[CRIU] [PATCHv3 01/10] compat/vDSO/restorer: flush rt symtable from criu

[Pavel Emelyanov]

On 08/08/2016 03:57 PM, Dmitry Safonov wrote:
> What's happening here:
> - rt_symtable is filled in criu on init
> - in restorer we map compatible vDSO blob and refilling rt_symtable
>   (in case of restoring 32-bit application)
> - compatible and native symtables may (and it's very likely) have
>   different symbols
> - the symtable's values for symbols which are present in native vDSO,
>   but absent in compatible vdso will be preserved from criu's process
>   (which is not right)
> - if saved compat vDSO blob has some symbols, which has native vDSO, but
>   does not have compat restorer's blob, they may confuse restorer
> 
> Impact: re-init rt symtable for compatible tasks in restorer.
> 
> While, I belive I will optimize this out in future by filling
> compatible symtable (and thus, making two rt symtabs) on criu init,
> yet fix this by reinitialization.

Well, we're not in a hurry :) So can we please fix this properly from
the very beginning?

> Cc: Cyrill Gorcunov <gorcunov at openvz.org>
> Signed-off-by: Dmitry Safonov <dsafonov at virtuozzo.com>
> Reviewed-by: Cyrill Gorcunov <gorcunov at openvz.org>
> ---
>  criu/pie/parasite-vdso.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/criu/pie/parasite-vdso.c b/criu/pie/parasite-vdso.c
> index f838f826d24c..c51a11b9236e 100644
> --- a/criu/pie/parasite-vdso.c
> +++ b/criu/pie/parasite-vdso.c
> @@ -80,7 +80,7 @@ int vdso_map_compat(unsigned long map_at, unsigned long park_size,
>  		struct vdso_symtable *sym_rt)
>  {
>  	unsigned long search_vdso;
> -	int ret;
> +	int i, ret;
>  
>  	pr_debug("Mapping compatible vDSO at %lx\n", map_at);
>  
> @@ -88,6 +88,9 @@ int vdso_map_compat(unsigned long map_at, unsigned long park_size,
>  	if (ret)
>  		return ret;
>  
> +	for (i = 0; i < VDSO_SYMBOL_MAX; i++)
> +		sym_rt->symbols[i].offset = VDSO_BAD_ADDR;
> +
>  	/*
>  	 * We could map VVAR firstly, or VDSO.
>  	 * Try to find VDSO pages in this couple of parking pages.
>