On Thu, Aug 6, 2020 at 8:34 PM Gedare Bloom <ged...@rtems.org> wrote:
> On Thu, Aug 6, 2020 at 6:21 AM Sebastian Huber > <sebastian.hu...@embedded-brains.de> wrote: > > > > On 06/08/2020 14:12, Utkarsh Rai wrote: > > > > > Hello, > > > The thread-stack protection needs to be configured by the user. Two of > > > the options that need configuring during build time are - > > > > Enabling thread stack protection ( THREAD_STACK_PROTECTION )- This > > > is a high-level option similar to RTEMS_SMP, RTEMS_POSIX_API etc. > > > > Size of the MMU pages - This is a BSP specific option. > > > Using the new build system we can configure these by adding BSP > > > option ( for eg. realview BSP has 'optmmusmallpages.yml' for 4K mmu > > > pages). Similarly, we can have 'optthreadstackprotection.yml' similar > > > to 'optsmp.yml' for enabling thread stack protection. Is there > > > something else we need to do, for specifying these options? > > > > > > Another option that needs to be specified is the number of thread > > > stacks that can be shared with a particular thread. This can be done > > > by specifying this in rtems/confdefs.h and then configured by the > > > application. I would request your opinion on this and whether this is > > > the right manner to proceed. > > > > Yes, we probably need a new CPU option RTEMS_THREAD_STACK_PROTECTION or > > similar. > > > +1 > Just copy one of the existing high-level switches and give it a try, > see how it turns out. > Ok, I am rebasing my repo to integrate the new build system and will send the v3 patch with these switches. > > > Why can't you use this option in the BSP to enable the 4KiB pages MMU? > > > Agreed. This one can be solved with documentation specific to the > BSP/CPU related to how to configure it for stack protection. > > > With respect to the application configuration, we should consider to use > > thread-local storage for this. TLS is well supported on ARM, SPARC, > > PowerPC, RISC-V, and m68k. > > > I'm not sure if I follow this thought all the way. > > Would the idea be to have the application populate some data structure > with the pointers/names of stacks it needs to access in the TLS? And > then maybe we have something that converts that structure into an > internal representation, something that is kind of like a page table. > Do we have a documented way of using TLS? > I have the same doubt, I looked around but could not find anything that describes a way of using TLS. We can have an array of shared stack attributes(address, length, flags) placed in the TLS. But how will it be different/beneficial than simply adding these attributes to the thread-stack control block and setting/unsetting them on each context switch? > Gedare >
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