[PATCH] lockdep: stacktrace subsystem, s390 support

stacktrace interface for s390 as needed by lock validator.

[clg@fr.ibm.com: build fix]
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/s390/Kconfig

@@ -7,6 +7,10 @@ config MMU
 	bool
 	default y
 
+config STACKTRACE_SUPPORT
+	bool
+	default y
+
 config RWSEM_GENERIC_SPINLOCK
 	bool
 

arch/s390/kernel/Makefile

@@ -21,6 +21,7 @@ obj-$(CONFIG_COMPAT)		+= compat_linux.o compat_signal.o \
 obj-$(CONFIG_BINFMT_ELF32)	+= binfmt_elf32.o
 
 obj-$(CONFIG_VIRT_TIMER)	+= vtime.o
+obj-$(CONFIG_STACKTRACE)	+= stacktrace.o
 
 # Kexec part
 S390_KEXEC_OBJS := machine_kexec.o crash.o

arch/s390/kernel/stacktrace.c

+/*
+ * arch/s390/kernel/stacktrace.c
+ *
+ * Stack trace management functions
+ *
+ *  Copyright (C) IBM Corp. 2006
+ *  Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>
+ */
+
+#include <linux/sched.h>
+#include <linux/stacktrace.h>
+#include <linux/kallsyms.h>
+
+static inline unsigned long save_context_stack(struct stack_trace *trace,
+					       unsigned int *skip,
+					       unsigned long sp,
+					       unsigned long low,
+					       unsigned long high)
+{
+	struct stack_frame *sf;
+	struct pt_regs *regs;
+	unsigned long addr;
+
+	while(1) {
+		sp &= PSW_ADDR_INSN;
+		if (sp < low || sp > high)
+			return sp;
+		sf = (struct stack_frame *)sp;
+		while(1) {
+			addr = sf->gprs[8] & PSW_ADDR_INSN;
+			if (!(*skip))
+				trace->entries[trace->nr_entries++] = addr;
+			else
+				(*skip)--;
+			if (trace->nr_entries >= trace->max_entries)
+				return sp;
+			low = sp;
+			sp = sf->back_chain & PSW_ADDR_INSN;
+			if (!sp)
+				break;
+			if (sp <= low || sp > high - sizeof(*sf))
+				return sp;
+			sf = (struct stack_frame *)sp;
+		}
+		/* Zero backchain detected, check for interrupt frame. */
+		sp = (unsigned long)(sf + 1);
+		if (sp <= low || sp > high - sizeof(*regs))
+			return sp;
+		regs = (struct pt_regs *)sp;
+		addr = regs->psw.addr & PSW_ADDR_INSN;
+		if (!(*skip))
+			trace->entries[trace->nr_entries++] = addr;
+		else
+			(*skip)--;
+		if (trace->nr_entries >= trace->max_entries)
+			return sp;
+		low = sp;
+		sp = regs->gprs[15];
+	}
+}
+
+void save_stack_trace(struct stack_trace *trace,
+		      struct task_struct *task, int all_contexts,
+		      unsigned int skip)
+{
+	register unsigned long sp asm ("15");
+	unsigned long orig_sp;
+
+	sp &= PSW_ADDR_INSN;
+	orig_sp = sp;
+
+	sp = save_context_stack(trace, &skip, sp,
+				S390_lowcore.panic_stack - PAGE_SIZE,
+				S390_lowcore.panic_stack);
+	if ((sp != orig_sp) && !all_contexts)
+		return;
+	sp = save_context_stack(trace, &skip, sp,
+				S390_lowcore.async_stack - ASYNC_SIZE,
+				S390_lowcore.async_stack);
+	if ((sp != orig_sp) && !all_contexts)
+		return;
+	if (task)
+		save_context_stack(trace, &skip, sp,
+				   (unsigned long) task_stack_page(task),
+				   (unsigned long) task_stack_page(task) + THREAD_SIZE);
+	else
+		save_context_stack(trace, &skip, sp, S390_lowcore.thread_info,
+				   S390_lowcore.thread_info + THREAD_SIZE);
+	return;
+}