[PATCH 0/1] proc: Introduce the /proc/<pid>/mfd/ directory
Pavel Emelyanov
xemul at parallels.com
Fri Jul 15 06:45:46 PDT 2011
This one behaves similarly to the /proc/<pid>/fd/ one - it contains symlinks
one for each mapping with file, the name of a symlink is vma->vm_start, the
target is the file. Opening a symlink results in a file that point exactly
to the same inode as them vma's one.
This thing is aimed to help checkpointing processes.
Signed-off-by: Pavel Emelyanov <xemul at parallels.com>
---
fs/proc/base.c | 204 +++++++++++++++++++++++++++++++++++++++++++++++
include/linux/proc_fs.h | 5 +-
2 files changed, 208 insertions(+), 1 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index dfa5327..633af12 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1995,6 +1995,49 @@ static int proc_fd_link(struct inode *inode, struct path *path)
return proc_fd_info(inode, path, NULL);
}
+static int proc_mfd_get_link(struct inode *inode, struct path *path)
+{
+ struct task_struct *task;
+ struct vm_area_struct *vma;
+ struct mm_struct *mm;
+ unsigned long vm_start;
+ int rc = -ENOENT;
+
+ task = get_proc_task(inode);
+ if (!task)
+ goto out;
+
+ mm = get_task_mm(task);
+ put_task_struct(task);
+
+ if (!mm)
+ goto out;
+
+ vm_start = PROC_I(inode)->vm_start;
+
+ down_read(&mm->mmap_sem);
+ for (vma = mm->mmap; vma; vma = vma->vm_next) {
+ if (vma->vm_start < vm_start)
+ continue;
+ if (vma->vm_start > vm_start)
+ break;
+ if (!vma->vm_file)
+ break;
+
+ *path = vma->vm_file->f_path;
+ path_get(path);
+
+ rc = 0;
+ break;
+ }
+
+ up_read(&mm->mmap_sem);
+ mmput(mm);
+
+out:
+ return rc;
+}
+
static int tid_fd_revalidate(struct dentry *dentry, struct nameidata *nd)
{
struct inode *inode;
@@ -2213,6 +2256,115 @@ static const struct file_operations proc_fd_operations = {
.llseek = default_llseek,
};
+static const struct dentry_operations tid_mfd_dentry_operations = {
+ .d_delete = pid_delete_dentry,
+};
+
+static struct dentry *proc_mfd_instantiate(struct inode *dir, struct dentry *dentry,
+ struct task_struct *task, const void *ptr)
+{
+ const struct vm_area_struct *vma = ptr;
+ struct file *file = vma->vm_file;
+ struct proc_inode *ei;
+ struct inode *inode;
+
+ if (!file)
+ return ERR_PTR(-ENOENT);
+
+ inode = proc_pid_make_inode(dir->i_sb, task);
+ if (!inode)
+ return ERR_PTR(-ENOENT);
+
+ ei = PROC_I(inode);
+ ei->vm_start = vma->vm_start;
+ ei->op.proc_get_link = proc_mfd_get_link;
+
+ inode->i_op = &proc_pid_link_inode_operations;
+ inode->i_size = 64;
+ inode->i_mode = S_IFLNK;
+
+ if (file->f_mode & FMODE_READ)
+ inode->i_mode |= S_IRUSR | S_IXUSR;
+ if (file->f_mode & FMODE_WRITE)
+ inode->i_mode |= S_IWUSR | S_IXUSR;
+
+ d_set_d_op(dentry, &tid_mfd_dentry_operations);
+ d_add(dentry, inode);
+
+ return NULL;
+}
+
+static int proc_mfd_readdir(struct file *filp, void *dirent, filldir_t filldir)
+{
+ struct dentry *dentry = filp->f_path.dentry;
+ struct inode *inode = dentry->d_inode;
+ struct vm_area_struct *vma;
+ struct task_struct *task;
+ struct mm_struct *mm;
+ unsigned int vmai;
+ ino_t ino;
+ int ret;
+
+ ret = -ENOENT;
+ task = get_proc_task(inode);
+ if (!task)
+ goto out_no_task;
+
+ ret = -EPERM;
+ if (!ptrace_may_access(task, PTRACE_MODE_READ))
+ goto out;
+
+ ret = 0;
+ switch (filp->f_pos) {
+ case 0:
+ ino = inode->i_ino;
+ if (filldir(dirent, ".", 1, 0, ino, DT_DIR) < 0)
+ goto out;
+ filp->f_pos++;
+ case 1:
+ ino = parent_ino(dentry);
+ if (filldir(dirent, "..", 2, 1, ino, DT_DIR) < 0)
+ goto out;
+ filp->f_pos++;
+ default:
+ mm = get_task_mm(task);
+ if (!mm)
+ goto out;
+ down_read(&mm->mmap_sem);
+ for (vma = mm->mmap, vmai = 2; vma; vma = vma->vm_next) {
+ char name[2 + 16 + 1];
+ int len;
+
+ if (!vma->vm_file)
+ continue;
+
+ vmai++;
+ if (vmai < filp->f_pos)
+ continue;
+
+ filp->f_pos++;
+ len = snprintf(name, sizeof(name), "0x%lx", vma->vm_start);
+ if (proc_fill_cache(filp, dirent, filldir,
+ name, len, proc_mfd_instantiate,
+ task, vma) < 0)
+ break;
+ }
+ up_read(&mm->mmap_sem);
+ mmput(mm);
+ }
+
+out:
+ put_task_struct(task);
+out_no_task:
+ return ret;
+}
+
+static const struct file_operations proc_mfd_operations = {
+ .read = generic_read_dir,
+ .readdir = proc_mfd_readdir,
+ .llseek = default_llseek,
+};
+
/*
* /proc/pid/fd needs a special permission handler so that a process can still
* access /proc/self/fd after it has executed a setuid().
@@ -2240,6 +2392,57 @@ static const struct inode_operations proc_fd_inode_operations = {
.setattr = proc_setattr,
};
+static struct dentry *proc_mfd_lookup(struct inode *dir,
+ struct dentry *dentry, struct nameidata *nd)
+{
+ struct task_struct *task;
+ unsigned long vm_start;
+ struct vm_area_struct *vma;
+ struct mm_struct *mm;
+ struct dentry *result;
+ char *endp;
+
+ result = ERR_PTR(-ENOENT);
+
+ task = get_proc_task(dir);
+ if (!task)
+ goto out_no_task;
+
+ vm_start = simple_strtoul(dentry->d_name.name, &endp, 16);
+ if (*endp != '\0')
+ goto out_no_mm;
+
+ mm = get_task_mm(task);
+ if (!mm)
+ goto out_no_mm;
+
+ down_read(&mm->mmap_sem);
+ for (vma = mm->mmap; vma; vma = vma->vm_next) {
+ if (vma->vm_start == vm_start)
+ break;
+ if (vma->vm_start > vm_start)
+ goto out_no_vma;
+ }
+
+ if (!vma)
+ goto out_no_vma;
+
+ result = proc_mfd_instantiate(dir, dentry, task, vma);
+
+out_no_vma:
+ up_read(&mm->mmap_sem);
+ mmput(mm);
+out_no_mm:
+ put_task_struct(task);
+out_no_task:
+ return result;
+}
+
+static const struct inode_operations proc_mfd_inode_operations = {
+ .lookup = proc_mfd_lookup,
+ .setattr = proc_setattr,
+};
+
static struct dentry *proc_fdinfo_instantiate(struct inode *dir,
struct dentry *dentry, struct task_struct *task, const void *ptr)
{
@@ -2819,6 +3022,7 @@ static const struct inode_operations proc_task_inode_operations;
static const struct pid_entry tgid_base_stuff[] = {
DIR("task", S_IRUGO|S_IXUGO, proc_task_inode_operations, proc_task_operations),
DIR("fd", S_IRUSR|S_IXUSR, proc_fd_inode_operations, proc_fd_operations),
+ DIR("mfd", S_IRUSR|S_IXUSR, proc_mfd_inode_operations, proc_mfd_operations),
DIR("fdinfo", S_IRUSR|S_IXUSR, proc_fdinfo_inode_operations, proc_fdinfo_operations),
#ifdef CONFIG_NET
DIR("net", S_IRUGO|S_IXUGO, proc_net_inode_operations, proc_net_operations),
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index eaf4350..c779c74 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -265,7 +265,10 @@ struct ctl_table;
struct proc_inode {
struct pid *pid;
- int fd;
+ union {
+ int fd;
+ unsigned long vm_start;
+ };
union proc_op op;
struct proc_dir_entry *pde;
struct ctl_table_header *sysctl;
--
1.5.5.6
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