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/*
* Copyright (C) 2008, 2009 Intel Corporation
* Authors: Andi Kleen, Fengguang Wu
*
* This software may be redistributed and/or modified under the terms of
* the GNU General Public License ("GPL") version 2 only as published by the
* Free Software Foundation.
*
* High level machine check handler. Handles pages reported by the
* hardware as being corrupted usually due to a 2bit ECC memory or cache
* failure.
*
* Handles page cache pages in various states. The tricky part
* here is that we can access any page asynchronous to other VM
* users, because memory failures could happen anytime and anywhere,
* possibly violating some of their assumptions. This is why this code
* has to be extremely careful. Generally it tries to use normal locking
* rules, as in get the standard locks, even if that means the
* error handling takes potentially a long time.
*
* The operation to map back from RMAP chains to processes has to walk
* the complete process list and has non linear complexity with the number
* mappings. In short it can be quite slow. But since memory corruptions
* are rare we hope to get away with this.
*/
/*
* Notebook:
* - hugetlb needs more code
* - kcore/oldmem/vmcore/mem/kmem check for hwpoison pages
* - pass bad pages to kdump next kernel
*/
#define DEBUG 1 /* remove me in 2.6.34 */
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/page-flags.h>
#include <linux/sched.h>
#include <linux/ksm.h>
#include <linux/rmap.h>
#include <linux/pagemap.h>
#include <linux/swap.h>
#include <linux/backing-dev.h>
#include "internal.h"
int sysctl_memory_failure_early_kill __read_mostly = 0;
int sysctl_memory_failure_recovery __read_mostly = 1;
atomic_long_t mce_bad_pages __read_mostly = ATOMIC_LONG_INIT(0);
/*
* Send all the processes who have the page mapped an ``action optional''
* signal.
*/
static int kill_proc_ao(struct task_struct *t, unsigned long addr, int trapno,
unsigned long pfn)
{
struct siginfo si;
int ret;
printk(KERN_ERR
"MCE %#lx: Killing %s:%d early due to hardware memory corruption\n",
pfn, t->comm, t->pid);
si.si_signo = SIGBUS;
si.si_errno = 0;
si.si_code = BUS_MCEERR_AO;
si.si_addr = (void *)addr;
#ifdef __ARCH_SI_TRAPNO
si.si_trapno = trapno;
#endif
si.si_addr_lsb = PAGE_SHIFT;
/*
* Don't use force here, it's convenient if the signal
* can be temporarily blocked.
* This could cause a loop when the user sets SIGBUS
* to SIG_IGN, but hopefully noone will do that?
*/
ret = send_sig_info(SIGBUS, &si, t); /* synchronous? */
if (ret < 0)
printk(KERN_INFO "MCE: Error sending signal to %s:%d: %d\n",
t->comm, t->pid, ret);
return ret;
}
/*
* Kill all processes that have a poisoned page mapped and then isolate
* the page.
*
* General strategy:
* Find all processes having the page mapped and kill them.
* But we keep a page reference around so that the page is not
* actually freed yet.
* Then stash the page away
*
* There's no convenient way to get back to mapped processes
* from the VMAs. So do a brute-force search over all
* running processes.
*
* Remember that machine checks are not common (or rather
* if they are common you have other problems), so this shouldn't
* be a performance issue.
*
* Also there are some races possible while we get from the
* error detection to actually handle it.
*/
struct to_kill {
struct list_head nd;
struct task_struct *tsk;
unsigned long addr;
unsigned addr_valid:1;
};
/*
* Failure handling: if we can't find or can't kill a process there's
* not much we can do. We just print a message and ignore otherwise.
*/
/*
* Schedule a process for later kill.
* Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
* TBD would GFP_NOIO be enough?
*/
static void add_to_kill(struct task_struct *tsk, struct page *p,
struct vm_area_struct *vma,
struct list_head *to_kill,
struct to_kill **tkc)
{
struct to_kill *tk;
if (*tkc) {
tk = *tkc;
*tkc = NULL;
} else {
tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
if (!tk) {
printk(KERN_ERR
"MCE: Out of memory while machine check handling\n");
return;
}
}
tk->addr = page_address_in_vma(p, vma);
tk->addr_valid = 1;
/*
* In theory we don't have to kill when the page was
* munmaped. But it could be also a mremap. Since that's
* likely very rare kill anyways just out of paranoia, but use
* a SIGKILL because the error is not contained anymore.
*/
if (tk->addr == -EFAULT) {
pr_debug("MCE: Unable to find user space address %lx in %s\n",
page_to_pfn(p), tsk->comm);
tk->addr_valid = 0;
}
get_task_struct(tsk);
tk->tsk = tsk;
list_add_tail(&tk->nd, to_kill);
}
/*
* Kill the processes that have been collected earlier.
*
* Only do anything when DOIT is set, otherwise just free the list
* (this is used for clean pages which do not need killing)
* Also when FAIL is set do a force kill because something went
* wrong earlier.
*/
static void kill_procs_ao(struct list_head *to_kill, int doit, int trapno,
int fail, unsigned long pfn)
{
struct to_kill *tk, *next;
list_for_each_entry_safe (tk, next, to_kill, nd) {
if (doit) {
/*
* In case something went wrong with munmaping
* make sure the process doesn't catch the
* signal and then access the memory. Just kill it.
* the signal handlers
*/
if (fail || tk->addr_valid == 0) {
printk(KERN_ERR
"MCE %#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n",
pfn, tk->tsk->comm, tk->tsk->pid);
force_sig(SIGKILL, tk->tsk);
}
/*
* In theory the process could have mapped
* something else on the address in-between. We could
* check for that, but we need to tell the
* process anyways.
*/
else if (kill_proc_ao(tk->tsk, tk->addr, trapno,
pfn) < 0)
printk(KERN_ERR
"MCE %#lx: Cannot send advisory machine check signal to %s:%d\n",
pfn, tk->tsk->comm, tk->tsk->pid);
}
put_task_struct(tk->tsk);
kfree(tk);
}
}
static int task_early_kill(struct task_struct *tsk)
{
if (!tsk->mm)
return 0;
if (tsk->flags & PF_MCE_PROCESS)
return !!(tsk->flags & PF_MCE_EARLY);
return sysctl_memory_failure_early_kill;
}
/*
* Collect processes when the error hit an anonymous page.
*/
static void collect_procs_anon(struct page *page, struct list_head *to_kill,
struct to_kill **tkc)
{
struct vm_area_struct *vma;
struct task_struct *tsk;
struct anon_vma *av;
read_lock(&tasklist_lock);
av = page_lock_anon_vma(page);
if (av == NULL) /* Not actually mapped anymore
|