diff options
Diffstat (limited to 'arch/x86/kernel/dumpstack.c')
| -rw-r--r-- | arch/x86/kernel/dumpstack.c | 479 |
1 files changed, 479 insertions, 0 deletions
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c new file mode 100644 index 000000000..b9736aac2 --- /dev/null +++ b/arch/x86/kernel/dumpstack.c @@ -0,0 +1,479 @@ +/* + * 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 noinstr 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; +} + +/* Called from get_stack_info_noinstr - so must be noinstr too */ +bool noinstr 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, + const char *log_lvl) +{ + touch_nmi_watchdog(); + printk("%s %s%pB\n", log_lvl, reliable ? "" : "? ", (void *)address); +} + +static int copy_code(struct pt_regs *regs, u8 *buf, unsigned long src, + unsigned int nbytes) +{ + if (!user_mode(regs)) + return copy_from_kernel_nofault(buf, (u8 *)src, nbytes); + + /* The user space code from other tasks cannot be accessed. */ + if (regs != task_pt_regs(current)) + return -EPERM; + /* + * Make sure userspace isn't trying to trick us into dumping kernel + * memory by pointing the userspace instruction pointer at it. + */ + if (__chk_range_not_ok(src, nbytes, TASK_SIZE_MAX)) + return -EINVAL; + + /* + * Even if named copy_from_user_nmi() this can be invoked from + * other contexts and will not try to resolve a pagefault, which is + * the correct thing to do here as this code can be called from any + * context. + */ + return copy_from_user_nmi(buf, (void __user *)src, nbytes); +} + +/* + * 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 +#define OPCODE_BUFSIZE (PROLOGUE_SIZE + 1 + EPILOGUE_SIZE) + u8 opcodes[OPCODE_BUFSIZE]; + unsigned long prologue = regs->ip - PROLOGUE_SIZE; + + switch (copy_code(regs, opcodes, prologue, sizeof(opcodes))) { + case 0: + printk("%sCode: %" __stringify(PROLOGUE_SIZE) "ph <%02x> %" + __stringify(EPILOGUE_SIZE) "ph\n", loglvl, opcodes, + opcodes[PROLOGUE_SIZE], opcodes + PROLOGUE_SIZE + 1); + break; + case -EPERM: + /* No access to the user space stack of other tasks. Ignore. */ + break; + default: + printk("%sCode: Unable to access opcode bytes at RIP 0x%lx.\n", + loglvl, prologue); + break; + } +} + +void show_ip(struct pt_regs *regs, const char *loglvl) +{ +#ifdef CONFIG_X86_32 + printk("%sEIP: %pS\n", loglvl, (void *)regs->ip); +#else + printk("%sRIP: %04x:%pS\n", loglvl, (int)regs->cs, (void *)regs->ip); +#endif + show_opcodes(regs, loglvl); +} + +void show_iret_regs(struct pt_regs *regs, const char *log_lvl) +{ + show_ip(regs, log_lvl); + printk("%sRSP: %04x:%016lx EFLAGS: %08lx", log_lvl, (int)regs->ss, + regs->sp, regs->flags); +} + +static void show_regs_if_on_stack(struct stack_info *info, struct pt_regs *regs, + bool partial, const char *log_lvl) +{ + /* + * 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, log_lvl); + + } else if (partial && on_stack(info, (void *)regs + IRET_FRAME_OFFSET, + IRET_FRAME_SIZE)) { + /* + * 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. + */ + show_iret_regs(regs, log_lvl); + } +} + +void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs, + unsigned long *stack, const 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); + 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 ?: get_stack_pointer(task, regs); + stack; + stack = stack_info.next_sp) { + const char *stack_name; + + stack = PTR_ALIGN(stack, sizeof(long)); + + 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)) + break; + } + + 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, log_lvl); + + /* + * 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 = + unwind_get_return_address_ptr(&state); + + if (!__kernel_text_address(addr)) + continue; + + /* + * Don't print regs->ip again if it was already printed + * by show_regs_if_on_stack(). + */ + if (regs && stack == ®s->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) + continue; + +next: + /* + * 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. + */ + unwind_next_frame(&state); + + /* 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, log_lvl); + } + + if (stack_name) + printk("%s </%s>\n", log_lvl, stack_name); + } +} + +void show_stack(struct task_struct *task, unsigned long *sp, + const char *loglvl) +{ + 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, loglvl); +} + +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; + + 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; +} +NOKPROBE_SYMBOL(oops_begin); + +void __noreturn rewind_stack_and_make_dead(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(); + + /* Executive summary in case the oops scrolled away */ + __show_regs(&exec_summary_regs, SHOW_REGS_ALL, KERN_DEFAULT); + + 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. + * 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. + */ + kasan_unpoison_task_stack(current); + rewind_stack_and_make_dead(signr); +} +NOKPROBE_SYMBOL(oops_end); + +static void __die_header(const char *str, struct pt_regs *regs, long err) +{ + const char *pr = ""; + + /* Save the regs of the first oops for the executive summary later. */ + if (!die_counter) + exec_summary_regs = *regs; + + if (IS_ENABLED(CONFIG_PREEMPTION)) + pr = IS_ENABLED(CONFIG_PREEMPT_RT) ? " PREEMPT_RT" : " PREEMPT"; + + printk(KERN_DEFAULT + "%s: %04lx [#%d]%s%s%s%s%s\n", str, err & 0xffff, ++die_counter, + pr, + IS_ENABLED(CONFIG_SMP) ? " SMP" : "", + debug_pagealloc_enabled() ? " DEBUG_PAGEALLOC" : "", + IS_ENABLED(CONFIG_KASAN) ? " KASAN" : "", + IS_ENABLED(CONFIG_PAGE_TABLE_ISOLATION) ? + (boot_cpu_has(X86_FEATURE_PTI) ? " PTI" : " NOPTI") : ""); +} +NOKPROBE_SYMBOL(__die_header); + +static int __die_body(const char *str, struct pt_regs *regs, long err) +{ + show_regs(regs); + print_modules(); + + if (notify_die(DIE_OOPS, str, regs, err, + current->thread.trap_nr, SIGSEGV) == NOTIFY_STOP) + return 1; + + return 0; +} +NOKPROBE_SYMBOL(__die_body); + +int __die(const char *str, struct pt_regs *regs, long err) +{ + __die_header(str, regs, err); + return __die_body(str, regs, err); +} +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 (__die(str, regs, err)) + sig = 0; + oops_end(flags, regs, sig); +} + +void die_addr(const char *str, struct pt_regs *regs, long err, long gp_addr) +{ + unsigned long flags = oops_begin(); + int sig = SIGSEGV; + + __die_header(str, regs, err); + if (gp_addr) + kasan_non_canonical_hook(gp_addr); + if (__die_body(str, regs, err)) + sig = 0; + oops_end(flags, regs, sig); +} + +void show_regs(struct pt_regs *regs) +{ + enum show_regs_mode print_kernel_regs; + + show_regs_print_info(KERN_DEFAULT); + + print_kernel_regs = user_mode(regs) ? SHOW_REGS_USER : SHOW_REGS_ALL; + __show_regs(regs, print_kernel_regs, KERN_DEFAULT); + + /* + * 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); +} |