// SPDX-License-Identifier: GPL-2.0-only
/*
* linux/arch/arm/lib/uaccess_with_memcpy.c
*
* Written by: Lennert Buytenhek and Nicolas Pitre
* Copyright (C) 2009 Marvell Semiconductor
*/
#include <linux/kernel.h>
#include <linux/ctype.h>
#include <linux/uaccess.h>
#include <linux/rwsem.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/hardirq.h> /* for in_atomic() */
#include <linux/gfp.h>
#include <linux/highmem.h>
#include <linux/hugetlb.h>
#include <asm/current.h>
#include <asm/page.h>
static int
pin_page_for_write(const void __user *_addr, pte_t **ptep, spinlock_t **ptlp)
{
unsigned long addr = (unsigned long)_addr;
pgd_t *pgd;
p4d_t *p4d;
pmd_t *pmd;
pte_t *pte;
pud_t *pud;
spinlock_t *ptl;
pgd = pgd_offset(current->mm, addr);
if (unlikely(pgd_none(*pgd) || pgd_bad(*pgd)))
return 0;
p4d = p4d_offset(pgd, addr);
if (unlikely(p4d_none(*p4d) || p4d_bad(*p4d)))
return 0;
pud = pud_offset(p4d, addr);
if (unlikely(pud_none(*pud) || pud_bad(*pud)))
return 0;
pmd = pmd_offset(pud, addr);
if (unlikely(pmd_none(*pmd)))
return 0;
/*
* A pmd can be bad if it refers to a HugeTLB or THP page.
*
* Both THP and HugeTLB pages have the same pmd layout
* and should not be manipulated by the pte functions.
*
* Lock the page table for the destination and check
* to see that it's still huge and whether or not we will
* need to fault on write.
*/
if (unlikely(pmd_leaf(*pmd))) {
ptl = ¤t->mm->page_table_lock;
spin_lock(ptl);
if (unlikely(!pmd_leaf(*pmd)
|| pmd_hugewillfault(*pmd))) {
spin_unlock(ptl);
return 0;
}
*ptep = NULL;
*ptlp = ptl;
return 1;
}
if (unlikely(pmd_bad(*pmd)))
return 0;
pte = pte_offset_map_lock(current->mm, pmd, addr, &ptl);
if (unlikely(!pte))
return 0;
if (unlikely(!pte_present(*pte) || !pte_young(*pte) ||
!pte_write(*pte) || !pte_dirty(*pte))) {
pte_unmap_unlock(pte, ptl);
return 0;
}
*ptep = pte;
*ptlp = ptl;
return 1;
}
static unsigned long noinline
__copy_to_user_memcpy(void __user *to, const void *from, unsigned long n)
{
unsigned long ua_flags;
int atomic;
/* the mmap semaphore is taken only if not in an atomic context */
atomic = faulthandler_disabled();
if (!atomic)
mmap_read_lock(current->mm);
while (n) {
pte_t *pte;
spinlock_t *ptl;
int tocopy;
while (!pin_page_for_write(to, &pte, &ptl)) {
if (!atomic)
mmap_read_unlock(current->mm);
if (__put_user(0, (char __user *)to))
goto out;
if (!atomic)
mmap_read_lock(current->mm);
}
tocopy = (~(unsigned long)to & ~PAGE_MASK) + 1;
if (tocopy > n)
tocopy = n;
ua_flags = uaccess_save_and_enable();
__memcpy((void *)to, from, tocopy);
uaccess_restore(ua_flags);
to += tocopy;
from += tocopy;
n -= tocopy;
if (pte)
pte_unmap_unlock(pte, ptl);
else
spin_unlock(ptl);
}
if (!atomic)
mmap_read_unlock(current->mm);
out:
return n;
}
unsigned long
arm_copy_to_user(void __user *to, const void *from, unsigned long n)
{
/*
* This test is stubbed out of the main function above to keep
* the overhead for small copies low by avoiding a large
* register dump on the stack just to reload them right away.
* With frame pointer disabled, tail call optimization kicks in
* as well making this test almost invisible.
*/
if (n < 64) {
unsigned long ua_flags = uaccess_save_and_enable();
n = __copy_to_user_std(to, from, n);
uaccess_restore(ua_flags);
} else {
n = __copy_to_user_memcpy(uaccess_mask_range_ptr(to, n),
from, n);
}
return n;
}
static unsigned long noinline
__clear_user_memset(void __user *addr, unsigned long n)
{
unsigned long ua_flags;
mmap_read_lock(current->mm);
while (n) {
pte_t *pte;
spinlock_t *ptl;
int tocopy;
while (!pin_page_for_write(addr, &pte, &ptl)) {
mmap_read_unlock(current->mm);
if (__put_user(0, (char __user *)addr))
goto out;
mmap_read_lock(current->mm);
}
tocopy = (~(unsigned long)addr & ~PAGE_MASK) + 1;
if (tocopy > n)
tocopy = n;
ua_flags = uaccess_save_and_enable();
__memset((void *)addr, 0, tocopy);
uaccess_restore(ua_flags);
addr += tocopy;
n -= tocopy;
if (pte)
pte_unmap_unlock(pte, ptl);
else
spin_unlock(ptl);
}
mmap_read_unlock(current->mm);
out:
return n;
}
unsigned long arm_clear_user(void __user *addr, unsigned long n)
{
/* See rational for this in __copy_to_user() above. */
if (n < 64) {
unsigned long ua_flags = uaccess_save_and_enable();
n = __clear_user_std(addr, n);
uaccess_restore(ua_flags);
} else {
n = __clear_user_memset(addr, n);
}
return n;
}
#if 0
/*
* This code is disabled by default, but kept around in case the chosen
* thresholds need to be revalidated. Some overhead (small but still)
* would be implied by a runtime determined variable threshold, and
* so far the measurement on concerned targets didn't show a worthwhile
* variation.
*
* Note that a fairly precise sched_clock() implementation is needed
* for results to make some sense.
*/
#include <linux/vmalloc.h>
static int __init test_size_treshold(void)
{
struct page *src_page, *dst_page;
void *user_ptr, *kernel_ptr;
unsigned long long t0, t1, t2;
int size, ret;
ret = -ENOMEM;
src_page = alloc_page(GFP_KERNEL);
if (!src_page)
goto no_src;
dst_page = alloc_page(GFP_KERNEL);
if (!dst_page)
goto no_dst;
kernel_ptr = page_address(src_page);
user_ptr = vmap(&dst_page, 1, VM_IOREMAP, __pgprot(__PAGE_COPY));
if (!user_ptr)
goto no_vmap;
/* warm up the src page dcache */
ret = __copy_to_user_memcpy(user_ptr, kernel_ptr, PAGE_SIZE);
for (size = PAGE_SIZE; size >= 4; size /= 2) {
t0 = sched_clock();
ret |= __copy_to_user_memcpy(user_ptr, kernel_ptr, size);
t1 = sched_clock();
ret |= __copy_to_user_std(user_ptr, kernel_ptr, size);
t2 = sched_clock();
printk("copy_to_user: %d %llu %llu\n", size, t1 - t0, t2 - t1);
}
for (size = PAGE_SIZE; size >= 4; size /= 2) {
t0 = sched_clock();
ret |= __clear_user_memset(user_ptr, size);
t1 = sched_clock();
ret |= __clear_user_std(user_ptr, size);
t2 = sched_clock();
printk("clear_user: %d %llu %llu\n", size, t1 - t0, t2 - t1);
}
if (ret)
ret = -EFAULT;
vunmap(user_ptr);
no_vmap:
put_page(dst_page);
no_dst:
put_page(src_page);
no_src:
return ret;
}
subsys_initcall(test_size_treshold);
#endif
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