ARM Cortex A-8 Bare-metal application with uboot

Hi,

In Beaglebone Black I'm trying to run a baremetal program (UART0 running in polling mode).

Using boot compiled using baremetal toolchain gcc-arm-none-eabi-10.3-2021.10 as Secound stage bootloader to load and run the baremetal program.

Uboot is compiled with config “am335x_evm_defconfig”. Copied MLO, u-boot.img from the uboot compiled to the SD-Card.

Compile the Baremetal program without vector table to run over uboot. In bare-metal program I have disabled FIQ and IRQ.

I'm try to run the application from two address both are behaving differently

Trying to load application to the RAM address 0x402f0400 from uboot - getting error "trying to overwrite reserved memory…"

$ fatload mmc 0 0x402f0400 helloworld

loading and running application from address 0x80000000 from uboot- baremetal program is running, but soon the target is restarting.

$ fatload mmc 0 0x80000000 helloworld

$ go 0x80000000

Below is the start-up code of the bare-metal application:

.globl _start

_start:
mrs r0, cpsr
bic r0, r0, #0x1F ;@ clear mode bits
orr r0, r0, #0x13 ;@ set SVC mode
orr r0, r0, #0xC0 ;@ disable FIQ and IRQ
msr cpsr, r0

mrc p15,0,r0,c1,c0,2 ;@ read cp access register
orr r0,r0,#0x00F00000 ;@ enable full access to neon/vfp (coproc 10&11)
mcr p15,0,r0,c1,c0,2 ;@ write cp access register
isb ;@ instruction synchronization barrier
mov r0,#0x40000000 ;@ switch on vfp & neon
vmsr fpexc,r0 ;@ set EN bit in fpexc

ldr sp, =0x4030CDFC ;@6kB public stack TRM 26.1.3.2, used when copying and running the program from  the RAM address 0x402f0400,
//ldr sp, =0x8030CDFC ;used when copying and running the program from  the RAM address 0x80000000
bl psr_main

.loop: b .loop


Below is the linker script of the baremetal program:

MEMORY
{
//RAM : ORIGIN = 0x80000000, LENGTH = 0x1B400 // used when copying and running the program from  the RAM address 0x80000000
RAM : ORIGIN = 0x402f0400, LENGTH = 0x1B400 // used when copying and running the program from  the RAM address 0x402f0400,
}

SECTIONS
{
	.text :
	{
		*(.text*);
	}> RAM

	.data :
	{
		*(.data*);
	}> RAM

	.bss :
	{
		*(.bss*);
	}> RAM
}

I'm new to the bare-metal programming and Cortex-A8,

Please guide me if something is missing from my side.

Thanks.

Parents
  • Trying to load application to the RAM address 0x402f0400 from uboot - getting error "trying to overwrite reserved memory…"

    It's better to read the datasheet of this Cortex-A8 board, which will define the memory range usage for 0x402f0400.  

    You should avoid the 0x402f0400 because it may be reserved by the system image or the first-stage bootloader based on above warning prompt.

    >  loading and running application from address 0x80000000 from uboot- baremetal program is running, but soon the target is restarting.

    For the bare-mental code, it is useful to debug the code step-by-step with the help of a debugger. (e.g. Arm DStream or Lauterbach Trace32)

    There are so many reasons that the code execution is out of control so that the processor restarts.  It is difficult to figure out the root cause in code analysis.

Reply
  • Trying to load application to the RAM address 0x402f0400 from uboot - getting error "trying to overwrite reserved memory…"

    It's better to read the datasheet of this Cortex-A8 board, which will define the memory range usage for 0x402f0400.  

    You should avoid the 0x402f0400 because it may be reserved by the system image or the first-stage bootloader based on above warning prompt.

    >  loading and running application from address 0x80000000 from uboot- baremetal program is running, but soon the target is restarting.

    For the bare-mental code, it is useful to debug the code step-by-step with the help of a debugger. (e.g. Arm DStream or Lauterbach Trace32)

    There are so many reasons that the code execution is out of control so that the processor restarts.  It is difficult to figure out the root cause in code analysis.

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