Messages in this thread | | | Date | Fri, 26 Sep 2014 15:26:40 -0700 | Subject | Re: eBPF verifier thoughts (Re: [PATCH v15 net-next 00/11] eBPF syscall, verifier, testsuite) | From | Alexei Starovoitov <> |
| |
On Fri, Sep 26, 2014 at 3:07 PM, Andy Lutomirski <luto@amacapital.net> wrote: > On Fri, Sep 26, 2014 at 3:03 PM, Alexei Starovoitov <ast@plumgrid.com> wrote: >> On Fri, Sep 26, 2014 at 2:47 PM, Andy Lutomirski <luto@amacapital.net> wrote: >>> >>> Can't you just disallow the 1-byte write to the stack? >> >> of course not. >> That would be extremely limiting to users. >> Can you actually see yourself living with stack that only >> allows 8-byte writes/reads? >> The stack usage will increase a lot, since all char/short >> stack variables will become 8-byte... > > How about requiring that sub-8-byte stack accesses only be to integer slots?
you mean to reject the sub-8-byte write early if it's going into space where pointers were stored? That will limit stack reuse. gcc/llvm generate code where the same stack location is used by different variables during life of the function. So if I reject the write early, it will break otherwise valid programs.
| |