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

[Wangnan (F)]

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;
> > +		}
> 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>