On Wed, Mar 02, 2016 at 08:28:30PM -0500, Rich Felker wrote: > On Thu, Mar 03, 2016 at 04:01:21AM +0300, Dmitry V. Levin wrote: > > On Mon, Feb 29, 2016 at 05:59:44PM -0500, Mike Frysinger wrote: > > > On 29 Feb 2016 15:56, Rich Felker wrote: > > [...] > > > > The attached (very hackish at the moment) patch makes it work for me > > > > by eliminating the need to define NOMMU_SYSTEM to 1 and using clone() > > > > with CLONE_VM and a new stack for the child, instead of vfork. I see > > > > some potential issues that need to be addressed before this could be > > > > made into a proper solution, though: > > > > > > > > 1. I'm not sure if all NOMMU systems strace supports have clone. If > > > > so, I think vfork could be dropped completely and this used > > > > instead. > > > > > > uClibc has long required clone, so seems safe to assume it exists > > > > strace assumes that PTRACE_SETOPTIONS works, which essentially means that > > linux kernel >= 2.6 is required. On some architectures, newer kernel is > > required (e.g. >= 2.6.15 on mips for PTRACE_GETREGS support). I don't > > know for sure whether all supported NOMMU systems have CLONE_VM, but > > I agree with Mike it seems safe to assume they do. > > I was merely unaware whether strace supported any non-Linux systems. > Linux has had clone/CLONE_VM since basically forever (2.0, maybe > earlier) so if strace is Linux-only this is a non-issue. Should I try > to prepare a patch converting all the forks to clone so that NOMMU is > not a special case?
Yes, the less NOMMU workarounds the better. > What should be done about daemonized tracer mode? If we could switch stack before clone and then switch stack back in the child process, it would be a relatively simple change. Otherwise I don't see any simple options. -- ldv
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