On 11/28, Ananth N Mavinakayanahalli wrote: > > syscall-reset is the only failure I see on > powerpc: > > errno 14 (Bad address) > syscall-reset: syscall-reset.c:95: main: Assertion `(*__errno_location > ()) == 38' failed. > unexpected child status 67f > FAIL: syscall-reset
(to remind, it also fails without utrace) Once again, I know nothing about powerc, perhaps I misread the code, but I believe this test-case is just wrong on powerpc and should be fixed. On powerpc, syscall_get_nr() returns regs->gpr[0], this means this register is used to pass the syscall number. This matches do_syscall_trace_enter(), it returns regs->gpr[0] as a (possibly changed by tracer) syscall nr. arch/powerpc/kernel/entry_64.S does syscall_dotrace: bl .do_syscall_trace_enter mr r0,r3 // I guess, r3 = r0 ? ... b syscall_dotrace_cont syscall_dotrace_cont: syscall_dotrace_cont: cmpldi 0,r0,NR_syscalls bge- syscall_enosys syscall_enosys: li r3,-ENOSYS b syscall_exit Now return to the test-case, syscall-reset.c. The tracee does l = syscall (-23, 1, 2, 3) and stops. The tracer does #define RETREG offsetof(struct pt_regs, gpr[0]) #define NEWVAL ((long) ENOTTY) l = ptrace(PTRACE_PEEKUSER, child, RETREG, 0l); l == -23, this is correct, note syscall(-23) above. l = ptrace(PTRACE_POKEUSER, child, RETREG, NEWVAL); And expects the tracee will see NEWVAL==ENOTTY after return from the systame call. Of course this can't happen. We changed the syscall number, the new value is ENOTTY == 25 == __NR_stime, sys_stime() correctly returns -EFAULT. ----------------------------------------------------------------- If I change the test-case to use NEWVAL == 1000 (or any other value greater than NR_syscalls), then the tracee sees ENOSYS and this is correct too. But I do not see how it is possible to change the retcode on powerpc. Unlike x86, powepc doesn't set -ENOSYS "in advance", before doing do_syscall_trace_enter() logic. This means that if the tracer "cancels" syscall, r3 will be overwritten by syscall_enosys. This probably means the kernel should be fixed too, but I am not brave enough to change the asm which I can't understand ;) Oleg.