[S390] Add dynamic size check for usercopy functions.

Use a wrapper for copy_to/from_user to chose the best usercopy method.
The mvcos instruction is better for sizes greater than 256 bytes, if
mvcos is not available a page table walk is better for sizes greater
than 1024 bytes. Also removed the redundant copy_to/from_user_std_small
functions.

Signed-off-by: Gerald Schaefer <geraldsc@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

4 files changed, 190 insertions, 59 deletions

diff --git a/arch/s390/lib/Makefile b/arch/s390/lib/Makefile
index b0cfa6c4883d..b5f94cf3bde8 100644
--- a/arch/s390/lib/Makefile
+++ b/arch/s390/lib/Makefile
@@ -4,7 +4,7 @@
 
 EXTRA_AFLAGS := -traditional
 
-lib-y += delay.o string.o uaccess_std.o
+lib-y += delay.o string.o uaccess_std.o uaccess_pt.o
 lib-$(CONFIG_32BIT) += div64.o
 lib-$(CONFIG_64BIT) += uaccess_mvcos.o
 lib-$(CONFIG_SMP) += spinlock.o
diff --git a/arch/s390/lib/uaccess_mvcos.c b/arch/s390/lib/uaccess_mvcos.c
index 121b2935a422..f9a23d57eb79 100644
--- a/arch/s390/lib/uaccess_mvcos.c
+++ b/arch/s390/lib/uaccess_mvcos.c
@@ -27,6 +27,9 @@
 #define SLR     "slgr"
 #endif
 
+extern size_t copy_from_user_std(size_t, const void __user *, void *);
+extern size_t copy_to_user_std(size_t, void __user *, const void *);
+
 size_t copy_from_user_mvcos(size_t size, const void __user *ptr, void *x)
 {
         register unsigned long reg0 asm("0") = 0x81UL;
@@ -66,6 +69,13 @@ size_t copy_from_user_mvcos(size_t size, const void __user *ptr, void *x)
         return size;
 }
 
+size_t copy_from_user_mvcos_check(size_t size, const void __user *ptr, void *x)
+{
+        if (size <= 256)
+                return copy_from_user_std(size, ptr, x);
+        return copy_from_user_mvcos(size, ptr, x);
+}
+
 size_t copy_to_user_mvcos(size_t size, void __user *ptr, const void *x)
 {
         register unsigned long reg0 asm("0") = 0x810000UL;
@@ -95,6 +105,13 @@ size_t copy_to_user_mvcos(size_t size, void __user *ptr, const void *x)
         return size;
 }
 
+size_t copy_to_user_mvcos_check(size_t size, void __user *ptr, const void *x)
+{
+        if (size <= 256)
+                return copy_to_user_std(size, ptr, x);
+        return copy_to_user_mvcos(size, ptr, x);
+}
+
 size_t copy_in_user_mvcos(size_t size, void __user *to, const void __user *from)
 {
         register unsigned long reg0 asm("0") = 0x810081UL;
@@ -145,18 +162,16 @@ size_t clear_user_mvcos(size_t size, void __user *to)
         return size;
 }
 
-extern size_t copy_from_user_std_small(size_t, const void __user *, void *);
-extern size_t copy_to_user_std_small(size_t, void __user *, const void *);
 extern size_t strnlen_user_std(size_t, const char __user *);
 extern size_t strncpy_from_user_std(size_t, const char __user *, char *);
 extern int futex_atomic_op(int, int __user *, int, int *);
 extern int futex_atomic_cmpxchg(int __user *, int, int);
 
 struct uaccess_ops uaccess_mvcos = {
-        .copy_from_user = copy_from_user_mvcos,
-        .copy_from_user_small = copy_from_user_std_small,
-        .copy_to_user = copy_to_user_mvcos,
-        .copy_to_user_small = copy_to_user_std_small,
+        .copy_from_user = copy_from_user_mvcos_check,
+        .copy_from_user_small = copy_from_user_std,
+        .copy_to_user = copy_to_user_mvcos_check,
+        .copy_to_user_small = copy_to_user_std,
         .copy_in_user = copy_in_user_mvcos,
         .clear_user = clear_user_mvcos,
         .strnlen_user = strnlen_user_std,
diff --git a/arch/s390/lib/uaccess_pt.c b/arch/s390/lib/uaccess_pt.c
new file mode 100644
index 000000000000..8741bdc09299
--- /dev/null
+++ b/arch/s390/lib/uaccess_pt.c
@@ -0,0 +1,153 @@
+/*
+ *  arch/s390/lib/uaccess_pt.c
+ *
+ *  User access functions based on page table walks.
+ *
+ *    Copyright IBM Corp. 2006
+ *    Author(s): Gerald Schaefer (gerald.schaefer@de.ibm.com)
+ */
+
+#include <linux/errno.h>
+#include <asm/uaccess.h>
+#include <linux/mm.h>
+#include <asm/futex.h>
+
+static inline int __handle_fault(struct mm_struct *mm, unsigned long address,
+                                 int write_access)
+{
+        struct vm_area_struct *vma;
+        int ret = -EFAULT;
+
+        down_read(&mm->mmap_sem);
+        vma = find_vma(mm, address);
+        if (unlikely(!vma))
+                goto out;
+        if (unlikely(vma->vm_start > address)) {
+                if (!(vma->vm_flags & VM_GROWSDOWN))
+                        goto out;
+                if (expand_stack(vma, address))
+                        goto out;
+        }
+
+        if (!write_access) {
+                /* page not present, check vm flags */
+                if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
+                        goto out;
+        } else {
+                if (!(vma->vm_flags & VM_WRITE))
+                        goto out;
+        }
+
+survive:
+        switch (handle_mm_fault(mm, vma, address, write_access)) {
+        case VM_FAULT_MINOR:
+                current->min_flt++;
+                break;
+        case VM_FAULT_MAJOR:
+                current->maj_flt++;
+                break;
+        case VM_FAULT_SIGBUS:
+                goto out_sigbus;
+        case VM_FAULT_OOM:
+                goto out_of_memory;
+        default:
+                BUG();
+        }
+        ret = 0;
+out:
+        up_read(&mm->mmap_sem);
+        return ret;
+
+out_of_memory:
+        up_read(&mm->mmap_sem);
+        if (current->pid == 1) {
+                yield();
+                goto survive;
+        }
+        printk("VM: killing process %s\n", current->comm);
+        return ret;
+
+out_sigbus:
+        up_read(&mm->mmap_sem);
+        current->thread.prot_addr = address;
+        current->thread.trap_no = 0x11;
+        force_sig(SIGBUS, current);
+        return ret;
+}
+
+static inline size_t __user_copy_pt(unsigned long uaddr, void *kptr,
+                                    size_t n, int write_user)
+{
+        struct mm_struct *mm = current->mm;
+        unsigned long offset, pfn, done, size;
+        pgd_t *pgd;
+        pmd_t *pmd;
+        pte_t *pte;
+        void *from, *to;
+
+        done = 0;
+retry:
+        spin_lock(&mm->page_table_lock);
+        do {
+                pgd = pgd_offset(mm, uaddr);
+                if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
+                        goto fault;
+
+                pmd = pmd_offset(pgd, uaddr);
+                if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
+                        goto fault;
+
+                pte = pte_offset_map(pmd, uaddr);
+                if (!pte || !pte_present(*pte) ||
+                    (write_user && !pte_write(*pte)))
+                        goto fault;
+
+                pfn = pte_pfn(*pte);
+                if (!pfn_valid(pfn))
+                        goto out;
+
+                offset = uaddr & (PAGE_SIZE - 1);
+                size = min(n - done, PAGE_SIZE - offset);
+                if (write_user) {
+                        to = (void *)((pfn << PAGE_SHIFT) + offset);
+                        from = kptr + done;
+                } else {
+                        from = (void *)((pfn << PAGE_SHIFT) + offset);
+                        to = kptr + done;
+                }
+                memcpy(to, from, size);
+                done += size;
+                uaddr += size;
+        } while (done < n);
+out:
+        spin_unlock(&mm->page_table_lock);
+        return n - done;
+fault:
+        spin_unlock(&mm->page_table_lock);
+        if (__handle_fault(mm, uaddr, write_user))
+                return n - done;
+        goto retry;
+}
+
+size_t copy_from_user_pt(size_t n, const void __user *from, void *to)
+{
+        size_t rc;
+
+        if (segment_eq(get_fs(), KERNEL_DS)) {
+                memcpy(to, (void __kernel __force *) from, n);
+                return 0;
+        }
+        rc = __user_copy_pt((unsigned long) from, to, n, 0);
+        if (unlikely(rc))
+                memset(to + n - rc, 0, rc);
+        return rc;
+}
+
+size_t copy_to_user_pt(size_t n, void __user *to, const void *from)
+{
+        if (segment_eq(get_fs(), KERNEL_DS)) {
+                memcpy((void __kernel __force *) to, from, n);
+                return 0;
+        }
+        return __user_copy_pt((unsigned long) to, (void *) from, n, 1);
+}
diff --git a/arch/s390/lib/uaccess_std.c b/arch/s390/lib/uaccess_std.c
index f44f0078b354..2d549ed2e113 100644
--- a/arch/s390/lib/uaccess_std.c
+++ b/arch/s390/lib/uaccess_std.c
@@ -28,6 +28,9 @@
 #define SLR     "slgr"
 #endif
 
+extern size_t copy_from_user_pt(size_t n, const void __user *from, void *to);
+extern size_t copy_to_user_pt(size_t n, void __user *to, const void *from);
+
 size_t copy_from_user_std(size_t size, const void __user *ptr, void *x)
 {
         unsigned long tmp1, tmp2;
@@ -69,34 +72,11 @@ size_t copy_from_user_std(size_t size, const void __user *ptr, void *x)
         return size;
 }
 
-size_t copy_from_user_std_small(size_t size, const void __user *ptr, void *x)
+size_t copy_from_user_std_check(size_t size, const void __user *ptr, void *x)
 {
-        unsigned long tmp1, tmp2;
-
-        tmp1 = 0UL;
-        asm volatile(
-                "0: mvcp  0(%0,%2),0(%1),%3\n"
-                "  "SLR"  %0,%0\n"
-                "   j     5f\n"
-                "1: la    %4,255(%1)\n" /* %4 = ptr + 255 */
-                "  "LHI"  %3,-4096\n"
-                "   nr    %4,%3\n"      /* %4 = (ptr + 255) & -4096 */
-                "  "SLR"  %4,%1\n"
-                "  "CLR"  %0,%4\n"      /* copy crosses next page boundary? */
-                "   jnh   5f\n"
-                "2: mvcp  0(%4,%2),0(%1),%3\n"
-                "  "SLR"  %0,%4\n"
-                "  "ALR"  %2,%4\n"
-                "3:"LHI"  %4,-1\n"
-                "  "ALR"  %4,%0\n"      /* copy remaining size, subtract 1 */
-                "   bras  %3,4f\n"
-                "   xc    0(1,%2),0(%2)\n"
-                "4: ex    %4,0(%3)\n"
-                "5:\n"
-                EX_TABLE(0b,1b) EX_TABLE(2b,3b)
-                : "+a" (size), "+a" (ptr), "+a" (x), "+a" (tmp1), "=a" (tmp2)
-                : : "cc", "memory");
-        return size;
+        if (size <= 1024)
+                return copy_from_user_std(size, ptr, x);
+        return copy_from_user_pt(size, ptr, x);
 }
 
 size_t copy_to_user_std(size_t size, void __user *ptr, const void *x)
@@ -130,28 +110,11 @@ size_t copy_to_user_std(size_t size, void __user *ptr, const void *x)
         return size;
 }
 
-size_t copy_to_user_std_small(size_t size, void __user *ptr, const void *x)
+size_t copy_to_user_std_check(size_t size, void __user *ptr, const void *x)
 {
-        unsigned long tmp1, tmp2;
-
-        tmp1 = 0UL;
-        asm volatile(
-                "0: mvcs  0(%0,%1),0(%2),%3\n"
-                "  "SLR"  %0,%0\n"
-                "   j     3f\n"
-                "1: la    %4,255(%1)\n" /* ptr + 255 */
-                "  "LHI"  %3,-4096\n"
-                "   nr    %4,%3\n"      /* (ptr + 255) & -4096UL */
-                "  "SLR"  %4,%1\n"
-                "  "CLR"  %0,%4\n"      /* copy crosses next page boundary? */
-                "   jnh   3f\n"
-                "2: mvcs  0(%4,%1),0(%2),%3\n"
-                "  "SLR"  %0,%4\n"
-                "3:\n"
-                EX_TABLE(0b,1b) EX_TABLE(2b,3b)
-                : "+a" (size), "+a" (ptr), "+a" (x), "+a" (tmp1), "=a" (tmp2)
-                : : "cc", "memory");
-        return size;
+        if (size <= 1024)
+                return copy_to_user_std(size, ptr, x);
+        return copy_to_user_pt(size, ptr, x);
 }
 
 size_t copy_in_user_std(size_t size, void __user *to, const void __user *from)
@@ -343,10 +306,10 @@ int futex_atomic_cmpxchg(int __user *uaddr, int oldval, int newval)
 }
 
 struct uaccess_ops uaccess_std = {
-        .copy_from_user = copy_from_user_std,
-        .copy_from_user_small = copy_from_user_std_small,
-        .copy_to_user = copy_to_user_std,
-        .copy_to_user_small = copy_to_user_std_small,
+        .copy_from_user = copy_from_user_std_check,
+        .copy_from_user_small = copy_from_user_std,
+        .copy_to_user = copy_to_user_std_check,
+        .copy_to_user_small = copy_to_user_std,
         .copy_in_user = copy_in_user_std,
         .clear_user = clear_user_std,
         .strnlen_user = strnlen_user_std,