1 files changed, 170 insertions, 65 deletions

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 2f0d1b032a8..51ab9e7e6c3 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -32,16 +32,17 @@
 #include <linux/perf_event.h>
 #include <linux/magic.h>
 #include <linux/ratelimit.h>
+#include <linux/context_tracking.h>
 
 #include <asm/firmware.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/tlbflush.h>
 #include <asm/siginfo.h>
+#include <asm/debug.h>
 #include <mm/mmu_decl.h>
 
 #include "icswx.h"
@@ -105,6 +106,80 @@ static int store_updates_sp(struct pt_regs *regs)
 	}
 	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)
+{
+	siginfo_t info;
+
+	up_read(&current->mm->mmap_sem);
+
+	if (user_mode(regs)) {
+		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;
+		force_sig_info(SIGBUS, &info, current);
+		return MM_FAULT_RETURN;
+	}
+	return MM_FAULT_ERR(SIGBUS);
+}
+
+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;
+	}
+
+	/* Bus error. x86 handles HWPOISON here, we'll add this if/when
+	 * we support the feature in HW
+	 */
+	if (fault & VM_FAULT_SIGBUS)
+		return do_sigbus(regs, addr);
+
+	/* 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
@@ -122,13 +197,16 @@ static int store_updates_sp(struct pt_regs *regs)
 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;
-	siginfo_t info;
+	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 	int code = SEGV_MAPERR;
-	int is_write = 0, ret;
+	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))
 	/*
@@ -152,36 +230,42 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
 	 * look at it
 	 */
 	if (error_code & ICSWX_DSI_UCT) {
-		int ret;
-
-		ret = acop_handle_fault(regs, address, error_code);
-		if (ret)
-			return ret;
+		rc = acop_handle_fault(regs, address, error_code);
+		if (rc)
+			goto bail;
 	}
-#endif
+#endif /* CONFIG_PPC_ICSWX */
 
 	if (notify_page_fault(regs))
-		return 0;
+		goto bail;
 
 	if (unlikely(debugger_fault_handler(regs)))
-		return 0;
+		goto bail;
 
 	/* On a kernel SLB miss we can only check for a valid exception entry */
-	if (!user_mode(regs) && (address >= TASK_SIZE))
-		return SIGSEGV;
+	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) {
-		/* DABR match */
-		do_dabr(regs, address, error_code);
-		return 0;
+		/* 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))
-			return SIGSEGV;
+		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 "
@@ -193,6 +277,17 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
 
 	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
@@ -212,7 +307,15 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
 		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);
@@ -250,8 +353,7 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
 		 * 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)))
+		if (address + 2048 < uregs->gpr[1] && !store_update_sp)
 			goto bad_area;
 	}
 	if (expand_stack(vma, address))
@@ -313,6 +415,7 @@ good_area:
 	} else if (is_write) {
 		if (!(vma->vm_flags & VM_WRITE))
 			goto bad_area;
+		flags |= FAULT_FLAG_WRITE;
 	/* a read */
 	} else {
 		/* protection fault */
@@ -327,32 +430,52 @@ good_area:
 	 * make sure we exit gracefully rather than endlessly redo
 	 * the fault.
 	 */
-	ret = handle_mm_fault(mm, vma, address, is_write ? FAULT_FLAG_WRITE : 0);
-	if (unlikely(ret & VM_FAULT_ERROR)) {
-		if (ret & VM_FAULT_OOM)
-			goto out_of_memory;
-		else if (ret & VM_FAULT_SIGBUS)
-			goto do_sigbus;
-		BUG();
+	fault = handle_mm_fault(mm, vma, address, flags);
+	if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {
+		rc = mm_fault_error(regs, address, fault);
+		if (rc >= MM_FAULT_RETURN)
+			goto bail;
+		else
+			rc = 0;
 	}
-	if (ret & VM_FAULT_MAJOR) {
-		current->maj_flt++;
-		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
-				     regs, address);
+
+	/*
+	 * 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)) {
-			preempt_disable();
-			get_lppaca()->page_ins += (1 << PAGE_FACTOR);
-			preempt_enable();
+			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;
 		}
-#endif
-	} else {
-		current->min_flt++;
-		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
-				     regs, address);
 	}
+
 	up_read(&mm->mmap_sem);
-	return 0;
+	goto bail;
 
 bad_area:
 	up_read(&mm->mmap_sem);
@@ -361,38 +484,20 @@ bad_area_nosemaphore:
 	/* User mode accesses cause a SIGSEGV */
 	if (user_mode(regs)) {
 		_exception(SIGSEGV, regs, code, address);
-		return 0;
+		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, current_uid());
+				   address, from_kuid(&init_user_ns, current_uid()));
 
-	return SIGSEGV;
+	rc = 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 (!user_mode(regs))
-		return SIGKILL;
-	pagefault_out_of_memory();
-	return 0;
+bail:
+	exception_exit(prev_state);
+	return rc;
 
-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;
 }
 
 /*