Re: [PATCH] Avoid dlopen on debuginfod-client when not configured

[Mark Wielaard <mark@klomp.org>]

Hi Dirk,

On Mon, Mar 28, 2022 at 11:36:41PM +0200, Dirk Müller wrote:
> Loading debuginfod-client is expensive, especially when
> FIPS is enabled, as it goes through time intensive self-checks
> on load.

I assume this is because debuginfod-client loads and initializes
libcurl, which triggers crypto checks for https support?

> Avoid dlopen() when no debuginfo url is set.

The patch itself looks right. But I am slightly afraid this
(theoretically?) will break some programs which set DEBUGINFOD_URLS
themselves. We currently have no other way to make libdwfl use
debuginfod-client. Thoughts?

Cheers,

Mark

> Signed-off-by: Dirk Müller <dirk@dmllr.de>
> ---
>  libdwfl/ChangeLog           |  5 +++++
>  libdwfl/debuginfod-client.c | 12 +++++++++++-
>  2 files changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/libdwfl/ChangeLog b/libdwfl/ChangeLog
> index 9c5c8517..1ec13f30 100644
> --- a/libdwfl/ChangeLog
> +++ b/libdwfl/ChangeLog
> @@ -1,3 +1,8 @@
> +2022-03-28  Dirk Müller <dirk@dmllr.de>
> +
> +	* debuginfod-client.c (__libdwfl_debuginfod_init): Skip dlopen
> +	if debuginfod url is unset.
> +
>  2022-02-18  Mark Wielaard  <mark@klomp.org>
>  
>  	* image-header.c (__libdw_image_header): Assign header values for
> diff --git a/libdwfl/debuginfod-client.c b/libdwfl/debuginfod-client.c
> index 99b66b6e..af9d1363 100644
> --- a/libdwfl/debuginfod-client.c
> +++ b/libdwfl/debuginfod-client.c
> @@ -101,7 +101,17 @@ __libdwfl_debuginfod_end (debuginfod_client *c)
>  void __attribute__ ((constructor))
>  __libdwfl_debuginfod_init (void)
>  {
> -  void *debuginfod_so = dlopen(DEBUGINFOD_SONAME, RTLD_LAZY);
> +  void *debuginfod_so;
> +
> +  /* Is there any server we can query?  If not, don't do any work,
> +     just return with ENOSYS.  Don't even access the cache.  */
> +  char *urls_envvar = getenv(DEBUGINFOD_URLS_ENV_VAR);
> +  if (urls_envvar == NULL || urls_envvar[0] == '\0')
> +    {
> +      return;
> +    }
> +
> +  debuginfod_so = dlopen(DEBUGINFOD_SONAME, RTLD_LAZY);
>  
>    if (debuginfod_so != NULL)
>      {
> -- 
> 2.35.1
>