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Revision 52d7523d84d534c241ebac5ac89f5c0a6cb51e41 authored by EunTaik Lee on 16 February 2016, 04:44:35 UTC, committed by Will Deacon on 19 February 2016, 12:20:37 UTC 
arm64: mm: allow the kernel to handle alignment faults on user accesses
 
Although we don't expect to take alignment faults on access to normal
memory, misbehaving (i.e. buggy) user code can pass MMIO pointers into
system calls, leading to things like get_user accessing device memory.

Rather than OOPS the kernel, allow any exception fixups to run and
return something like -EFAULT back to userspace. This makes the
behaviour more consistent with userspace, even though applications with
access to device mappings can easily cause other issues if they try
hard enough.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Eun Taik Lee <eun.taik.lee@samsung.com>
[will: dropped __kprobes annotation and rewrote commit mesage]
Signed-off-by: Will Deacon <will.deacon@arm.com>
1 parent 8684fa3
Raw File
stacktrace.c 
/*
 * kernel/stacktrace.c
 *
 * Stack trace management functions
 *
 *  Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 */
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/kallsyms.h>
#include <linux/stacktrace.h>

void print_stack_trace(struct stack_trace *trace, int spaces)
{
	int i;

	if (WARN_ON(!trace->entries))
		return;

	for (i = 0; i < trace->nr_entries; i++) {
		printk("%*c", 1 + spaces, ' ');
		print_ip_sym(trace->entries[i]);
	}
}
EXPORT_SYMBOL_GPL(print_stack_trace);

int snprint_stack_trace(char *buf, size_t size,
			struct stack_trace *trace, int spaces)
{
	int i;
	unsigned long ip;
	int generated;
	int total = 0;

	if (WARN_ON(!trace->entries))
		return 0;

	for (i = 0; i < trace->nr_entries; i++) {
		ip = trace->entries[i];
		generated = snprintf(buf, size, "%*c[<%p>] %pS\n",
				1 + spaces, ' ', (void *) ip, (void *) ip);

		total += generated;

		/* Assume that generated isn't a negative number */
		if (generated >= size) {
			buf += size;
			size = 0;
		} else {
			buf += generated;
			size -= generated;
		}
	}

	return total;
}
EXPORT_SYMBOL_GPL(snprint_stack_trace);

/*
 * Architectures that do not implement save_stack_trace_tsk or
 * save_stack_trace_regs get this weak alias and a once-per-bootup warning
 * (whenever this facility is utilized - for example by procfs):
 */
__weak void
save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
{
	WARN_ONCE(1, KERN_INFO "save_stack_trace_tsk() not implemented yet.\n");
}

__weak void
save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
{
	WARN_ONCE(1, KERN_INFO "save_stack_trace_regs() not implemented yet.\n");
}
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