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Kernel+Userland: Split bind-mounting and re-mounting from mount syscall

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These 2 are an actual separate types of syscalls, so let's stop using
special flags for bind mounting or re-mounting and instead let userspace
calling directly for this kind of actions.
This commit is contained in:
Liav A 2023-02-25 19:30:28 +02:00 • committed by Andrew Kaster
parent 04b44a827a
commit 0bbd9040ef
10 changed files with 204 additions and 42 deletions
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39
Base/usr/share/man/man2/bindmount.md Normal file
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@ -0,0 +1,39 @@
## Name
bindmount - create a bindmount from `source_fd` to a target path.
## Synopsis
```**c++
#include <LibCore/System.h>
ErrorOr<void> bindmount(int source_fd, StringView target, int flags);
```
## Description
`bindmount()` create a bindmount from `source_fd` to a target path `target`, with mount flags of `flags`.
The following `flags` are supported:
* `MS_NODEV`: Disallow opening any devices from this file system.
* `MS_NOEXEC`: Disallow executing any executables from this file system.
* `MS_NOSUID`: Ignore set-user-id bits on executables from this file system.
* `MS_RDONLY`: Mount the filesystem read-only.
* `MS_WXALLOWED`: Allow W^X protection circumvention for executables on this file system.
* `MS_AXALLOWED`: Allow anonymous executable mappings for executables on this file system.
* `MS_NOREGULAR`: Disallow opening any regular files from this file system.
These flags can be used as a security measure to limit the possible abuses of the mounted file system.
## Errors
* `EINVAL`: The `flags` value contains deprecated flags such as `MS_REMOUNT` or `MS_BIND`.
* `EPERM`: The current process does not have superuser privileges.
* `ENODEV`: The `source_fd` is not an open file descriptor to a valid filesystem inode.
All of the usual path resolution errors may also occur.
## See also
* [`mount`(2)](help://man/2/mount)

16
Base/usr/share/man/man2/mount.md
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@ -34,9 +34,7 @@ The following `flags` are supported:
* `MS_NODEV`: Disallow opening any devices from this file system.
* `MS_NOEXEC`: Disallow executing any executables from this file system.
* `MS_NOSUID`: Ignore set-user-id bits on executables from this file system.
* `MS_BIND`: Perform a bind-mount (see below).
* `MS_RDONLY`: Mount the filesystem read-only.
* `MS_REMOUNT`: Remount an already mounted filesystem (see below).
* `MS_WXALLOWED`: Allow W^X protection circumvention for executables on this file system.
* `MS_AXALLOWED`: Allow anonymous executable mappings for executables on this file system.
* `MS_NOREGULAR`: Disallow opening any regular files from this file system.
@ -57,11 +55,6 @@ itself, which may be useful for changing mount flags for a part of a filesystem.
### Remounting
If `MS_REMOUNT` is specified in `flags`, `source_fd` and `fs_type` are ignored,
and a remount is performed instead. `target` must point to an existing mount
point. The mount flags for that mount point are reset to `flags` (except the
`MS_REMOUNT` flag itself, which is stripped from the value).
Note that remounting a file system will only affect future operations with the
file system, not any already opened files. For example, if you open a directory
on a filesystem that's mounted with `MS_NODEV`, then remount the filesystem to
@ -74,14 +67,9 @@ in mount flags of the underlying file system. To "refresh" the working directory
to use the new mount flags after remounting a filesystem, a process can call
`chdir()` with the path to the same directory.
Similarly, to change the mount flags used by the root directory, a process can
remount the root filesystem using `MS_REMOUNT`.
However, it only have a noticeable effect if
the kernel was to launch more userspace processes directly, the way it does
launch the initial userspace process.
## Errors
* `EINVAL`: The `flags` value contains deprecated flags such as `MS_REMOUNT` or `MS_BIND`.
* `EFAULT`: The `fs_type` or `target` are invalid strings.
* `EPERM`: The current process does not have superuser privileges.
* `ENODEV`: The `fs_type` is unrecognized, or the file descriptor to source is
@ -99,3 +87,5 @@ All of the usual path resolution errors may also occur.
## See also
* [`mount`(8)](help://man/8/mount)
* [`remount`(2)](help://man/2/remount)
* [`bindmount`(2)](help://man/2/bindmount)

39
Base/usr/share/man/man2/remount.md Normal file
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## Name
remount - remount a filesystem with new mount flags
## Synopsis
```**c++
#include <LibCore/System.h>
ErrorOr<void> remount(StringView target, int flags);
```
## Description
`remount()` mounts a filesystem that is mounted at `target` with new mount flags of `flags`.
The following `flags` are supported:
* `MS_NODEV`: Disallow opening any devices from this file system.
* `MS_NOEXEC`: Disallow executing any executables from this file system.
* `MS_NOSUID`: Ignore set-user-id bits on executables from this file system.
* `MS_RDONLY`: Mount the filesystem read-only.
* `MS_WXALLOWED`: Allow W^X protection circumvention for executables on this file system.
* `MS_AXALLOWED`: Allow anonymous executable mappings for executables on this file system.
* `MS_NOREGULAR`: Disallow opening any regular files from this file system.
These flags can be used as a security measure to limit the possible abuses of the mounted file system.
## Errors
* `EINVAL`: The `flags` value contains deprecated flags such as `MS_REMOUNT` or `MS_BIND`.
* `EPERM`: The current process does not have superuser privileges.
* `ENODEV`: No mount point was found for `target` path target.
All of the usual path resolution errors may also occur.
## See also
* [`mount`(2)](help://man/2/mount)