Re: [PATCH V3 2/3] ARM: net: bpf_jit: make code generation less dependenton struct sk_filter.

[Daniel Borkmann]

This is a multi-part message in MIME format.On 04/26/2013 10:09 PM, Andrew Morton wrote:
> On Fri, 26 Apr 2013 21:47:46 +0200 Daniel Borkmann <dborkman@xxxxxxxxxx> wrote:
> > On 04/26/2013 09:26 PM, Andrew Morton wrote:
> > > On Fri, 26 Apr 2013 16:04:44 +0200 Arnd Bergmann <arnd@xxxxxxxx> wrote:
> > > > On Wednesday 24 April 2013 19:27:08 Nicolas Schichan wrote:
> > > > > @@ -858,7 +858,7 @@ b_epilogue:
> > > > >    }
> > > > >
> > > > >
> > > > > -void bpf_jit_compile(struct sk_filter *fp)
> > > > > +static void __bpf_jit_compile(struct jit_ctx *out_ctx)
> > > > >    {
> > > > >           struct jit_ctx ctx;
> > > > >           unsigned tmp_idx;
> > > > > @@ -867,11 +867,10 @@ void bpf_jit_compile(struct sk_filter *fp)
> > > > >           if (!bpf_jit_enable)
> > > > >                   return;
> > > > >
> > > > > -       memset(&ctx, 0, sizeof(ctx));
> > > > > -       ctx.skf         = fp;
> > > > > +       ctx = *out_ctx;
> > > > >           ctx.ret0_fp_idx = -1;
> > > > >
> > > > > -       ctx.offsets = kzalloc(4 * (ctx.skf->len + 1), GFP_KERNEL);
> > > > > +       ctx.offsets = kzalloc(4 * (ctx.prog_len + 1), GFP_KERNEL);
> > > > >           if (ctx.offsets == NULL)
> > > > >                   return;
> > > > >
> > > > > @@ -921,13 +920,26 @@ void bpf_jit_compile(struct sk_filter *fp)
> > > > >                   print_hex_dump(KERN_INFO, "BPF JIT code: ",
> > > > >                                  DUMP_PREFIX_ADDRESS, 16, 4, ctx.target,
> > > > >                                  alloc_size, false);
> > > > > -
> > > > > -       fp->bpf_func = (void *)ctx.target;
> > > > >    out:
> > > > >           kfree(ctx.offsets);
> > > > > +
> > > > > +       *out_ctx = ctx;
> > > > >           return;
> > > >
> > > > This part of the patch, in combination with 79617801e "filter: bpf_jit_comp:
> > > > refactor and unify BPF JIT image dump output" is now causing build errors
> > > > in linux-next:
> > > >
> > > > arch/arm/net/bpf_jit_32.c: In function '__bpf_jit_compile':
> > > > arch/arm/net/bpf_jit_32.c:930:16: error: 'fp' undeclared (first use in this function)
> > > >      bpf_jit_dump(fp->len, alloc_size, 2, ctx.target);
> > >
> > > Thanks, I did this.  There may be a smarter way...
> >
> > I think also seccomp_jit_compile() would need this change then, otherwise the build
> > with CONFIG_SECCOMP_FILTER_JIT might break.
>
> urgh, that tears it.
>
> > I can fix this up for you if not already applied. I presume it's against
> > linux-next tree?
>
> Yup, please send something.

Patch is attached. However, I currently don't have an ARM toolchain at hand, so
uncompiled, untested.

@Nicolas, Xi (cc, ref: http://thread.gmane.org/gmane.linux.kernel/1481464):

If there is someday support for other archs as well, it would be nice if we
do not have each time duplicated seccomp_jit_compile() etc functions in each
JIT implementation, i.e. because they do basically the same. So follow-up
{fix,clean}up is appreciated.

Also, I find it a bit weird that seccomp_filter_get_len() and some other
_one-line_ functions from kernel/seccomp.c are not placed into the
corresponding header file as inlines.