blob: 2b5886401e5f4eb2c221f813675927a53cc97d61 [file] [log] [blame]
* 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/sched/debug.h>
#include <linux/sched/task_stack.h>
#include <linux/ftrace.h>
#include <linux/kexec.h>
#include <linux/bug.h>
#include <linux/nmi.h>
#include <linux/sysfs.h>
#include <linux/kasan.h>
#include <asm/cpu_entry_area.h>
#include <asm/stacktrace.h>
#include <asm/unwind.h>
int panic_on_unrecovered_nmi;
int panic_on_io_nmi;
static int die_counter;
static struct pt_regs exec_summary_regs;
bool in_task_stack(unsigned long *stack, struct task_struct *task,
struct stack_info *info)
unsigned long *begin = task_stack_page(task);
unsigned long *end = task_stack_page(task) + THREAD_SIZE;
if (stack < begin || stack >= end)
return false;
info->type = STACK_TYPE_TASK;
info->begin = begin;
info->end = end;
info->next_sp = NULL;
return true;
bool in_entry_stack(unsigned long *stack, struct stack_info *info)
struct entry_stack *ss = cpu_entry_stack(smp_processor_id());
void *begin = ss;
void *end = ss + 1;
if ((void *)stack < begin || (void *)stack >= end)
return false;
info->type = STACK_TYPE_ENTRY;
info->begin = begin;
info->end = end;
info->next_sp = NULL;
return true;
static void printk_stack_address(unsigned long address, int reliable,
char *log_lvl)
printk("%s %s%pB\n", log_lvl, reliable ? "" : "? ", (void *)address);
* There are a couple of reasons for the 2/3rd prologue, courtesy of Linus:
* In case where we don't have the exact kernel image (which, if we did, we can
* simply disassemble and navigate to the RIP), the purpose of the bigger
* prologue is to have more context and to be able to correlate the code from
* the different toolchains better.
* In addition, it helps in recreating the register allocation of the failing
* kernel and thus make sense of the register dump.
* What is more, the additional complication of a variable length insn arch like
* x86 warrants having longer byte sequence before rIP so that the disassembler
* can "sync" up properly and find instruction boundaries when decoding the
* opcode bytes.
* Thus, the 2/3rds prologue and 64 byte OPCODE_BUFSIZE is just a random
* guesstimate in attempt to achieve all of the above.
void show_opcodes(struct pt_regs *regs, const char *loglvl)
#define PROLOGUE_SIZE 42
#define EPILOGUE_SIZE 21
u8 opcodes[OPCODE_BUFSIZE];
unsigned long prologue = regs->ip - PROLOGUE_SIZE;
bool bad_ip;
* Make sure userspace isn't trying to trick us into dumping kernel
* memory by pointing the userspace instruction pointer at it.
bad_ip = user_mode(regs) &&
__chk_range_not_ok(prologue, OPCODE_BUFSIZE, TASK_SIZE_MAX);
if (bad_ip || probe_kernel_read(opcodes, (u8 *)prologue,
printk("%sCode: Bad RIP value.\n", loglvl);
} else {
printk("%sCode: %" __stringify(PROLOGUE_SIZE) "ph <%02x> %"
__stringify(EPILOGUE_SIZE) "ph\n", loglvl, opcodes,
opcodes[PROLOGUE_SIZE], opcodes + PROLOGUE_SIZE + 1);
void show_ip(struct pt_regs *regs, const char *loglvl)
#ifdef CONFIG_X86_32
printk("%sEIP: %pS\n", loglvl, (void *)regs->ip);
printk("%sRIP: %04x:%pS\n", loglvl, (int)regs->cs, (void *)regs->ip);
show_opcodes(regs, loglvl);
void show_iret_regs(struct pt_regs *regs)
show_ip(regs, KERN_DEFAULT);
printk(KERN_DEFAULT "RSP: %04x:%016lx EFLAGS: %08lx", (int)regs->ss,
regs->sp, regs->flags);
static void show_regs_if_on_stack(struct stack_info *info, struct pt_regs *regs,
bool partial)
* These on_stack() checks aren't strictly necessary: the unwind code
* has already validated the 'regs' pointer. The checks are done for
* ordering reasons: if the registers are on the next stack, we don't
* want to print them out yet. Otherwise they'll be shown as part of
* the wrong stack. Later, when show_trace_log_lvl() switches to the
* next stack, this function will be called again with the same regs so
* they can be printed in the right context.
if (!partial && on_stack(info, regs, sizeof(*regs))) {
__show_regs(regs, SHOW_REGS_SHORT);
} else if (partial && on_stack(info, (void *)regs + IRET_FRAME_OFFSET,
* When an interrupt or exception occurs in entry code, the
* full pt_regs might not have been saved yet. In that case
* just print the iret frame.
void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
unsigned long *stack, char *log_lvl)
struct unwind_state state;
struct stack_info stack_info = {0};
unsigned long visit_mask = 0;
int graph_idx = 0;
bool partial = false;
printk("%sCall Trace:\n", log_lvl);
unwind_start(&state, task, regs, stack);
stack = stack ? : get_stack_pointer(task, regs);
regs = unwind_get_entry_regs(&state, &partial);
* Iterate through the stacks, starting with the current stack pointer.
* Each stack has a pointer to the next one.
* x86-64 can have several stacks:
* - task stack
* - interrupt stack
* - HW exception stacks (double fault, nmi, debug, mce)
* - entry stack
* x86-32 can have up to four stacks:
* - task stack
* - softirq stack
* - hardirq stack
* - entry stack
for ( ; stack; stack = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
const char *stack_name;
if (get_stack_info(stack, task, &stack_info, &visit_mask)) {
* We weren't on a valid stack. It's possible that
* we overflowed a valid stack into a guard page.
* See if the next page up is valid so that we can
* generate some kind of backtrace if this happens.
stack = (unsigned long *)PAGE_ALIGN((unsigned long)stack);
if (get_stack_info(stack, task, &stack_info, &visit_mask))
stack_name = stack_type_name(stack_info.type);
if (stack_name)
printk("%s <%s>\n", log_lvl, stack_name);
if (regs)
show_regs_if_on_stack(&stack_info, regs, partial);
* Scan the stack, printing any text addresses we find. At the
* same time, follow proper stack frames with the unwinder.
* Addresses found during the scan which are not reported by
* the unwinder are considered to be additional clues which are
* sometimes useful for debugging and are prefixed with '?'.
* This also serves as a failsafe option in case the unwinder
* goes off in the weeds.
for (; stack < stack_info.end; stack++) {
unsigned long real_addr;
int reliable = 0;
unsigned long addr = READ_ONCE_NOCHECK(*stack);
unsigned long *ret_addr_p =
if (!__kernel_text_address(addr))
* Don't print regs->ip again if it was already printed
* by show_regs_if_on_stack().
if (regs && stack == &regs->ip)
goto next;
if (stack == ret_addr_p)
reliable = 1;
* 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_idx,
addr, stack);
if (real_addr != addr)
printk_stack_address(addr, 0, log_lvl);
printk_stack_address(real_addr, reliable, log_lvl);
if (!reliable)
* Get the next frame from the unwinder. No need to
* check for an error: if anything goes wrong, the rest
* of the addresses will just be printed as unreliable.
/* if the frame has entry regs, print them */
regs = unwind_get_entry_regs(&state, &partial);
if (regs)
show_regs_if_on_stack(&stack_info, regs, partial);
if (stack_name)
printk("%s </%s>\n", log_lvl, stack_name);
void show_stack(struct task_struct *task, unsigned long *sp)
task = task ? : current;
* Stack frames below this one aren't interesting. Don't show them
* if we're printing for %current.
if (!sp && task == current)
sp = get_stack_pointer(current, NULL);
show_trace_log_lvl(task, NULL, sp, KERN_DEFAULT);
void show_stack_regs(struct pt_regs *regs)
show_trace_log_lvl(current, regs, NULL, KERN_DEFAULT);
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;
/* racy, but better than risking deadlock. */
cpu = smp_processor_id();
if (!arch_spin_trylock(&die_lock)) {
if (cpu == die_owner)
/* nested oops. should stop eventually */;
die_owner = cpu;
return flags;
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))
die_owner = -1;
if (!die_nest_count)
/* Nest count reaches zero, release the lock. */
/* Executive summary in case the oops scrolled away */
__show_regs(&exec_summary_regs, SHOW_REGS_ALL);
if (!signr)
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.
* Before we rewind the stack, we have to tell KASAN that we're going to
* reuse the task stack and that existing poisons are invalid.
int __die(const char *str, struct pt_regs *regs, long err)
/* Save the regs of the first oops for the executive summary later. */
if (!die_counter)
exec_summary_regs = *regs;
"%s: %04lx [#%d]%s%s%s%s%s\n", str, err & 0xffff, ++die_counter,
debug_pagealloc_enabled() ? " DEBUG_PAGEALLOC" : "",
(boot_cpu_has(X86_FEATURE_PTI) ? " PTI" : " NOPTI") : "");
if (notify_die(DIE_OOPS, str, regs, err,
current->thread.trap_nr, SIGSEGV) == NOTIFY_STOP)
return 1;
return 0;
* 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 (__die(str, regs, err))
sig = 0;
oops_end(flags, regs, sig);
void show_regs(struct pt_regs *regs)
__show_regs(regs, user_mode(regs) ? SHOW_REGS_USER : SHOW_REGS_ALL);
* When in-kernel, we also print out the stack at the time of the fault..
if (!user_mode(regs))
show_trace_log_lvl(current, regs, NULL, KERN_DEFAULT);