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

Thanks for CCing.  One way to clean up this would be to refactor the
bpf jit interface as:

  bpf_func_t bpf_jit_compile(struct sock_filter *filter, unsigned int flen);
  void bpf_jit_free(bpf_func_t bpf_func);

Then both packet and seccomp filters can share the unified interface.
Also, we don't need seccomp_filter_get_len() and other helpers.

Do you want me to rebase my patch against linux-next and see how that goes?

- xi

On Fri, Apr 26, 2013 at 6:01 PM, Daniel Borkmann [off-list ref] wrote:

On 04/26/2013 10:09 PM, Andrew Morton wrote:

quoted

On Fri, 26 Apr 2013 21:47:46 +0200 Daniel Borkmann [off-list ref]
wrote:

quoted

On 04/26/2013 09:26 PM, Andrew Morton wrote:

quoted

On Fri, 26 Apr 2013 16:04:44 +0200 Arnd Bergmann [off-list ref] wrote:

quoted

On Wednesday 24 April 2013 19:27:08 Nicolas Schichan wrote:

quoted

@@ -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.

quoted

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.