[libvirt] [PATCH] util: activate directory override when used from library

[Peter Krempa]

On Thu, Aug 29, 2019 at 11:54:37 +0100, Daniel Berrange wrote:
> The Perl bindings for libvirt use the test driver for unit tests. This
> tries to load the cpu_map/index.xml file, and when run from an
> uninstalled build will fail.
> 
> The problem is that virFileActivateDirOverride is called by our various
> binaries like libvirtd, virsh, but is not called when a 3rd party app
> uses libvirt.so
> 
> To deal with this we allow the LIBVIRT_DIR_OVERRIDE=1 env variable to be
> set and make virInitialize look for this. The 'run' script will set it,
> so now build using this script to run against an uninstalled tree we
> will correctly resolve files to the source tree.
> 
> Signed-off-by: Daniel P. Berrangé <berrange at redhat.com>
> ---
>  run.in             |  3 +++
>  src/libvirt.c      |  2 ++
>  src/util/virfile.c | 21 +++++++++++++--------
>  3 files changed, 18 insertions(+), 8 deletions(-)
> 
> diff --git a/run.in b/run.in
> index 9a1c6ea11a..de7af78f67 100644
> --- a/run.in
> +++ b/run.in
> @@ -60,6 +60,9 @@ else
>  fi
>  export PKG_CONFIG_PATH
>  
> +LIBVIRT_DIR_OVERRIDE=1
> +export LIBVIRT_DIR_OVERRIDE

For future reference you should document what this does.

> +
>  # This is a cheap way to find some use-after-free and uninitialized
>  # read problems when using glibc.
>  random_val="$(awk 'BEGIN{srand(); print 1+int(255*rand())}' < /dev/null)"
> diff --git a/src/libvirt.c b/src/libvirt.c
> index 956ccdea30..6b1b4a54c3 100644
> --- a/src/libvirt.c
> +++ b/src/libvirt.c
> @@ -250,6 +250,8 @@ virGlobalInit(void)
>          virErrorInitialize() < 0)
>          goto error;
>  
> +    virFileActivateDirOverride(NULL);
> +
>      if (getuid() != geteuid() ||
>          getgid() != getegid()) {
>          virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> diff --git a/src/util/virfile.c b/src/util/virfile.c
> index 81a3c096eb..391b6a9e6e 100644
> --- a/src/util/virfile.c
> +++ b/src/util/virfile.c
> @@ -1776,14 +1776,19 @@ virFileFindResource(const char *filename,
>  void
>  virFileActivateDirOverride(const char *argv0)
>  {
> -    char *file = strrchr(argv0, '/');
> -    if (!file || file[1] == '\0')
> -        return;
> -    file++;
> -    if (STRPREFIX(file, "lt-") ||
> -        strstr(argv0, "/.libs/")) {
> -        useDirOverride = true;
> -        VIR_DEBUG("Activating build dir override for %s", argv0);
> +    if (argv0 == NULL) {
> +        if (getenv("LIBVIRT_DIR_OVERRIDE") != NULL)
> +            useDirOverride = true;

I'm not a fan that you have different behaviour depending on whether
'argv0' is set or not. Also the comment for the function is now stale
and the point of the env variable is cryptic.

> +    } else {
> +        char *file = strrchr(argv0, '/');
> +        if (!file || file[1] == '\0')
> +            return;
> +        file++;
> +        if (STRPREFIX(file, "lt-") ||
> +            strstr(argv0, "/.libs/")) {
> +            useDirOverride = true;
> +            VIR_DEBUG("Activating build dir override for %s", argv0);
> +        }
>      }
>  }
>  
> -- 
> 2.21.0
> 
> --
> libvir-list mailing list
> libvir-list at redhat.com
> https://www.redhat.com/mailman/listinfo/libvir-list
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