path: root/arch/tile/kernel/stack.c

/*
 * Copyright 2010 Tilera Corporation. All Rights Reserved.
 *
 *   This program is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU General Public License
 *   as published by the Free Software Foundation, version 2.
 *
 *   This program is distributed in the hope that it will be useful, but
 *   WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
 *   NON INFRINGEMENT.  See the GNU General Public License for
 *   more details.
 */

#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/kprobes.h>
#include <linux/module.h>
#include <linux/pfn.h>
#include <linux/kallsyms.h>
#include <linux/stacktrace.h>
#include <linux/uaccess.h>
#include <linux/mmzone.h>
#include <linux/dcache.h>
#include <linux/fs.h>
#include <asm/backtrace.h>
#include <asm/page.h>
#include <asm/ucontext.h>
#include <asm/switch_to.h>
#include <asm/sigframe.h>
#include <asm/stack.h>
#include <arch/abi.h>
#include <arch/interrupts.h>

#define KBT_ONGOING	0  /* Backtrace still ongoing */
#define KBT_DONE	1  /* Backtrace cleanly completed */
#define KBT_RUNNING	2  /* Can't run backtrace on a running task */
#define KBT_LOOP	3  /* Backtrace entered a loop */

/* Is address on the specified kernel stack? */
static int in_kernel_stack(struct KBacktraceIterator *kbt, unsigned long sp)
{
	ulong kstack_base = (ulong) kbt->task->stack;
	if (kstack_base == 0)  /* corrupt task pointer; just follow stack... */
		return sp >= PAGE_OFFSET && sp < (unsigned long)high_memory;
	return sp >= kstack_base && sp < kstack_base + THREAD_SIZE;
}

/* Callback for backtracer; basically a glorified memcpy */
static bool read_memory_func(void *result, unsigned long address,
			     unsigned int size, void *vkbt)
{
	int retval;
	struct KBacktraceIterator *kbt = (struct KBacktraceIterator *)vkbt;

	if (address == 0)
		return 0;
	if (__kernel_text_address(address)) {
		/* OK to read kernel code. */
	} else if (address >= PAGE_OFFSET) {
		/* We only tolerate kernel-space reads of this task's stack */
		if (!in_kernel_stack(kbt, address))
			return 0;
	} else if (!kbt->is_current) {
		return 0;	/* can't read from other user address spaces */
	}
	pagefault_disable();
	retval = __copy_from_user_inatomic(result,
					   (void __user __force *)address,
					   size);
	pagefault_enable();
	return (retval == 0);
}

/* Return a pt_regs pointer for a valid fault handler frame */
static struct pt_regs *valid_fault_handler(struct KBacktraceIterator* kbt)
{
	const char *fault = NULL;  /* happy compiler */
	char fault_buf[64];
	unsigned long sp = kbt->it.sp;
	struct pt_regs *p;

	if (sp % sizeof(long) != 0)
		return NULL;
	if (!in_kernel_stack(kbt, sp))
		return NULL;
	if (!in_kernel_stack(kbt, sp + C_ABI_SAVE_AREA_SIZE + PTREGS_SIZE-1))
		return NULL;
	p = (struct pt_regs *)(sp + C_ABI_SAVE_AREA_SIZE);
	if (p->faultnum == INT_SWINT_1 || p->faultnum == INT_SWINT_1_SIGRETURN)
		fault = "syscall";
	else {
		if (kbt->verbose) {     /* else we aren't going to use it */
			snprintf(fault_buf, sizeof(fault_buf),
				 "interrupt %ld", p->faultnum);
			fault = fault_buf;
		}
	}
	if (EX1_PL(p->ex1) == KERNEL_PL &&
	    __kernel_text_address(p->pc) &&
	    in_kernel_stack(kbt, p->sp) &&
	    p->sp >= sp) {
		if (kbt->verbose)
			pr_err("  <%s while in kernel mode>\n", fault);
	} else if (EX1_PL(p->ex1) == USER_PL &&
	    p->pc < PAGE_OFFSET &&
	    p->sp < PAGE_OFFSET) {
		if (kbt->verbose)
			pr_err("  <%s while in user mode>\n", fault);
	} else if (kbt->verbose) {
		pr_err("  (odd fault: pc %#lx, sp %#lx, ex1 %#lx?)\n",
		       p->pc, p->sp, p->ex1);
		p = NULL;
	}
	if (!kbt->profile || ((1ULL << p->faultnum) & QUEUED_INTERRUPTS) == 0)
		return p;
	return NULL;
}

/* Is the pc pointing to a sigreturn trampoline? */
static int is_sigreturn(unsigned long pc)
{
	return (pc == VDSO_BASE);
}

/* Return a pt_regs pointer for a valid signal handler frame */
static struct pt_regs *valid_sigframe(struct KBacktraceIterator* kbt,
				      struct rt_sigframe* kframe)
{
	BacktraceIterator *b = &kbt->it;

	if (b->pc == VDSO_BASE && b->sp < PAGE_OFFSET &&
	    b->sp % sizeof(long) == 0) {
		int retval;
		pagefault_disable();
		retval = __copy_from_user_inatomic(
			kframe, (void __user __force *)b->sp,
			sizeof(*kframe));
		pagefault_enable();
		if (retval != 0 ||
		    (unsigned int)(kframe->info.si_signo) >= _NSIG)
			return NULL;
		if (kbt->verbose) {
			pr_err("  <received signal %d>\n",
			       kframe->info.si_signo);
		}
		return (struct pt_regs *)&kframe->uc.uc_mcontext;
	}
	return NULL;
}

static int KBacktraceIterator_is_sigreturn(struct KBacktraceIterator *kbt)
{
	return is_sigreturn(kbt->it.pc);
}

static int KBacktraceIterator_restart(struct KBacktraceIterator *kbt)
{
	struct pt_regs *p;
	struct rt_sigframe kframe;

	p = valid_fault_handler(kbt);
	if (p == NULL)
		p = valid_sigframe(kbt, &kframe);
	if (p == NULL)
		return 0;
	backtrace_init(&kbt->it, read_memory_func, kbt,
		       p->pc, p->lr, p->sp, p->regs[52]);
	kbt->new_context = 1;
	return 1;
}

/* Find a frame that isn't a sigreturn, if there is one. */
static int KBacktraceIterator_next_item_inclusive(
	struct KBacktraceIterator *kbt)
{
	for (;;) {
		do {
			if (!KBacktraceIterator_is_sigreturn(kbt))
				return KBT_ONGOING;
		} while (backtrace_next(&kbt->it));

		if (!KBacktraceIterator_restart(kbt))
			return KBT_DONE;
	}
}

/*
 * If the current sp is on a page different than what we recorded
 * as the top-of-kernel-stack last time we context switched, we have
 * probably blown the stack, and nothing is going to work out well.
 * If we can at least get out a warning, that may help the debug,
 * though we probably won't be able to backtrace into the code that
 * actually did the recursive damage.
 */
static void validate_stack(struct pt_regs *regs)
{
	int cpu = smp_processor_id();
	unsigned long ksp0 = get_current_ksp0();
	unsigned long ksp0_base = ksp0 - THREAD_SIZE;
	unsigned long sp = stack_pointer;

	if (EX1_PL(regs->ex1) == KERNEL_PL && regs->sp >= ksp0) {
		pr_err("WARNING: cpu %d: kernel stack page %#lx underrun!\n"
		       "  sp %#lx (%#lx in caller), caller pc %#lx, lr %#lx\n",
		       cpu, ksp0_base, sp, regs->sp, regs->pc, regs->lr);
	}

	else if (sp < ksp0_base + sizeof(struct thread_info)) {
		pr_err("WARNING: cpu %d: kernel stack page %#lx overrun!\n"
		       "  sp %#lx (%#lx in caller), caller pc %#lx, lr %#lx\n",
		       cpu, ksp0_base, sp, regs->sp, regs->pc, regs->lr);
	}
}

void