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dc4e0021b0
There are three problems with the current layout of the doublefault
stack and TSS. First, the TSS is only cacheline-aligned, which is
not enough -- if the hardware portion of the TSS (struct x86_hw_tss)
crosses a page boundary, horrible things happen [0]. Second, the
stack and TSS are global, so simultaneous double faults on different
CPUs will cause massive corruption. Third, the whole mechanism
won't work if user CR3 is loaded, resulting in a triple fault [1].
Let the doublefault stack and TSS share a page (which prevents the
TSS from spanning a page boundary), make it percpu, and move it into
cpu_entry_area. Teach the stack dump code about the doublefault
stack.
[0] Real hardware will read past the end of the page onto the next
*physical* page if a task switch happens. Virtual machines may
have any number of bugs, and I would consider it reasonable for
a VM to summarily kill the guest if it tries to task-switch to
a page-spanning TSS.
[1] Real hardware triple faults. At least some VMs seem to hang.
I'm not sure what's going on.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
160 lines
3.5 KiB
C
160 lines
3.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 1991, 1992 Linus Torvalds
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* Copyright (C) 2000, 2001, 2002 Andi Kleen, SuSE Labs
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*/
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#include <linux/sched/debug.h>
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#include <linux/kallsyms.h>
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#include <linux/kprobes.h>
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#include <linux/uaccess.h>
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#include <linux/hardirq.h>
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#include <linux/kdebug.h>
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#include <linux/export.h>
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#include <linux/ptrace.h>
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#include <linux/kexec.h>
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#include <linux/sysfs.h>
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#include <linux/bug.h>
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#include <linux/nmi.h>
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#include <asm/stacktrace.h>
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const char *stack_type_name(enum stack_type type)
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{
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if (type == STACK_TYPE_IRQ)
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return "IRQ";
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if (type == STACK_TYPE_SOFTIRQ)
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return "SOFTIRQ";
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if (type == STACK_TYPE_ENTRY)
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return "ENTRY_TRAMPOLINE";
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if (type == STACK_TYPE_EXCEPTION)
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return "#DF";
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return NULL;
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}
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static bool in_hardirq_stack(unsigned long *stack, struct stack_info *info)
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{
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unsigned long *begin = (unsigned long *)this_cpu_read(hardirq_stack_ptr);
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unsigned long *end = begin + (THREAD_SIZE / sizeof(long));
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/*
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* This is a software stack, so 'end' can be a valid stack pointer.
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* It just means the stack is empty.
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*/
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if (stack < begin || stack > end)
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return false;
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info->type = STACK_TYPE_IRQ;
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info->begin = begin;
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info->end = end;
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/*
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* See irq_32.c -- the next stack pointer is stored at the beginning of
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* the stack.
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*/
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info->next_sp = (unsigned long *)*begin;
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return true;
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}
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static bool in_softirq_stack(unsigned long *stack, struct stack_info *info)
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{
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unsigned long *begin = (unsigned long *)this_cpu_read(softirq_stack_ptr);
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unsigned long *end = begin + (THREAD_SIZE / sizeof(long));
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/*
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* This is a software stack, so 'end' can be a valid stack pointer.
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* It just means the stack is empty.
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*/
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if (stack < begin || stack > end)
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return false;
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info->type = STACK_TYPE_SOFTIRQ;
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info->begin = begin;
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info->end = end;
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/*
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* The next stack pointer is stored at the beginning of the stack.
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* See irq_32.c.
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*/
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info->next_sp = (unsigned long *)*begin;
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return true;
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}
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static bool in_doublefault_stack(unsigned long *stack, struct stack_info *info)
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{
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#ifdef CONFIG_DOUBLEFAULT
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struct cpu_entry_area *cea = get_cpu_entry_area(raw_smp_processor_id());
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struct doublefault_stack *ss = &cea->doublefault_stack;
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void *begin = ss->stack;
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void *end = begin + sizeof(ss->stack);
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if ((void *)stack < begin || (void *)stack >= end)
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return false;
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info->type = STACK_TYPE_EXCEPTION;
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info->begin = begin;
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info->end = end;
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info->next_sp = (unsigned long *)this_cpu_read(cpu_tss_rw.x86_tss.sp);
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return true;
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#else
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return false;
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#endif
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}
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int get_stack_info(unsigned long *stack, struct task_struct *task,
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struct stack_info *info, unsigned long *visit_mask)
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{
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if (!stack)
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goto unknown;
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task = task ? : current;
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if (in_task_stack(stack, task, info))
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goto recursion_check;
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if (task != current)
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goto unknown;
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if (in_entry_stack(stack, info))
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goto recursion_check;
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if (in_hardirq_stack(stack, info))
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goto recursion_check;
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if (in_softirq_stack(stack, info))
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goto recursion_check;
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if (in_doublefault_stack(stack, info))
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goto recursion_check;
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goto unknown;
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recursion_check:
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/*
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* Make sure we don't iterate through any given stack more than once.
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* If it comes up a second time then there's something wrong going on:
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* just break out and report an unknown stack type.
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*/
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if (visit_mask) {
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if (*visit_mask & (1UL << info->type)) {
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printk_deferred_once(KERN_WARNING "WARNING: stack recursion on stack type %d\n", info->type);
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goto unknown;
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}
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*visit_mask |= 1UL << info->type;
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}
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return 0;
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unknown:
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info->type = STACK_TYPE_UNKNOWN;
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return -EINVAL;
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}
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