#include <syscall-nr.h>
#include <stdio.h>
#include <stdint.h>
#include "tests/lib.h"
#include "tests/main.h"

/**
 * From threads/vaddr.h:
 */
#define BITMASK(SHIFT, CNT) (((1ul << (CNT)) - 1) << (SHIFT))

#define PGSHIFT 0                          /* Index of first offset bit. */
#define PGBITS  12                         /* Number of offset bits. */
#define PGSIZE  (1 << PGBITS)              /* Bytes in a page. */
#define PGMASK  BITMASK(PGSHIFT, PGBITS)   /* Page offset bits (0:12). */

static inline void *pg_round_up (const void *va) {
  return (void *) (((uintptr_t) va + PGSIZE - 1) & ~PGMASK);
}

/**
 * External symbol which address is the first address after all data in the BSS segment.
 */
extern int _end_bss;

void test_main(void)
{
	// Get the addres of the first unmapped page in the system.
	unsigned page = (unsigned)pg_round_up(&_end_bss);

	// Reserve space for 2 parameters.
	unsigned base = page - sizeof(int) * 2;

	// Call write() with space for 4 parameters (should be fine).
	asm volatile (
		"movl %%esp, %%edi;"
		"movl %0, %%esp;"       // Set stack pointer to right below page boundary.
		"movl %1, (%%esp);"     // Try to call SYS_CLOSE
		"movl $8, 4(%%esp);"    // Close fileno #8
		"int $0x30;"
		"movl %%edi, %%esp;"    // Restore esp.
		:
		: "r" (base),
		  "i" (SYS_CLOSE)
		: "%esp", "%eax", "%edi");


	write(STDOUT_FILENO, "OK\n", 3);

	// Reserve space for 1 parameter (open requires 2).
	base = page - sizeof(int) * 1;

	// Call write() with space for 3 parameters (the kernel should kill us for doing this).
	asm volatile (
		"movl %%esp, %%edi;"
		"movl %0, %%esp;"       // Set stack pointer to right below page boundary.
		"movl %1, (%%esp);"     // Try to call SYS_CLOSE
		// "movl $8, 4(%%esp);"    // Close fileno #8
		"int $0x30;"
		"movl %%edi, %%esp;"    // Restore esp in case we do not crash (as we should).
		:
		: "r" (base),
		  "i" (SYS_CLOSE)
		: "%esp", "%eax", "%edi");

	fail("should have died.");
}