On Thu, Jul 3, 2014 at 3:24 AM, Will Deacon <will.dea...@arm.com> wrote: > On Thu, Jul 03, 2014 at 08:43:07AM +0100, AKASHI Takahiro wrote: >> Hi Will, > > Hi Akashi, > >> On 06/24/2014 05:54 PM, Will Deacon wrote: >> > On Mon, Jun 23, 2014 at 08:46:52PM +0100, Kees Cook wrote: >> >> What's the state of seccomp on arm64? I saw a series back in March, >> >> but nothing since then? It looked complete, but I haven't set up a >> >> test environment yet to verify. >> > >> > I think Akashi was going to repost `real soon now' so we can include them >> > for 3.17. He missed the merge window last time around. >> >> I took a quick look at the current implementation of ptrace. >> ptrace(PTRACE_GETREGSET/SETREGSET), eventually gpr_get/set(), handles only >> 'struct user_pt_regs', and we have no way to modify orig_x0 nor syscallno >> in 'struct pt_regs' directly. >> So it seems to me that we can't change a system call by ptrace(). >> Do I misunderstand anything? > > No, it looks like you have a point here. I don't think userspace has any > business with orig_x0, but changing syscallno is certainly useful. I can > think of two ways to fix this: > > (1) Updating syscallno based on w8, but this ties us to the current ABI > and could get messy if this register changes in the future. > > (2) Adding a PTRACE_SET_SYSCALL request, like we have for arch/arm/, > but that means adding arch-specific stuff to arch_ptrace (which > currently goes straight to ptrace_request on arm64). > > It looks like x86 uses orig_ax, which I *think* means we would go with > (1) above if we followed their lead.
w8 is a real register, right? On x86, at least orig_ax isn't a real register, so it's quite unlikely to conflict with hardware stuff. On x86, the "user_struct" thing has nothing to do with any real kernel data structure, so it's extensible. Can you just add syscallno to it? --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
