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microblaze: Add stack unwinder

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Implement intelligent backtracing by searching for stack frame creation,
and emitting only return addresses. Use print_hex_dump() to display the
entire binary kernel stack.

Limitation: MMU kernels are not currently able to trace beyond a system trap
(interrupt, syscall, etc.). It is the intent of this patch to provide
infrastructure that can be extended to add this capability later.

Changes from V1:
* Removed checks in find_frame_creation() that prevented location of the frame
  creation instruction in heavily optimized code
* Various formatting/commenting/file location tweaks per review comments
* Dropped Kconfig option to enable STACKTRACE as something logically separate

Signed-off-by: Steven J. Magnani <steve@digidescorp.com>
This commit is contained in:
Steven J. Magnani 2010-04-27 12:37:54 -05:00 committed by Michal Simek
parent ba9c4f88d7
commit ce3266c047
10 changed files with 454 additions and 95 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
arch/microblaze/include/asm/exceptions.h
View File

@ -14,6 +14,11 @@
#define _ASM_MICROBLAZE_EXCEPTIONS_H
#ifdef __KERNEL__
#ifndef CONFIG_MMU
#define EX_HANDLER_STACK_SIZ (4*19)
#endif
#ifndef __ASSEMBLY__
/* Macros to enable and disable HW exceptions in the MSR */

1
arch/microblaze/include/asm/system.h
View File

@ -45,7 +45,6 @@ extern struct task_struct *_switch_to(struct thread_info *prev,
#define smp_rmb() rmb()
#define smp_wmb() wmb()
void show_trace(struct task_struct *task, unsigned long *stack);
void __bad_xchg(volatile void *ptr, int size);
static inline unsigned long __xchg(unsigned long x, volatile void *ptr,

29
arch/microblaze/include/asm/unwind.h Normal file
View File

@ -0,0 +1,29 @@
/*
* Backtrace support for Microblaze
*
* Copyright (C) 2010 Digital Design Corporation
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*/
#ifndef __MICROBLAZE_UNWIND_H
#define __MICROBLAZE_UNWIND_H
struct stack_trace;
struct trap_handler_info {
unsigned long start_addr;
unsigned long end_addr;
const char *trap_name;
};
extern struct trap_handler_info microblaze_trap_handlers;
extern const char _hw_exception_handler;
extern const char ex_handler_unhandled;
void microblaze_unwind(struct task_struct *task, struct stack_trace *trace);
#endif /* __MICROBLAZE_UNWIND_H */

2
arch/microblaze/kernel/Makefile
View File

@ -17,7 +17,7 @@ extra-y := head.o vmlinux.lds
obj-y += dma.o exceptions.o \
hw_exception_handler.o init_task.o intc.o irq.o of_device.o \
of_platform.o process.o prom.o prom_parse.o ptrace.o \
setup.o signal.o sys_microblaze.o timer.o traps.o reset.o
reset.o setup.o signal.o sys_microblaze.o timer.o traps.o unwind.o
obj-y += cpu/

28
arch/microblaze/kernel/entry-nommu.S
View File

@ -588,3 +588,31 @@ sys_rt_sigsuspend_wrapper:
#include "syscall_table.S"
syscall_table_size=(.-sys_call_table)
type_SYSCALL:
.ascii "SYSCALL\0"
type_IRQ:
.ascii "IRQ\0"
type_IRQ_PREEMPT:
.ascii "IRQ (PREEMPTED)\0"
type_SYSCALL_PREEMPT:
.ascii " SYSCALL (PREEMPTED)\0"
/*
* Trap decoding for stack unwinder
* Tuples are (start addr, end addr, string)
* If return address lies on [start addr, end addr],
* unwinder displays 'string'
*/
.align 4
.global microblaze_trap_handlers
microblaze_trap_handlers:
/* Exact matches come first */
.word ret_to_user ; .word ret_to_user ; .word type_SYSCALL
.word ret_from_intr; .word ret_from_intr ; .word type_IRQ
/* Fuzzy matches go here */
.word ret_from_intr; .word no_intr_resched; .word type_IRQ_PREEMPT
.word work_pending ; .word no_work_pending; .word type_SYSCALL_PREEMPT
/* End of table */
.word 0 ; .word 0 ; .word 0

27
arch/microblaze/kernel/entry.S
View File

@ -1127,3 +1127,30 @@ ENTRY(_break)
syscall_table_size=(.-sys_call_table)
type_SYSCALL:
.ascii "SYSCALL\0"
type_IRQ:
.ascii "IRQ\0"
type_IRQ_PREEMPT:
.ascii "IRQ (PREEMPTED)\0"
type_SYSCALL_PREEMPT:
.ascii " SYSCALL (PREEMPTED)\0"
/*
* Trap decoding for stack unwinder
* Tuples are (start addr, end addr, string)
* If return address lies on [start addr, end addr],
* unwinder displays 'string'
*/
.align 4
.global microblaze_trap_handlers
microblaze_trap_handlers:
/* Exact matches come first */
.word ret_from_trap; .word ret_from_trap ; .word type_SYSCALL
.word ret_from_irq ; .word ret_from_irq ; .word type_IRQ
/* Fuzzy matches go here */
.word ret_from_irq ; .word no_intr_resched ; .word type_IRQ_PREEMPT
.word ret_from_trap; .word TRAP_return ; .word type_SYSCALL_PREEMPT
/* End of table */
.word 0 ; .word 0 ; .word 0

4
arch/microblaze/kernel/hw_exception_handler.S
View File

@ -78,9 +78,6 @@
#include <asm/asm-offsets.h>
/* Helpful Macros */
#ifndef CONFIG_MMU
#define EX_HANDLER_STACK_SIZ (4*19)
#endif
#define NUM_TO_REG(num) r ## num
#ifdef CONFIG_MMU
@ -988,6 +985,7 @@ ex_unaligned_fixup:
.end _unaligned_data_exception
#endif /* CONFIG_MMU */
.global ex_handler_unhandled
ex_handler_unhandled:
/* FIXME add handle function for unhandled exception - dump register */
bri 0

44
arch/microblaze/kernel/stacktrace.c
View File

@ -14,52 +14,18 @@
#include <linux/thread_info.h>
#include <linux/ptrace.h>
#include <linux/module.h>
#include <asm/unwind.h>
/* FIXME initial support */
void save_stack_trace(struct stack_trace *trace)
{
unsigned long *sp;
unsigned long addr;
asm("addik %0, r1, 0" : "=r" (sp));
while (!kstack_end(sp)) {
addr = *sp++;
if (__kernel_text_address(addr)) {
if (trace->skip > 0)
trace->skip--;
else
trace->entries[trace->nr_entries++] = addr;
if (trace->nr_entries >= trace->max_entries)
break;
}
}
/* Exclude our helper functions from the trace*/
trace->skip += 2;
microblaze_unwind(NULL, trace);
}
EXPORT_SYMBOL_GPL(save_stack_trace);
void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
{
unsigned int *sp;
unsigned long addr;
struct thread_info *ti = task_thread_info(tsk);
if (tsk == current)
asm("addik %0, r1, 0" : "=r" (sp));
else
sp = (unsigned int *)ti->cpu_context.r1;
while (!kstack_end(sp)) {
addr = *sp++;
if (__kernel_text_address(addr)) {
if (trace->skip > 0)
trace->skip--;
else
trace->entries[trace->nr_entries++] = addr;
if (trace->nr_entries >= trace->max_entries)
break;
}
}
microblaze_unwind(tsk, trace);
}
EXPORT_SYMBOL_GPL(save_stack_trace_tsk);

91
arch/microblaze/kernel/traps.c
View File

@ -16,13 +16,14 @@
#include <asm/exceptions.h>
#include <asm/system.h>
#include <asm/unwind.h>
void trap_init(void)
{
__enable_hw_exceptions();
}
static unsigned long kstack_depth_to_print = 24;
static unsigned long kstack_depth_to_print; /* 0 == entire stack */
static int __init kstack_setup(char *s)
{
@ -30,31 +31,47 @@ static int __init kstack_setup(char *s)
}
__setup("kstack=", kstack_setup);
void show_trace(struct task_struct *task, unsigned long *stack)
void show_stack(struct task_struct *task, unsigned long *sp)
{
unsigned long addr;
unsigned long words_to_show;
u32 fp = (u32) sp;
if (!stack)
stack = (unsigned long *)&stack;
printk(KERN_NOTICE "Call Trace: ");
#ifdef CONFIG_KALLSYMS
printk(KERN_NOTICE "\n");
#endif
while (!kstack_end(stack)) {
addr = *stack++;
/*
* If the address is either in the text segment of the
* kernel, or in the region which contains vmalloc'ed
* memory, it *may* be the address of a calling
* routine; if so, print it so that someone tracing
* down the cause of the crash will be able to figure
* out the call path that was taken.
*/
if (kernel_text_address(addr))
print_ip_sym(addr);
if (fp == 0) {
if (task) {
fp = ((struct thread_info *)
(task->stack))->cpu_context.r1;
} else {
/* Pick up caller of dump_stack() */
fp = (u32)&sp - 8;
}
}
printk(KERN_NOTICE "\n");
words_to_show = (THREAD_SIZE - (fp & (THREAD_SIZE - 1))) >> 2;
if (kstack_depth_to_print && (words_to_show > kstack_depth_to_print))
words_to_show = kstack_depth_to_print;
pr_info("Kernel Stack:\n");
/*
* Make the first line an 'odd' size if necessary to get
* remaining lines to start at an address multiple of 0x10
*/
if (fp & 0xF) {
unsigned long line1_words = (0x10 - (fp & 0xF)) >> 2;
if (line1_words < words_to_show) {
print_hex_dump(KERN_INFO, "", DUMP_PREFIX_ADDRESS, 32,
4, (void *)fp, line1_words << 2, 0);
fp += line1_words << 2;
words_to_show -= line1_words;
}
}
print_hex_dump(KERN_INFO, "", DUMP_PREFIX_ADDRESS, 32, 4, (void *)fp,
words_to_show << 2, 0);
printk(KERN_INFO "\n\n");
pr_info("Call Trace:\n");
microblaze_unwind(task, NULL);
pr_info("\n");
if (!task)
task = current;
@ -62,34 +79,6 @@ void show_trace(struct task_struct *task, unsigned long *stack)
debug_show_held_locks(task);
}
void show_stack(struct task_struct *task, unsigned long *sp)
{
unsigned long *stack;
int i;
if (sp == NULL) {
if (task)
sp = (unsigned long *) ((struct thread_info *)
(task->stack))->cpu_context.r1;
else
sp = (unsigned long *)&sp;
}
stack = sp;
printk(KERN_INFO "\nStack:\n ");
for (i = 0; i < kstack_depth_to_print; i++) {
if (kstack_end(sp))
break;
if (i && ((i % 8) == 0))
printk("\n ");
printk("%08lx ", *sp++);
}
printk("\n");
show_trace(task, stack);
}
void dump_stack(void)
{
show_stack(NULL, NULL);

318
arch/microblaze/kernel/unwind.c Normal file
View File

@ -0,0 +1,318 @@
/*
* Backtrace support for Microblaze
*
* Copyright (C) 2010 Digital Design Corporation
*
* Based on arch/sh/kernel/cpu/sh5/unwind.c code which is:
* Copyright (C) 2004 Paul Mundt
* Copyright (C) 2004 Richard Curnow
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*/
/* #define DEBUG 1 */
#include <linux/kallsyms.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/stacktrace.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/module.h>
#include <linux/io.h>
#include <asm/sections.h>
#include <asm/exceptions.h>
#include <asm/unwind.h>
struct stack_trace;
/*
* On Microblaze, finding the previous stack frame is a little tricky.
* At this writing (3/2010), Microblaze does not support CONFIG_FRAME_POINTERS,
* and even if it did, gcc (4.1.2) does not store the frame pointer at
* a consistent offset within each frame. To determine frame size, it is
* necessary to search for the assembly instruction that creates or reclaims
* the frame and extract the size from it.
*
* Microblaze stores the stack pointer in r1, and creates a frame via
*
* addik r1, r1, -FRAME_SIZE
*
* The frame is reclaimed via
*
* addik r1, r1, FRAME_SIZE
*
* Frame creation occurs at or near the top of a function.
* Depending on the compiler, reclaim may occur at the end, or before
* a mid-function return.
*
* A stack frame is usually not created in a leaf function.
*
*/
/**
* get_frame_size - Extract the stack adjustment from an
* "addik r1, r1, adjust" instruction
* @instr : Microblaze instruction
*
* Return - Number of stack bytes the instruction reserves or reclaims
*/
inline long get_frame_size(unsigned long instr)
{
return abs((s16)(instr & 0xFFFF));
}
/**
* find_frame_creation - Search backward to find the instruction that creates
* the stack frame (hopefully, for the same function the
* initial PC is in).
* @pc : Program counter at which to begin the search
*
* Return - PC at which stack frame creation occurs
* NULL if this cannot be found, i.e. a leaf function
*/
static unsigned long *find_frame_creation(unsigned long *pc)
{
int i;
/* NOTE: Distance to search is arbitrary
* 250 works well for most things,
* 750 picks up things like tcp_recvmsg(),
* 1000 needed for fat_fill_super()
*/
for (i = 0; i < 1000; i++, pc--) {
unsigned long instr;
s16 frame_size;
if (!kernel_text_address((unsigned long) pc))
return NULL;
instr = *pc;
/* addik r1, r1, foo ? */
if ((instr & 0xFFFF0000) != 0x30210000)
continue; /* No */
frame_size = get_frame_size(instr);
if ((frame_size < 8) || (frame_size & 3)) {
pr_debug(" Invalid frame size %d at 0x%p\n",
frame_size, pc);
return NULL;
}
pr_debug(" Found frame creation at 0x%p, size %d\n", pc,
frame_size);
return pc;
}
return NULL;
}
/**
* lookup_prev_stack_frame - Find the stack frame of the previous function.
* @fp : Frame (stack) pointer for current function
* @pc : Program counter within current function
* @leaf_return : r15 value within current function. If the current function
* is a leaf, this is the caller's return address.
* @pprev_fp : On exit, set to frame (stack) pointer for previous function
* @pprev_pc : On exit, set to current function caller's return address
*
* Return - 0 on success, -EINVAL if the previous frame cannot be found
*/
static int lookup_prev_stack_frame(unsigned long fp, unsigned long pc,
unsigned long leaf_return,
unsigned long *pprev_fp,
unsigned long *pprev_pc)
{
unsigned long *prologue = NULL;
/* _switch_to is a special leaf function */
if (pc != (unsigned long) &_switch_to)
prologue = find_frame_creation((unsigned long *)pc);
if (prologue) {
long frame_size = get_frame_size(*prologue);
*pprev_fp = fp + frame_size;
*pprev_pc = *(unsigned long *)fp;
} else {
if (!leaf_return)
return -EINVAL;
*pprev_pc = leaf_return;
*pprev_fp = fp;
}
/* NOTE: don't check kernel_text_address here, to allow display
* of userland return address
*/
return (!*pprev_pc || (*pprev_pc & 3)) ? -EINVAL : 0;
}
static void microblaze_unwind_inner(struct task_struct *task,
unsigned long pc, unsigned long fp,
unsigned long leaf_return,
struct stack_trace *trace);
/**
* unwind_trap - Unwind through a system trap, that stored previous state
* on the stack.
*/
#ifdef CONFIG_MMU
static inline void unwind_trap(struct task_struct *task, unsigned long pc,
unsigned long fp, struct stack_trace *trace)
{
/* To be implemented */
}
#else
static inline void unwind_trap(struct task_struct *task, unsigned long pc,
unsigned long fp, struct stack_trace *trace)
{
const struct pt_regs *regs = (const struct pt_regs *) fp;
microblaze_unwind_inner(task, regs->pc, regs->r1, regs->r15, trace);
}
#endif
/**
* microblaze_unwind_inner - Unwind the stack from the specified point
* @task : Task whose stack we are to unwind (may be NULL)
* @pc : Program counter from which we start unwinding
* @fp : Frame (stack) pointer from which we start unwinding
* @leaf_return : Value of r15 at pc. If the function is a leaf, this is
* the caller's return address.
* @trace : Where to store stack backtrace (PC values).
* NULL == print backtrace to kernel log
*/
void microblaze_unwind_inner(struct task_struct *task,
unsigned long pc, unsigned long fp,
unsigned long leaf_return,
struct stack_trace *trace)
{
int ofs = 0;
pr_debug(" Unwinding with PC=%p, FP=%p\n", (void *)pc, (void *)fp);
if (!pc || !fp || (pc & 3) || (fp & 3)) {
pr_debug(" Invalid state for unwind, aborting\n");
return;
}
for (; pc != 0;) {
unsigned long next_fp, next_pc = 0;
unsigned long return_to = pc + 2 * sizeof(unsigned long);
const struct trap_handler_info *handler =
&microblaze_trap_handlers;
/* Is previous function the HW exception handler? */
if ((return_to >= (unsigned long)&_hw_exception_handler)
&&(return_to < (unsigned long)&ex_handler_unhandled)) {
/*
* HW exception handler doesn't save all registers,
* so we open-code a special case of unwind_trap()
*/
#ifndef CONFIG_MMU
const struct pt_regs *regs =
(const struct pt_regs *) fp;
#endif
pr_info("HW EXCEPTION\n");
#ifndef CONFIG_MMU
microblaze_unwind_inner(task, regs->r17 - 4,
fp + EX_HANDLER_STACK_SIZ,
regs->r15, trace);
#endif
return;
}
/* Is previous function a trap handler? */
for (; handler->start_addr; ++handler) {
if ((return_to >= handler->start_addr)
&& (return_to <= handler->end_addr)) {
if (!trace)
pr_info("%s\n", handler->trap_name);
unwind_trap(task, pc, fp, trace);
return;
}
}
pc -= ofs;
if (trace) {
#ifdef CONFIG_STACKTRACE
if (trace->skip > 0)
trace->skip--;
else
trace->entries[trace->nr_entries++] = pc;
if (trace->nr_entries >= trace->max_entries)
break;
#endif
} else {
/* Have we reached userland? */
if (unlikely(pc == task_pt_regs(task)->pc)) {
pr_info("[<%p>] PID %lu [%s]\n",
(void *) pc,
(unsigned long) task->pid,
task->comm);
break;
} else
print_ip_sym(pc);
}
/* Stop when we reach anything not part of the kernel */
if (!kernel_text_address(pc))
break;
if (lookup_prev_stack_frame(fp, pc, leaf_return, &next_fp,
&next_pc) == 0) {
ofs = sizeof(unsigned long);
pc = next_pc & ~3;
fp = next_fp;
leaf_return = 0;
} else {
pr_debug(" Failed to find previous stack frame\n");
break;
}
pr_debug(" Next PC=%p, next FP=%p\n",
(void *)next_pc, (void *)next_fp);
}
}
/**
* microblaze_unwind - Stack unwinder for Microblaze (external entry point)
* @task : Task whose stack we are to unwind (NULL == current)
* @trace : Where to store stack backtrace (PC values).
* NULL == print backtrace to kernel log
*/
void microblaze_unwind(struct task_struct *task, struct stack_trace *trace)
{
if (task) {
if (task == current) {
const struct pt_regs *regs = task_pt_regs(task);
microblaze_unwind_inner(task, regs->pc, regs->r1,
regs->r15, trace);
} else {
struct thread_info *thread_info =
(struct thread_info *)(task->stack);
const struct cpu_context *cpu_context =
&thread_info->cpu_context;
microblaze_unwind_inner(task,
(unsigned long) &_switch_to,
cpu_context->r1,
cpu_context->r15, trace);
}
} else {
unsigned long pc, fp;
__asm__ __volatile__ ("or %0, r1, r0" : "=r" (fp));
__asm__ __volatile__ (
"brlid %0, 0f;"
"nop;"
"0:"
: "=r" (pc)
);
/* Since we are not a leaf function, use leaf_return = 0 */
microblaze_unwind_inner(current, pc, fp, 0, trace);
}
}