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gcc tool chain/dissasembly question

Hi guys,

I'm new to arm and am having problems to recognize the ouput of objdump. I'm compiling for cortex-m0, and the following is an excerpt of my vector table:

0: 10002000 andne r2, r0, r0 4: 00000305 andeq r0, r0, r5, lsl #6 8: 000002fd strdeq r0, [r0], -sp c: 000002fd strdeq r0, [r0], -sp

I can upload and debug, so I know the code is fine. This output doesn't match, however, any of the tutorials I could find on the internet. What could I be doing wrong?

I assume the first entry is 32 bits wide (as opossed to 16 it should be, being a thumb only core), as it needs to point to the top of the stack. But if I force thumb output on objdump, I get a bunch of `lsl' instructions which make even less sense to me for a vector table.

Also, `--target-help' will show me `armv6-m' architecture as supported, but then objdump won't show it:

arm-none-eabi-objdump: supported targets: elf32-littlearm elf32-bigarm elf32-little elf32-big srec symbolsrec verilog tekhex binary ihex

arm-none-eabi-objdump: supported architectures: arm armv2 armv2a armv3 armv3m armv4 armv4t armv5 armv5t armv5te xscale ep9312 iwmmxt iwmmxt2

Can somebody give me hint on any of these?

Regards,

Reply to
me
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On the Cortex M0, the vector table does not contain code (like on an ARM core), but addresses of the exception handlers.

formatting link

So, 0x10002000 is your initial stack pointer, and 0x304 is the entry point of your reset handler (it says 0x035 to indicate Thumb code).

Reply to
Arlet Ottens

Don't know how to change the way that data is displayed but, in any case, a vector table is a list of addresses, not a code segment. Trying to interpret the addresses as instructions is meaningless.

For example in this C snippet, the contents of the vector_table array are not instructions:

void f1(void); void f2(void); void f3(void); int i; typedef void (*vector)(void);

vector vector_table[] = {f1, f2, f3}; ... if ((i > 0) && (i < (sizeof(vector_table)/sizeof(vector)))) { vector_table[i](); }

-- Roberto Waltman

[ Please reply to the group, return address is invalid ]
Reply to
Roberto Waltman

Thanks guys!

how dumb!, I just didn't think of it, After all I'm not using other than pointers within the vector table. Got a bit messed up with this, the thumb set, and probably also expecting it to be similar to avr, which I have previously used.

Thanks for the quick response, I've been pulling my hair off with this one a bit lately! hehe

Reply to
me

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