Initial import

1 files changed, 543 insertions, 0 deletions

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
new file mode 100644
index 000000000..b396868d2
--- /dev/null
+++ b/arch/powerpc/mm/fault.c
@@ -0,0 +1,543 @@
+/*
+ *  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/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/interrupt.h>
+#include <linux/highmem.h>
+#include <linux/module.h>
+#include <linux/kprobes.h>
+#include <linux/kdebug.h>
+#include <linux/perf_event.h>
+#include <linux/ratelimit.h>
+#include <linux/context_tracking.h>
+#include <linux/hugetlb.h>
+
+#include <asm/firmware.h>
+#include <asm/page.h>
+#include <asm/pgtable.h>
+#include <asm/mmu.h>
+#include <asm/mmu_context.h>
+#include <asm/uaccess.h>
+#include <asm/tlbflush.h>
+#include <asm/siginfo.h>
+#include <asm/debug.h>
+
+#include "icswx.h"
+
+#ifdef CONFIG_KPROBES
+static inline int notify_page_fault(struct pt_regs *regs)
+{
+	int ret = 0;
+
+	/* kprobe_running() needs smp_processor_id() */
+	if (!user_mode(regs)) {
+		preempt_disable();
+		if (kprobe_running() && kprobe_fault_handler(regs, 11))
+			ret = 1;
+		preempt_enable();
+	}
+
+	return ret;
+}
+#else
+static inline int notify_page_fault(struct pt_regs *regs)
+{
+	return 0;
+}
+#endif
+
+/*
+ * 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;
+}
+/*
+ * do_page_fault error handling helpers
+ */
+
+#define MM_FAULT_RETURN		0
+#define MM_FAULT_CONTINUE	-1
+#define MM_FAULT_ERR(sig)	(sig)
+
+static int do_sigbus(struct pt_regs *regs, unsigned long address,
+		     unsigned int fault)
+{
+	siginfo_t info;
+	unsigned int lsb = 0;
+
+	up_read(&current->mm->mmap_sem);
+
+	if (!user_mode(regs))
+		return MM_FAULT_ERR(SIGBUS);
+
+	current->thread.trap_nr = BUS_ADRERR;
+	info.si_signo = SIGBUS;
+	info.si_errno = 0;
+	info.si_code = BUS_ADRERR;
+	info.si_addr = (void __user *)address;
+#ifdef CONFIG_MEMORY_FAILURE
+	if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
+		pr_err("MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
+			current->comm, current->pid, address);
+		info.si_code = BUS_MCEERR_AR;
+	}
+
+	if (fault & VM_FAULT_HWPOISON_LARGE)
+		lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
+	if (fault & VM_FAULT_HWPOISON)
+		lsb = PAGE_SHIFT;
+#endif
+	info.si_addr_lsb = lsb;
+	force_sig_info(SIGBUS, &info, current);
+	return MM_FAULT_RETURN;
+}
+
+static int mm_fault_error(struct pt_regs *regs, unsigned long addr, int fault)
+{
+	/*
+	 * Pagefault was interrupted by SIGKILL. We have no reason to
+	 * continue the pagefault.
+	 */
+	if (fatal_signal_pending(current)) {
+		/*
+		 * If we have retry set, the mmap semaphore will have
+		 * alrady been released in __lock_page_or_retry(). Else
+		 * we release it now.
+		 */
+		if (!(fault & VM_FAULT_RETRY))
+			up_read(&current->mm->mmap_sem);
+		/* Coming from kernel, we need to deal with uaccess fixups */
+		if (user_mode(regs))
+			return MM_FAULT_RETURN;
+		return MM_FAULT_ERR(SIGKILL);
+	}
+
+	/* No fault: be happy */
+	if (!(fault & VM_FAULT_ERROR))
+		return MM_FAULT_CONTINUE;
+
+	/* Out of memory */
+	if (fault & VM_FAULT_OOM) {
+		up_read(&current->mm->mmap_sem);
+
+		/*
+		 * We ran out of memory, or some other thing happened to us that
+		 * made us unable to handle the page fault gracefully.
+		 */
+		if (!user_mode(regs))
+			return MM_FAULT_ERR(SIGKILL);
+		pagefault_out_of_memory();
+		return MM_FAULT_RETURN;
+	}
+
+	if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE))
+		return do_sigbus(regs, addr, fault);
+
+	/* We don't understand the fault code, this is fatal */
+	BUG();
+	return MM_FAULT_CONTINUE;
+}
+
+/*
+ * For 600- and 800-family processors, the error_code parameter is DSISR
+ * for a data fault, SRR1 for an instruction fault. For 400-family processors
+ * the error_code parameter is ESR for a data fault, 0 for an instruction
+ * fault.
+ * For 64-bit processors, 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 __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
+			    unsigned long error_code)
+{
+	enum ctx_state prev_state = exception_enter();
+	struct vm_area_struct * vma;
+	struct mm_struct *mm = current->mm;
+	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
+	int code = SEGV_MAPERR;
+	int is_write = 0;
+	int trap = TRAP(regs);
+ 	int is_exec = trap == 0x400;
+	int fault;
+	int rc = 0, store_update_sp = 0;
+
+#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
+	/*
+	 * Fortunately the bit assignments in SRR1 for an instruction
+	 * fault and DSISR for a data fault are mostly the same for the
+	 * bits we are interested in.  But there are some bits which
+	 * indicate errors in DSISR but can validly be set in SRR1.
+	 */
+	if (trap == 0x400)
+		error_code &= 0x48200000;
+	else
+		is_write = error_code & DSISR_ISSTORE;
+#else
+	is_write = error_code & ESR_DST;
+#endif /* CONFIG_4xx || CONFIG_BOOKE */
+
+#ifdef CONFIG_PPC_ICSWX
+	/*
+	 * we need to do this early because this "data storage
+	 * interrupt" does not update the DAR/DEAR so we don't want to
+	 * look at it
+	 */
+	if (error_code & ICSWX_DSI_UCT) {
+		rc = acop_handle_fault(regs, address, error_code);
+		if (rc)
+			goto bail;
+	}
+#endif /* CONFIG_PPC_ICSWX */
+
+	if (notify_page_fault(regs))
+		goto bail;
+
+	if (unlikely(debugger_fault_handler(regs)))
+		goto bail;
+
+	/* On a kernel SLB miss we can only check for a valid exception entry */
+	if (!user_mode(regs) && (address >= TASK_SIZE)) {
+		rc = SIGSEGV;
+		goto bail;
+	}
+
+#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE) || \
+			     defined(CONFIG_PPC_BOOK3S_64))
+  	if (error_code & DSISR_DABRMATCH) {
+		/* breakpoint match */
+		do_break(regs, address, error_code);
+		goto bail;
+	}
+#endif
+
+	/* We restore the interrupt state now */
+	if (!arch_irq_disabled_regs(regs))
+		local_irq_enable();
+
+	if (in_atomic() || mm == NULL) {
+		if (!user_mode(regs)) {
+			rc = SIGSEGV;
+			goto bail;
+		}
+		/* 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);
+	}
+
+	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
+
+	/*
+	 * We want to do this outside mmap_sem, because reading code around nip
+	 * can result in fault, which will cause a deadlock when called with
+	 * mmap_sem held
+	 */
+	if (user_mode(regs))
+		store_update_sp = store_updates_sp(regs);
+
+	if (user_mode(regs))
+		flags |= FAULT_FLAG_USER;
+
+	/* 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.  Unfortunately, in the case of an
+	 * erroneous fault occurring 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 possibility 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;
+
+retry:
+		down_read(&mm->mmap_sem);
+	} else {
+		/*
+		 * The above down_read_trylock() might have succeeded in
+		 * which case we'll have missed the might_sleep() from
+		 * down_read():
+		 */
+		might_sleep();
+	}
+
+	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] && !store_update_sp)
+			goto bad_area;
+	}
+	if (expand_stack(vma, address))
+		goto bad_area;
+
+good_area:
+	code = SEGV_ACCERR;
+#if defined(CONFIG_6xx)
+	if (error_code & 0x95700000)
+		/* an error such as lwarx to I/O controller space,
+		   address matching DABR, eciwx, etc. */
+		goto bad_area;
+#endif /* CONFIG_6xx */
+#if defined(CONFIG_8xx)
+        /* The MPC8xx seems to always set 0x80000000, which is
+         * "undefined".  Of those that can be set, this is the only
+         * one which seems bad.
+         */
+	if (error_code & 0x10000000)
+                /* Guarded storage error. */
+		goto bad_area;
+#endif /* CONFIG_8xx */
+
+	if (is_exec) {
+		/*
+		 * Allow execution from readable areas if the MMU does not
+		 * provide separate controls over reading and executing.
+		 *
+		 * Note: That code used to not be enabled for 4xx/BookE.
+		 * It is now as I/D cache coherency for these is done at
+		 * set_pte_at() time and I see no reason why the test
+		 * below wouldn't be valid on those processors. This -may-
+		 * break programs compiled with a really old ABI though.
+		 */
+		if (!(vma->vm_flags & VM_EXEC) &&
+		    (cpu_has_feature(CPU_FTR_NOEXECUTE) ||
+		     !(vma->vm_flags & (VM_READ | VM_WRITE))))
+			goto bad_area;
+#ifdef CONFIG_PPC_STD_MMU
+		/*
+		 * protfault should only happen due to us
+		 * mapping a region readonly temporarily. PROT_NONE
+		 * is also covered by the VMA check above.
+		 */
+		WARN_ON_ONCE(error_code & DSISR_PROTFAULT);
+#endif /* CONFIG_PPC_STD_MMU */
+	/* a write */
+	} else if (is_write) {
+		if (!(vma->vm_flags & VM_WRITE))
+			goto bad_area;
+		flags |= FAULT_FLAG_WRITE;
+	/* a read */
+	} else {
+		if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
+			goto bad_area;
+		WARN_ON_ONCE(error_code & DSISR_PROTFAULT);
+	}
+
+	/*
+	 * If for any reason at all we couldn't handle the fault,
+	 * make sure we exit gracefully rather than endlessly redo
+	 * the fault.
+	 */
+	fault = handle_mm_fault(mm, vma, address, flags);
+	if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {
+		if (fault & VM_FAULT_SIGSEGV)
+			goto bad_area;
+		rc = mm_fault_error(regs, address, fault);
+		if (rc >= MM_FAULT_RETURN)
+			goto bail;
+		else
+			rc = 0;
+	}
+
+	/*
+	 * Major/minor page fault accounting is only done on the
+	 * initial attempt. If we go through a retry, it is extremely
+	 * likely that the page will be found in page cache at that point.
+	 */
+	if (flags & FAULT_FLAG_ALLOW_RETRY) {
+		if (fault & VM_FAULT_MAJOR) {
+			current->maj_flt++;
+			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
+				      regs, address);
+#ifdef CONFIG_PPC_SMLPAR
+			if (firmware_has_feature(FW_FEATURE_CMO)) {
+				u32 page_ins;
+
+				preempt_disable();
+				page_ins = be32_to_cpu(get_lppaca()->page_ins);
+				page_ins += 1 << PAGE_FACTOR;
+				get_lppaca()->page_ins = cpu_to_be32(page_ins);
+				preempt_enable();
+			}
+#endif /* CONFIG_PPC_SMLPAR */
+		} else {
+			current->min_flt++;
+			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
+				      regs, address);
+		}
+		if (fault & VM_FAULT_RETRY) {
+			/* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
+			 * of starvation. */
+			flags &= ~FAULT_FLAG_ALLOW_RETRY;
+			flags |= FAULT_FLAG_TRIED;
+			goto retry;
+		}
+	}
+
+	up_read(&mm->mmap_sem);
+	goto bail;
+
+bad_area:
+	up_read(&mm->mmap_sem);
+
+bad_area_nosemaphore:
+	/* User mode accesses cause a SIGSEGV */
+	if (user_mode(regs)) {
+		_exception(SIGSEGV, regs, code, address);
+		goto bail;
+	}
+
+	if (is_exec && (error_code & DSISR_PROTFAULT))
+		printk_ratelimited(KERN_CRIT "kernel tried to execute NX-protected"
+				   " page (%lx) - exploit attempt? (uid: %d)\n",
+				   address, from_kuid(&init_user_ns, current_uid()));
+
+	rc = SIGSEGV;
+
+bail:
+	exception_exit(prev_state);
+	return rc;
+
+}
+
+/*
+ * bad_page_fault is called when we have a bad access from the kernel.
+ * It is called from the DSI and ISI handlers in head.S 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 */
+
+	switch (regs->trap) {
+	case 0x300:
+	case 0x380:
+		printk(KERN_ALERT "Unable to handle kernel paging request for "
+			"data at address 0x%08lx\n", regs->dar);
+		break;
+	case 0x400:
+	case 0x480:
+		printk(KERN_ALERT "Unable to handle kernel paging request for "
+			"instruction fetch\n");
+		break;
+	default:
+		printk(KERN_ALERT "Unable to handle kernel paging request for "
+			"unknown fault\n");
+		break;
+	}
+	printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n",
+		regs->nip);
+
+	if (task_stack_end_corrupted(current))
+		printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");
+
+	die("Kernel access of bad area", regs, sig);
+}