[syslinux] [PATCH 2/2] core: Fix stack overflow when reloading config

[H. Peter Anvin]

On January 22, 2016 3:59:09 AM PST, Celelibi <celelibi at gmail.com> wrote:
>2016-01-22 3:37 UTC+01:00, H. Peter Anvin <hpa at zytor.com>:
>> On 01/21/16 18:33, Celelibi wrote:
>>>
>>> BTW, this code is due to Matt Flemming with commit 3a316db1 (later
>>> modified). The commit log say this:
>>>     ldlinux: Loading a config file should cause re-initialisation
>>>
>>>     There are a number of initialisation steps that need to be
>performed
>>>     *every* time a config file is loaded. Reload ldlinux.c32 so that
>we
>>>     can re-initialise the environment whenever a new config file is
>>>     loaded. This involves unloading all the modules that have been
>loaded
>>>     since ldlinux.c32. Luckily the list of loaded modules is sorted
>by
>>>     load order, which means it's trivial to "pop" them from the
>front of
>>>     the list.
>>>
>>
>> Yes, it is the easy way to initialize.  Part of me wonders if we
>should
>> keep a copy of the data section and just wipe it out.
>>
>> 	-hpa
>
>I see 3 ways of handling this.
>1) Have some specific code in ldlinux.c32 that handles
>reinitialization.
>2) Have some specific cache for the COM32 modules and load them only
>once for the lifetime of the whole boot loader.
>3) Put a file system cache that would also benefit to other files.
>
>I would tend to prefer the third way, but I don't know how much work
>it would be or if it would integrate well in the current design.
>
>
>Celelibi

#2 is really easy; we just need to keep a copy of the unmodified data section.  The only risk with this approach is running out of memory, but I think that risk is minor.
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