1 files changed, 289 insertions, 0 deletions
diff --git a/arch/arm/lib/uaccess_with_memcpy.c b/arch/arm/lib/uaccess_with_memcpy.c
new file mode 100644
index 000000000..106f83a5e
--- /dev/null
+++ b/arch/arm/lib/uaccess_with_memcpy.c
@@ -0,0 +1,289 @@
+// 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_thp_or_huge(*pmd))) {
+		ptl = &current->mm->page_table_lock;
+		spin_lock(ptl);
+		if (unlikely(!pmd_thp_or_huge(*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_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;
+
+	if (uaccess_kernel()) {
+		memcpy((void *)to, from, n);
+		return 0;
+	}
+
+	/* 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;
+
+	if (uaccess_kernel()) {
+		memset((void *)addr, 0, n);
+		return 0;
+	}
+
+	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(__P010));
+	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