On Fri, Jun 21, 2013 at 08:59:32AM -0700, David Daney wrote: > On 06/21/2013 06:39 AM, James Hogan wrote: > >MIPS has 128 signals, the highest of which has the number 128 (they > >start from 1). The following command causes get_signal_to_deliver() to > >pass this signal number straight through to do_group_exit() as the exit > >code: > > > > strace sleep 10 & sleep 1 && kill -128 `pidof sleep` > > > >However do_group_exit() checks for the core dump bit (0x80) in the exit > >code which matches in this particular case and the kernel panics: > > > > BUG_ON(exit_code & 0x80); /* core dumps don't get here */ > > > >Fundamentally the exit / wait status code cannot represent SIG128. In > >fact it cannot represent SIG127 either as 0x7f represents a stopped > >child. > > > >Therefore add sig_to_exitcode() and exitcode_to_sig() functions which > >map signal numbers > 126 to exit code 126 and puts the remainder (i.e. > >sig - 126) in higher bits. This allows WIFSIGNALED() to return true for > >both SIG127 and SIG128, and allows WTERMSIG to be later updated to read > >the correct signal number for SIG127 and SIG128. > > I really hate this approach. > > Can we just change the ABI to reduce the number of signals so that > all the standard C library wait related macros don't have to be > changed? Changing the ABI is a very strong medicine that wants to be used very carefully. > Think about it, any user space program using signal numbers 127 and > 128 doesn't work correctly as things exist today, so removing those > two will be no great loss. Glibc has it's own sigset_t of 1024 signals. I wonder if it will even use more than 64 signals. Similar for other libcs. Ralf
