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Update of /cvsroot/linuxconsole/ruby/linux/arch/s390x/mm
In directory usw-pr-cvs1:/tmp/cvs-serv10630/arch/s390x/mm

Modified Files:
	fault.c 
Log Message:
Synced to 2.4.13

Index: fault.c
===================================================================
RCS file: /cvsroot/linuxconsole/ruby/linux/arch/s390x/mm/fault.c,v
retrieving revision 1.1
retrieving revision 1.2
diff -u -d -r1.1 -r1.2

--- fault.c	2001/09/02 23:14:23	1.1
+++ fault.c	2001/10/29 00:10:58	1.2
@@ -4,6 +4,7 @@
  *  S390 version
  *    Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
  *    Author(s): Hartmut Penner (hp...@de...)
+ *               Ulrich Weigand (uwe...@de...)
  *
  *  Derived from "arch/i386/mm/fault.c"
  *    Copyright (C) 1995  Linus Torvalds
@@ -21,6 +22,7 @@
 #include <linux/mm.h>
 #include <linux/smp.h>
 #include <linux/smp_lock.h>
+#include <linux/init.h>
 
 #include <asm/system.h>
 #include <asm/uaccess.h>
@@ -32,6 +34,7 @@
 #endif
 
 extern void die(const char *,struct pt_regs *,long);
+static void force_sigsegv(struct task_struct *tsk, int code, void *address);
 
 /*
  * This routine handles page faults.  It determines the address,
@@ -52,19 +55,32 @@
         unsigned long address;
         unsigned long fixup;
         int write;
-        unsigned long psw_mask;
-        unsigned long psw_addr;
 	int si_code = SEGV_MAPERR;
 	int kernel_address = 0;
 
-        /*
-         *  get psw mask of Program old psw to find out,
-         *  if user or kernel mode
-         */
+        tsk = current;
+        mm = tsk->mm;
+	
+	/* 
+         * Check for low-address protection.  This needs to be treated
+	 * as a special case because the translation exception code 
+	 * field is not guaranteed to contain valid data in this case.
+	 */
+	if ((error_code & 0xff) == 4 && !(S390_lowcore.trans_exc_code & 4)) {
 
-        psw_mask = S390_lowcore.program_old_psw.mask;
-        psw_addr = S390_lowcore.program_old_psw.addr;
+		/* Low-address protection hit in kernel mode means 
+		   NULL pointer write access in kernel mode.  */
+ 		if (!(regs->psw.mask & PSW_PROBLEM_STATE)) {
+			address = 0;
+			kernel_address = 1;
+			goto no_context;
+		}
 
+		/* Low-address protection hit in user mode 'cannot happen'.  */
+		die ("Low-address protection", regs, error_code);
+        	do_exit(SIGKILL);
+	}
+
         /* 
          * get the failing address 
          * more specific the segment and page table portion of 
@@ -73,11 +89,6 @@
 
         address = S390_lowcore.trans_exc_code&-4096L;
 
-        tsk = current;
-        mm = tsk->mm;
-
-        if (in_interrupt() || !mm)
-                goto no_context;
 
 	/*
 	 * Check which address space the address belongs to
@@ -108,6 +119,7 @@
 			}
 		}
 		die("page fault via unknown access register", regs, error_code);
+        	do_exit(SIGKILL);
 		break;
 
 	case 2: /* Secondary Segment Table Descriptor */
@@ -116,6 +128,11 @@
 		break;
 	}
 
+	/*
+	 * Check whether we have a user MM in the first place.
+	 */
+        if (in_interrupt() || !mm)
+                goto no_context;
 
 	/*
 	 * When we get here, the fault happened in the current
@@ -125,10 +142,8 @@
         down_read(&mm->mmap_sem);
 
         vma = find_vma(mm, address);
-        if (!vma) {
-	        printk("no vma for address %lX\n",address);
+        if (!vma)
                 goto bad_area;
-        }
         if (vma->vm_start <= address) 
                 goto good_area;
         if (!(vma->vm_flags & VM_GROWSDOWN))
@@ -158,6 +173,7 @@
                        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
@@ -187,8 +203,7 @@
         up_read(&mm->mmap_sem);
 
         /* User mode accesses just cause a SIGSEGV */
-        if (psw_mask & PSW_PROBLEM_STATE) {
-		struct siginfo si;
+        if (regs->psw.mask & PSW_PROBLEM_STATE) {
                 tsk->thread.prot_addr = address;
                 tsk->thread.trap_no = error_code;
 #ifndef CONFIG_SYSCTL
@@ -205,10 +220,8 @@
 			show_regs(regs);
 		}
 #endif
-		si.si_signo = SIGSEGV;
-		si.si_code = si_code;
-		si.si_addr = (void*) address;
-		force_sig_info(SIGSEGV, &si, tsk);
+
+		force_sigsegv(tsk, si_code, (void *)address);
                 return;
 	}
 
@@ -223,6 +236,7 @@
  * Oops. The kernel tried to access some bad page. We'll have to
  * terminate things with extreme prejudice.
  */
+
         if (kernel_address)
                 printk(KERN_ALERT "Unable to handle kernel pointer dereference"
         	       " at virtual kernel address %016lx\n", address);
@@ -230,10 +244,6 @@
                 printk(KERN_ALERT "Unable to handle kernel paging request"
 		       " at virtual user address %016lx\n", address);
 
-/*
- * need to define, which information is useful here
- */
-
         die("Oops", regs, error_code);
         do_exit(SIGKILL);
 
@@ -244,8 +254,14 @@
 */
 out_of_memory:
 	up_read(&mm->mmap_sem);
+	if (tsk->pid == 1) {
+		tsk->policy |= SCHED_YIELD;
+		schedule();
+		down_read(&mm->mmap_sem);
+		goto survive;
+	}
 	printk("VM: killing process %s\n", tsk->comm);
-	if (psw_mask & PSW_PROBLEM_STATE)
+	if (regs->psw.mask & PSW_PROBLEM_STATE)
 		do_exit(SIGKILL);
 	goto no_context;
 
@@ -261,6 +277,151 @@
 	force_sig(SIGBUS, tsk);
 
 	/* Kernel mode? Handle exceptions or die */
-	if (!(psw_mask & PSW_PROBLEM_STATE))
+	if (!(regs->psw.mask & PSW_PROBLEM_STATE))
 		goto no_context;
 }
+
+/*
+ * Send SIGSEGV to task.  This is an external routine
+ * to keep the stack usage of do_page_fault small.
+ */
+static void force_sigsegv(struct task_struct *tsk, int code, void *address)
+{
+	struct siginfo si;
+	si.si_signo = SIGSEGV;
+	si.si_code = code;
+	si.si_addr = address;
+	force_sig_info(SIGSEGV, &si, tsk);
+}
+
+
+#ifdef CONFIG_PFAULT
+/*
+ * 'pfault' pseudo page faults routines.
+ */
+static int pfault_disable = 0;
+
+static int __init nopfault(char *str)
+{
+	pfault_disable = 1;
+	return 1;
+}
+
+__setup("nopfault", nopfault);
+
+typedef struct {
+	__u16 refdiagc;
+	__u16 reffcode;
+	__u16 refdwlen;
+	__u16 refversn;
+	__u64 refgaddr;
+	__u64 refselmk;
+	__u64 refcmpmk;
+	__u64 reserved;
+} __attribute__ ((packed)) pfault_refbk_t;
+
+typedef struct _pseudo_wait_t {
+       struct _pseudo_wait_t *next;
+       wait_queue_head_t queue;
+       unsigned long address;
+       int resolved;
+} pseudo_wait_t;
+
+int pfault_init(void)
+{
+	pfault_refbk_t refbk =
+	{ 0x258, 0, 5, 2, __LC_KERNEL_STACK, 1ULL << 48, 1ULL << 48,
+          0x8000000000000000ULL };
+        int rc;
+
+	if (pfault_disable)
+		return -1;
+        __asm__ __volatile__(
+                "    diag  %1,%0,0x258\n"
+		"0:  j     2f\n"
+		"1:  la    %0,8\n"
+		"2:\n"
+		".section __ex_table,\"a\"\n"
+		"   .align 4\n"
+		"   .quad  0b,1b\n"
+		".previous"
+                : "=d" (rc) : "a" (&refbk) : "cc" );
+	__ctl_set_bit(0, 9);
+        return rc;
+}
+
+void pfault_fini(void)
+{
+	pfault_refbk_t refbk =
+	{ 0x258, 1, 5, 2, 0ULL, 0ULL, 0ULL, 0ULL };
+
+	if (pfault_disable)
+		return;
+	__ctl_clear_bit(0, 9);
+        __asm__ __volatile__(
+                "    diag  %0,0,0x258\n"
+		"0:\n"
+		".section __ex_table,\"a\"\n"
+		"   .align 4\n"
+		"   .quad  0b,0b\n"
+		".previous"
+		: : "a" (&refbk) : "cc" );
+}
+
+asmlinkage void
+pfault_interrupt(struct pt_regs *regs, __u16 error_code)
+{
+	struct task_struct *tsk;
+	wait_queue_head_t queue;
+	wait_queue_head_t *qp;
+	__u16 subcode;
+
+	/*
+	 * Get the external interruption subcode & pfault
+	 * initial/completion signal bit. VM stores this 
+	 * in the 'cpu address' field associated with the
+         * external interrupt. 
+	 */
+	subcode = S390_lowcore.cpu_addr;
+	if ((subcode & 0xff00) != 0x0600)
+		return;
+
+	/*
+	 * Get the token (= address of kernel stack of affected task).
+	 */
+	tsk = (struct task_struct *)
+		(*((unsigned long *) __LC_PFAULT_INTPARM) - THREAD_SIZE);
+
+	if (subcode & 0x0080) {
+		/* signal bit is set -> a page has been swapped in by VM */
+		qp = (wait_queue_head_t *)
+			xchg(&tsk->thread.pfault_wait, -1);
+		if (qp != NULL) {
+			/* Initial interrupt was faster than the completion
+			 * interrupt. pfault_wait is valid. Set pfault_wait
+			 * back to zero and wake up the process. This can
+			 * safely be done because the task is still sleeping
+			 * and can't procude new pfaults. */
+			tsk->thread.pfault_wait = 0ULL;
+			wake_up(qp);
+		}
+	} else {
+		/* signal bit not set -> a real page is missing. */
+                init_waitqueue_head (&queue);
+		qp = (wait_queue_head_t *)
+			xchg(&tsk->thread.pfault_wait, (addr_t) &queue);
+		if (qp != NULL) {
+			/* Completion interrupt was faster than the initial
+			 * interrupt (swapped in a -1 for pfault_wait). Set
+			 * pfault_wait back to zero and exit. This can be
+			 * done safely because tsk is running in kernel 
+			 * mode and can't produce new pfaults. */
+			tsk->thread.pfault_wait = 0ULL;
+		}
+
+                /* go to sleep */
+                wait_event(queue, tsk->thread.pfault_wait == 0ULL);
+	}
+}
+#endif
+





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