[LTP] [PATCH v2 1/2] syscalls/cma: test case should return TCONF if syscall doesn't exist

Jan Stancek
2019-02-22T18:29:27Z

----- Original Message -----
>
>
> ----- Original Message -----
> > On Fri, Feb 15, 2019 at 9:53 PM Jan Stancek <jstancek@redhat.com> wrote:
> >
> > >
> > >
> > > ------------------------------
> > >
> > > Hi Jason,
> > >
> > > A new failure was occured after applying this new patch.
> > >
> > > From our observation, the latest process_vm_readv03.c failed with
> > > process_vm_readv() Invalid argument error on rhel7.3 platfrom. We suspect
> > > that this problem maybe caused by glibc or compiler, because if compile
> > > the
> > > test program with -O0 it get pass, but with the ltp
> > > default optimization -O2 it get fail. Also, if we revert this new patch,
> > > the test PASS whatever with -O2 and -O0, that's very strange.
> > >
> > >
> > > One difference is that the extra function promoted int to long.
> > >
> >
> > Good catch.
> >
> > > Can you try with patch below? (Note that I dropped also root requirement,
> > > man page
> > > says that it has same requirements as ptrace - you should be able to read
> > > from processes you own)
> > >
> > > This change works for me(one comment in below).
> >
> > But there still have a tiny question, in the syscall tracing log, I noticed
> > a process_vm_readv() calling does not get this failure in function
> > fetch_remote_addrs, what makes it difference with other two calls is
> > something I'm thinking now.
>
> "Garbage" on stack most likely. On x86_64, 6th parameter is passed
> via stack, glibc copies quadword:
>
> ENTRY (syscall)
> movq %rdi, %rax /* Syscall number -> rax. */
> movq %rsi, %rdi /* shift arg1 - arg5. */
> movq %rdx, %rsi
> movq %rcx, %rdx
> movq %r8, %r10
> movq %r9, %r8
> movq 8(%rsp),%r9 /* arg6 is on the stack. */
> syscall /* Do the system call. */
>
> >
> > ====Tracing log without '0L' change====
> > 12211 process_vm_readv(12211, 0, 0, 0, 0, 140728898420736) = -1 EINVAL
> > (Invalid argument)
> > ...
> > 12213 process_vm_readv(12212,
> > [{"\300`\334\0\0\0\0\0`\2\335\0\0\0\0\0\340\26\335\0\0\0\0\0\220h\335\0\0\0\0\0"...,
> > 80}], 1, [{0xdc6060, 80}], 1, 0) = 80
> > ...
> > 12213 process_vm_readv(12212, 0x7ffecef1e330, 4, 0xdc60c0, 10,
> > 140728898420736) = -1 EINVAL (Invalid argument)
> >
> >
> >
> > >
> > > diff --git a/testcases/kernel/syscalls/cma/process_vm_readv03.c
> > > b/testcases/kernel/syscalls/cma/process_vm_readv03.c
> > > index 45f7c92e499c..1cec442b3456 100644
> > > --- a/testcases/kernel/syscalls/cma/process_vm_readv03.c
> > > +++ b/testcases/kernel/syscalls/cma/process_vm_readv03.c
> > > @@ -181,7 +181,7 @@ static long *fetch_remote_addrs(void)
> > > remote.iov_len = len;
> > >
> > > TEST(ltp_syscall(__NR_process_vm_readv, pids[0], &local,
> > > - 1, &remote, 1, 0));
> > > + 1, &remote, 1, 0L));
> > >
> >
> > To make things more safely, probably we'd better change all the integer
> > parameter too?
> >
> > - 1, &remote, 1, 0));
> > + 1L, &remote, 1L, 0L));
>
> Agreed, let's match all parameters types as before commit:
> 9b02cd465f70 ("syscalls/cma: test case should return TCONF if syscall
> doesn't exist")

So, it looks like this thread has stalled. I'll look into posting a patch,
unless I hear someone is already working on it.

Regards,
Jan

>
> >
> > --
> > Regards,
> > Li Wang
> >
>