[PATCH v4 0/7] util: Introduce qemu_get_runtime_dir()

[Akihiko Odaki]

qemu_get_runtime_dir() returns a dynamically allocated directory path
that is appropriate for storing runtime files. It corresponds to "run"
directory in Unix.

With a tree-wide search, it was found that there are several cases
where such a functionality is implemented so let's have one as a common
utlity function.

A notable feature of qemu_get_runtime_dir() is that it uses
$XDG_RUNTIME_DIR if available. While the function is often called by
executables which requires root privileges, it is still possible that
they are called from a user without privilege to write the system
runtime directory. In fact, I decided to write this patch when I ran
virtiofsd in a Linux namespace created by a normal user and realized
it tries to write the system runtime directory, not writable in this
case. $XDG_RUNTIME_DIR should provide a writable directory in such
cases.

This function does not use qemu_get_local_state_dir() or its logic
for Windows. Actually the implementation of qemu_get_local_state_dir()
for Windows seems not right as it calls g_get_system_data_dirs(),
which refers to $XDG_DATA_DIRS. In Unix terminology, it is basically
"/usr/share", not "/var", which qemu_get_local_state_dir() is intended
to provide. Instead, this function try to use the following in order:
- $XDG_RUNTIME_DIR
- LocalAppData folder
- get_relocated_path(CONFIG_QEMU_LOCALSTATEDIR "/run")

This function does not use g_get_user_runtime_dir() either as it
falls back to g_get_user_cache_dir() when $XDG_DATA_DIRS is not
available. In the case, we rather use:
get_relocated_path(CONFIG_QEMU_LOCALSTATEDIR "/run")

V2 -> V3:
  Rebase to the current master.
  Dropped patch "qga: Remove platform GUID definitions" since it is
  irrelevant.

V1 -> V2:
  Rebased to the current master since Patchew complains.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
---
Changes in v4:
- Rebased.
- Link to v3: 
https://lore.kernel.org/r/20230921075425.16738-1-akihiko.odaki@daynix.com

---
Akihiko Odaki (7):
      util: Introduce qemu_get_runtime_dir()
      ivshmem-server: Use qemu_get_runtime_dir()
      qga: Use qemu_get_runtime_dir()
      scsi: Use qemu_get_runtime_dir()
      module: Use qemu_get_runtime_dir()
      util: Remove qemu_get_local_state_dir()
      spice-app: Use qemu_get_runtime_dir()

 include/qemu/osdep.h          | 10 +++++++---
 contrib/ivshmem-server/main.c | 20 ++++++++++++++++----
 qga/main.c                    |  9 ++++-----
 scsi/qemu-pr-helper.c         |  6 +++---
 ui/spice-app.c                |  4 ++--
 util/module.c                 |  3 ++-
 util/oslib-posix.c            |  9 +++++++--
 util/oslib-win32.c            | 24 ++++++++++++++++++++----
 8 files changed, 61 insertions(+), 24 deletions(-)
---
base-commit: f2cb4026fccfe073f84a4b440e41d3ed0c3134f6
change-id: 20240218-run-6f0d91ec7439

Best regards,
-- 
Akihiko Odaki <akihiko.odaki@daynix.com>