// SPDX-License-Identifier: GPL-2.0

#include <linux/mm.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/fs_struct.h>
#include <linux/mount.h>
#include <linux/ptrace.h>
#include <linux/slab.h>
#include <linux/seq_file.h>
#include <linux/sched/mm.h>

#include "internal.h"

/*
 * Logic: we've got two memory sums for each process, "shared", and
 * "non-shared". Shared memory may get counted more than once, for
 * each process that owns it. Non-shared memory is counted
 * accurately.
 */
void task_mem(struct seq_file *m, struct mm_struct *mm)
{
        struct vm_area_struct *vma;
        struct vm_region *region;
        struct rb_node *p;
        unsigned long bytes = 0, sbytes = 0, slack = 0, size;
        
        down_read(&mm->mmap_sem);
        for (p = rb_first(&mm->mm_rb); p; p = rb_next(p)) {
                vma = rb_entry(p, struct vm_area_struct, vm_rb);

                bytes += kobjsize(vma);

                region = vma->vm_region;
                if (region) {
                        size = kobjsize(region);
                        size += region->vm_end - region->vm_start;
                } else {
                        size = vma->vm_end - vma->vm_start;
                }

                if (atomic_read(&mm->mm_count) > 1 ||
                    vma->vm_flags & VM_MAYSHARE) {
                        sbytes += size;
                } else {
                        bytes += size;
                        if (region)
                                slack = region->vm_end - vma->vm_end;
                }
        }

        if (atomic_read(&mm->mm_count) > 1)
                sbytes += kobjsize(mm);
        else
                bytes += kobjsize(mm);
        
        if (current->fs && current->fs->users > 1)
                sbytes += kobjsize(current->fs);
        else
                bytes += kobjsize(current->fs);

        if (current->files && atomic_read(&current->files->count) > 1)
                sbytes += kobjsize(current->files);
        else
                bytes += kobjsize(current->files);

        if (current->sighand && refcount_read(&current->sighand->count) > 1)
                sbytes += kobjsize(current->sighand);
        else
                bytes += kobjsize(current->sighand);

        bytes += kobjsize(current); /* includes kernel stack */

        seq_printf(m,
                "Mem:\t%8lu bytes\n"
                "Slack:\t%8lu bytes\n"
                "Shared:\t%8lu bytes\n",
                bytes, slack, sbytes);

        up_read(&mm->mmap_sem);
}

unsigned long task_vsize(struct mm_struct *mm)
{
        struct vm_area_struct *vma;
        struct rb_node *p;
        unsigned long vsize = 0;

        down_read(&mm->mmap_sem);
        for (p = rb_first(&mm->mm_rb); p; p = rb_next(p)) {
                vma = rb_entry(p, struct vm_area_struct, vm_rb);
                vsize += vma->vm_end - vma->vm_start;
        }
        up_read(&mm->mmap_sem);
        return vsize;
}

unsigned long task_statm(struct mm_struct *mm,
                         unsigned long *shared, unsigned long *text,
                         unsigned long *data, unsigned long *resident)
{
        struct vm_area_struct *vma;
        struct vm_region *region;
        struct rb_node *p;
        unsigned long size = kobjsize(mm);

        down_read(&mm->mmap_sem);
        for (p = rb_first(&mm->mm_rb); p; p = rb_next(p)) {
                vma = rb_entry(p, struct vm_area_struct, vm_rb);
                size += kobjsize(vma);
                region = vma->vm_region;
                if (region) {
                        size += kobjsize(region);
                        size += region->vm_end - region->vm_start;
                }
        }

        *text = (PAGE_ALIGN(mm->end_code) - (mm->start_code & PAGE_MASK))
                >> PAGE_SHIFT;
        *data = (PAGE_ALIGN(mm->start_stack) - (mm->start_data & PAGE_MASK))
                >> PAGE_SHIFT;
        up_read(&mm->mmap_sem);
        size >>= PAGE_SHIFT;
        size += *text + *data;
        *resident = size;
        return size;
}

static int is_stack(struct vm_area_struct *vma)
{
        struct mm_struct *mm = vma->vm_mm;

        /*
         * We make no effort to guess what a given thread considers to be
         * its "stack".  It's not even well-defined for programs written
         * languages like Go.
         */
        return vma->vm_start <= mm->start_stack &&
                vma->vm_end >= mm->start_stack;
}

/*
 * display a single VMA to a sequenced file
 */
static int nommu_vma_show(struct seq_file *m, struct vm_area_struct *vma)
{
        struct mm_struct *mm = vma->vm_mm;
        unsigned long ino = 0;
        struct file *file;
        dev_t dev = 0;
        int flags;
        unsigned long long pgoff = 0;

        flags = vma->vm_flags;
        file = vma->vm_file;

        if (file) {
                struct inode *inode = file_inode(vma->vm_file);
                dev = inode->i_sb->s_dev;
                ino = inode->i_ino;
                pgoff = (loff_t)vma->vm_pgoff << PAGE_SHIFT;
        }

        seq_setwidth(m, 25 + sizeof(void *) * 6 - 1);
        seq_printf(m,
                   "%08lx-%08lx %c%c%c%c %08llx %02x:%02x %lu ",
                   vma->vm_start,
                   vma->vm_end,
                   flags & VM_READ ? 'r' : '-',
                   flags & VM_WRITE ? 'w' : '-',
                   flags & VM_EXEC ? 'x' : '-',
                   flags & VM_MAYSHARE ? flags & VM_SHARED ? 'S' : 's' : 'p',
                   pgoff,
                   MAJOR(dev), MINOR(dev), ino);

        if (file) {
                seq_pad(m, ' ');
                seq_file_path(m, file, "");
        } else if (mm && is_stack(vma)) {
                seq_pad(m, ' ');
                seq_puts(m, "[stack]");
        }

        seq_putc(m, '\n');
        return 0;
}

/*
 * display mapping lines for a particular process's /proc/pid/maps
 */
static int show_map(struct seq_file *m, void *_p)
{
        struct rb_node *p = _p;

        return nommu_vma_show(m, rb_entry(p, struct vm_area_struct, vm_rb));
}

static void *m_start(struct seq_file *m, loff_t *pos)
{
        struct proc_maps_private *priv = m->private;
        struct mm_struct *mm;
        struct rb_node *p;
        loff_t n = *pos;

        /* pin the task and mm whilst we play with them */
        priv->task = get_proc_task(priv->inode);
        if (!priv->task)
                return ERR_PTR(-ESRCH);

        mm = priv->mm;
        if (!mm || !mmget_not_zero(mm))
                return NULL;

        if (down_read_killable(&mm->mmap_sem)) {
                mmput(mm);
                return ERR_PTR(-EINTR);
        }

        /* start from the Nth VMA */
        for (p = rb_first(&mm->mm_rb); p; p = rb_next(p))
                if (n-- == 0)
                        return p;

        up_read(&mm->mmap_sem);
        mmput(mm);
        return NULL;
}

static void m_stop(struct seq_file *m, void *_vml)
{
        struct proc_maps_private *priv = m->private;

        if (!IS_ERR_OR_NULL(_vml)) {
                up_read(&priv->mm->mmap_sem);
                mmput(priv->mm);
        }
        if (priv->task) {
                put_task_struct(priv->task);
                priv->task = NULL;
        }
}

static void *m_next(struct seq_file *m, void *_p, loff_t *pos)
{
        struct rb_node *p = _p;

        (*pos)++;
        return p ? rb_next(p) : NULL;
}

static const struct seq_operations proc_pid_maps_ops = {
        .start  = m_start,
        .next   = m_next,
        .stop   = m_stop,
        .show   = show_map
};

static int maps_open(struct inode *inode, struct file *file,
                     const struct seq_operations *ops)
{
        struct proc_maps_private *priv;

        priv = __seq_open_private(file, ops, sizeof(*priv));
        if (!priv)
                return -ENOMEM;

        priv->inode = inode;
        priv->mm = proc_mem_open(inode, PTRACE_MODE_READ);
        if (IS_ERR(priv->mm)) {
                int err = PTR_ERR(priv->mm);

                seq_release_private(inode, file);
                return err;
        }

        return 0;
}


static int map_release(struct inode *inode, struct file *file)
{
        struct seq_file *seq = file->private_data;
        struct proc_maps_private *priv = seq->private;

        if (priv->mm)
                mmdrop(priv->mm);

        return seq_release_private(inode, file);
}

static int pid_maps_open(struct inode *inode, struct file *file)
{
        return maps_open(inode, file, &proc_pid_maps_ops);
}

const struct file_operations proc_pid_maps_operations = {
        .open           = pid_maps_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = map_release,
};