We Can No Longer Easily Disable CR0 WP (Write-Protection)

commit

this commit makes write_cr0(read_cr0() | 0x10000) useless, next time you see a 5.x linux kernel, good luck

according to this stackoverflow question, we cannot:

  • disable CR0's Write-Protection bits
  • set RO page to RW

i think ive found a solution:

since lkm runs in ring0, why not just write to cr0 directly, why bother using write_cr0?

/* needed for hooking */
static inline void
write_cr0_forced(unsigned long val)
{
    unsigned long __force_order;

    /* __asm__ __volatile__( */
    asm volatile(
        "mov %0, %%cr0"
        : "+r"(val), "+m"(__force_order));
}

static inline void
protect_memory(void)
{
    write_cr0_forced(cr0);
}

static inline void
unprotect_memory(void)
{
    write_cr0_forced(cr0 & ~0x00010000);
}

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