ARM GCC -- First 64KB of application code

ice0 — Wed, 03 Jul 2019 11:56:24 GMT

Does anybody know where is the ASM code for first 64KB of compiled ELF

I'm looking for the code which define magic ELF 0x7F454C46 signature

Linker sets memory:

MEMORY
{
    ROM_VECTORS (rx) : ORIGIN = 0x00000000, LENGTH = 0x00000400
    ROM_FLASH_CFG (rx) : ORIGIN = 0x00000400, LENGTH = 0x00000010
    ROM_TEXT (rx) : ORIGIN = 0x00000410, LENGTH = 512K
    RAM (rw) : ORIGIN = 0x20000000, LENGTH = 192K
}

When I read the ELF file the ROM vectors are located one byte over 64KB

Startup code is:

.cpu cortex-m4
.thumb

.section .vectors, "a"
    .word __stack
    .word _reset
    .word _hang /* NMI */
    .word _hang /* HardFault */
    .word _hang /* MemManage */
    .word _hang /* BusFault */
    .word _hang /* UsageFault */
    .word _hang /* Reserved */
    .word _hang /* Reserved */
    .word _hang /* Reserved */
    .word _hang /* Reserved */
    .word vPortSVCHandler
    .word _hang /* DebugMonitor */
    .word _hang /* Reserved */
    .word xPortPendSVHandler
    .word xPortSysTickHandler

.section .flash_config, "a"
    .long 0xFFFFFFFF
    .long 0xFFFFFFFF
    .long 0xFFFFFFFF
    .long 0xFFFFFFFE

.section .text
.thumb_func
.global _reset
_reset:
    bl disable_wdog
    bl init_data_and_bss
    bl main

.global _exit
_exit:
b .

.global _hang
_hang:
b .

And the ELF binary:

1:    7f45 4c46 0101 0100 0000 0000 0000 0000          CODE ???
2:   0200 2800 0100 0000 1004 0000 3400 0000          CODE ???
3:   14ec 0200 0002 0005 3400 2000 0400 2800          CODE ???
4:   1100 1000 0100 0000 0000 0100 0000 0000          CODE ???
5:   0000 0000 4000 0000 4000 0000 0400 0000          CODE ???
6:   0000 0100 0100 0000 0004 0100 0004 0000          CODE ???
7:   0004 0000 1000 0000 1000 0000 0400 0000          CODE ???
8:   0000 0100 0100 0000 1004 0100 1004 0000          CODE ???
9:   1004 0000 d82f 0000 d82f 0000 0500 0000            CODE ???
10: 0000 0100 0100 0000 0000 0200 0000 0020          CODE ???
11: e833 0000 0400 0000 d480 0000 0600 0000          CODE ???
12: 0000 0100 0000 0000 0000 0000 0000 0000
13: 0000 0000 0000 0000 0000 0000 0000 0000
14: 0000 0000 0000 0000 0000 0000 0000 0000
15: 0000 0000 0000 0000 0000 0000 0000 0000
16: 0000 0000 0000 0000 0000 0000 0000 0000

...

...
4095: 0000 0000 0000 0000 0000 0000 0000 0000
4096: 0000 0000 0000 0000 0000 0000 0000 0000
4097: 0000 0320 1104 0000 1e04 0000 1e04 0000   ROM VECTORS
4098: 1e04 0000 1e04 0000 1e04 0000 1e04 0000   ROM VECTORS
4099: 1e04 0000 1e04 0000 1e04 0000 5105 0000   ROM VECTORS
4100: 1e04 0000 1e04 0000 8907 0000 eb07 0000   ROM VECTORS
4101: 0000 0000 0000 0000 0000 0000 0000 0000

4102: 0000 0000 0000 0000 0000 0000 0000 0000

Does anybody know where I could find a code for first 64KB of compiled ELF ???

Thanks

Ice

Re: ARM GCC -- First 64KB of application code

mjbcswitzerland — Wed, 03 Jul 2019 18:11:40 GMT

Hi Ice

The ELF header is generated by the output converter and is not part of the code:

https://linux-audit.com/elf-binaries-on-linux-understanding-and-analysis/

Regards

Mark

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ARM GCC -- First 64KB of application code

Re: ARM GCC -- First 64KB of application code