On Fri, Aug 28, 2020 at 4:38 AM H.J. Lu <hjl.tools@xxxxxxxxx> wrote: > > On Thu, Aug 27, 2020 at 11:24 PM Florian Weimer <fweimer@xxxxxxxxxx> wrote: > > > > * H. J. Lu: > > > > > Can you think of ANY issues of passing more arguments to arch_prctl? > > > > On x32, the glibc arch_prctl system call wrapper only passes two > > arguments to the kernel, and applications have no way of detecting that. > > musl only passes two arguments on all architectures. It happens to work > > anyway with default compiler flags, but that's an accident. > > In the current glibc, there is no arch_prctl wrapper for i386. There are > arch_prctl wrappers with 2 arguments for x86-64 and x32. But this isn't an > issue for glibc since glibc is both the provider and the user of the new > arch_prctl extension. Besides, > > long syscall(long number, ...); > > is always available. Userspace is probably full of tools and libraries that contain tables of system calls and their signatures. Think tracing, audit, container management, etc. I don't know how they will react to the addition of new arguments.
