Hey Björn, On Tue, Feb 14, 2023 at 2:43 PM Björn Töpel <bjorn@xxxxxxxxxx> wrote: > So, two changes: > > 1. Disallow V-enablement if the existing altstack does not fit a V-sized > frame. This could potentially break old programs (non-V) that load new system libraries (with V), If the program sets a small alt stack and takes the fault in some libraries that use V. However, existing implementation will also kill the process when the signal arrives, finding insufficient stack frame in such cases. I'd choose the second one if we only have these two options, because there is a chance that the signal handler may not even run. > 2. Sanitize altstack changes when V is enabled. Yes, I'd like to have this. But it may be tricky when it comes to deciding whether V is enabled, due to the first-use trap. If V is commonly used in system libraries then it is likely that V will be enabled before an user set an altstack. Sanitizing this case would be easy and straightforward. But what if the user sets an altstack before enabling V in the first-use trap? This could happen on a statically program that has hand-written V routines. This takes us to the 1st question above, should we fail the user program immediately if the altstack is set too small? > > Other than the altstack handling, I think the series is a good state! It > would great if we could see a v14 land in -next... Thanks. I am reforming the v14 patch and hoping the same to happen soon too! Cheers, Andy
