[PATCH 1/4] um: Rewrite show_stack()

From: Richard Weinberger
Date: Mon Sep 23 2013 - 11:38:25 EST

Currently on UML stack traces are not very reliable and both
x86 and x86_64 have their on implementations.
This patch unifies both and adds support to outline unreliable
functions calls.

Signed-off-by: Richard Weinberger <richard@xxxxxx>
---
arch/um/kernel/sysrq.c | 85 ++++++++++++++++++++++++++----------------
arch/um/kernel/um_arch.c | 1 -
arch/x86/um/asm/processor_32.h | 5 +++
arch/x86/um/asm/processor_64.h | 5 +++
arch/x86/um/sysrq_32.c | 66 --------------------------------
arch/x86/um/sysrq_64.c | 8 +---
6 files changed, 64 insertions(+), 106 deletions(-)

diff --git a/arch/um/kernel/sysrq.c b/arch/um/kernel/sysrq.c
index 0dc4d1c..33cc72e 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@xxxxxx>
+ *
+ * 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>
@@ -9,58 +13,75 @@
#include <linux/sched.h>
#include <asm/sysrq.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;

-/* 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_frame_pointer(struct task_struct *task)
+{
+ if (!task || task == current)
+ return current_bp();
+ else
+ return KSTK_EBP(task);
+}
+
+void show_stack(struct task_struct *task, unsigned long *stack)
{
- unsigned long *stack;
+ unsigned long *sp = stack, bp = 0;
int i;

- if (esp == NULL) {
- if (task != current && task != NULL) {
- esp = (unsigned long *) KSTK_ESP(task);
- } else {
- esp = (unsigned long *) &esp;
- }
+#ifdef CONFIG_FRAME_POINTER
+ bp = get_frame_pointer(task);
+#endif
+
+ if (!stack) {
+ if (!task || task == current)
+ sp = current_sp();
+ else
+ sp = (unsigned long *)KSTK_ESP(task);
}

- stack = esp;
+ printk(KERN_INFO "Stack:\n");
+ stack = sp;
for (i = 0; i < kstack_depth_to_print; 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/um_arch.c b/arch/um/kernel/um_arch.c
index 87df5e3..b9dd13e 100644
--- a/arch/um/kernel/um_arch.c
+++ b/arch/um/kernel/um_arch.c
@@ -234,7 +234,6 @@ 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();
diff --git a/arch/x86/um/asm/processor_32.h b/arch/x86/um/asm/processor_32.h
index 6c6689e..c112de8 100644
--- a/arch/x86/um/asm/processor_32.h
+++ b/arch/x86/um/asm/processor_32.h
@@ -33,6 +33,8 @@ struct arch_thread {
.faultinfo = { 0, 0, 0 } \
}

+#define STACKSLOTS_PER_LINE 8
+
static inline void arch_flush_thread(struct arch_thread *thread)
{
/* Clear any TLS still hanging */
@@ -53,4 +55,7 @@ static inline void arch_copy_thread(struct arch_thread *from,
#define current_text_addr() \
({ void *pc; __asm__("movl $1f,%0\n1:":"=g" (pc)); pc; })

+#define current_sp() ({ void *sp; __asm__("movl %%esp, %0" : "=r" (sp) : ); sp; })
+#define current_bp() ({ unsigned long bp; __asm__("movl %%ebp, %0" : "=r" (bp) : ); bp; })
+
#endif
diff --git a/arch/x86/um/asm/processor_64.h b/arch/x86/um/asm/processor_64.h
index 4b02a84..c3be852 100644
--- a/arch/x86/um/asm/processor_64.h
+++ b/arch/x86/um/asm/processor_64.h
@@ -19,6 +19,8 @@ struct arch_thread {
.fs = 0, \
.faultinfo = { 0, 0, 0 } }

+#define STACKSLOTS_PER_LINE 4
+
static inline void arch_flush_thread(struct arch_thread *thread)
{
}
@@ -32,4 +34,7 @@ static inline void arch_copy_thread(struct arch_thread *from,
#define current_text_addr() \
({ void *pc; __asm__("movq $1f,%0\n1:":"=g" (pc)); pc; })

+#define current_sp() ({ void *sp; __asm__("movq %%rsp, %0" : "=r" (sp) : ); sp; })
+#define current_bp() ({ unsigned long bp; __asm__("movq %%rbp, %0" : "=r" (bp) : ); bp; })
+
#endif
diff --git a/arch/x86/um/sysrq_32.c b/arch/x86/um/sysrq_32.c
index c9bee5b..16ee0e4 100644
--- a/arch/x86/um/sysrq_32.c
+++ b/arch/x86/um/sysrq_32.c
@@ -30,70 +30,4 @@ void show_regs(struct pt_regs *regs)
printk(" DS: %04lx ES: %04lx\n",
0xffff & PT_REGS_DS(regs),
0xffff & PT_REGS_ES(regs));
-
- show_trace(NULL, (unsigned long *) &regs);
}
-
-/* Copied from i386. */
-static inline int valid_stack_ptr(struct thread_info *tinfo, void *p)
-{
- return p > (void *)tinfo &&
- p < (void *)tinfo + THREAD_SIZE - 3;
-}
-
-/* Adapted from i386 (we also print the address we read from). */
-static inline unsigned long print_context_stack(struct thread_info *tinfo,
- unsigned long *stack, unsigned long ebp)
-{
- unsigned long addr;
-
-#ifdef CONFIG_FRAME_POINTER
- while (valid_stack_ptr(tinfo, (void *)ebp)) {
- addr = *(unsigned long *)(ebp + 4);
- printk("%08lx: [<%08lx>]", ebp + 4, addr);
- print_symbol(" %s", addr);
- printk("\n");
- ebp = *(unsigned long *)ebp;
- }
-#else
- while (valid_stack_ptr(tinfo, stack)) {
- addr = *stack;
- if (__kernel_text_address(addr)) {
- printk("%08lx: [<%08lx>]", (unsigned long) stack, addr);
- print_symbol(" %s", addr);
- printk("\n");
- }
- stack++;
- }
-#endif
- return ebp;
-}
-
-void show_trace(struct task_struct* task, unsigned long * stack)
-{
- unsigned long ebp;
- struct thread_info *context;
-
- /* Turn this into BUG_ON if possible. */
- if (!stack) {
- stack = (unsigned long*) &stack;
- printk("show_trace: got NULL stack, implicit assumption task == current");
- WARN_ON(1);
- }
-
- if (!task)
- task = current;
-
- if (task != current) {
- ebp = (unsigned long) KSTK_EBP(task);
- } else {
- asm ("movl %%ebp, %0" : "=r" (ebp) : );
- }
-
- context = (struct thread_info *)
- ((unsigned long)stack & (~(THREAD_SIZE - 1)));
- print_context_stack(context, stack, ebp);
-
- printk("\n");
-}
-
diff --git a/arch/x86/um/sysrq_64.c b/arch/x86/um/sysrq_64.c
index a0e7fb1..38b4e4a 100644
--- a/arch/x86/um/sysrq_64.c
+++ b/arch/x86/um/sysrq_64.c
@@ -12,7 +12,7 @@
#include <asm/ptrace.h>
#include <asm/sysrq.h>

-void __show_regs(struct pt_regs *regs)
+void show_regs(struct pt_regs *regs)
{
printk("\n");
print_modules();
@@ -33,9 +33,3 @@ void __show_regs(struct pt_regs *regs)
printk(KERN_INFO "R13: %016lx R14: %016lx R15: %016lx\n",
PT_REGS_R13(regs), PT_REGS_R14(regs), PT_REGS_R15(regs));
}
-
-void show_regs(struct pt_regs *regs)
-{
- __show_regs(regs);
- show_trace(current, (unsigned long *) &regs);
-}
--
1.8.3.1

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