Re: [PATCH] Fix traceaio with IO_CMD_{PREAD,PWRITE}

[Nir Soffer <nsoffer@redhat.com>]

On Fri, Sep 24, 2021 at 2:00 AM Frank Ch. Eigler <fche@redhat.com> wrote:
>
> Hi -
>
> > This works:
> >
> > global IO_CMD_PREADV = 7
> > global IO_CMD_PWRITEV = 8
> >
> > Do we have a better way to handle this?
>
> Within a tapset snippet, code can use
>    @const("IO_CMD_PREADV")
> referring to an identifier in embedded-C scope.

This works, bug require -g in stap script. I don't think it makes sense
to require Guru mode just to access an enum. It would be nice it this
could work without -g, since accessing constants seems to be a safe
operation.

> If the IO_CMD_PREADV identifier were an enum value that shows up in
> DWARF, then $IO_CMD_PREADV can resolve in recent versions of stap.

I could not find the enum in debuginfo files or in stap -L output, but maybe
I was not using the right tool for this.

In a test program using libaio, I cannot find the enum values in the symbols
so I guess this info is not available.

> If none of the above, yeah, use the global gadget.

I sent v2 using globals.

Nir