linux/arch/x86/kernel/dumpstack.c
Josh Poimboeuf 13e25bab7e x86/dumpstack/ftrace: Don't print unreliable addresses in print_context_stack_bp()
When function graph tracing is enabled, print_context_stack_bp() can
report return_to_handler() as an unreliable address, which is confusing
and misleading: return_to_handler() is really only useful as a hint for
debugging, whereas print_context_stack_bp() users only care about the
actual 'reliable' call path.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/c51aef578d8027791b38d2ad9bac0c7f499fde91.1471607358.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-08-24 12:15:15 +02:00

346 lines
7.9 KiB
C

/*
* Copyright (C) 1991, 1992 Linus Torvalds
* Copyright (C) 2000, 2001, 2002 Andi Kleen, SuSE Labs
*/
#include <linux/kallsyms.h>
#include <linux/kprobes.h>
#include <linux/uaccess.h>
#include <linux/utsname.h>
#include <linux/hardirq.h>
#include <linux/kdebug.h>
#include <linux/module.h>
#include <linux/ptrace.h>
#include <linux/ftrace.h>
#include <linux/kexec.h>
#include <linux/bug.h>
#include <linux/nmi.h>
#include <linux/sysfs.h>
#include <asm/stacktrace.h>
int panic_on_unrecovered_nmi;
int panic_on_io_nmi;
unsigned int code_bytes = 64;
int kstack_depth_to_print = 3 * STACKSLOTS_PER_LINE;
static int die_counter;
static void printk_stack_address(unsigned long address, int reliable,
void *data)
{
printk("%s [<%p>] %s%pB\n",
(char *)data, (void *)address, reliable ? "" : "? ",
(void *)address);
}
void printk_address(unsigned long address)
{
pr_cont(" [<%p>] %pS\n", (void *)address, (void *)address);
}
/*
* x86-64 can have up to three kernel stacks:
* process stack
* interrupt stack
* severe exception (double fault, nmi, stack fault, debug, mce) hardware stack
*/
static inline int valid_stack_ptr(struct task_struct *task,
void *p, unsigned int size, void *end)
{
void *t = task_stack_page(task);
if (end) {
if (p < end && p >= (end-THREAD_SIZE))
return 1;
else
return 0;
}
return p >= t && p < t + THREAD_SIZE - size;
}
unsigned long
print_context_stack(struct task_struct *task,
unsigned long *stack, unsigned long bp,
const struct stacktrace_ops *ops, void *data,
unsigned long *end, int *graph)
{
struct stack_frame *frame = (struct stack_frame *)bp;
/*
* If we overflowed the stack into a guard page, jump back to the
* bottom of the usable stack.
*/
if ((unsigned long)task_stack_page(task) - (unsigned long)stack <
PAGE_SIZE)
stack = (unsigned long *)task_stack_page(task);
while (valid_stack_ptr(task, stack, sizeof(*stack), end)) {
unsigned long addr = *stack;
if (__kernel_text_address(addr)) {
unsigned long real_addr;
int reliable = 0;
if ((unsigned long) stack == bp + sizeof(long)) {
reliable = 1;
frame = frame->next_frame;
bp = (unsigned long) frame;
}
/*
* When function graph tracing is enabled for a
* function, its return address on the stack is
* replaced with the address of an ftrace handler
* (return_to_handler). In that case, before printing
* the "real" address, we want to print the handler
* address as an "unreliable" hint that function graph
* tracing was involved.
*/
real_addr = ftrace_graph_ret_addr(task, graph, addr,
stack);
if (real_addr != addr)
ops->address(data, addr, 0);
ops->address(data, real_addr, reliable);
}
stack++;
}
return bp;
}
EXPORT_SYMBOL_GPL(print_context_stack);
unsigned long
print_context_stack_bp(struct task_struct *task,
unsigned long *stack, unsigned long bp,
const struct stacktrace_ops *ops, void *data,
unsigned long *end, int *graph)
{
struct stack_frame *frame = (struct stack_frame *)bp;
unsigned long *retp = &frame->return_address;
while (valid_stack_ptr(task, retp, sizeof(*retp), end)) {
unsigned long addr = *retp;
unsigned long real_addr;
if (!__kernel_text_address(addr))
break;
real_addr = ftrace_graph_ret_addr(task, graph, addr, retp);
if (ops->address(data, real_addr, 1))
break;
frame = frame->next_frame;
retp = &frame->return_address;
}
return (unsigned long)frame;
}
EXPORT_SYMBOL_GPL(print_context_stack_bp);
static int print_trace_stack(void *data, char *name)
{
printk("%s <%s> ", (char *)data, name);
return 0;
}
/*
* Print one address/symbol entries per line.
*/
static int print_trace_address(void *data, unsigned long addr, int reliable)
{
touch_nmi_watchdog();
printk_stack_address(addr, reliable, data);
return 0;
}
static const struct stacktrace_ops print_trace_ops = {
.stack = print_trace_stack,
.address = print_trace_address,
.walk_stack = print_context_stack,
};
void
show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
unsigned long *stack, unsigned long bp, char *log_lvl)
{
printk("%sCall Trace:\n", log_lvl);
dump_trace(task, regs, stack, bp, &print_trace_ops, log_lvl);
}
void show_stack(struct task_struct *task, unsigned long *sp)
{
unsigned long bp = 0;
unsigned long stack;
/*
* Stack frames below this one aren't interesting. Don't show them
* if we're printing for %current.
*/
if (!sp && (!task || task == current)) {
sp = &stack;
bp = stack_frame(current, NULL);
}
show_stack_log_lvl(task, NULL, sp, bp, "");
}
void show_stack_regs(struct pt_regs *regs)
{
show_stack_log_lvl(current, regs, (unsigned long *)regs->sp, regs->bp, "");
}
static arch_spinlock_t die_lock = __ARCH_SPIN_LOCK_UNLOCKED;
static int die_owner = -1;
static unsigned int die_nest_count;
unsigned long oops_begin(void)
{
int cpu;
unsigned long flags;
oops_enter();
/* racy, but better than risking deadlock. */
raw_local_irq_save(flags);
cpu = smp_processor_id();
if (!arch_spin_trylock(&die_lock)) {
if (cpu == die_owner)
/* nested oops. should stop eventually */;
else
arch_spin_lock(&die_lock);
}
die_nest_count++;
die_owner = cpu;
console_verbose();
bust_spinlocks(1);
return flags;
}
EXPORT_SYMBOL_GPL(oops_begin);
NOKPROBE_SYMBOL(oops_begin);
void __noreturn rewind_stack_do_exit(int signr);
void oops_end(unsigned long flags, struct pt_regs *regs, int signr)
{
if (regs && kexec_should_crash(current))
crash_kexec(regs);
bust_spinlocks(0);
die_owner = -1;
add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
die_nest_count--;
if (!die_nest_count)
/* Nest count reaches zero, release the lock. */
arch_spin_unlock(&die_lock);
raw_local_irq_restore(flags);
oops_exit();
if (!signr)
return;
if (in_interrupt())
panic("Fatal exception in interrupt");
if (panic_on_oops)
panic("Fatal exception");
/*
* We're not going to return, but we might be on an IST stack or
* have very little stack space left. Rewind the stack and kill
* the task.
*/
rewind_stack_do_exit(signr);
}
NOKPROBE_SYMBOL(oops_end);
int __die(const char *str, struct pt_regs *regs, long err)
{
#ifdef CONFIG_X86_32
unsigned short ss;
unsigned long sp;
#endif
printk(KERN_DEFAULT
"%s: %04lx [#%d]%s%s%s%s\n", str, err & 0xffff, ++die_counter,
IS_ENABLED(CONFIG_PREEMPT) ? " PREEMPT" : "",
IS_ENABLED(CONFIG_SMP) ? " SMP" : "",
debug_pagealloc_enabled() ? " DEBUG_PAGEALLOC" : "",
IS_ENABLED(CONFIG_KASAN) ? " KASAN" : "");
if (notify_die(DIE_OOPS, str, regs, err,
current->thread.trap_nr, SIGSEGV) == NOTIFY_STOP)
return 1;
print_modules();
show_regs(regs);
#ifdef CONFIG_X86_32
if (user_mode(regs)) {
sp = regs->sp;
ss = regs->ss & 0xffff;
} else {
sp = kernel_stack_pointer(regs);
savesegment(ss, ss);
}
printk(KERN_EMERG "EIP: [<%08lx>] ", regs->ip);
print_symbol("%s", regs->ip);
printk(" SS:ESP %04x:%08lx\n", ss, sp);
#else
/* Executive summary in case the oops scrolled away */
printk(KERN_ALERT "RIP ");
printk_address(regs->ip);
printk(" RSP <%016lx>\n", regs->sp);
#endif
return 0;
}
NOKPROBE_SYMBOL(__die);
/*
* This is gone through when something in the kernel has done something bad
* and is about to be terminated:
*/
void die(const char *str, struct pt_regs *regs, long err)
{
unsigned long flags = oops_begin();
int sig = SIGSEGV;
if (!user_mode(regs))
report_bug(regs->ip, regs);
if (__die(str, regs, err))
sig = 0;
oops_end(flags, regs, sig);
}
static int __init kstack_setup(char *s)
{
ssize_t ret;
unsigned long val;
if (!s)
return -EINVAL;
ret = kstrtoul(s, 0, &val);
if (ret)
return ret;
kstack_depth_to_print = val;
return 0;
}
early_param("kstack", kstack_setup);
static int __init code_bytes_setup(char *s)
{
ssize_t ret;
unsigned long val;
if (!s)
return -EINVAL;
ret = kstrtoul(s, 0, &val);
if (ret)
return ret;
code_bytes = val;
if (code_bytes > 8192)
code_bytes = 8192;
return 1;
}
__setup("code_bytes=", code_bytes_setup);