Re: [PATCH 2/2] perf bpf: Check relocation target section

[Wangnan (F)]

On 2016/1/25 9:56, Wangnan (F) wrote:
> On 2016/1/23 1:11, Alexei Starovoitov wrote:
> > On Fri, Jan 22, 2016 at 09:27:21AM +0000, Wang Nan wrote:
> > > Libbpf should check target section before doing relocation to ensure
> > > the relocation is correct. If not, a bug in LLVM causes error. See [1].
> > > Also, if an incorrect BPF script uses both global variable and
> > > map, global variable whould be treated as map and be relocated
> > > without error.
> > >
> > > This patch saves id of map section into obj->efile and compare
> > > target section of a relocation symbol against it during relocation.
> > ...
> > > [1] https://llvm.org/bugs/show_bug.cgi?id=26243
> > ...
> > > Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
> > >   +        if (sym.st_shndx != maps_shndx) {
> > > +            pr_warning("Program '%s' contains non-map related relo 
> > > data pointing to section %u\n",
> > > +                   prog->section_name, sym.st_shndx);
> > > +            return -LIBBPF_ERRNO__RELOC;

There's a trailing whitespace. Sorry.

> > > +        }
> > May be 'pr_err' instead of 'pr_warning', since such program will fail
> > to load by kernel anyway.
>
> Libbpf doesn't issue pr_error even in fatal exception because it 
> doesn't define
> pr_err at all. It reports error code and let perf deal with error.
>
> Thank you.
>
> >   Looks good otherwise.
> > Acked-by: Alexei Starovoitov <ast@xxxxxxxxxx>