On Tue, Mar 28, 2017 at 7:54 AM, Oleg Nesterov <[email protected]> wrote: > get_nr_restart_syscall() checks TS_I386_REGS_POKED but this bit is only > set if debugger is 32-bit. If a 64-bit debugger restores the registers > of a 32-bit debugee outside of syscall exit path get_nr_restart_syscall() > wrongly returns __NR_restart_syscall.
I had sent a patch that introduced a new syscall nr, but it's not quite safe because it could break seccomp-using programs. But your patch here is also screwy. How about we store the syscall arch to be restored in task_struct along with restart_block? It's not perfect, but it should be 99% of the way there without heuristics as nasty as yours. --Andy P.S. __USER32_CS is the wrong check even if we used your approach. user_64bit_regs() is much better.
