On Fri, Jan 26, 2024 at 3:41 PM Rob Landley <r...@landley.net> wrote:
> On 1/26/24 11:28, enh via Toybox wrote: > > The ULONG_MAX turns into -1 here, which isn't what was intended. > > Ah. That one ONLY works on 32 bit. Oops. > (yeah, sorry, i realized after sending my patch that my LP64 bigotry was showing again, and it might not be obvious _why_.) > (I went down a research rathole trying to work out whether the > spectre/meltdown > mitigations that unmapped the kernel from normal userspace brought back > Ingo's > old 4G/4G mapping or not on 32 bit, didn't really get a useful answer, > went with > unsigned rather than try to read through the kernel code... and missed the > obvious.) > > > I'll avoid the bikeshed of the least worst full fix and take half > > the range which is plenty for my purposes. > > Neither Intel nor Arm support the full 64 bits (Intel did 5-level page > tables to > hit 57 bits, Arm increased page size to hit 52, and atomic limits are > really > starting to bite ala https://www.youtube.com/watch?v=2G4_RZo41Zw), so > signed > long is probably fine for the forseeable future. :) > the main users for this are working on 32-bit devices anyway, and explicitly only devices that have less than 4GiB anyway (if i've understood https://source.android.com/docs/compatibility/14/android-14-cdd#76_memory_and_storage correctly). > > Also fix the array indexing to not segfault. > > Sigh, I only ran "memeater 10k" on my laptop (in a 32 bit build). My > musl-cross > toolchain hasn't got ASAN wired up and hangs right after so never noticed. > (Still embarassing...) > > Your fix is writing more than once per page. I'm adjusting stride already > in the > increment, the problem is size needs to be adjusted to not go off the end. > (Moving adjustment to the index adds math to the loop instead of resolving > it at > compile time, but eh, keep that one. I fixed up your patch with vi, but > actually > tested the result this time. :) > > The _next_ problem is trying "memeater 1m" so it actually gets some > nontrivial > exercise, I had to sudo it to avoid: > > $ ./memeater 1m > memeater: mlock: Cannot allocate memory > > With the 10k I didn't get that objection, because: > > $ ulimit -l > 64 > > Should I make the mlock() not be the default, presumably switching to -m to > enable rather than disable it? (Dunno what your android environment looks > like > here...) > "works for me" on _my_ hosts, but i haven't actually tested on Android yet, and that's very likely to be next week at this point... > Commit 1e04fb285c3c. > ...especially because this isn't showing in github yet :-) > Rob >
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