Re: [PATCH 5/5] MIPS: Add support for eBPF JIT.

[Daniel Borkmann]

On 05/26/2017 02:38 AM, David Daney wrote:

Since the eBPF machine has 64-bit registers, we only support this in
64-bit kernels.  As of the writing of this commit log test-bpf is showing:

   test_bpf: Summary: 316 PASSED, 0 FAILED, [308/308 JIT'ed]

All current test cases are successfully compiled.

Signed-off-by: David Daney <david.da...@cavium.com>

Awesome work!

Did you also manage to run tools/testing/selftests/bpf/ fine with
the JIT enabled?

[...]

+struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
+{
+       struct jit_ctx ctx;
+       unsigned int alloc_size;
+
+       /* Only 64-bit kernel supports eBPF */
+       if (!IS_ENABLED(CONFIG_64BIT) || !bpf_jit_enable)

Isn't this already reflected by the following?

  select HAVE_EBPF_JIT if (64BIT && !CPU_MICROMIPS)

+               return prog;
+
+       memset(&ctx, 0, sizeof(ctx));
+
+       ctx.offsets = kcalloc(prog->len + 1, sizeof(*ctx.offsets), GFP_KERNEL);
+       if (ctx.offsets == NULL)
+               goto out;
+
+       ctx.reg_val_types = kcalloc(prog->len + 1, sizeof(*ctx.reg_val_types), 
GFP_KERNEL);
+       if (ctx.reg_val_types == NULL)
+               goto out;
+
+       ctx.skf = prog;
+
+       if (reg_val_propagate(&ctx))
+               goto out;
+
+       /* First pass discovers used resources */
+       if (build_int_body(&ctx))
+               goto out;
+
+       /* Second pass generates offsets */
+       ctx.idx = 0;
+       if (gen_int_prologue(&ctx))
+               goto out;
+       if (build_int_body(&ctx))
+               goto out;
+       if (build_int_epilogue(&ctx))
+               goto out;
+
+       alloc_size = 4 * ctx.idx;
+
+       ctx.target = module_alloc(alloc_size);

You would need to use bpf_jit_binary_alloc() like all other
eBPF JITs do, otherwise kallsyms of the JITed progs would
break.

+       if (ctx.target == NULL)
+               goto out;
+
+       /* Clean it */
+       memset(ctx.target, 0, alloc_size);
+
+       /* Third pass generates the code */
+       ctx.idx = 0;
+       if (gen_int_prologue(&ctx))
+               goto out;
+       if (build_int_body(&ctx))
+               goto out;
+       if (build_int_epilogue(&ctx))
+               goto out;
+       /* Update the icache */
+       flush_icache_range((ptr)ctx.target, (ptr)(ctx.target + ctx.idx));
+
+       if (bpf_jit_enable > 1)
+               /* Dump JIT code */
+               bpf_jit_dump(prog->len, alloc_size, 2, ctx.target);
+
+       prog->bpf_func = (void *)ctx.target;
+       prog->jited = 1;
+
+out:
+       kfree(ctx.offsets);
+       kfree(ctx.reg_val_types);
+
+       return prog;
+}