On Wed, 2022-03-30 at 14:29 -0700, Reinette Chatre wrote: > Hi Jarkko, > > On 3/30/2022 1:40 PM, Jarkko Sakkinen wrote: > > On Wed, 2022-03-30 at 13:05 -0700, Reinette Chatre wrote: > > > > > > > > > On 3/30/2022 12:03 PM, Jarkko Sakkinen wrote: > > > > On Wed, 2022-03-30 at 10:40 -0700, Reinette Chatre wrote: > > > > > Could you please elaborate how the compiler will fix it up? > > > > > > > > Sure. > > > > > > > > Here's the disassembly of the RBX version: > > > > > > > > [0x000021a9]> pi 1 > > > > lea rax, [rbx + loc.encl_stack] > > > > > > > > Here's the same with s/RBX/RIP/: > > > > > > > > [0x000021a9]> pi 5 > > > > lea rax, loc.encl_stack > > > > > > > > Compiler will substitute correct offset relative to the RIP, > > > > well, because it can and it makes sense. > > > > > > It does not make sense to me because, as proven with my test, > > > the two threads end up sharing the same stack memory. > > > > I see, I need to correct my patch, thanks! > > > > RBX gives correct results because of the binary organization, > > i.e. TCS's are placed to zero offset and forward, and > > unrelocated symbol is just compiled in as an untranslated > > offset. > > > > RPI is given correct results but how the semantics work > > right now is incompatible. > > > > Still, even for kselftest, I would consider a switch > > because that way: > > > > 1. You can layout binary however you wan and things > > won't break. > > 2. You can point to any symbol not just stack, if > > ever need. > > > > I admit it works semantically but it just super > > unrobust. > > I do not think that we need an exceptionally flexible > runtime as part of the SGX selftests but instead something > that is easy(*) to understand while also sufficient to support > the tests. > > Reinette > > * I do not actually consider the existing enclave test binary > easy to understand (this thread is proof) but keeping its > complexity to be minimal would benefit folks needing to > ramp up on SGX and/or debug kselftest failures. Based on you feedback I refined the patch: https://lore.kernel.org/linux-sgx/20220330222834.139769-1-jarkko@xxxxxxxxxx/T/#u BR, Jarkko BR, Jarkko
