Re: [Qemu-devel] [PATCH v4] module: Use QEMU_MODULE_DIR as a search path

[Fam Zheng <famz@redhat.com>]

On Wed, 07/04 14:10, ryang wrote:
> The current paths for modules are CONFIG_QEMU_MODDIR and paths relative
> to the executable. Qemu and its modules can be installed and executed in
> paths that are different from these search paths. This change allows
> a search path to be specified by environment variable.
> 
> An example usage for this is postmarketOS[1]. This is a build environment
> for Alpine Linux. It sets up Alpine Linux in a chroot environment.
> Alpine's Qemu packages are installed in the chroot. The Alpine Linux Qemu
> package is used to test compiled Alpine Linux system images. This way there
> isn't a reliance on the which ever version of Qemu the host system / distro
> provides.
> 
> postmarketOS executes Qemu on host system outside of the chroot
> The Qemu module search path needs to point to the location of the
> chroot relative to the host system.
> 
> e.g.
> The root of the Alpine Linux chroot is:
> ~/.local/var/pmbootstrap/chroot_native/
> 
> Alpine's Qemu is installed at
> ~/.local/var/pmbootstrap/chroot_native/usr/bin/
> 
> The Qemu module search path needs to be:
> QEMU_MODULE_DIR=~/.local/var/pmbootstrap/chroot_native/usr/lib/qemu/
> 
> [1] https://postmarketos.org/
> 
> Signed-off-by: ryang <decatf@gmail.com>
> ---
> 
> v2:
>  - fix checkpatch errors
> v3:
>  - initialize n_dirs variable
> v4:
>  - change env variable suffix from _PATH to _DIR
>  - renamed search_path to search_dir and make it const
> 
>  util/module.c | 22 ++++++++++++++--------
>  1 file changed, 14 insertions(+), 8 deletions(-)
> 
> diff --git a/util/module.c b/util/module.c
> index c909737..1259dd3 100644
> --- a/util/module.c
> +++ b/util/module.c
> @@ -162,9 +162,10 @@ void module_load_one(const char *prefix, const char *lib_name)
>  #ifdef CONFIG_MODULES
>      char *fname = NULL;
>      char *exec_dir;
> -    char *dirs[3];
> +    const char *search_dir;
> +    char *dirs[4];
>      char *module_name;
> -    int i = 0;
> +    int i = 0, n_dirs = 0;
>      int ret;
>      static GHashTable *loaded_modules;
>  
> @@ -186,14 +187,19 @@ void module_load_one(const char *prefix, const char *lib_name)
>      g_hash_table_insert(loaded_modules, module_name, module_name);
>  
>      exec_dir = qemu_get_exec_dir();
> -    dirs[i++] = g_strdup_printf("%s", CONFIG_QEMU_MODDIR);
> -    dirs[i++] = g_strdup_printf("%s/..", exec_dir ? : "");
> -    dirs[i++] = g_strdup_printf("%s", exec_dir ? : "");
> -    assert(i == ARRAY_SIZE(dirs));
> +    search_dir = getenv("QEMU_MODULE_DIR");
> +    if (search_dir != NULL) {
> +        dirs[n_dirs++] = g_strdup_printf("%s", search_dir);
> +    }
> +    dirs[n_dirs++] = g_strdup_printf("%s", CONFIG_QEMU_MODDIR);
> +    dirs[n_dirs++] = g_strdup_printf("%s/..", exec_dir ? : "");
> +    dirs[n_dirs++] = g_strdup_printf("%s", exec_dir ? : "");
> +    assert(n_dirs <= ARRAY_SIZE(dirs));
> +
>      g_free(exec_dir);
>      exec_dir = NULL;
>  
> -    for (i = 0; i < ARRAY_SIZE(dirs); i++) {
> +    for (i = 0; i < n_dirs; i++) {
>          fname = g_strdup_printf("%s/%s%s",
>                  dirs[i], module_name, HOST_DSOSUF);
>          ret = module_load_file(fname);
> @@ -205,7 +211,7 @@ void module_load_one(const char *prefix, const char *lib_name)
>          }
>      }
>  
> -    for (i = 0; i < ARRAY_SIZE(dirs); i++) {
> +    for (i = 0; i < n_dirs; i++) {
>          g_free(dirs[i]);
>      }
>  
> -- 
> 2.7.4
> 

Reviewed-by: Fam Zheng <famz@redhat.com>