[ECOS] vector.s branch 0 problem
Mon Jul 2 14:30:00 GMT 2007
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> Doesn't the call for "-Ttarget.ld" in the arm-elf-gcc command make the
> link ?
> Those are the commands I use to compile my project under eclipse:
> arm-elf-gcc -c -o boot.o
> -Wa,-adhlns=boot.lst -mcpu=arm7tdmi -mno-short-load-words -Wall
> -Wpointer-arith -Wstrict-prototypes -Winline -Wundef
> -Woverloaded-virtual -g -O2 -ffunction-sections -fdata-sections
> -fno-rtti -fno-exceptions -fvtable-gc -finit-priority boot.c
> arm-elf-gcc -nostartfiles
> -Ttarget.ld -Wl,-Map=boot.map -mcpu=arm7tdmi -mno-short-load-words
> -Wl,--gc-sections -Wl,-static -g -nostdlib -o boot boot.o
> arm-elf-objdump -h -S -C boot.o > boot.lss
> yet the boot.lss file I obtain as a result isn't by far resembling the
> vectors.lss i spoke earlier.
> Do i have to add a arm-elf-ld command after the arm-elf-gcc ones ?
No, but you *must* run 'arm-elf-objdumop' on "boot", not "boot.o"
> On 7/2/07, Gary Thomas <firstname.lastname@example.org> wrote:
> Alexandre wrote:
>> Hi everyone,
>> I may have a found why my ecos does not work at all but i'd like so
>> feedback on it.
>> I used the command:
>> arm-elf-objdump -h -S -C vectors.o > vectors.lss
>> to have a clearer view of what was going on at the init scale.
>> Everything seemed nice so far but this morning i noticed that on the
>> rom vectors init:
>> Disassembly of section .vectors:
>> 00000000 <__exception_handlers>:
>> 0: eafffffe b 0 <__exception_handlers>
>> 4: e59ff018 ldr pc, [pc, #24] ; 24
>> 8: e59ff018 ldr pc, [pc, #24] ; 28 <.software_interrupt>
>> c: e59ff018 ldr pc, [pc, #24] ; 2c <.abort_prefetch>
>> 10: e59ff018 ldr pc, [pc, #24] ; 30 <.abort_data>
>> 14: b4405f62 strltb r5, [r0], -#3938
>> 18: e59ff018 ldr pc, [pc, #24] ; 38 <.IRQ>
>> 1c: e59ff018 ldr pc, [pc, #24] ; 3c <.FIQ>
>> I'm not a real genius when it come to assembly language but seems to
>> me the thing just loops forever at address 0.
>> I lurked a bit into vector.s and found the code that generated the
>> part above was that:
>> .global __exception_handlers
>> #ifdef CYGSEM_HAL_ROM_RESET_USES_JUMP
>> // Assumption: ROM code has these vectors at the hardware reset
>> // A simple jump removes any address-space dependencies [i.e. safer]
>> b reset_vector // 0x00
>> ldr pc,.reset_vector // 0x00
>> ldr pc,.undefined_instruction // 0x04
>> ldr pc,.software_interrupt // 0x08 start &&
>> ldr pc,.abort_prefetch // 0x0C
>> ldr pc,.abort_data // 0x10
>> #ifdef CYGNUM_HAL_ARM_VECTOR_0x14
>> .word CYGNUM_HAL_ARM_VECTOR_0x14
>> .word 0 // unused
>> ldr pc,.IRQ // 0x18
>> ldr pc,.FIQ // 0x1C
>> Now if we take a closer look at the code at 0, it is supposed to
>> branch to the start of the reset_vector. I noticed there's isn't a "."
>> (dot) at the start of the name, don't know if it's important or not
>> but as those are right from the cvs i thought it would be improper to
>> change it.
>> Do you guys have any idea what comes wrong here ?
> You're looking at "vectors.o", correct? This doesn't work
> because the instruction you are looking at needs some additional
> "relocation" - in particular the address of 'reset_vector' - to
> be added into it. This is done by the linker (arm-elf-ld).
> Try looking at the same piece of code in the final ELF
> image and you'll see that it's quite different.
Gary Thomas | Consulting for the
MLB Associates | Embedded world
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