L_loop3
.L_loop3_done:
#endif /* __STARTUP_CLEAR_BSS */
My linker script is like this
MEMORY
{
FLASH (rx) : ORIGIN = 0x00000000, LENGTH = 0x80000
RAM (rwx) : ORIGIN = 0x20000000, LENGTH = 0x10000
}
...
.bss :
{
. = ALIGN(4);
__bss_start__ = .;
*(.bss*) # bss section content should be located between __bss_start__ and __bss_end__
*(COMMON)
. = ALIGN(4);
__bss_end__ = .;
} > RAM
...
-
I don't know why bss_start and bss_end are not set to right values
-
I don't know why crt routine doesn't initialize correctly the memory
Thanks for reply.
Regards, Thierry
