On Fri, Aug 22, 2014 at 01:19:13AM +0100, AKASHI Takahiro wrote: > On 08/22/2014 01:47 AM, Kees Cook wrote: > > On Thu, Aug 21, 2014 at 3:56 AM, AKASHI Takahiro > > <takahiro.aka...@linaro.org> wrote: > >> To allow tracer to be able to change/skip a system call by re-writing > >> a syscall number, there are several approaches: > >> > >> (1) modify x8 register with ptrace(PTRACE_SETREGSET), and handle this case > >> later on in syscall_trace_enter(), or > >> (2) support ptrace(PTRACE_SET_SYSCALL) as on arm > >> > >> Thinking of the fact that user_pt_regs doesn't expose 'syscallno' to > >> tracer as well as that secure_computing() expects a changed syscall number > >> to be visible, especially case of -1, before this function returns in > >> syscall_trace_enter(), we'd better take (2). > >> > >> Signed-off-by: AKASHI Takahiro <takahiro.aka...@linaro.org> > > > > Thanks, I like having this on both arm and arm64. > > Yeah, having this simplified the code of syscall_trace_enter() a bit, but > also imposes some restriction on arm64, too. > > > I wonder if other archs should add this option too. > > Do you think so? I assumed that SET_SYSCALL is to be avoided if possible. > > I also think that SET_SYSCALL should take an extra argument for a return value > just in case of -1 (or we have SKIP_SYSCALL?).
I think we should propose this as a new request in the generic ptrace code. We can have an architecture-hook for actually setting the syscall, and allow architectures to define their own implementation of the request so they can be moved over one by one. Will -- 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/
