On Sun, 2024-06-30 at 09:40 +0800, Huacai Chen wrote: > On Tue, Jun 25, 2024 at 11:00 PM Xi Ruoyao <xry111@xxxxxxxxxxx> wrote: > > > > On Tue, 2024-06-25 at 22:09 +0800, Huacai Chen wrote: > > > On Tue, Jun 25, 2024 at 7:01 PM Mateusz Guzik <mjguzik@xxxxxxxxx> > > > wrote: > > > > > > > > The newly used helper also checks for 0-sized buffers. > > > > > > > > This avoids path lookup code, lockref management, memory > > > > allocation > > > > and > > > > in case of NULL path userspace memory access (which can be quite > > > > expensive with SMAP on x86_64). > > > > > > > > statx with AT_EMPTY_PATH paired with "" or NULL argument as > > > > appropriate > > > > issued on Sapphire Rapids (ops/s): > > > > stock: 4231237 > > > > 0-check: 5944063 (+40%) > > > > NULL path: 6601619 (+11%/+56%) > > > > > > > > Signed-off-by: Mateusz Guzik <mjguzik@xxxxxxxxx> > > > Hi, Ruoyao, > > > > > > I'm a bit confused. Ii this patch a replacement of your recent > > > patch? > > > > Yes, both Linus and Christian hates introducing a new AT_ flag for > > this. > > > > This patch just makes statx(fd, NULL, AT_EMPTY_PATH, ...) behave > > like > > statx(fd, "", AT_EMPTY_PATH, ...) instead. NULL avoids the > > performance > > issue and it's also audit-able by seccomp BPF. > To be honest, I still want to restore __ARCH_WANT_NEW_STAT. Because > even if statx() becomes audit-able, it is still blacklisted now. Then patch the sandbox to allow it. The sandbox **must** be patched anyway or it'll be broken on all 32-bit systems after 2037. [Unless they'll unsupport all 32-bit systems before 2037.] > Restoring __ARCH_WANT_NEW_STAT is a very small change that doesn't > introduce any complexity, but it makes life easier. And I think libLoL > also likes __ARCH_WANT_NEW_STAT, though it isn't an upstream > project... At least you should not restore it for 32-bit. libLoL also has nothing to do with 32-bit systems anyway. Maybe conditional it with a #if checking __BITS_PER_LONG. And the vendors should really port their software to the upstreamed ABI instead of relying on liblol. <rant>Is a recompiling so difficult, or are the programmers so stupid to invoke plenty of low-level syscalls directly (bypassing Glibc) in their code?</rant> -- Xi Ruoyao <xry111@xxxxxxxxxxx> School of Aerospace Science and Technology, Xidian University
