Hi All,
I am trying to customize linux 2.6.37 on x86. I have a function written in C which need to be called from entry_32.S. This function takes 2 arguments and return an integer. Prototype for function is -
unsigned int some_fn(int *addr,int length);
I am invoking this function before sys_call_table is invoked. But kernel panic is coming. Error message says "Kernel panic BAD EIP". If I am invoking a function that has no parameters it works fine. Please help me out of this issue.
See the relevant modification I done.
arch/x86/kernel/entry_32.S:

sysenter_do_call:
cmpl $(nr_syscalls), %eax
jae syscall_badsys
/* start of my modification */
pushl %eax /* Save system call no: in stack*/
pushl $(length) /* pushing second argument*/
pushl addr /* pushing first argument.*/
call some_fn /* calling my own c function*/
popl %eax /* restoring system call no to eax*/
/* end of my modification */
call *sys_call_table(,%eax,4)

I guess one possible reason is the stack is not ready yet, so the original code is written in assembly which, unlike C, does not need a stack.

One workaround is try to use some registers to pass the arguments.