1 files changed, 312 insertions, 0 deletions
diff --git a/arch/ppc64/mm/fault.c b/arch/ppc64/mm/fault.c
new file mode 100644
index 000000000000..20b0f37e8bf8
--- /dev/null
+++ b/arch/ppc64/mm/fault.c
@@ -0,0 +1,312 @@
+/*
+ *  arch/ppc/mm/fault.c
+ *
+ *  PowerPC version 
+ *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
+ *
+ *  Derived from "arch/i386/mm/fault.c"
+ *    Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
+ *
+ *  Modified by Cort Dougan and Paul Mackerras.
+ *
+ *  Modified for PPC64 by Dave Engebretsen (engebret@ibm.com)
+ *
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public License
+ *  as published by the Free Software Foundation; either version
+ *  2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/config.h>
+#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/mman.h>
+#include <linux/mm.h>
+#include <linux/interrupt.h>
+#include <linux/smp_lock.h>
+#include <linux/module.h>
+
+#include <asm/page.h>
+#include <asm/pgtable.h>
+#include <asm/mmu.h>
+#include <asm/mmu_context.h>
+#include <asm/system.h>
+#include <asm/uaccess.h>
+#include <asm/kdebug.h>
+
+/*
+ * Check whether the instruction at regs->nip is a store using
+ * an update addressing form which will update r1.
+ */
+static int store_updates_sp(struct pt_regs *regs)
+{
+	unsigned int inst;
+
+	if (get_user(inst, (unsigned int __user *)regs->nip))
+		return 0;
+	/* check for 1 in the rA field */
+	if (((inst >> 16) & 0x1f) != 1)
+		return 0;
+	/* check major opcode */
+	switch (inst >> 26) {
+	case 37:	/* stwu */
+	case 39:	/* stbu */
+	case 45:	/* sthu */
+	case 53:	/* stfsu */
+	case 55:	/* stfdu */
+		return 1;
+	case 62:	/* std or stdu */
+		return (inst & 3) == 1;
+	case 31:
+		/* check minor opcode */
+		switch ((inst >> 1) & 0x3ff) {
+		case 181:	/* stdux */
+		case 183:	/* stwux */
+		case 247:	/* stbux */
+		case 439:	/* sthux */
+		case 695:	/* stfsux */
+		case 759:	/* stfdux */
+			return 1;
+		}
+	}
+	return 0;
+}
+
+/*
+ * The error_code parameter is
+ *  - DSISR for a non-SLB data access fault,
+ *  - SRR1 & 0x08000000 for a non-SLB instruction access fault
+ *  - 0 any SLB fault.
+ * The return value is 0 if the fault was handled, or the signal
+ * number if this is a kernel fault that can't be handled here.
+ */
+int do_page_fault(struct pt_regs *regs, unsigned long address,
+		  unsigned long error_code)
+{
+	struct vm_area_struct * vma;
+	struct mm_struct *mm = current->mm;
+	siginfo_t info;
+	unsigned long code = SEGV_MAPERR;
+	unsigned long is_write = error_code & DSISR_ISSTORE;
+	unsigned long trap = TRAP(regs);
+ 	unsigned long is_exec = trap == 0x400;
+
+	BUG_ON((trap == 0x380) || (trap == 0x480));
+
+	if (notify_die(DIE_PAGE_FAULT, "page_fault", regs, error_code,
+				11, SIGSEGV) == NOTIFY_STOP)
+		return 0;
+
+	if (trap == 0x300) {
+		if (debugger_fault_handler(regs))
+			return 0;
+	}
+
+	/* On a kernel SLB miss we can only check for a valid exception entry */
+	if (!user_mode(regs) && (address >= TASK_SIZE))
+		return SIGSEGV;
+
+	if (error_code & DSISR_DABRMATCH) {
+		if (notify_die(DIE_DABR_MATCH, "dabr_match", regs, error_code,
+					11, SIGSEGV) == NOTIFY_STOP)
+			return 0;
+		if (debugger_dabr_match(regs))
+			return 0;
+	}
+
+	if (in_atomic() || mm == NULL) {
+		if (!user_mode(regs))
+			return SIGSEGV;
+		/* in_atomic() in user mode is really bad,
+		   as is current->mm == NULL. */
+		printk(KERN_EMERG "Page fault in user mode with"
+		       "in_atomic() = %d mm = %p\n", in_atomic(), mm);
+		printk(KERN_EMERG "NIP = %lx  MSR = %lx\n",
+		       regs->nip, regs->msr);
+		die("Weird page fault", regs, SIGSEGV);
+	}
+
+	/* 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 (!user_mode(regs) && !search_exception_tables(regs->nip))
+			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;
+
+	/*
+	 * N.B. The POWER/Open ABI allows programs to access up to
+	 * 288 bytes below the stack pointer.
+	 * The kernel signal delivery code writes up to about 1.5kB
+	 * below the stack pointer (r1) before decrementing it.
+	 * The exec code can write slightly over 640kB to the stack
+	 * before setting the user r1.  Thus we allow the stack to
+	 * expand to 1MB without further checks.
+	 */
+	if (address + 0x100000 < vma->vm_end) {
+		/* get user regs even if this fault is in kernel mode */
+		struct pt_regs *uregs = current->thread.regs;
+		if (uregs == NULL)
+			goto bad_area;
+
+		/*
+		 * A user-mode access to an address a long way below
+		 * the stack pointer is only valid if the instruction
+		 * is one which would update the stack pointer to the
+		 * address accessed if the instruction completed,
+		 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb
+		 * (or the byte, halfword, float or double forms).
+		 *
+		 * If we don't check this then any write to the area
+		 * between the last mapped region and the stack will
+		 * expand the stack rather than segfaulting.
+		 */
+		if (address + 2048 < uregs->gpr[1]
+		    && (!user_mode(regs) || !store_updates_sp(regs)))
+			goto bad_area;
+	}
+
+	if (expand_stack(vma, address))
+		goto bad_area;
+
+good_area:
+	code = SEGV_ACCERR;
+
+	if (is_exec) {
+		/* protection fault */
+		if (error_code & DSISR_PROTFAULT)
+			goto bad_area;
+		if (!(vma->vm_flags & VM_EXEC))
+			goto bad_area;
+	/* a write */
+	} else if (is_write) {
+		if (!(vma->vm_flags & VM_WRITE))
+			goto bad_area;
+	/* a read */
+	} else {
+		if (!(vma->vm_flags & VM_READ))
+			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, is_write)) {
+
+	case VM_FAULT_MINOR:
+		current->min_flt++;
+		break;
+	case VM_FAULT_MAJOR:
+		current->maj_flt++;
+		break;
+	case VM_FAULT_SIGBUS:
+		goto do_sigbus;
+	case VM_FAULT_OOM:
+		goto out_of_memory;
+	default:
+		BUG();
+	}
+
+	up_read(&mm->mmap_sem);
+	return 0;
+
+bad_area:
+	up_read(&mm->mmap_sem);
+
+bad_area_nosemaphore:
+	/* User mode accesses cause a SIGSEGV */
+	if (user_mode(regs)) {
+		info.si_signo = SIGSEGV;
+		info.si_errno = 0;
+		info.si_code = code;
+		info.si_addr = (void __user *) address;
+		force_sig_info(SIGSEGV, &info, current);
+		return 0;
+	}
+
+	if (trap == 0x400 && (error_code & DSISR_PROTFAULT)
+	    && printk_ratelimit())
+		printk(KERN_CRIT "kernel tried to execute NX-protected"
+		       " page (%lx) - exploit attempt? (uid: %d)\n",
+		       address, current->uid);
+
+	return SIGSEGV;
+
+/*
+ * 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 (current->pid == 1) {
+		yield();
+		down_read(&mm->mmap_sem);
+		goto survive;
+	}
+	printk("VM: killing process %s\n", current->comm);
+	if (user_mode(regs))
+		do_exit(SIGKILL);
+	return SIGKILL;
+
+do_sigbus:
+	up_read(&mm->mmap_sem);
+	if (user_mode(regs)) {
+		info.si_signo = SIGBUS;
+		info.si_errno = 0;
+		info.si_code = BUS_ADRERR;
+		info.si_addr = (void __user *)address;
+		force_sig_info(SIGBUS, &info, current);
+		return 0;
+	}
+	return SIGBUS;
+}
+
+/*
+ * bad_page_fault is called when we have a bad access from the kernel.
+ * It is called from do_page_fault above and from some of the procedures
+ * in traps.c.
+ */
+void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
+{
+	const struct exception_table_entry *entry;
+
+	/* Are we prepared to handle this fault?  */
+	if ((entry = search_exception_tables(regs->nip)) != NULL) {
+		regs->nip = entry->fixup;
+		return;
+	}
+
+	/* kernel has accessed a bad area */
+	die("Kernel access of bad area", regs, sig);
+}