[patch 06/52] [PATCH] Use do_exception() in pagetable walk usercopy functions.

Martin Schwidefsky
2009-11-13T15:09:22Z

[-- Attachment #1: 105-mm-pt-walk.diff --]
[-- Type: text/plain, Size: 8609 bytes --]

From: Gerald Schaefer <gerald.schaefer@de.ibm.com>

The pagetable walk usercopy functions have used a modified copy of the
do_exception() function for fault handling. This lead to inconsistencies
with recent changes to do_exception(), e.g. performance counters. This
patch changes the pagetable walk usercopy code to call do_exception()
directly, eliminating the redundancy. A new parameter is added to
do_exception() to specify the fault address.

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

arch/s390/include/asm/uaccess.h | 2
arch/s390/lib/uaccess_pt.c | 147 +++++++++++++---------------------------
arch/s390/mm/fault.c | 23 ++++++
3 files changed, 76 insertions(+), 96 deletions(-)

Index: quilt-2.6/arch/s390/include/asm/uaccess.h
===================================================================
--- quilt-2.6.orig/arch/s390/include/asm/uaccess.h 2009-11-13 15:48:32.000000000 +0100
+++ quilt-2.6/arch/s390/include/asm/uaccess.h 2009-11-13 16:08:13.000000000 +0100
@@ -93,6 +93,8 @@
extern struct uaccess_ops uaccess_mvcos_switch;
extern struct uaccess_ops uaccess_pt;

+extern int __handle_fault(unsigned long, unsigned long, int);
+
static inline int __put_user_fn(size_t size, void __user *ptr, void *x)
{
size = uaccess.copy_to_user_small(size, ptr, x);
Index: quilt-2.6/arch/s390/lib/uaccess_pt.c
===================================================================
--- quilt-2.6.orig/arch/s390/lib/uaccess_pt.c 2009-11-13 15:48:32.000000000 +0100
+++ quilt-2.6/arch/s390/lib/uaccess_pt.c 2009-11-13 16:08:13.000000000 +0100
@@ -23,86 +23,21 @@

pgd = pgd_offset(mm, addr);
if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
- return NULL;
+ return (pte_t *) 0x3a;

pud = pud_offset(pgd, addr);
if (pud_none(*pud) || unlikely(pud_bad(*pud)))
- return NULL;
+ return (pte_t *) 0x3b;

pmd = pmd_offset(pud, addr);
if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
- return NULL;
+ return (pte_t *) 0x10;

return pte_offset_map(pmd, addr);
}

-static int __handle_fault(struct mm_struct *mm, unsigned long address,
- int write_access)
-{
- struct vm_area_struct *vma;
- int ret = -EFAULT;
- int fault;
-
- if (in_atomic())
- return ret;
- 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:
- fault = handle_mm_fault(mm, vma, address, write_access ? FAULT_FLAG_WRITE : 0);
- if (unlikely(fault & VM_FAULT_ERROR)) {
- if (fault & VM_FAULT_OOM)
- goto out_of_memory;
- else if (fault & VM_FAULT_SIGBUS)
- goto out_sigbus;
- BUG();
- }
- if (fault & VM_FAULT_MAJOR)
- current->maj_flt++;
- else
- current->min_flt++;
- ret = 0;
-out:
- up_read(&mm->mmap_sem);
- return ret;
-
-out_of_memory:
- up_read(&mm->mmap_sem);
- if (is_global_init(current)) {
- yield();
- down_read(&mm->mmap_sem);
- 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 size_t __user_copy_pt(unsigned long uaddr, void *kptr,
- size_t n, int write_user)
+static __always_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;
@@ -114,12 +49,17 @@
spin_lock(&mm->page_table_lock);
do {
pte = follow_table(mm, uaddr);
- if (!pte || !pte_present(*pte) ||
- (write_user && !pte_write(*pte)))
+ if ((unsigned long) pte < 0x1000)
goto fault;
+ if (!pte_present(*pte)) {
+ pte = (pte_t *) 0x11;
+ goto fault;
+ } else if (write_user && !pte_write(*pte)) {
+ pte = (pte_t *) 0x04;
+ goto fault;
+ }

pfn = pte_pfn(*pte);
-
offset = uaddr & (PAGE_SIZE - 1);
size = min(n - done, PAGE_SIZE - offset);
if (write_user) {
@@ -137,7 +77,7 @@
return n - done;
fault:
spin_unlock(&mm->page_table_lock);
- if (__handle_fault(mm, uaddr, write_user))
+ if (__handle_fault(uaddr, (unsigned long) pte, write_user))
return n - done;
goto retry;
}
@@ -146,30 +86,31 @@
* Do DAT for user address by page table walk, return kernel address.
* This function needs to be called with current->mm->page_table_lock held.
*/
-static unsigned long __dat_user_addr(unsigned long uaddr)
+static __always_inline unsigned long __dat_user_addr(unsigned long uaddr)
{
struct mm_struct *mm = current->mm;
- unsigned long pfn, ret;
+ unsigned long pfn;
pte_t *pte;
int rc;

- ret = 0;
retry:
pte = follow_table(mm, uaddr);
- if (!pte || !pte_present(*pte))
+ if ((unsigned long) pte < 0x1000)
goto fault;
+ if (!pte_present(*pte)) {
+ pte = (pte_t *) 0x11;
+ goto fault;
+ }

pfn = pte_pfn(*pte);
- ret = (pfn << PAGE_SHIFT) + (uaddr & (PAGE_SIZE - 1));
-out:
- return ret;
+ return (pfn << PAGE_SHIFT) + (uaddr & (PAGE_SIZE - 1));
fault:
spin_unlock(&mm->page_table_lock);
- rc = __handle_fault(mm, uaddr, 0);
+ rc = __handle_fault(uaddr, (unsigned long) pte, 0);
spin_lock(&mm->page_table_lock);
- if (rc)
- goto out;
- goto retry;
+ if (!rc)
+ goto retry;
+ return 0;
}

size_t copy_from_user_pt(size_t n, const void __user *from, void *to)
@@ -234,8 +175,12 @@
spin_lock(&mm->page_table_lock);
do {
pte = follow_table(mm, uaddr);
- if (!pte || !pte_present(*pte))
+ if ((unsigned long) pte < 0x1000)
+ goto fault;
+ if (!pte_present(*pte)) {
+ pte = (pte_t *) 0x11;
goto fault;
+ }

pfn = pte_pfn(*pte);
offset = uaddr & (PAGE_SIZE-1);
@@ -249,9 +194,8 @@
return done + 1;
fault:
spin_unlock(&mm->page_table_lock);
- if (__handle_fault(mm, uaddr, 0)) {
+ if (__handle_fault(uaddr, (unsigned long) pte, 0))
return 0;
- }
goto retry;
}

@@ -284,7 +228,7 @@
{
struct mm_struct *mm = current->mm;
unsigned long offset_from, offset_to, offset_max, pfn_from, pfn_to,
- uaddr, done, size;
+ uaddr, done, size, error_code;
unsigned long uaddr_from = (unsigned long) from;
unsigned long uaddr_to = (unsigned long) to;
pte_t *pte_from, *pte_to;
@@ -298,17 +242,28 @@
retry:
spin_lock(&mm->page_table_lock);
do {
+ write_user = 0;
+ uaddr = uaddr_from;
pte_from = follow_table(mm, uaddr_from);
- if (!pte_from || !pte_present(*pte_from)) {
- uaddr = uaddr_from;
- write_user = 0;
+ error_code = (unsigned long) pte_from;
+ if (error_code < 0x1000)
+ goto fault;
+ if (!pte_present(*pte_from)) {
+ error_code = 0x11;
goto fault;
}

+ write_user = 1;
+ uaddr = uaddr_to;
pte_to = follow_table(mm, uaddr_to);
- if (!pte_to || !pte_present(*pte_to) || !pte_write(*pte_to)) {
- uaddr = uaddr_to;
- write_user = 1;
+ error_code = (unsigned long) pte_to;
+ if (error_code < 0x1000)
+ goto fault;
+ if (!pte_present(*pte_to)) {
+ error_code = 0x11;
+ goto fault;
+ } else if (!pte_write(*pte_to)) {
+ error_code = 0x04;
goto fault;
}

@@ -329,7 +284,7 @@
return n - done;
fault:
spin_unlock(&mm->page_table_lock);
- if (__handle_fault(mm, uaddr, write_user))
+ if (__handle_fault(uaddr, error_code, write_user))
return n - done;
goto retry;
}
Index: quilt-2.6/arch/s390/mm/fault.c
===================================================================
--- quilt-2.6.orig/arch/s390/mm/fault.c 2009-11-13 16:08:12.000000000 +0100
+++ quilt-2.6/arch/s390/mm/fault.c 2009-11-13 16:08:13.000000000 +0100
@@ -442,6 +442,29 @@
}
#endif

+int __handle_fault(unsigned long uaddr, unsigned long int_code, int write_user)
+{
+ struct pt_regs regs;
+ int access, fault;
+
+ regs.psw.mask = psw_kernel_bits;
+ if (!irqs_disabled())
+ regs.psw.mask |= PSW_MASK_IO | PSW_MASK_EXT;
+ regs.psw.addr = (unsigned long) __builtin_return_address(0);
+ regs.psw.addr |= PSW_ADDR_AMODE;
+ uaddr &= PAGE_MASK;
+ access = write_user ? VM_WRITE : VM_READ;
+ fault = do_exception(&regs, access, uaddr | 2);
+ if (unlikely(fault)) {
+ if (fault & VM_FAULT_OOM) {
+ pagefault_out_of_memory();
+ fault = 0;
+ } else if (fault & VM_FAULT_SIGBUS)
+ do_sigbus(&regs, int_code, uaddr);
+ }
+ return fault ? -EFAULT : 0;
+}
+
#ifdef CONFIG_PFAULT
/*
* 'pfault' pseudo page faults routines.