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#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);
}
/**
* A global variable that will give us an address in the BSS segment.
*/
int global = 3;
void test_main(void)
{
// Get the addres of the first unmapped page in the system.
unsigned page = (unsigned)pg_round_up(&global);
// Reserve space for 3 parameters (write requires 4).
page -= sizeof(int) * 3;
asm volatile (
"movl %%esp, %%edi;"
"movl %0, %%esp;" // Set stack pointer to right below page boundary.
"movl %1, (%%esp);" // Try to call SYS_WRITE
"movl %2, 4(%%esp);" // Write to STDOUT
"movl %3, 8(%%esp);" // Load buffer.
//"movl $5, 12(%%esp);" // Can not write the last parameter as we would get a pagefault.
"int $0x30;"
"movl %%edi, %%esp;" // Restore esp in case we do not crash (as we should).
:
: "r" (page),
"i" (SYS_WRITE),
"i" (STDOUT_FILENO),
"i" ("TEST\n")
: "%esp", "%eax", "%edi");
fail("should have died.");
}
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