Question

I would like to define a function that will be invoked from entry_32.S. It will be invoked just before the real system call handling function is called.

In order to avoid the overhead of function calling and parameter passing, can I declare my_foo as

   fastcall inline int my_foo (int n);

    /*in entry_32.S*/
    pushl %eax
    CFI_ADJUST_CFA_OFFSET 4
    SAVE_ALL
    ....
/* My code begins*/
    call my_foo
    cmpl $0, %eax
    jne syscall_wrong
    movl PT_ORIG_EAX(%esp), %eax
/* My code ends */
    call *sys_call_table(,%eax,4)

Answer 1

The compiler can inline functions in C code (whether they have the inline keyword or not) but the assembler is not that smart. What you write in assembly is exactly what will be assembled, no optimization (like inlining) at all.