Re: [PATCH] ppc: Fix BPF JIT for ABIv2

On Sun, Jun 19, 2016 at 11:19:14PM +0530, Naveen N. Rao wrote:

On 2016/06/17 10:00AM, Thadeu Lima de Souza Cascardo wrote:

quoted

On Fri, Jun 17, 2016 at 10:53:21PM +1000, Michael Ellerman wrote:

quoted

On Tue, 2016-07-06 at 13:32:23 UTC, "Naveen N. Rao" wrote:

quoted

diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
new file mode 100644
index 0000000..954ff53
--- /dev/null
+++ b/arch/powerpc/net/bpf_jit_comp64.c

@@ -0,0 +1,956 @@

...

quoted

+
+static void bpf_jit_fill_ill_insns(void *area, unsigned int size)
+{
+	int *p = area;
+
+	/* Fill whole space with trap instructions */
+	while (p < (int *)((char *)area + size))
+		*p++ = BREAKPOINT_INSTRUCTION;
+}

This breaks the build for some configs, presumably you're missing a header:

  arch/powerpc/net/bpf_jit_comp64.c:30:10: error: 'BREAKPOINT_INSTRUCTION' undeclared (first use in this function)

http://kisskb.ellerman.id.au/kisskb/buildresult/12720611/

cheers

Hi, Michael and Naveen.

I noticed independently that there is a problem with BPF JIT and ABIv2, and
worked out the patch below before I noticed Naveen's patchset and the latest
changes in ppc tree for a better way to check for ABI versions.

However, since the issue described below affect mainline and stable kernels,
would you consider applying it before merging your two patchsets, so that we can
more easily backport the fix?

Hi Cascardo,
Given that this has been broken on ABIv2 since forever, I didn't bother 
fixing it. But, I can see why this would be a good thing to have for 
-stable and existing distros. However, while your patch below may fix 
the crash you're seeing on ppc64le, it is not sufficient -- you'll need 
changes in bpf_jit_asm.S as well.

Hi, Naveen.

Any tips on how to exercise possible issues there? Or what changes you think
would be sufficient?

I will see what I can find by myself, but would appreciate any help.

Regards.
Cascardo.

Regards,
Naveen

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