On Thu, Jan 03, 2019 at 11:50:12AM +0000, Dave Martin wrote: > On Thu, Jan 03, 2019 at 03:45:47PM +0800, Pi-Hsun Shih wrote: > > For syscall number smaller than 0xf0000, arm calls sys_ni_syscall > > instead of arm_syscall in arch/arm/kernel/entry-common.S, which returns > > -ENOSYS instead of raising SIGILL. Mirror this behavior for compat > > syscalls in arm64. > > > > Fixes: 532826f3712b607 ("arm64: Mirror arm for unimplemented compat > > syscalls") > > Signed-off-by: Pi-Hsun Shih <pih...@chromium.org> > > --- > > arch/arm64/kernel/syscall.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c > > index 8f3371415642ad..95fd8c7ec8a171 100644 > > --- a/arch/arm64/kernel/syscall.c > > +++ b/arch/arm64/kernel/syscall.c > > @@ -21,7 +21,7 @@ asmlinkage long do_ni_syscall(struct pt_regs *regs) > > { > > #ifdef CONFIG_COMPAT > > long ret; > > - if (is_compat_task()) { > > + if (is_compat_task() && regs->regs[7] >= __ARM_NR_COMPAT_BASE) { > > compat_arm_syscall() ignores all bits r7 except for bits [15:0]. > > So, doesn't this mean that 0xf0000, 0x100000, 0x110000 will all do the > same thing now? (Previously to your patch, 0xe0000, 0xd0000 etc. would > also match in this code I've misunderstood something.) > > The gating check in arch/arm/kernel/trapc.s:arm_syscall() is > > if ((no >> 16) != (__ARM_NR_BASE>> 16)) > > I would expect that arm64 needs a similar check somewhere. Is the check > already present? I may have missed it.
When not using OABI, __ARM_NR_BASE is zero, so I think the 32-bit semantics for non-OABI are: 0 - 399 : Invoke syscall via syscall table 400 - 0xeffff : -ENOSYS (to be allocated in future) 0xf0000 - 0xfffff : Private syscall or -ENOSYS if not allocated > 0xfffff : SIGILL so for arm64 compat, we need to do the following: 1. Ensure we only SIGILL for that last region 2. Don't pull the syscall number directly from pt_regs, since it may have been changed by a tracer 3. Hook up compat_sys_io_pgetevents Patches incoming... Will