maccess.c

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/*
 * Access kernel memory without faulting.
 */
#include <linux/export.h>
#include <linux/mm.h>
#include <linux/uaccess.h>

long __weak probe_kernel_read(void *dst, const void *src, size_t size)
    __attribute__((alias("__probe_kernel_read")));

long __probe_kernel_read(void *dst, const void *src, size_t size)
{
    long ret;
    mm_segment_t old_fs = get_fs();

    set_fs(KERNEL_DS);
    pagefault_disable();
    ret = __copy_from_user_inatomic(dst,
            (__force const void __user *)src, size);
    pagefault_enable();
    set_fs(old_fs);

    return ret ? -EFAULT : 0;
}
EXPORT_SYMBOL_GPL(probe_kernel_read);

long __weak probe_kernel_write(void *dst, const void *src, size_t size)
    __attribute__((alias("__probe_kernel_write")));

long __probe_kernel_write(void *dst, const void *src, size_t size)
{
    long ret;
    mm_segment_t old_fs = get_fs();

    set_fs(KERNEL_DS);
    pagefault_disable();
    ret = __copy_to_user_inatomic((__force void __user *)dst, src, size);
    pagefault_enable();
    set_fs(old_fs);

    return ret ? -EFAULT : 0;
}
EXPORT_SYMBOL_GPL(probe_kernel_write);