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linux/fs/proc/task_mmu.c
Andrea Arcangeli 1a5a9906d4 mm: thp: fix pmd_bad() triggering in code paths holding mmap_sem read mode 
In some cases it may happen that pmd_none_or_clear_bad() is called with
the mmap_sem hold in read mode.  In those cases the huge page faults can
allocate hugepmds under pmd_none_or_clear_bad() and that can trigger a
false positive from pmd_bad() that will not like to see a pmd
materializing as trans huge.

It's not khugepaged causing the problem, khugepaged holds the mmap_sem
in write mode (and all those sites must hold the mmap_sem in read mode
to prevent pagetables to go away from under them, during code review it
seems vm86 mode on 32bit kernels requires that too unless it's
restricted to 1 thread per process or UP builds).  The race is only with
the huge pagefaults that can convert a pmd_none() into a
pmd_trans_huge().

Effectively all these pmd_none_or_clear_bad() sites running with
mmap_sem in read mode are somewhat speculative with the page faults, and
the result is always undefined when they run simultaneously.  This is
probably why it wasn't common to run into this.  For example if the
madvise(MADV_DONTNEED) runs zap_page_range() shortly before the page
fault, the hugepage will not be zapped, if the page fault runs first it
will be zapped.

Altering pmd_bad() not to error out if it finds hugepmds won't be enough
to fix this, because zap_pmd_range would then proceed to call
zap_pte_range (which would be incorrect if the pmd become a
pmd_trans_huge()).

The simplest way to fix this is to read the pmd in the local stack
(regardless of what we read, no need of actual CPU barriers, only
compiler barrier needed), and be sure it is not changing under the code
that computes its value.  Even if the real pmd is changing under the
value we hold on the stack, we don't care.  If we actually end up in
zap_pte_range it means the pmd was not none already and it was not huge,
and it can't become huge from under us (khugepaged locking explained
above).

All we need is to enforce that there is no way anymore that in a code
path like below, pmd_trans_huge can be false, but pmd_none_or_clear_bad
can run into a hugepmd.  The overhead of a barrier() is just a compiler
tweak and should not be measurable (I only added it for THP builds).  I
don't exclude different compiler versions may have prevented the race
too by caching the value of *pmd on the stack (that hasn't been
verified, but it wouldn't be impossible considering
pmd_none_or_clear_bad, pmd_bad, pmd_trans_huge, pmd_none are all inlines
and there's no external function called in between pmd_trans_huge and
pmd_none_or_clear_bad).

		if (pmd_trans_huge(*pmd)) {
			if (next-addr != HPAGE_PMD_SIZE) {
				VM_BUG_ON(!rwsem_is_locked(&tlb->mm->mmap_sem));
				split_huge_page_pmd(vma->vm_mm, pmd);
			} else if (zap_huge_pmd(tlb, vma, pmd, addr))
				continue;
			/* fall through */
		}
		if (pmd_none_or_clear_bad(pmd))

Because this race condition could be exercised without special
privileges this was reported in CVE-2012-1179.

The race was identified and fully explained by Ulrich who debugged it.
I'm quoting his accurate explanation below, for reference.

====== start quote =======
      mapcount 0 page_mapcount 1
      kernel BUG at mm/huge_memory.c:1384!

    At some point prior to the panic, a "bad pmd ..." message similar to the
    following is logged on the console:

      mm/memory.c:145: bad pmd ffff8800376e1f98(80000000314000e7).

    The "bad pmd ..." message is logged by pmd_clear_bad() before it clears
    the page's PMD table entry.

        143 void pmd_clear_bad(pmd_t *pmd)
        144 {
    ->  145         pmd_ERROR(*pmd);
        146         pmd_clear(pmd);
        147 }

    After the PMD table entry has been cleared, there is an inconsistency
    between the actual number of PMD table entries that are mapping the page
    and the page's map count (_mapcount field in struct page). When the page
    is subsequently reclaimed, __split_huge_page() detects this inconsistency.

       1381         if (mapcount != page_mapcount(page))
       1382                 printk(KERN_ERR "mapcount %d page_mapcount %d\n",
       1383                        mapcount, page_mapcount(page));
    -> 1384         BUG_ON(mapcount != page_mapcount(page));

    The root cause of the problem is a race of two threads in a multithreaded
    process. Thread B incurs a page fault on a virtual address that has never
    been accessed (PMD entry is zero) while Thread A is executing an madvise()
    system call on a virtual address within the same 2 MB (huge page) range.

               virtual address space
              .---------------------.
              |                     |
              |                     |
            .-|---------------------|
            | |                     |
            | |                     |<-- B(fault)
            | |                     |
      2 MB  | |/////////////////////|-.
      huge <  |/////////////////////|  > A(range)
      page  | |/////////////////////|-'
            | |                     |
            | |                     |
            '-|---------------------|
              |                     |
              |                     |
              '---------------------'

    - Thread A is executing an madvise(..., MADV_DONTNEED) system call
      on the virtual address range "A(range)" shown in the picture.

    sys_madvise
      // Acquire the semaphore in shared mode.
      down_read(&current->mm->mmap_sem)
      ...
      madvise_vma
        switch (behavior)
        case MADV_DONTNEED:
             madvise_dontneed
               zap_page_range
                 unmap_vmas
                   unmap_page_range
                     zap_pud_range
                       zap_pmd_range
                         //
                         // Assume that this huge page has never been accessed.
                         // I.e. content of the PMD entry is zero (not mapped).
                         //
                         if (pmd_trans_huge(*pmd)) {
                             // We don't get here due to the above assumption.
                         }
                         //
                         // Assume that Thread B incurred a page fault and
             .---------> // sneaks in here as shown below.
             |           //
             |           if (pmd_none_or_clear_bad(pmd))
             |               {
             |                 if (unlikely(pmd_bad(*pmd)))
             |                     pmd_clear_bad
             |                     {
             |                       pmd_ERROR
             |                         // Log "bad pmd ..." message here.
             |                       pmd_clear
             |                         // Clear the page's PMD entry.
             |                         // Thread B incremented the map count
             |                         // in page_add_new_anon_rmap(), but
             |                         // now the page is no longer mapped
             |                         // by a PMD entry (-> inconsistency).
             |                     }
             |               }
             |
             v
    - Thread B is handling a page fault on virtual address "B(fault)" shown
      in the picture.

    ...
    do_page_fault
      __do_page_fault
        // Acquire the semaphore in shared mode.
        down_read_trylock(&mm->mmap_sem)
        ...
        handle_mm_fault
          if (pmd_none(*pmd) && transparent_hugepage_enabled(vma))
              // We get here due to the above assumption (PMD entry is zero).
              do_huge_pmd_anonymous_page
                alloc_hugepage_vma
                  // Allocate a new transparent huge page here.
                ...
                __do_huge_pmd_anonymous_page
                  ...
                  spin_lock(&mm->page_table_lock)
                  ...
                  page_add_new_anon_rmap
                    // Here we increment the page's map count (starts at -1).
                    atomic_set(&page->_mapcount, 0)
                  set_pmd_at
                    // Here we set the page's PMD entry which will be cleared
                    // when Thread A calls pmd_clear_bad().
                  ...
                  spin_unlock(&mm->page_table_lock)

    The mmap_sem does not prevent the race because both threads are acquiring
    it in shared mode (down_read).  Thread B holds the page_table_lock while
    the page's map count and PMD table entry are updated.  However, Thread A
    does not synchronize on that lock.

====== end quote =======

[akpm@linux-foundation.org: checkpatch fixes]
Reported-by: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dave Jones <davej@redhat.com>
Acked-by: Larry Woodman <lwoodman@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: <stable@vger.kernel.org>		[2.6.38+]
Cc: Mark Salter <msalter@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-03-21 17:54:54 -07:00

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#include <linux/mm.h>
#include <linux/hugetlb.h>
#include <linux/huge_mm.h>
#include <linux/mount.h>
#include <linux/seq_file.h>
#include <linux/highmem.h>
#include <linux/ptrace.h>
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/mempolicy.h>
#include <linux/rmap.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <asm/elf.h>
#include <asm/uaccess.h>
#include <asm/tlbflush.h>
#include "internal.h"
void task_mem(struct seq_file *m, struct mm_struct *mm)
{
unsigned long data, text, lib, swap;
unsigned long hiwater_vm, total_vm, hiwater_rss, total_rss;
/*
* Note: to minimize their overhead, mm maintains hiwater_vm and
* hiwater_rss only when about to *lower* total_vm or rss. Any
* collector of these hiwater stats must therefore get total_vm
* and rss too, which will usually be the higher. Barriers? not
* worth the effort, such snapshots can always be inconsistent.
*/
hiwater_vm = total_vm = mm->total_vm;
if (hiwater_vm < mm->hiwater_vm)
hiwater_vm = mm->hiwater_vm;
hiwater_rss = total_rss = get_mm_rss(mm);
if (hiwater_rss < mm->hiwater_rss)
hiwater_rss = mm->hiwater_rss;
data = mm->total_vm - mm->shared_vm - mm->stack_vm;
text = (PAGE_ALIGN(mm->end_code) - (mm->start_code & PAGE_MASK)) >> 10;
lib = (mm->exec_vm << (PAGE_SHIFT-10)) - text;
swap = get_mm_counter(mm, MM_SWAPENTS);
seq_printf(m,
"VmPeak:\t%8lu kB\n"
"VmSize:\t%8lu kB\n"
"VmLck:\t%8lu kB\n"
"VmPin:\t%8lu kB\n"
"VmHWM:\t%8lu kB\n"
"VmRSS:\t%8lu kB\n"
"VmData:\t%8lu kB\n"
"VmStk:\t%8lu kB\n"
"VmExe:\t%8lu kB\n"
"VmLib:\t%8lu kB\n"
"VmPTE:\t%8lu kB\n"
"VmSwap:\t%8lu kB\n",
hiwater_vm << (PAGE_SHIFT-10),
(total_vm - mm->reserved_vm) << (PAGE_SHIFT-10),
mm->locked_vm << (PAGE_SHIFT-10),
mm->pinned_vm << (PAGE_SHIFT-10),
hiwater_rss << (PAGE_SHIFT-10),
total_rss << (PAGE_SHIFT-10),
data << (PAGE_SHIFT-10),
mm->stack_vm << (PAGE_SHIFT-10), text, lib,
(PTRS_PER_PTE*sizeof(pte_t)*mm->nr_ptes) >> 10,
swap << (PAGE_SHIFT-10));
}
unsigned long task_vsize(struct mm_struct *mm)
{
return PAGE_SIZE * mm->total_vm;
}
unsigned long task_statm(struct mm_struct *mm,
unsigned long *shared, unsigned long *text,
unsigned long *data, unsigned long *resident)
{
*shared = get_mm_counter(mm, MM_FILEPAGES);
*text = (PAGE_ALIGN(mm->end_code) - (mm->start_code & PAGE_MASK))
>> PAGE_SHIFT;
*data = mm->total_vm - mm->shared_vm;
*resident = *shared + get_mm_counter(mm, MM_ANONPAGES);
return mm->total_vm;
}
static void pad_len_spaces(struct seq_file *m, int len)
{
len = 25 + sizeof(void*) * 6 - len;
if (len < 1)
len = 1;
seq_printf(m, "%*c", len, ' ');
}
static void vma_stop(struct proc_maps_private *priv, struct vm_area_struct *vma)
{
if (vma && vma != priv->tail_vma) {
struct mm_struct *mm = vma->vm_mm;
up_read(&mm->mmap_sem);
mmput(mm);
}
}
static void *m_start(struct seq_file *m, loff_t *pos)
{
struct proc_maps_private *priv = m->private;
unsigned long last_addr = m->version;
struct mm_struct *mm;
struct vm_area_struct *vma, *tail_vma = NULL;
loff_t l = *pos;
/* Clear the per syscall fields in priv */
priv->task = NULL;
priv->tail_vma = NULL;
/*
* We remember last_addr rather than next_addr to hit with
* mmap_cache most of the time. We have zero last_addr at
* the beginning and also after lseek. We will have -1 last_addr
* after the end of the vmas.
*/
if (last_addr == -1UL)
return NULL;
priv->task = get_pid_task(priv->pid, PIDTYPE_PID);
if (!priv->task)
return ERR_PTR(-ESRCH);
mm = mm_for_maps(priv->task);
if (!mm || IS_ERR(mm))
return mm;
down_read(&mm->mmap_sem);
tail_vma = get_gate_vma(priv->task->mm);
priv->tail_vma = tail_vma;
/* Start with last addr hint */
vma = find_vma(mm, last_addr);
if (last_addr && vma) {
vma = vma->vm_next;
goto out;
}
/*
* Check the vma index is within the range and do
* sequential scan until m_index.
*/
vma = NULL;
if ((unsigned long)l < mm->map_count) {
vma = mm->mmap;
while (l-- && vma)
vma = vma->vm_next;
goto out;
}
if (l != mm->map_count)
tail_vma = NULL; /* After gate vma */
out:
if (vma)
return vma;
/* End of vmas has been reached */
m->version = (tail_vma != NULL)? 0: -1UL;
up_read(&mm->mmap_sem);
mmput(mm);
return tail_vma;
}
static void *m_next(struct seq_file *m, void *v, loff_t *pos)
{
struct proc_maps_private *priv = m->private;
struct vm_area_struct *vma = v;
struct vm_area_struct *tail_vma = priv->tail_vma;
(*pos)++;
if (vma && (vma != tail_vma) && vma->vm_next)
return vma->vm_next;
vma_stop(priv, vma);
return (vma != tail_vma)? tail_vma: NULL;
}
static void m_stop(struct seq_file *m, void *v)
{
struct proc_maps_private *priv = m->private;
struct vm_area_struct *vma = v;
if (!IS_ERR(vma))
vma_stop(priv, vma);
if (priv->task)
put_task_struct(priv->task);
}
static int do_maps_open(struct inode *inode, struct file *file,
const struct seq_operations *ops)
{
struct proc_maps_private *priv;
int ret = -ENOMEM;
priv = kzalloc(sizeof(*priv), GFP_KERNEL);
if (priv) {
priv->pid = proc_pid(inode);
ret = seq_open(file, ops);
if (!ret) {
struct seq_file *m = file->private_data;
m->private = priv;
} else {
kfree(priv);
}
}
return ret;
}
static void show_map_vma(struct seq_file *m, struct vm_area_struct *vma)
{
struct mm_struct *mm = vma->vm_mm;
struct file *file = vma->vm_file;
vm_flags_t flags = vma->vm_flags;
unsigned long ino = 0;
unsigned long long pgoff = 0;
unsigned long start, end;
dev_t dev = 0;
int len;
if (file) {
struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
dev = inode->i_sb->s_dev;
ino = inode->i_ino;
pgoff = ((loff_t)vma->vm_pgoff) << PAGE_SHIFT;
}
/* We don't show the stack guard page in /proc/maps */
start = vma->vm_start;
if (stack_guard_page_start(vma, start))
start += PAGE_SIZE;
end = vma->vm_end;
if (stack_guard_page_end(vma, end))
end -= PAGE_SIZE;
seq_printf(m, "%08lx-%08lx %c%c%c%c %08llx %02x:%02x %lu %n",
start,
end,
flags & VM_READ ? 'r' : '-',
flags & VM_WRITE ? 'w' : '-',
flags & VM_EXEC ? 'x' : '-',
flags & VM_MAYSHARE ? 's' : 'p',
pgoff,
MAJOR(dev), MINOR(dev), ino, &len);
/*
* Print the dentry name for named mappings, and a
* special [heap] marker for the heap:
*/
if (file) {
pad_len_spaces(m, len);
seq_path(m, &file->f_path, "\n");
} else {
const char *name = arch_vma_name(vma);
if (!name) {
if (mm) {
if (vma->vm_start <= mm->brk &&
vma->vm_end >= mm->start_brk) {
name = "[heap]";
} else if (vma->vm_start <= mm->start_stack &&
vma->vm_end >= mm->start_stack) {
name = "[stack]";
}
} else {
name = "[vdso]";
}
}
if (name) {
pad_len_spaces(m, len);
seq_puts(m, name);
}
}
seq_putc(m, '\n');
}
static int show_map(struct seq_file *m, void *v)
{
struct vm_area_struct *vma = v;
struct proc_maps_private *priv = m->private;
struct task_struct *task = priv->task;
show_map_vma(m, vma);
if (m->count < m->size) /* vma is copied successfully */
m->version = (vma != get_gate_vma(task->mm))
? vma->vm_start : 0;
return 0;
}
static const struct seq_operations proc_pid_maps_op = {
.start = m_start,
.next = m_next,
.stop = m_stop,
.show = show_map
};
static int maps_open(struct inode *inode, struct file *file)
{
return do_maps_open(inode, file, &proc_pid_maps_op);
}
const struct file_operations proc_maps_operations = {
.open = maps_open,
.read = seq_read,
.llseek = seq_lseek,
.release = seq_release_private,
};
/*
* Proportional Set Size(PSS): my share of RSS.
*
* PSS of a process is the count of pages it has in memory, where each
* page is divided by the number of processes sharing it. So if a
* process has 1000 pages all to itself, and 1000 shared with one other
* process, its PSS will be 1500.
*
* To keep (accumulated) division errors low, we adopt a 64bit
* fixed-point pss counter to minimize division errors. So (pss >>
* PSS_SHIFT) would be the real byte count.
*
* A shift of 12 before division means (assuming 4K page size):
* - 1M 3-user-pages add up to 8KB errors;
* - supports mapcount up to 2^24, or 16M;
* - supports PSS up to 2^52 bytes, or 4PB.
*/
#define PSS_SHIFT 12
#ifdef CONFIG_PROC_PAGE_MONITOR
struct mem_size_stats {
struct vm_area_struct *vma;
unsigned long resident;
unsigned long shared_clean;
unsigned long shared_dirty;
unsigned long private_clean;
unsigned long private_dirty;
unsigned long referenced;
unsigned long anonymous;
unsigned long anonymous_thp;
unsigned long swap;
u64 pss;
};
static void smaps_pte_entry(pte_t ptent, unsigned long addr,
unsigned long ptent_size, struct mm_walk *walk)
{
struct mem_size_stats *mss = walk->private;
struct vm_area_struct *vma = mss->vma;
struct page *page;
int mapcount;
if (is_swap_pte(ptent)) {
mss->swap += ptent_size;
return;
}
if (!pte_present(ptent))
return;
page = vm_normal_page(vma, addr, ptent);
if (!page)
return;
if (PageAnon(page))
mss->anonymous += ptent_size;
mss->resident += ptent_size;
/* Accumulate the size in pages that have been accessed. */
if (pte_young(ptent) || PageReferenced(page))
mss->referenced += ptent_size;
mapcount = page_mapcount(page);
if (mapcount >= 2) {
if (pte_dirty(ptent) || PageDirty(page))
mss->shared_dirty += ptent_size;
else
mss->shared_clean += ptent_size;
mss->pss += (ptent_size << PSS_SHIFT) / mapcount;
} else {
if (pte_dirty(ptent) || PageDirty(page))
mss->private_dirty += ptent_size;
else
mss->private_clean += ptent_size;
mss->pss += (ptent_size << PSS_SHIFT);
}
}
static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
struct mem_size_stats *mss = walk->private;
struct vm_area_struct *vma = mss->vma;
pte_t *pte;
spinlock_t *ptl;
spin_lock(&walk->mm->page_table_lock);
if (pmd_trans_huge(*pmd)) {
if (pmd_trans_splitting(*pmd)) {
spin_unlock(&walk->mm->page_table_lock);
wait_split_huge_page(vma->anon_vma, pmd);
} else {
smaps_pte_entry(*(pte_t *)pmd, addr,
HPAGE_PMD_SIZE, walk);
spin_unlock(&walk->mm->page_table_lock);
mss->anonymous_thp += HPAGE_PMD_SIZE;
return 0;
}
} else {
spin_unlock(&walk->mm->page_table_lock);
}
if (pmd_trans_unstable(pmd))
return 0;
/*
* The mmap_sem held all the way back in m_start() is what
* keeps khugepaged out of here and from collapsing things
* in here.
*/
pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
for (; addr != end; pte++, addr += PAGE_SIZE)
smaps_pte_entry(*pte, addr, PAGE_SIZE, walk);
pte_unmap_unlock(pte - 1, ptl);
cond_resched();
return 0;
}
static int show_smap(struct seq_file *m, void *v)
{
struct proc_maps_private *priv = m->private;
struct task_struct *task = priv->task;
struct vm_area_struct *vma = v;
struct mem_size_stats mss;
struct mm_walk smaps_walk = {
.pmd_entry = smaps_pte_range,
.mm = vma->vm_mm,
.private = &mss,
};
memset(&mss, 0, sizeof mss);
mss.vma = vma;
/* mmap_sem is held in m_start */
if (vma->vm_mm && !is_vm_hugetlb_page(vma))
walk_page_range(vma->vm_start, vma->vm_end, &smaps_walk);
show_map_vma(m, vma);
seq_printf(m,
"Size: %8lu kB\n"
"Rss: %8lu kB\n"
"Pss: %8lu kB\n"
"Shared_Clean: %8lu kB\n"
"Shared_Dirty: %8lu kB\n"
"Private_Clean: %8lu kB\n"
"Private_Dirty: %8lu kB\n"
"Referenced: %8lu kB\n"
"Anonymous: %8lu kB\n"
"AnonHugePages: %8lu kB\n"
"Swap: %8lu kB\n"
"KernelPageSize: %8lu kB\n"
"MMUPageSize: %8lu kB\n"
"Locked: %8lu kB\n",
(vma->vm_end - vma->vm_start) >> 10,
mss.resident >> 10,
(unsigned long)(mss.pss >> (10 + PSS_SHIFT)),
mss.shared_clean >> 10,
mss.shared_dirty >> 10,
mss.private_clean >> 10,
mss.private_dirty >> 10,
mss.referenced >> 10,
mss.anonymous >> 10,
mss.anonymous_thp >> 10,
mss.swap >> 10,
vma_kernel_pagesize(vma) >> 10,
vma_mmu_pagesize(vma) >> 10,
(vma->vm_flags & VM_LOCKED) ?
(unsigned long)(mss.pss >> (10 + PSS_SHIFT)) : 0);
if (m->count < m->size) /* vma is copied successfully */
m->version = (vma != get_gate_vma(task->mm))
? vma->vm_start : 0;
return 0;
}
static const struct seq_operations proc_pid_smaps_op = {
.start = m_start,
.next = m_next,
.stop = m_stop,
.show = show_smap
};
static int smaps_open(struct inode *inode, struct file *file)
{
return do_maps_open(inode, file, &proc_pid_smaps_op);
}
const struct file_operations proc_smaps_operations = {
.open = smaps_open,
.read = seq_read,
.llseek = seq_lseek,
.release = seq_release_private,
};
static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr,
unsigned long end, struct mm_walk *walk)
{
struct vm_area_struct *vma = walk->private;
pte_t *pte, ptent;
spinlock_t *ptl;
struct page *page;
split_huge_page_pmd(walk->mm, pmd);
if (pmd_trans_unstable(pmd))
return 0;
pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
for (; addr != end; pte++, addr += PAGE_SIZE) {
ptent = *pte;
if (!pte_present(ptent))
continue;
page = vm_normal_page(vma, addr, ptent);
if (!page)
continue;
if (PageReserved(page))
continue;
/* Clear accessed and referenced bits. */
ptep_test_and_clear_young(vma, addr, pte);
ClearPageReferenced(page);
}
pte_unmap_unlock(pte - 1, ptl);
cond_resched();
return 0;
}
#define CLEAR_REFS_ALL 1
#define CLEAR_REFS_ANON 2
#define CLEAR_REFS_MAPPED 3
static ssize_t clear_refs_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
struct task_struct *task;
char buffer[PROC_NUMBUF];
struct mm_struct *mm;
struct vm_area_struct *vma;
int type;
int rv;
memset(buffer, 0, sizeof(buffer));
if (count > sizeof(buffer) - 1)
count = sizeof(buffer) - 1;
if (copy_from_user(buffer, buf, count))
return -EFAULT;
rv = kstrtoint(strstrip(buffer), 10, &type);
if (rv < 0)
return rv;
if (type < CLEAR_REFS_ALL || type > CLEAR_REFS_MAPPED)
return -EINVAL;
task = get_proc_task(file->f_path.dentry->d_inode);
if (!task)
return -ESRCH;
mm = get_task_mm(task);
if (mm) {
struct mm_walk clear_refs_walk = {
.pmd_entry = clear_refs_pte_range,
.mm = mm,
};
down_read(&mm->mmap_sem);
for (vma = mm->mmap; vma; vma = vma->vm_next) {
clear_refs_walk.private = vma;
if (is_vm_hugetlb_page(vma))
continue;
/*
* Writing 1 to /proc/pid/clear_refs affects all pages.
*
* Writing 2 to /proc/pid/clear_refs only affects
* Anonymous pages.
*
* Writing 3 to /proc/pid/clear_refs only affects file
* mapped pages.
*/
if (type == CLEAR_REFS_ANON && vma->vm_file)
continue;
if (type == CLEAR_REFS_MAPPED && !vma->vm_file)
continue;
walk_page_range(vma->vm_start, vma->vm_end,
&clear_refs_walk);
}
flush_tlb_mm(mm);
up_read(&mm->mmap_sem);
mmput(mm);
}
put_task_struct(task);
return count;
}
const struct file_operations proc_clear_refs_operations = {
.write = clear_refs_write,
.llseek = noop_llseek,
};
struct pagemapread {
int pos, len;
u64 *buffer;
};
#define PM_ENTRY_BYTES sizeof(u64)
#define PM_STATUS_BITS 3
#define PM_STATUS_OFFSET (64 - PM_STATUS_BITS)
#define PM_STATUS_MASK (((1LL << PM_STATUS_BITS) - 1) << PM_STATUS_OFFSET)
#define PM_STATUS(nr) (((nr) << PM_STATUS_OFFSET) & PM_STATUS_MASK)
#define PM_PSHIFT_BITS 6
#define PM_PSHIFT_OFFSET (PM_STATUS_OFFSET - PM_PSHIFT_BITS)
#define PM_PSHIFT_MASK (((1LL << PM_PSHIFT_BITS) - 1) << PM_PSHIFT_OFFSET)
#define PM_PSHIFT(x) (((u64) (x) << PM_PSHIFT_OFFSET) & PM_PSHIFT_MASK)
#define PM_PFRAME_MASK ((1LL << PM_PSHIFT_OFFSET) - 1)
#define PM_PFRAME(x) ((x) & PM_PFRAME_MASK)
#define PM_PRESENT PM_STATUS(4LL)
#define PM_SWAP PM_STATUS(2LL)
#define PM_NOT_PRESENT PM_PSHIFT(PAGE_SHIFT)
#define PM_END_OF_BUFFER 1
static int add_to_pagemap(unsigned long addr, u64 pfn,
struct pagemapread *pm)
{
pm->buffer[pm->pos++] = pfn;
if (pm->pos >= pm->len)
return PM_END_OF_BUFFER;
return 0;
}
static int pagemap_pte_hole(unsigned long start, unsigned long end,
struct mm_walk *walk)
{
struct pagemapread *pm = walk->private;
unsigned long addr;
int err = 0;
for (addr = start; addr < end; addr += PAGE_SIZE) {
err = add_to_pagemap(addr, PM_NOT_PRESENT, pm);
if (err)
break;
}
return err;
}
static u64 swap_pte_to_pagemap_entry(pte_t pte)
{
swp_entry_t e = pte_to_swp_entry(pte);
return swp_type(e) | (swp_offset(e) << MAX_SWAPFILES_SHIFT);
}
static u64 pte_to_pagemap_entry(pte_t pte)
{
u64 pme = 0;
if (is_swap_pte(pte))
pme = PM_PFRAME(swap_pte_to_pagemap_entry(pte))
| PM_PSHIFT(PAGE_SHIFT) | PM_SWAP;
else if (pte_present(pte))
pme = PM_PFRAME(pte_pfn(pte))
| PM_PSHIFT(PAGE_SHIFT) | PM_PRESENT;
return pme;
}
static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
struct vm_area_struct *vma;
struct pagemapread *pm = walk->private;
pte_t *pte;
int err = 0;
split_huge_page_pmd(walk->mm, pmd);
if (pmd_trans_unstable(pmd))
return 0;
/* find the first VMA at or above 'addr' */
vma = find_vma(walk->mm, addr);
for (; addr != end; addr += PAGE_SIZE) {
u64 pfn = PM_NOT_PRESENT;
/* check to see if we've left 'vma' behind
* and need a new, higher one */
if (vma && (addr >= vma->vm_end))
vma = find_vma(walk->mm, addr);
/* check that 'vma' actually covers this address,
* and that it isn't a huge page vma */
if (vma && (vma->vm_start <= addr) &&
!is_vm_hugetlb_page(vma)) {
pte = pte_offset_map(pmd, addr);
pfn = pte_to_pagemap_entry(*pte);
/* unmap before userspace copy */
pte_unmap(pte);
}
err = add_to_pagemap(addr, pfn, pm);
if (err)
return err;
}
cond_resched();
return err;
}
#ifdef CONFIG_HUGETLB_PAGE
static u64 huge_pte_to_pagemap_entry(pte_t pte, int offset)
{
u64 pme = 0;
if (pte_present(pte))
pme = PM_PFRAME(pte_pfn(pte) + offset)
| PM_PSHIFT(PAGE_SHIFT) | PM_PRESENT;
return pme;
}
/* This function walks within one hugetlb entry in the single call */
static int pagemap_hugetlb_range(pte_t *pte, unsigned long hmask,
unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
struct pagemapread *pm = walk->private;
int err = 0;
u64 pfn;
for (; addr != end; addr += PAGE_SIZE) {
int offset = (addr & ~hmask) >> PAGE_SHIFT;
pfn = huge_pte_to_pagemap_entry(*pte, offset);
err = add_to_pagemap(addr, pfn, pm);
if (err)
return err;
}
cond_resched();
return err;
}
#endif /* HUGETLB_PAGE */
/*
* /proc/pid/pagemap - an array mapping virtual pages to pfns
*
* For each page in the address space, this file contains one 64-bit entry
* consisting of the following:
*
* Bits 0-55 page frame number (PFN) if present
* Bits 0-4 swap type if swapped
* Bits 5-55 swap offset if swapped
* Bits 55-60 page shift (page size = 1<<page shift)
* Bit 61 reserved for future use
* Bit 62 page swapped
* Bit 63 page present
*
* If the page is not present but in swap, then the PFN contains an
* encoding of the swap file number and the page's offset into the
* swap. Unmapped pages return a null PFN. This allows determining
* precisely which pages are mapped (or in swap) and comparing mapped
* pages between processes.
*
* Efficient users of this interface will use /proc/pid/maps to
* determine which areas of memory are actually mapped and llseek to
* skip over unmapped regions.
*/
#define PAGEMAP_WALK_SIZE (PMD_SIZE)
#define PAGEMAP_WALK_MASK (PMD_MASK)
static ssize_t pagemap_read(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
{
struct task_struct *task = get_proc_task(file->f_path.dentry->d_inode);
struct mm_struct *mm;
struct pagemapread pm;
int ret = -ESRCH;
struct mm_walk pagemap_walk = {};
unsigned long src;
unsigned long svpfn;
unsigned long start_vaddr;
unsigned long end_vaddr;
int copied = 0;
if (!task)
goto out;
ret = -EINVAL;
/* file position must be aligned */
if ((*ppos % PM_ENTRY_BYTES) || (count % PM_ENTRY_BYTES))
goto out_task;
ret = 0;
if (!count)
goto out_task;
pm.len = PM_ENTRY_BYTES * (PAGEMAP_WALK_SIZE >> PAGE_SHIFT);
pm.buffer = kmalloc(pm.len, GFP_TEMPORARY);
ret = -ENOMEM;
if (!pm.buffer)
goto out_task;
mm = mm_for_maps(task);
ret = PTR_ERR(mm);
if (!mm || IS_ERR(mm))
goto out_free;
pagemap_walk.pmd_entry = pagemap_pte_range;
pagemap_walk.pte_hole = pagemap_pte_hole;
#ifdef CONFIG_HUGETLB_PAGE
pagemap_walk.hugetlb_entry = pagemap_hugetlb_range;
#endif
pagemap_walk.mm = mm;
pagemap_walk.private = &pm;
src = *ppos;
svpfn = src / PM_ENTRY_BYTES;
start_vaddr = svpfn << PAGE_SHIFT;
end_vaddr = TASK_SIZE_OF(task);
/* watch out for wraparound */
if (svpfn > TASK_SIZE_OF(task) >> PAGE_SHIFT)
start_vaddr = end_vaddr;
/*
* The odds are that this will stop walking way
* before end_vaddr, because the length of the
* user buffer is tracked in "pm", and the walk
* will stop when we hit the end of the buffer.
*/
ret = 0;
while (count && (start_vaddr < end_vaddr)) {
int len;
unsigned long end;
pm.pos = 0;
end = (start_vaddr + PAGEMAP_WALK_SIZE) & PAGEMAP_WALK_MASK;
/* overflow ? */
if (end < start_vaddr || end > end_vaddr)
end = end_vaddr;
down_read(&mm->mmap_sem);
ret = walk_page_range(start_vaddr, end, &pagemap_walk);
up_read(&mm->mmap_sem);
start_vaddr = end;
len = min(count, PM_ENTRY_BYTES * pm.pos);
if (copy_to_user(buf, pm.buffer, len)) {
ret = -EFAULT;
goto out_mm;
}
copied += len;
buf += len;
count -= len;
}
*ppos += copied;
if (!ret || ret == PM_END_OF_BUFFER)
ret = copied;
out_mm:
mmput(mm);
out_free:
kfree(pm.buffer);
out_task:
put_task_struct(task);
out:
return ret;
}
const struct file_operations proc_pagemap_operations = {
.llseek = mem_lseek, /* borrow this */
.read = pagemap_read,
};
#endif /* CONFIG_PROC_PAGE_MONITOR */
#ifdef CONFIG_NUMA
struct numa_maps {
struct vm_area_struct *vma;
unsigned long pages;
unsigned long anon;
unsigned long active;
unsigned long writeback;
unsigned long mapcount_max;
unsigned long dirty;
unsigned long swapcache;
unsigned long node[MAX_NUMNODES];
};
struct numa_maps_private {
struct proc_maps_private proc_maps;
struct numa_maps md;
};
static void gather_stats(struct page *page, struct numa_maps *md, int pte_dirty,
unsigned long nr_pages)
{
int count = page_mapcount(page);
md->pages += nr_pages;
if (pte_dirty || PageDirty(page))
md->dirty += nr_pages;
if (PageSwapCache(page))
md->swapcache += nr_pages;
if (PageActive(page) || PageUnevictable(page))
md->active += nr_pages;
if (PageWriteback(page))
md->writeback += nr_pages;
if (PageAnon(page))
md->anon += nr_pages;
if (count > md->mapcount_max)
md->mapcount_max = count;
md->node[page_to_nid(page)] += nr_pages;
}
static struct page *can_gather_numa_stats(pte_t pte, struct vm_area_struct *vma,
unsigned long addr)
{
struct page *page;
int nid;
if (!pte_present(pte))
return NULL;
page = vm_normal_page(vma, addr, pte);
if (!page)
return NULL;
if (PageReserved(page))
return NULL;
nid = page_to_nid(page);
if (!node_isset(nid, node_states[N_HIGH_MEMORY]))
return NULL;
return page;
}
static int gather_pte_stats(pmd_t *pmd, unsigned long addr,
unsigned long end, struct mm_walk *walk)
{
struct numa_maps *md;
spinlock_t *ptl;
pte_t *orig_pte;
pte_t *pte;
md = walk->private;
spin_lock(&walk->mm->page_table_lock);
if (pmd_trans_huge(*pmd)) {
if (pmd_trans_splitting(*pmd)) {
spin_unlock(&walk->mm->page_table_lock);
wait_split_huge_page(md->vma->anon_vma, pmd);
} else {
pte_t huge_pte = *(pte_t *)pmd;
struct page *page;
page = can_gather_numa_stats(huge_pte, md->vma, addr);
if (page)
gather_stats(page, md, pte_dirty(huge_pte),
HPAGE_PMD_SIZE/PAGE_SIZE);
spin_unlock(&walk->mm->page_table_lock);
return 0;
}
} else {
spin_unlock(&walk->mm->page_table_lock);
}
if (pmd_trans_unstable(pmd))
return 0;
orig_pte = pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
do {
struct page *page = can_gather_numa_stats(*pte, md->vma, addr);
if (!page)
continue;
gather_stats(page, md, pte_dirty(*pte), 1);
} while (pte++, addr += PAGE_SIZE, addr != end);
pte_unmap_unlock(orig_pte, ptl);
return 0;
}
#ifdef CONFIG_HUGETLB_PAGE
static int gather_hugetbl_stats(pte_t *pte, unsigned long hmask,
unsigned long addr, unsigned long end, struct mm_walk *walk)
{
struct numa_maps *md;
struct page *page;
if (pte_none(*pte))
return 0;
page = pte_page(*pte);
if (!page)
return 0;
md = walk->private;
gather_stats(page, md, pte_dirty(*pte), 1);
return 0;
}
#else
static int gather_hugetbl_stats(pte_t *pte, unsigned long hmask,
unsigned long addr, unsigned long end, struct mm_walk *walk)
{
return 0;
}
#endif
/*
* Display pages allocated per node and memory policy via /proc.
*/
static int show_numa_map(struct seq_file *m, void *v)
{
struct numa_maps_private *numa_priv = m->private;
struct proc_maps_private *proc_priv = &numa_priv->proc_maps;
struct vm_area_struct *vma = v;
struct numa_maps *md = &numa_priv->md;
struct file *file = vma->vm_file;
struct mm_struct *mm = vma->vm_mm;
struct mm_walk walk = {};
struct mempolicy *pol;
int n;
char buffer[50];
if (!mm)
return 0;
/* Ensure we start with an empty set of numa_maps statistics. */
memset(md, 0, sizeof(*md));
md->vma = vma;
walk.hugetlb_entry = gather_hugetbl_stats;
walk.pmd_entry = gather_pte_stats;
walk.private = md;
walk.mm = mm;
pol = get_vma_policy(proc_priv->task, vma, vma->vm_start);
mpol_to_str(buffer, sizeof(buffer), pol, 0);
mpol_cond_put(pol);
seq_printf(m, "%08lx %s", vma->vm_start, buffer);
if (file) {
seq_printf(m, " file=");
seq_path(m, &file->f_path, "\n\t= ");
} else if (vma->vm_start <= mm->brk && vma->vm_end >= mm->start_brk) {
seq_printf(m, " heap");
} else if (vma->vm_start <= mm->start_stack &&
vma->vm_end >= mm->start_stack) {
seq_printf(m, " stack");
}
if (is_vm_hugetlb_page(vma))
seq_printf(m, " huge");
walk_page_range(vma->vm_start, vma->vm_end, &walk);
if (!md->pages)
goto out;
if (md->anon)
seq_printf(m, " anon=%lu", md->anon);
if (md->dirty)
seq_printf(m, " dirty=%lu", md->dirty);
if (md->pages != md->anon && md->pages != md->dirty)
seq_printf(m, " mapped=%lu", md->pages);
if (md->mapcount_max > 1)
seq_printf(m, " mapmax=%lu", md->mapcount_max);
if (md->swapcache)
seq_printf(m, " swapcache=%lu", md->swapcache);
if (md->active < md->pages && !is_vm_hugetlb_page(vma))
seq_printf(m, " active=%lu", md->active);
if (md->writeback)
seq_printf(m, " writeback=%lu", md->writeback);
for_each_node_state(n, N_HIGH_MEMORY)
if (md->node[n])
seq_printf(m, " N%d=%lu", n, md->node[n]);
out:
seq_putc(m, '\n');
if (m->count < m->size)
m->version = (vma != proc_priv->tail_vma) ? vma->vm_start : 0;
return 0;
}
static const struct seq_operations proc_pid_numa_maps_op = {
.start = m_start,
.next = m_next,
.stop = m_stop,
.show = show_numa_map,
};
static int numa_maps_open(struct inode *inode, struct file *file)
{
struct numa_maps_private *priv;
int ret = -ENOMEM;
priv = kzalloc(sizeof(*priv), GFP_KERNEL);
if (priv) {
priv->proc_maps.pid = proc_pid(inode);
ret = seq_open(file, &proc_pid_numa_maps_op);
if (!ret) {
struct seq_file *m = file->private_data;
m->private = priv;
} else {
kfree(priv);
}
}
return ret;
}
const struct file_operations proc_numa_maps_operations = {
.open = numa_maps_open,
.read = seq_read,
.llseek = seq_lseek,
.release = seq_release_private,
};
#endif /* CONFIG_NUMA */
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