// SPDX-License-Identifier: GPL-2.0
/*
 * This is for all the tests related to validating kernel memory
 * permissions: non-executable regions, non-writable regions, and
 * even non-readable regions.
 */
#include "lkdtm.h"
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/mman.h>
#include <linux/uaccess.h>
#include <asm/cacheflush.h>

/* Whether or not to fill the target memory area with do_nothing(). */
#define CODE_WRITE      true
#define CODE_AS_IS      false

/* How many bytes to copy to be sure we've copied enough of do_nothing(). */
#define EXEC_SIZE 64

/* This is non-const, so it will end up in the .data section. */
static u8 data_area[EXEC_SIZE];

/* This is cost, so it will end up in the .rodata section. */
static const unsigned long rodata = 0xAA55AA55;

/* This is marked __ro_after_init, so it should ultimately be .rodata. */
static unsigned long ro_after_init __ro_after_init = 0x55AA5500;

/*
 * This just returns to the caller. It is designed to be copied into
 * non-executable memory regions.
 */
static void do_nothing(void)
{
        return;
}

/* Must immediately follow do_nothing for size calculuations to work out. */
static void do_overwritten(void)
{
        pr_info("do_overwritten wasn't overwritten!\n");
        return;
}

static noinline void execute_location(void *dst, bool write)
{
        void (*func)(void) = dst;

        pr_info("attempting ok execution at %p\n", do_nothing);
        do_nothing();

        if (write == CODE_WRITE) {
                memcpy(dst, do_nothing, EXEC_SIZE);
                flush_icache_range((unsigned long)dst,
                                   (unsigned long)dst + EXEC_SIZE);
        }
        pr_info("attempting bad execution at %p\n", func);
        func();
}

static void execute_user_location(void *dst)
{
        int copied;

        /* Intentionally crossing kernel/user memory boundary. */
        void (*func)(void) = dst;

        pr_info("attempting ok execution at %p\n", do_nothing);
        do_nothing();

        copied = access_process_vm(current, (unsigned long)dst, do_nothing,
                                   EXEC_SIZE, FOLL_WRITE);
        if (copied < EXEC_SIZE)
                return;
        pr_info("attempting bad execution at %p\n", func);
        func();
}

void lkdtm_WRITE_RO(void)
{
        /* Explicitly cast away "const" for the test. */
        unsigned long *ptr = (unsigned long *)&rodata;

        pr_info("attempting bad rodata write at %p\n", ptr);
        *ptr ^= 0xabcd1234;
}

void lkdtm_WRITE_RO_AFTER_INIT(void)
{
        unsigned long *ptr = &ro_after_init;

        /*
         * Verify we were written to during init. Since an Oops
         * is considered a "success", a failure is to just skip the
         * real test.
         */
        if ((*ptr & 0xAA) != 0xAA) {
                pr_info("%p was NOT written during init!?\n", ptr);
                return;
        }

        pr_info("attempting bad ro_after_init write at %p\n", ptr);
        *ptr ^= 0xabcd1234;
}

void lkdtm_WRITE_KERN(void)
{
        size_t size;
        unsigned char *ptr;

        size = (unsigned long)do_overwritten - (unsigned long)do_nothing;
        ptr = (unsigned char *)do_overwritten;

        pr_info("attempting bad %zu byte write at %p\n", size, ptr);
        memcpy(ptr, (unsigned char *)do_nothing, size);
        flush_icache_range((unsigned long)ptr, (unsigned long)(ptr + size));

        do_overwritten();
}

void lkdtm_EXEC_DATA(void)
{
        execute_location(data_area, CODE_WRITE);
}

void lkdtm_EXEC_STACK(void)
{
        u8 stack_area[EXEC_SIZE];
        execute_location(stack_area, CODE_WRITE);
}

void lkdtm_EXEC_KMALLOC(void)
{
        u32 *kmalloc_area = kmalloc(EXEC_SIZE, GFP_KERNEL);
        execute_location(kmalloc_area, CODE_WRITE);
        kfree(kmalloc_area);
}

void lkdtm_EXEC_VMALLOC(void)
{
        u32 *vmalloc_area = vmalloc(EXEC_SIZE);
        execute_location(vmalloc_area, CODE_WRITE);
        vfree(vmalloc_area);
}

void lkdtm_EXEC_RODATA(void)
{
        execute_location(lkdtm_rodata_do_nothing, CODE_AS_IS);
}

void lkdtm_EXEC_USERSPACE(void)
{
        unsigned long user_addr;

        user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
                            PROT_READ | PROT_WRITE | PROT_EXEC,
                            MAP_ANONYMOUS | MAP_PRIVATE, 0);
        if (user_addr >= TASK_SIZE) {
                pr_warn("Failed to allocate user memory\n");
                return;
        }
        execute_user_location((void *)user_addr);
        vm_munmap(user_addr, PAGE_SIZE);
}

void lkdtm_ACCESS_USERSPACE(void)
{
        unsigned long user_addr, tmp = 0;
        unsigned long *ptr;

        user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
                            PROT_READ | PROT_WRITE | PROT_EXEC,
                            MAP_ANONYMOUS | MAP_PRIVATE, 0);
        if (user_addr >= TASK_SIZE) {
                pr_warn("Failed to allocate user memory\n");
                return;
        }

        if (copy_to_user((void __user *)user_addr, &tmp, sizeof(tmp))) {
                pr_warn("copy_to_user failed\n");
                vm_munmap(user_addr, PAGE_SIZE);
                return;
        }

        ptr = (unsigned long *)user_addr;

        pr_info("attempting bad read at %p\n", ptr);
        tmp = *ptr;
        tmp += 0xc0dec0de;

        pr_info("attempting bad write at %p\n", ptr);
        *ptr = tmp;

        vm_munmap(user_addr, PAGE_SIZE);
}

void __init lkdtm_perms_init(void)
{
        /* Make sure we can write to __ro_after_init values during __init */
        ro_after_init |= 0xAA;

}