On Mon, Aug 26, 2019 at 12:42:28PM -0300, Jason Gunthorpe wrote:
> On Mon, Aug 26, 2019 at 08:38:00AM -0700, Nathan Chancellor wrote:
> > On Fri, Aug 23, 2019 at 11:24:27AM -0300, Jason Gunthorpe wrote:
> > > The latest clang-9 packages from apt.llvm.org do seem to build the
> > > kernel, I get one puzzling warning under RDMA:
> > >
> > > drivers/infiniband/hw/hfi1/platform.o: warning: objtool: tune_serdes()+0x1f4: can't find jump dest instruction at .text+0x118a
> >
> > Any particular config that I should use to easily reproduce this?
>
> Sure, attached. With the clang-9 build for Bionic
This is reproducible with the kernel config attached and a tip of tree
build of LLVM.
$ make -j$(nproc) CC=clang O=out clean olddefconfig drivers/infiniband/hw/hfi1/platform.o
...
CC drivers/infiniband/hw/hfi1/platform.o
drivers/infiniband/hw/hfi1/platform.o: warning: objtool: tune_serdes()+0x1f4: can't find jump dest instruction at .text+0x117a
I ran creduce on that file and it spits out:
a() {
char *b = a;
switch (b[7] & 240 >> 4) {
case 10 ... 11:
c();
case 0 ... 9:
case 12:
case 14:
d();
case 13:
case 15:;
}
}
to simply reproduce the warning. The original preprocessed file +
interestingness test are available here:
https://github.com/nathanchance/creduce-files/tree/4e252c0ca19742c90be1445e6c722a43ae561144/rdma-objtool
Looks like that comes from tune_qsfp, which gets inlined into
tune_serdes but I am far from an objtool expert so I am not
really sure what kind of issues I am looking for. Adding Josh
and Peter for a little more visibility.
Here is the original .o file as well:
https://github.com/nathanchance/creduce-files/raw/4e252c0ca19742c90be1445e6c722a43ae561144/rdma-objtool/platform.o.orig
Cheers,
Nathan
