1 files changed, 552 insertions, 0 deletions

diff --git a/arch/i386/mm/fault.c b/arch/i386/mm/fault.c
new file mode 100644
index 000000000000..a509237c4815
--- /dev/null
+++ b/arch/i386/mm/fault.c
@@ -0,0 +1,552 @@
+/*
+ *  linux/arch/i386/mm/fault.c
+ *
+ *  Copyright (C) 1995  Linus Torvalds
+ */
+
+#include <linux/signal.h>
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/ptrace.h>
+#include <linux/mman.h>
+#include <linux/mm.h>
+#include <linux/smp.h>
+#include <linux/smp_lock.h>
+#include <linux/interrupt.h>
+#include <linux/init.h>
+#include <linux/tty.h>
+#include <linux/vt_kern.h>              /* For unblank_screen() */
+#include <linux/highmem.h>
+#include <linux/module.h>
+
+#include <asm/system.h>
+#include <asm/uaccess.h>
+#include <asm/desc.h>
+#include <asm/kdebug.h>
+
+extern void die(const char *,struct pt_regs *,long);
+
+/*
+ * Unlock any spinlocks which will prevent us from getting the
+ * message out 
+ */
+void bust_spinlocks(int yes)
+{
+        int loglevel_save = console_loglevel;
+
+        if (yes) {
+                oops_in_progress = 1;
+                return;
+        }
+#ifdef CONFIG_VT
+        unblank_screen();
+#endif
+        oops_in_progress = 0;
+        /*
+         * OK, the message is on the console.  Now we call printk()
+         * without oops_in_progress set so that printk will give klogd
+         * a poke.  Hold onto your hats...
+         */
+        console_loglevel = 15;          /* NMI oopser may have shut the console up */
+        printk(" ");
+        console_loglevel = loglevel_save;
+}
+
+/*
+ * Return EIP plus the CS segment base.  The segment limit is also
+ * adjusted, clamped to the kernel/user address space (whichever is
+ * appropriate), and returned in *eip_limit.
+ *
+ * The segment is checked, because it might have been changed by another
+ * task between the original faulting instruction and here.
+ *
+ * If CS is no longer a valid code segment, or if EIP is beyond the
+ * limit, or if it is a kernel address when CS is not a kernel segment,
+ * then the returned value will be greater than *eip_limit.
+ * 
+ * This is slow, but is very rarely executed.
+ */
+static inline unsigned long get_segment_eip(struct pt_regs *regs,
+                                            unsigned long *eip_limit)
+{
+        unsigned long eip = regs->eip;
+        unsigned seg = regs->xcs & 0xffff;
+        u32 seg_ar, seg_limit, base, *desc;
+
+        /* The standard kernel/user address space limit. */
+        *eip_limit = (seg & 3) ? USER_DS.seg : KERNEL_DS.seg;
+
+        /* Unlikely, but must come before segment checks. */
+        if (unlikely((regs->eflags & VM_MASK) != 0))
+                return eip + (seg << 4);
+        
+        /* By far the most common cases. */
+        if (likely(seg == __USER_CS || seg == __KERNEL_CS))
+                return eip;
+
+        /* Check the segment exists, is within the current LDT/GDT size,
+           that kernel/user (ring 0..3) has the appropriate privilege,
+           that it's a code segment, and get the limit. */
+        __asm__ ("larl %3,%0; lsll %3,%1"
+                 : "=&r" (seg_ar), "=r" (seg_limit) : "0" (0), "rm" (seg));
+        if ((~seg_ar & 0x9800) || eip > seg_limit) {
+                *eip_limit = 0;
+                return 1;        /* So that returned eip > *eip_limit. */
+        }
+
+        /* Get the GDT/LDT descriptor base. 
+           When you look for races in this code remember that
+           LDT and other horrors are only used in user space. */
+        if (seg & (1<<2)) {
+                /* Must lock the LDT while reading it. */
+                down(&current->mm->context.sem);
+                desc = current->mm->context.ldt;
+                desc = (void *)desc + (seg & ~7);
+        } else {
+                /* Must disable preemption while reading the GDT. */
+                desc = (u32 *)&per_cpu(cpu_gdt_table, get_cpu());
+                desc = (void *)desc + (seg & ~7);
+        }
+
+        /* Decode the code segment base from the descriptor */
+        base = get_desc_base((unsigned long *)desc);
+
+        if (seg & (1<<2)) { 
+                up(&current->mm->context.sem);
+        } else
+                put_cpu();
+
+        /* Adjust EIP and segment limit, and clamp at the kernel limit.
+           It's legitimate for segments to wrap at 0xffffffff. */
+        seg_limit += base;
+        if (seg_limit < *eip_limit && seg_limit >= base)
+                *eip_limit = seg_limit;
+        return eip + base;
+}
+
+/* 
+ * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
+ * Check that here and ignore it.
+ */
+static int __is_prefetch(struct pt_regs *regs, unsigned long addr)
+{ 
+        unsigned long limit;
+        unsigned long instr = get_segment_eip (regs, &limit);
+        int scan_more = 1;
+        int prefetch = 0; 
+        int i;
+
+        for (i = 0; scan_more && i < 15; i++) { 
+                unsigned char opcode;
+                unsigned char instr_hi;
+                unsigned char instr_lo;
+
+                if (instr > limit)
+                        break;
+                if (__get_user(opcode, (unsigned char *) instr))
+                        break; 
+
+                instr_hi = opcode & 0xf0; 
+                instr_lo = opcode & 0x0f; 
+                instr++;
+
+                switch (instr_hi) { 
+                case 0x20:
+                case 0x30:
+                        /* Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes. */
+                        scan_more = ((instr_lo & 7) == 0x6);
+                        break;
+                        
+                case 0x60:
+                        /* 0x64 thru 0x67 are valid prefixes in all modes. */
+                        scan_more = (instr_lo & 0xC) == 0x4;
+                        break;          
+                case 0xF0:
+                        /* 0xF0, 0xF2, and 0xF3 are valid prefixes */
+                        scan_more = !instr_lo || (instr_lo>>1) == 1;
+                        break;                  
+                case 0x00:
+                        /* Prefetch instruction is 0x0F0D or 0x0F18 */
+                        scan_more = 0;
+                        if (instr > limit)
+                                break;
+                        if (__get_user(opcode, (unsigned char *) instr)) 
+                                break;
+                        prefetch = (instr_lo == 0xF) &&
+                                (opcode == 0x0D || opcode == 0x18);
+                        break;                  
+                default:
+                        scan_more = 0;
+                        break;
+                } 
+        }
+        return prefetch;
+}
+
+static inline int is_prefetch(struct pt_regs *regs, unsigned long addr,
+                              unsigned long error_code)
+{
+        if (unlikely(boot_cpu_data.x86_vendor == X86_VENDOR_AMD &&
+                     boot_cpu_data.x86 >= 6)) {
+                /* Catch an obscure case of prefetch inside an NX page. */
+                if (nx_enabled && (error_code & 16))
+                        return 0;
+                return __is_prefetch(regs, addr);
+        }
+        return 0;
+} 
+
+fastcall void do_invalid_op(struct pt_regs *, unsigned long);
+
+/*
+ * This routine handles page faults.  It determines the address,
+ * and the problem, and then passes it off to one of the appropriate
+ * routines.
+ *
+ * error_code:
+ *      bit 0 == 0 means no page found, 1 means protection fault
+ *      bit 1 == 0 means read, 1 means write
+ *      bit 2 == 0 means kernel, 1 means user-mode
+ */
+fastcall void do_page_fault(struct pt_regs *regs, unsigned long error_code)
+{
+        struct task_struct *tsk;
+        struct mm_struct *mm;
+        struct vm_area_struct * vma;
+        unsigned long address;
+        unsigned long page;
+        int write;
+        siginfo_t info;
+
+        /* get the address */
+        __asm__("movl %%cr2,%0":"=r" (address));
+
+        if (notify_die(DIE_PAGE_FAULT, "page fault", regs, error_code, 14,
+                                        SIGSEGV) == NOTIFY_STOP)
+                return;
+        /* It's safe to allow irq's after cr2 has been saved */
+        if (regs->eflags & (X86_EFLAGS_IF|VM_MASK))
+                local_irq_enable();
+
+        tsk = current;
+
+        info.si_code = SEGV_MAPERR;
+
+        /*
+         * We fault-in kernel-space virtual memory on-demand. The
+         * 'reference' page table is init_mm.pgd.
+         *
+         * NOTE! We MUST NOT take any locks for this case. We may
+         * be in an interrupt or a critical region, and should
+         * only copy the information from the master page table,
+         * nothing more.
+         *
+         * This verifies that the fault happens in kernel space
+         * (error_code & 4) == 0, and that the fault was not a
+         * protection error (error_code & 1) == 0.
+         */
+        if (unlikely(address >= TASK_SIZE)) { 
+                if (!(error_code & 5))
+                        goto vmalloc_fault;
+                /* 
+                 * Don't take the mm semaphore here. If we fixup a prefetch
+                 * fault we could otherwise deadlock.
+                 */
+                goto bad_area_nosemaphore;
+        } 
+
+        mm = tsk->mm;
+
+        /*
+         * If we're in an interrupt, have no user context or are running in an
+         * atomic region then we must not take the fault..
+         */
+        if (in_atomic() || !mm)
+                goto bad_area_nosemaphore;
+
+        /* When running in the kernel we expect faults to occur only to
+         * addresses in user space.  All other faults represent errors in the
+         * kernel and should generate an OOPS.  Unfortunatly, in the case of an
+         * erroneous fault occuring in a code path which already holds mmap_sem
+         * we will deadlock attempting to validate the fault against the
+         * address space.  Luckily the kernel only validly references user
+         * space from well defined areas of code, which are listed in the
+         * exceptions table.
+         *
+         * As the vast majority of faults will be valid we will only perform
+         * the source reference check when there is a possibilty of a deadlock.
+         * Attempt to lock the address space, if we cannot we then validate the
+         * source.  If this is invalid we can skip the address space check,
+         * thus avoiding the deadlock.
+         */
+        if (!down_read_trylock(&mm->mmap_sem)) {
+                if ((error_code & 4) == 0 &&
+                    !search_exception_tables(regs->eip))
+                        goto bad_area_nosemaphore;
+                down_read(&mm->mmap_sem);
+        }
+
+        vma = find_vma(mm, address);
+        if (!vma)
+                goto bad_area;
+        if (vma->vm_start <= address)
+                goto good_area;
+        if (!(vma->vm_flags & VM_GROWSDOWN))
+                goto bad_area;
+        if (error_code & 4) {
+                /*
+                 * accessing the stack below %esp is always a bug.
+                 * The "+ 32" is there due to some instructions (like
+                 * pusha) doing post-decrement on the stack and that
+                 * doesn't show up until later..
+                 */
+                if (address + 32 < regs->esp)
+                        goto bad_area;
+        }
+        if (expand_stack(vma, address))
+                goto bad_area;
+/*
+ * Ok, we have a good vm_area for this memory access, so
+ * we can handle it..
+ */
+good_area:
+        info.si_code = SEGV_ACCERR;
+        write = 0;
+        switch (error_code & 3) {
+                default:        /* 3: write, present */
+#ifdef TEST_VERIFY_AREA
+                        if (regs->cs == KERNEL_CS)
+                                printk("WP fault at %08lx\n", regs->eip);
+#endif
+                        /* fall through */
+                case 2:         /* write, not present */
+                        if (!(vma->vm_flags & VM_WRITE))
+                                goto bad_area;
+                        write++;
+                        break;
+                case 1:         /* read, present */
+                        goto bad_area;
+                case 0:         /* read, not present */
+                        if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
+                                goto bad_area;
+        }
+
+ survive:
+        /*
+         * If for any reason at all we couldn't handle the fault,
+         * make sure we exit gracefully rather than endlessly redo
+         * the fault.
+         */
+        switch (handle_mm_fault(mm, vma, address, write)) {
+                case VM_FAULT_MINOR:
+                        tsk->min_flt++;
+                        break;
+                case VM_FAULT_MAJOR:
+                        tsk->maj_flt++;
+                        break;
+                case VM_FAULT_SIGBUS:
+                        goto do_sigbus;
+                case VM_FAULT_OOM:
+                        goto out_of_memory;
+                default:
+                        BUG();
+        }
+
+        /*
+         * Did it hit the DOS screen memory VA from vm86 mode?
+         */
+        if (regs->eflags & VM_MASK) {
+                unsigned long bit = (address - 0xA0000) >> PAGE_SHIFT;
+                if (bit < 32)
+                        tsk->thread.screen_bitmap |= 1 << bit;
+        }
+        up_read(&mm->mmap_sem);
+        return;
+
+/*
+ * Something tried to access memory that isn't in our memory map..
+ * Fix it, but check if it's kernel or user first..
+ */
+bad_area:
+        up_read(&mm->mmap_sem);
+
+bad_area_nosemaphore:
+        /* User mode accesses just cause a SIGSEGV */
+        if (error_code & 4) {
+                /* 
+                 * Valid to do another page fault here because this one came 
+                 * from user space.
+                 */
+                if (is_prefetch(regs, address, error_code))
+                        return;
+
+                tsk->thread.cr2 = address;
+                /* Kernel addresses are always protection faults */
+                tsk->thread.error_code = error_code | (address >= TASK_SIZE);
+                tsk->thread.trap_no = 14;
+                info.si_signo = SIGSEGV;
+                info.si_errno = 0;
+                /* info.si_code has been set above */
+                info.si_addr = (void __user *)address;
+                force_sig_info(SIGSEGV, &info, tsk);
+                return;
+        }
+
+#ifdef CONFIG_X86_F00F_BUG
+        /*
+         * Pentium F0 0F C7 C8 bug workaround.
+         */
+        if (boot_cpu_data.f00f_bug) {
+                unsigned long nr;
+                
+                nr = (address - idt_descr.address) >> 3;
+
+                if (nr == 6) {
+                        do_invalid_op(regs, 0);
+                        return;
+                }
+        }
+#endif
+
+no_context:
+        /* Are we prepared to handle this kernel fault?  */
+        if (fixup_exception(regs))
+                return;
+
+        /* 
+         * Valid to do another page fault here, because if this fault
+         * had been triggered by is_prefetch fixup_exception would have 
+         * handled it.
+         */
+        if (is_prefetch(regs, address, error_code))
+                return;
+
+/*
+ * Oops. The kernel tried to access some bad page. We'll have to
+ * terminate things with extreme prejudice.
+ */
+
+        bust_spinlocks(1);
+
+#ifdef CONFIG_X86_PAE
+        if (error_code & 16) {
+                pte_t *pte = lookup_address(address);
+
+                if (pte && pte_present(*pte) && !pte_exec_kernel(*pte))
+                        printk(KERN_CRIT "kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n", current->uid);
+        }
+#endif
+        if (address < PAGE_SIZE)
+                printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference");
+        else
+                printk(KERN_ALERT "Unable to handle kernel paging request");
+        printk(" at virtual address %08lx\n",address);
+        printk(KERN_ALERT " printing eip:\n");
+        printk("%08lx\n", regs->eip);
+        asm("movl %%cr3,%0":"=r" (page));
+        page = ((unsigned long *) __va(page))[address >> 22];
+        printk(KERN_ALERT "*pde = %08lx\n", page);
+        /*
+         * We must not directly access the pte in the highpte
+         * case, the page table might be allocated in highmem.
+         * And lets rather not kmap-atomic the pte, just in case
+         * it's allocated already.
+         */
+#ifndef CONFIG_HIGHPTE
+        if (page & 1) {
+                page &= PAGE_MASK;
+                address &= 0x003ff000;
+                page = ((unsigned long *) __va(page))[address >> PAGE_SHIFT];
+                printk(KERN_ALERT "*pte = %08lx\n", page);
+        }
+#endif
+        die("Oops", regs, error_code);
+        bust_spinlocks(0);
+        do_exit(SIGKILL);
+
+/*
+ * We ran out of memory, or some other thing happened to us that made
+ * us unable to handle the page fault gracefully.
+ */
+out_of_memory:
+        up_read(&mm->mmap_sem);
+        if (tsk->pid == 1) {
+                yield();
+                down_read(&mm->mmap_sem);
+                goto survive;
+        }
+        printk("VM: killing process %s\n", tsk->comm);
+        if (error_code & 4)
+                do_exit(SIGKILL);
+        goto no_context;
+
+do_sigbus:
+        up_read(&mm->mmap_sem);
+
+        /* Kernel mode? Handle exceptions or die */
+        if (!(error_code & 4))
+                goto no_context;
+
+        /* User space => ok to do another page fault */
+        if (is_prefetch(regs, address, error_code))
+                return;
+
+        tsk->thread.cr2 = address;
+        tsk->thread.error_code = error_code;
+        tsk->thread.trap_no = 14;
+        info.si_signo = SIGBUS;
+        info.si_errno = 0;
+        info.si_code = BUS_ADRERR;
+        info.si_addr = (void __user *)address;
+        force_sig_info(SIGBUS, &info, tsk);
+        return;
+
+vmalloc_fault:
+        {
+                /*
+                 * Synchronize this task's top level page-table
+                 * with the 'reference' page table.
+                 *
+                 * Do _not_ use "tsk" here. We might be inside
+                 * an interrupt in the middle of a task switch..
+                 */
+                int index = pgd_index(address);
+                unsigned long pgd_paddr;
+                pgd_t *pgd, *pgd_k;
+                pud_t *pud, *pud_k;
+                pmd_t *pmd, *pmd_k;
+                pte_t *pte_k;
+
+                asm("movl %%cr3,%0":"=r" (pgd_paddr));
+                pgd = index + (pgd_t *)__va(pgd_paddr);
+                pgd_k = init_mm.pgd + index;
+
+                if (!pgd_present(*pgd_k))
+                        goto no_context;
+
+                /*
+                 * set_pgd(pgd, *pgd_k); here would be useless on PAE
+                 * and redundant with the set_pmd() on non-PAE. As would
+                 * set_pud.
+                 */
+
+                pud = pud_offset(pgd, address);
+                pud_k = pud_offset(pgd_k, address);
+                if (!pud_present(*pud_k))
+                        goto no_context;
+                
+                pmd = pmd_offset(pud, address);
+                pmd_k = pmd_offset(pud_k, address);
+                if (!pmd_present(*pmd_k))
+                        goto no_context;
+                set_pmd(pmd, *pmd_k);
+
+                pte_k = pte_offset_kernel(pmd_k, address);
+                if (!pte_present(*pte_k))
+                        goto no_context;
+                return;
+        }
+}