#include <setjmp.h>

/*  https://nullprogram.com/blog/2023/02/12 */

__attribute__ ((naked, returns_twice)) int setjmp (jmp_buf buf) {
  __asm__ volatile ("mov (%rsp), %rax\n"
                    "mov %rax,  0(%rcx)\n"
                    "lea 8(%rsp), %rax\n"
                    "mov %rax,  8(%rcx)\n"
                    "mov %rbp, 16(%rcx)\n"
                    "mov %rbx, 24(%rcx)\n"
                    "mov %rdi, 32(%rcx)\n"
                    "mov %rsi, 40(%rcx)\n"
                    "mov %r12, 48(%rcx)\n"
                    "mov %r13, 56(%rcx)\n"
                    "mov %r14, 64(%rcx)\n"
                    "mov %r15, 72(%rcx)\n"
                    "xor %eax, %eax\n"
                    "ret\n");
}

__attribute__ ((naked, noreturn)) void longjmp (jmp_buf buf, int ret) {
  __asm__ volatile ("mov 72(%rcx), %r15\n"
                    "mov 64(%rcx), %r14\n"
                    "mov 56(%rcx), %r13\n"
                    "mov 48(%rcx), %r12\n"
                    "mov 40(%rcx), %rsi\n"
                    "mov 32(%rcx), %rdi\n"
                    "mov 24(%rcx), %rbx\n"
                    "mov 16(%rcx), %rbp\n"
                    "mov  8(%rcx), %rsp\n"
                    "mov %edx, %eax\n"
                    "jmp *0(%rcx)\n");
}