diff options
Diffstat (limited to 'arch/arm/lib/uaccess_with_memcpy.c')
| -rw-r--r-- | arch/arm/lib/uaccess_with_memcpy.c | 228 |
1 files changed, 228 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 00000000000..6b967ffb655 --- /dev/null +++ b/arch/arm/lib/uaccess_with_memcpy.c @@ -0,0 +1,228 @@ +/* + * linux/arch/arm/lib/uaccess_with_memcpy.c + * + * Written by: Lennert Buytenhek and Nicolas Pitre + * Copyright (C) 2009 Marvell Semiconductor + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ + +#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 <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; + pmd_t *pmd; + pte_t *pte; + spinlock_t *ptl; + + pgd = pgd_offset(current->mm, addr); + if (unlikely(pgd_none(*pgd) || pgd_bad(*pgd))) + return 0; + + pmd = pmd_offset(pgd, addr); + if (unlikely(pmd_none(*pmd) || 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) +{ + int atomic; + + if (unlikely(segment_eq(get_fs(), KERNEL_DS))) { + memcpy((void *)to, from, n); + return 0; + } + + /* the mmap semaphore is taken only if not in an atomic context */ + atomic = in_atomic(); + + if (!atomic) + down_read(¤t->mm->mmap_sem); + while (n) { + pte_t *pte; + spinlock_t *ptl; + int tocopy; + + while (!pin_page_for_write(to, &pte, &ptl)) { + if (!atomic) + up_read(¤t->mm->mmap_sem); + if (__put_user(0, (char __user *)to)) + goto out; + if (!atomic) + down_read(¤t->mm->mmap_sem); + } + + tocopy = (~(unsigned long)to & ~PAGE_MASK) + 1; + if (tocopy > n) + tocopy = n; + + memcpy((void *)to, from, tocopy); + to += tocopy; + from += tocopy; + n -= tocopy; + + pte_unmap_unlock(pte, ptl); + } + if (!atomic) + up_read(¤t->mm->mmap_sem); + +out: + return n; +} + +unsigned long +__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) + return __copy_to_user_std(to, from, n); + return __copy_to_user_memcpy(to, from, n); +} + +static unsigned long noinline +__clear_user_memset(void __user *addr, unsigned long n) +{ + if (unlikely(segment_eq(get_fs(), KERNEL_DS))) { + memset((void *)addr, 0, n); + return 0; + } + + down_read(¤t->mm->mmap_sem); + while (n) { + pte_t *pte; + spinlock_t *ptl; + int tocopy; + + while (!pin_page_for_write(addr, &pte, &ptl)) { + up_read(¤t->mm->mmap_sem); + if (__put_user(0, (char __user *)addr)) + goto out; + down_read(¤t->mm->mmap_sem); + } + + tocopy = (~(unsigned long)addr & ~PAGE_MASK) + 1; + if (tocopy > n) + tocopy = n; + + memset((void *)addr, 0, tocopy); + addr += tocopy; + n -= tocopy; + + pte_unmap_unlock(pte, ptl); + } + up_read(¤t->mm->mmap_sem); + +out: + return n; +} + +unsigned long __clear_user(void __user *addr, unsigned long n) +{ + /* See rational for this in __copy_to_user() above. */ + if (n < 64) + return __clear_user_std(addr, n); + return __clear_user_memset(addr, 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 |