4 files changed, 81 insertions, 52 deletions

diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
index bbcef522bcb1..eecc4142764c 100644
--- a/arch/um/kernel/process.c
+++ b/arch/um/kernel/process.c
@@ -82,19 +82,8 @@ void *__switch_to(struct task_struct *from, struct task_struct *to)
 	to->thread.prev_sched = from;
 	set_current(to);
 
-	do {
-		current->thread.saved_task = NULL;
-
-		switch_threads(&from->thread.switch_buf,
-			       &to->thread.switch_buf);
-
-		arch_switch_to(current);
-
-		if (current->thread.saved_task)
-			show_regs(&(current->thread.regs));
-		to = current->thread.saved_task;
-		from = current;
-	} while (current->thread.saved_task);
+	switch_threads(&from->thread.switch_buf, &to->thread.switch_buf);
+	arch_switch_to(current);
 
 	return current->thread.prev_sched;
 }
diff --git a/arch/um/kernel/sysrq.c b/arch/um/kernel/sysrq.c
index 0dc4d1c6f98a..4d6fdf68edf3 100644
--- a/arch/um/kernel/sysrq.c
+++ b/arch/um/kernel/sysrq.c
@@ -1,6 +1,10 @@
 /*
  * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
- * Licensed under the GPL
+ * Copyright (C) 2013 Richard Weinberger <richrd@nod.at>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
  */
 
 #include <linux/kallsyms.h>
@@ -8,59 +12,87 @@
 #include <linux/module.h>
 #include <linux/sched.h>
 #include <asm/sysrq.h>
+#include <os.h>
 
-/* Catch non-i386 SUBARCH's. */
-#if !defined(CONFIG_UML_X86) || defined(CONFIG_64BIT)
-void show_trace(struct task_struct *task, unsigned long * stack)
+struct stack_frame {
+	struct stack_frame *next_frame;
+	unsigned long return_address;
+};
+
+static void print_stack_trace(unsigned long *sp, unsigned long bp)
 {
+	int reliable;
 	unsigned long addr;
+	struct stack_frame *frame = (struct stack_frame *)bp;
 
-	if (!stack) {
-		stack = (unsigned long*) &stack;
-		WARN_ON(1);
-	}
-
-	printk(KERN_INFO "Call Trace: \n");
-	while (((long) stack & (THREAD_SIZE-1)) != 0) {
-		addr = *stack;
+	printk(KERN_INFO "Call Trace:\n");
+	while (((long) sp & (THREAD_SIZE-1)) != 0) {
+		addr = *sp;
 		if (__kernel_text_address(addr)) {
-			printk(KERN_INFO "%08lx:  [<%08lx>]",
-			       (unsigned long) stack, addr);
-			print_symbol(KERN_CONT " %s", addr);
+			reliable = 0;
+			if ((unsigned long) sp == bp + sizeof(long)) {
+				frame = frame ? frame->next_frame : NULL;
+				bp = (unsigned long)frame;
+				reliable = 1;
+			}
+
+			printk(KERN_INFO " [<%08lx>]", addr);
+			printk(KERN_CONT " %s", reliable ? "" : "? ");
+			print_symbol(KERN_CONT "%s", addr);
 			printk(KERN_CONT "\n");
 		}
-		stack++;
+		sp++;
 	}
 	printk(KERN_INFO "\n");
 }
-#endif
 
-/*Stolen from arch/i386/kernel/traps.c */
-static const int kstack_depth_to_print = 24;
+static unsigned long get_frame_pointer(struct task_struct *task,
+				       struct pt_regs *segv_regs)
+{
+	if (!task || task == current)
+		return segv_regs ? PT_REGS_BP(segv_regs) : current_bp();
+	else
+		return KSTK_EBP(task);
+}
 
-/* This recently started being used in arch-independent code too, as in
- * kernel/sched/core.c.*/
-void show_stack(struct task_struct *task, unsigned long *esp)
+static unsigned long *get_stack_pointer(struct task_struct *task,
+					struct pt_regs *segv_regs)
 {
-	unsigned long *stack;
+	if (!task || task == current)
+		return segv_regs ? (unsigned long *)PT_REGS_SP(segv_regs) : current_sp();
+	else
+		return (unsigned long *)KSTK_ESP(task);
+}
+
+void show_stack(struct task_struct *task, unsigned long *stack)
+{
+	unsigned long *sp = stack, bp = 0;
+	struct pt_regs *segv_regs = current->thread.segv_regs;
 	int i;
 
-	if (esp == NULL) {
-		if (task != current && task != NULL) {
-			esp = (unsigned long *) KSTK_ESP(task);
-		} else {
-			esp = (unsigned long *) &esp;
-		}
+	if (!segv_regs && os_is_signal_stack()) {
+		printk(KERN_ERR "Received SIGSEGV in SIGSEGV handler,"
+				" aborting stack trace!\n");
+		return;
 	}
 
-	stack = esp;
-	for (i = 0; i < kstack_depth_to_print; i++) {
+#ifdef CONFIG_FRAME_POINTER
+	bp = get_frame_pointer(task, segv_regs);
+#endif
+
+	if (!stack)
+		sp = get_stack_pointer(task, segv_regs);
+
+	printk(KERN_INFO "Stack:\n");
+	stack = sp;
+	for (i = 0; i < 3 * STACKSLOTS_PER_LINE; i++) {
 		if (kstack_end(stack))
 			break;
-		if (i && ((i % 8) == 0))
-			printk(KERN_INFO "       ");
-		printk(KERN_CONT "%08lx ", *stack++);
+		if (i && ((i % STACKSLOTS_PER_LINE) == 0))
+			printk(KERN_CONT "\n");
+		printk(KERN_CONT " %08lx", *stack++);
 	}
+	printk(KERN_CONT "\n");
 
-	show_trace(task, esp);
+	print_stack_trace(sp, bp);
 }
diff --git a/arch/um/kernel/trap.c b/arch/um/kernel/trap.c
index 5c3aef74237f..974b87474a99 100644
--- a/arch/um/kernel/trap.c
+++ b/arch/um/kernel/trap.c
@@ -206,9 +206,12 @@ unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
 	int is_write = FAULT_WRITE(fi);
 	unsigned long address = FAULT_ADDRESS(fi);
 
+	if (regs)
+		current->thread.segv_regs = container_of(regs, struct pt_regs, regs);
+
 	if (!is_user && (address >= start_vm) && (address < end_vm)) {
 		flush_tlb_kernel_vm();
-		return 0;
+		goto out;
 	}
 	else if (current->mm == NULL) {
 		show_regs(container_of(regs, struct pt_regs, regs));
@@ -230,7 +233,7 @@ unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
 
 	catcher = current->thread.fault_catcher;
 	if (!err)
-		return 0;
+		goto out;
 	else if (catcher != NULL) {
 		current->thread.fault_addr = (void *) address;
 		UML_LONGJMP(catcher, 1);
@@ -238,7 +241,7 @@ unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
 	else if (current->thread.fault_addr != NULL)
 		panic("fault_addr set but no fault catcher");
 	else if (!is_user && arch_fixup(ip, regs))
-		return 0;
+		goto out;
 
 	if (!is_user) {
 		show_regs(container_of(regs, struct pt_regs, regs));
@@ -262,6 +265,11 @@ unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
 		current->thread.arch.faultinfo = fi;
 		force_sig_info(SIGSEGV, &si, current);
 	}
+
+out:
+	if (regs)
+		current->thread.segv_regs = NULL;
+
 	return 0;
 }
 
diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
index 87df5e3acc26..016adf0985d5 100644
--- a/arch/um/kernel/um_arch.c
+++ b/arch/um/kernel/um_arch.c
@@ -13,6 +13,7 @@
 #include <linux/sched.h>
 #include <asm/pgtable.h>
 #include <asm/processor.h>
+#include <asm/sections.h>
 #include <asm/setup.h>
 #include <as-layout.h>
 #include <arch.h>
@@ -234,7 +235,6 @@ static int panic_exit(struct notifier_block *self, unsigned long unused1,
 		      void *unused2)
 {
 	bust_spinlocks(1);
-	show_regs(&(current->thread.regs));
 	bust_spinlocks(0);
 	uml_exitcode = 1;
 	os_dump_core();