source: bootcd/isolinux/syslinux-6.03/com32/lib/setjmp.S

/*
 * arch/i386/setjmp.S
 *
 * setjmp/longjmp for the i386 architecture
 *
 *
 *
 * The jmp_buf is assumed to contain the following, in order:
 *      %ebx
 *      %esp
 *      %ebp
 *      %esi
 *      %edi
 *      <return address>
 */
/*
        .text
        .align 4

        .globl _setjmp
        .type _setjmp, @function
_setjmp:                                # gcc 4.0.1 wants this as an alias?

        .globl setjmp
        .type setjmp, @function
setjmp:
#ifdef REGPARM
        movl %eax,%edx
#else
        movl 4(%esp),%edx
#endif
        popl %ecx                       # Return address, and adjust the stack
        xorl %eax,%eax                  # Return value
        movl %ebx,(%edx)
        movl %esp,4(%edx)               # Post-return %esp!
        pushl %ecx                      # Make the call/return stack happy
        movl %ebp,8(%edx)
        movl %esi,12(%edx)
        movl %edi,16(%edx)
        movl %ecx,20(%edx)              # Return address
        ret

        .size setjmp,.-setjmp

        .text
        .align 4
        .globl longjmp
        .type longjmp, @function
longjmp:
#ifdef REGPARM
        xchgl %eax,%edx
#else
        movl 4(%esp),%edx               # jmp_ptr address
        movl 8(%esp),%eax               # Return value
#endif
        movl (%edx),%ebx
        movl 4(%edx),%esp
        movl 8(%edx),%ebp
        movl 12(%edx),%esi
        movl 16(%edx),%edi
        jmp *20(%edx)

        .size longjmp,.-longjmp
*/
#if __SIZEOF_POINTER__ == 4
#include <i386/setjmp.S>
#elif __SIZEOF_POINTER__ == 8
#include <x86_64/setjmp.S>
#else
#error "Unable to build for to-be-defined architecture type"
#endif