Re: how to use linux system call in cross compiling environment

[Lawrence <law@cbf.chinese2000.net>]

Dear Herbert,

Thanks for your reply.

I have to apologize that I am not much familiar with C, thus I have some 
difficulty to digest the code.

I assume the purpose of the C code is to generate the swi call in 
assembly format.  From the objdump I see "swi 0x009000de", therefore I 
just add this to my assembly code and comment out the other swi.  After 
the asm->ld->run procedure I still got the same answer from arm-elf-run 
of "sim: unknow SWI encountered - 0999de - ignoring".  Besides, I can't 
find of any linux syscall that correspondent with 0x9000de, is that a 
new syscall in kernerl 2.6?

Once I am thinking if it is because the GNU ARM toolchain doesn't have 
an arm linux kernel that make any swi syscall impossible.  If this is 
the case, is there a way to load an arm kernerl first and then debug the 
assembly program?

I've also tried a simple "Hello World" program with the toolchain  and 
arm-elf-run can show the printf string to the screen.  I wonder how they 
do this without a kernel.

Thanks and Regards,
Lawrence


>On Wed, Nov 17, 2004 at 04:39:06PM +0800, Lawrence wrote:
>  
>
>>Hi all,
>>
>>I'm figuring out the linux-arm assembly right now. I use the GNU ARM
>>toolchain 3.4.1 provided by www.gnuarm.com on my x86 Linux hosts.
>>
>>I've successfully assembled and linked the following code:
>>
>>@filename: hello.s
>>
>>.text
>>        .align  2
>>        .global _start
>>_start:
>>        adr     r1, msg         @ address
>>        mov     r0, #1          @ stdout
>>        mov     r2, #13         @ length
>>        swi     #0x900004       @ sys_write
>>
>>        mov     r0, #0
>>        swi     #0x900001       @ sys_exit
>>
>>        .align  2
>>msg:
>>        .asciz  "hello, world\n"
>>
>>the commands I used are as follows:
>>
>>arm-elf-as -gdwarf2 -o hello.o hello.s
>>arm-elf-ld -o hello hello.o
>>    
>>
>
>hmm, 
>
>static inline long mhelper(uint32_t cmd, uint32_t addr, uint32_t value)
>{
>        register long _r2 asm("r2")=(long)(value);
>        register long _r1 asm("r1")=(long)(addr);
>        register long _r0 asm("r0")=(long)(cmd);
>        asm volatile(
>                "swi %1"
>                : "=r"(_r0)
>                : "i"(__NR_mhelper), "r"(_r0), "r"(_r1), "r"(_r2)
>                : "memory");
>        if(_r0 >=(unsigned long) -4095) {
>                long err = _r0;
>                (*__errno_location())=(-err);
>                _r0=(unsigned long) -1;
>        }
>        return (long) _r0;
>}
>
>
>which looks like this in objdump:
>
>    844c:       e1a0200a        mov     r2, sl
>    8450:       e1a0100a        mov     r1, sl
>    8454:       e1a0000a        mov     r0, sl
>    8458:       ef9000de        swi     0x009000de
>    845c:       e3700a01        cmn     r0, #4096       ; 0x1000
>    8460:       9a000004        bls     0x8478
>    ...
>
>
>works fine here ...
>
>HTH,
>Herbert
>
>  
>
>>When I run the program as "arm-elf-run hello", I got the reply sim:
>>unknown SWI encountered - 900004 - ignoring. I got the same result when
>>debugging the program with insight and gdb.
>>
>>I would like to know if there is a way to use the arm linux system call
>>under such simulation environment. Thanks.
>>
>>Regards,
>>Lawrence
>>
>>
>>-
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>>    
>>
>
>
>  
>