Hi Oliver,
Yes. the code was running on Linux. Thank you very much for the
correction.
You are right. i just check the AMD64 ABI
(http://www.x86-64.org/documentation.html) that Solaris conforms to.
Because the parameter I need transfer is char array, it needs to be put
in the stack during the calling.
But do you know where i can find the x86 ABI that Solaris uses?
Regards,
adam
Oliver Yang wrote:
Oliver Yang wrote:
Adam Zhang wrote:
Hi all,
i just write an independent write function in assembly language to
write a string to stderr.
But the code doesn't work on Solaris.
It seems you are using Gcc inline asm which will generate a system
call by issuing "int 0x91".
But you should know, doesn't like Linux, on 32bit x86, Solaris passes
parameters via stack by "push" instead of using registers.
That means, you should besides using %eax as syscall number, you
should push necessary parameters into stack before issuing "int 0x91".
Hi Adam,
Sorry for my poor English. :-[
I have checked your code, I think you inline ASM code are learned from
Linux, not Solaris. In your code, you are trying to pass parameters by
registers before issuing int 0x91:
%eax: 0x4 -> syscall number %ebx: 0x2 --> fd
%ecx buf address
%edx: int size
But actually, on Solaris x86 32bit kernel, except syscall number
should be passed by %eax, other parameters should be passed by pushing
them in stack, please refer to following code:
# /usr/sfw/bin/gcc test.c
# ./a.out
hello
# cat test.c
void write_stderr ( char * buf, int n )
{
int block[2];
block[0] = (int) buf;
block[1] = n;
__asm__ volatile (
"pushl %%ebx\n"
"movl %0, %%ebx\n"
"pushl %%ebx\n"
"movl $4, %%eax\n"
"push 4(%%ebx)\n"
"push 0(%%ebx)\n"
"push $2\n"
"push %%esp\n"
"int $0x91\n"
"addl $3,%%esp\n"
"movl %%eax, 0(%%ebx)\n"
"popl %%ebx\n"
: /*wr*/
: /*rd*/ "g" (block)
: /*trash*/ "eax", "edi", "ecx", "edx", "memory", "cc"
);
}
int main()
{
char s[]="hello\n";
write_stderr(s, sizeof(s) );
return 0;
}
Another thing is, you should run your program on Solaris Nevada,
because you used "int 0x91".
You could use mdb debug your program by setting break point before
int 0x91, check whether you provide right parameters in stack and
%eax.
Below is the code:
void write_stderr ( char * buf, int n )
{
int block[2];
block[0] = (int) buf;
block[1] = n;
__asm__ volatile (
"pushl %%ebx\n" "movl %0, %%ebx\n"
"pushl %%ebx\n" "movl 0(%%ebx), %%ecx\n"
"movl 4(%%ebx), %%edx\n"
"movl $4, %%eax\n" "movl $2, %%ebx\n" "int
$0x91\n" "popl %%ebx\n" "movl %%eax,
0(%%ebx)\n"
"popl %%ebx\n" : /*wr*/
: /*rd*/ "g" (block)
: /*trash*/ "eax", "edi", "ecx", "edx", "memory", "cc"
);
}
Does anyone know where i am wrong?
Thank you!
Regards,
adam
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