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![David Hildenbrand](/assets/img/avatar_default.png)
Patch series "mm/nommu: don't use VM_MAYSHARE for MAP_PRIVATE mappings". Trying to reduce the confusion around VM_SHARED and VM_MAYSHARE first requires !CONFIG_MMU to stop using VM_MAYSHARE for MAP_PRIVATE mappings. CONFIG_MMU only sets VM_MAYSHARE for MAP_SHARED mappings. This paves the way for further VM_MAYSHARE and VM_SHARED cleanups: for example, renaming VM_MAYSHARED to VM_MAP_SHARED to make it cleaner what is actually means. Let's first get the weird case out of the way and not use VM_MAYSHARE in MAP_PRIVATE mappings, using a new VM_MAYOVERLAY flag instead. This patch (of 3): We want to stop using VM_MAYSHARE in private mappings to pave the way for clarifying the semantics of VM_MAYSHARE vs. VM_SHARED and reduce the confusion. While CONFIG_MMU uses VM_MAYSHARE to represent MAP_SHARED, !CONFIG_MMU also sets VM_MAYSHARE for selected R/O private file mappings that are an effective overlay of a file mapping. Let's factor out all relevant VM_MAYSHARE checks in !CONFIG_MMU code into is_nommu_shared_mapping() first. Note that whenever VM_SHARED is set, VM_MAYSHARE must be set as well (unless there is a serious BUG). So there is not need to test for VM_SHARED manually. No functional change intended. Link: https://lkml.kernel.org/r/20230102160856.500584-1-david@redhat.com Link: https://lkml.kernel.org/r/20230102160856.500584-2-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: David Hildenbrand <david@redhat.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Jens Axboe <axboe@kernel.dk> Cc: Nicolas Pitre <nico@fluxnic.net> Cc: Pavel Begunkov <asml.silence@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
299 lines
6.4 KiB
C
299 lines
6.4 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/mm.h>
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#include <linux/file.h>
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#include <linux/fdtable.h>
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#include <linux/fs_struct.h>
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#include <linux/mount.h>
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#include <linux/ptrace.h>
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#include <linux/slab.h>
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#include <linux/seq_file.h>
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#include <linux/sched/mm.h>
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#include "internal.h"
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/*
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* Logic: we've got two memory sums for each process, "shared", and
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* "non-shared". Shared memory may get counted more than once, for
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* each process that owns it. Non-shared memory is counted
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* accurately.
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*/
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void task_mem(struct seq_file *m, struct mm_struct *mm)
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{
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VMA_ITERATOR(vmi, mm, 0);
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struct vm_area_struct *vma;
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struct vm_region *region;
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unsigned long bytes = 0, sbytes = 0, slack = 0, size;
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mmap_read_lock(mm);
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for_each_vma(vmi, vma) {
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bytes += kobjsize(vma);
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region = vma->vm_region;
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if (region) {
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size = kobjsize(region);
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size += region->vm_end - region->vm_start;
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} else {
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size = vma->vm_end - vma->vm_start;
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}
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if (atomic_read(&mm->mm_count) > 1 ||
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is_nommu_shared_mapping(vma->vm_flags)) {
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sbytes += size;
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} else {
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bytes += size;
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if (region)
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slack = region->vm_end - vma->vm_end;
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}
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}
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if (atomic_read(&mm->mm_count) > 1)
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sbytes += kobjsize(mm);
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else
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bytes += kobjsize(mm);
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if (current->fs && current->fs->users > 1)
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sbytes += kobjsize(current->fs);
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else
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bytes += kobjsize(current->fs);
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if (current->files && atomic_read(¤t->files->count) > 1)
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sbytes += kobjsize(current->files);
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else
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bytes += kobjsize(current->files);
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if (current->sighand && refcount_read(¤t->sighand->count) > 1)
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sbytes += kobjsize(current->sighand);
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else
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bytes += kobjsize(current->sighand);
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bytes += kobjsize(current); /* includes kernel stack */
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seq_printf(m,
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"Mem:\t%8lu bytes\n"
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"Slack:\t%8lu bytes\n"
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"Shared:\t%8lu bytes\n",
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bytes, slack, sbytes);
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mmap_read_unlock(mm);
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}
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unsigned long task_vsize(struct mm_struct *mm)
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{
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VMA_ITERATOR(vmi, mm, 0);
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struct vm_area_struct *vma;
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unsigned long vsize = 0;
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mmap_read_lock(mm);
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for_each_vma(vmi, vma)
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vsize += vma->vm_end - vma->vm_start;
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mmap_read_unlock(mm);
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return vsize;
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}
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unsigned long task_statm(struct mm_struct *mm,
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unsigned long *shared, unsigned long *text,
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unsigned long *data, unsigned long *resident)
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{
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VMA_ITERATOR(vmi, mm, 0);
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struct vm_area_struct *vma;
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struct vm_region *region;
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unsigned long size = kobjsize(mm);
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mmap_read_lock(mm);
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for_each_vma(vmi, vma) {
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size += kobjsize(vma);
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region = vma->vm_region;
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if (region) {
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size += kobjsize(region);
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size += region->vm_end - region->vm_start;
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}
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}
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*text = (PAGE_ALIGN(mm->end_code) - (mm->start_code & PAGE_MASK))
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>> PAGE_SHIFT;
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*data = (PAGE_ALIGN(mm->start_stack) - (mm->start_data & PAGE_MASK))
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>> PAGE_SHIFT;
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mmap_read_unlock(mm);
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size >>= PAGE_SHIFT;
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size += *text + *data;
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*resident = size;
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return size;
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}
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static int is_stack(struct vm_area_struct *vma)
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{
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struct mm_struct *mm = vma->vm_mm;
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/*
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* We make no effort to guess what a given thread considers to be
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* its "stack". It's not even well-defined for programs written
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* languages like Go.
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*/
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return vma->vm_start <= mm->start_stack &&
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vma->vm_end >= mm->start_stack;
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}
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/*
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* display a single VMA to a sequenced file
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*/
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static int nommu_vma_show(struct seq_file *m, struct vm_area_struct *vma)
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{
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struct mm_struct *mm = vma->vm_mm;
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unsigned long ino = 0;
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struct file *file;
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dev_t dev = 0;
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int flags;
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unsigned long long pgoff = 0;
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flags = vma->vm_flags;
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file = vma->vm_file;
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if (file) {
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struct inode *inode = file_inode(vma->vm_file);
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dev = inode->i_sb->s_dev;
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ino = inode->i_ino;
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pgoff = (loff_t)vma->vm_pgoff << PAGE_SHIFT;
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}
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seq_setwidth(m, 25 + sizeof(void *) * 6 - 1);
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seq_printf(m,
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"%08lx-%08lx %c%c%c%c %08llx %02x:%02x %lu ",
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vma->vm_start,
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vma->vm_end,
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flags & VM_READ ? 'r' : '-',
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flags & VM_WRITE ? 'w' : '-',
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flags & VM_EXEC ? 'x' : '-',
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flags & VM_MAYSHARE ? flags & VM_SHARED ? 'S' : 's' : 'p',
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pgoff,
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MAJOR(dev), MINOR(dev), ino);
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if (file) {
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seq_pad(m, ' ');
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seq_file_path(m, file, "");
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} else if (mm && is_stack(vma)) {
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seq_pad(m, ' ');
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seq_puts(m, "[stack]");
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}
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seq_putc(m, '\n');
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return 0;
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}
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/*
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* display mapping lines for a particular process's /proc/pid/maps
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*/
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static int show_map(struct seq_file *m, void *_p)
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{
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return nommu_vma_show(m, _p);
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}
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static void *m_start(struct seq_file *m, loff_t *pos)
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{
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struct proc_maps_private *priv = m->private;
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struct mm_struct *mm;
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struct vm_area_struct *vma;
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unsigned long addr = *pos;
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/* See m_next(). Zero at the start or after lseek. */
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if (addr == -1UL)
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return NULL;
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/* pin the task and mm whilst we play with them */
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priv->task = get_proc_task(priv->inode);
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if (!priv->task)
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return ERR_PTR(-ESRCH);
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mm = priv->mm;
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if (!mm || !mmget_not_zero(mm))
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return NULL;
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if (mmap_read_lock_killable(mm)) {
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mmput(mm);
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return ERR_PTR(-EINTR);
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}
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/* start the next element from addr */
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vma = find_vma(mm, addr);
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if (vma)
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return vma;
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mmap_read_unlock(mm);
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mmput(mm);
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return NULL;
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}
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static void m_stop(struct seq_file *m, void *_vml)
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{
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struct proc_maps_private *priv = m->private;
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if (!IS_ERR_OR_NULL(_vml)) {
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mmap_read_unlock(priv->mm);
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mmput(priv->mm);
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}
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if (priv->task) {
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put_task_struct(priv->task);
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priv->task = NULL;
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}
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}
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static void *m_next(struct seq_file *m, void *_p, loff_t *pos)
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{
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struct vm_area_struct *vma = _p;
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*pos = vma->vm_end;
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return find_vma(vma->vm_mm, vma->vm_end);
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}
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static const struct seq_operations proc_pid_maps_ops = {
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.start = m_start,
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.next = m_next,
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.stop = m_stop,
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.show = show_map
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};
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static int maps_open(struct inode *inode, struct file *file,
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const struct seq_operations *ops)
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{
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struct proc_maps_private *priv;
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priv = __seq_open_private(file, ops, sizeof(*priv));
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if (!priv)
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return -ENOMEM;
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priv->inode = inode;
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priv->mm = proc_mem_open(inode, PTRACE_MODE_READ);
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if (IS_ERR(priv->mm)) {
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int err = PTR_ERR(priv->mm);
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seq_release_private(inode, file);
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return err;
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}
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return 0;
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}
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static int map_release(struct inode *inode, struct file *file)
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{
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struct seq_file *seq = file->private_data;
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struct proc_maps_private *priv = seq->private;
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if (priv->mm)
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mmdrop(priv->mm);
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return seq_release_private(inode, file);
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}
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static int pid_maps_open(struct inode *inode, struct file *file)
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{
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return maps_open(inode, file, &proc_pid_maps_ops);
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}
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const struct file_operations proc_pid_maps_operations = {
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.open = pid_maps_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = map_release,
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};
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