Hi Laurent, the code in musl libc probing the stack is in
https://git.musl-libc.org/cgit/musl/plain/src/thread/pthread_getattr_np.c The setup in elfload.c does work, but only when reserved_va is not set. In that case, any stack guard violation is handled by the host kernel and thus results in the expected EFAULT. However, in case of e.g. a 32bit target being emulated on a 64bit host, reserved_va is set and the current code in mmap.c will only produce a more generic ENOMEM, deviating from the kernel's behavior. On 5/7/20 5:35 PM, Laurent Vivier wrote: > Le 05/03/2020 à 22:05, Tobias Koch a écrit : >> If the address range starting at old_address overlaps with the stack guard it >> is invalid and mremap must fail with EFAULT. The musl c library relies on >> this >> behavior to detect the stack size, which it does by doing consecutive mremaps >> until it hits the stack guard. Without this patch, software (such as the Ruby >> interpreter) that calls pthread_getattr_np under musl will crash on 32 bit >> targets emulated on a 64 bit host. > Could you share some pointers to the code that is doing this? > > We have already this kind of code in linux-user/elfload.c, > setup_arg_pages(): could you check why it doesn't work? > > Thanks, > Laurent
