Re: [PATCH 23/33] x86/asm/bpf: Create stack frames in bpf_jit.S

* Alexei Starovoitov [off-list ref] wrote:

quoted

quoted

I could be missing something. I think either this patch is not need or you 
need to teach the tool to ignore all JITed stuff. I don't think it's 
practical to annotate everything. Different JITs do their own magic. s390 
JIT is even more fancy.

Well, but the point of these patches isn't to make the tool happy.  It's 
really to make sure that runtime stack traces can be made reliable. Maybe I'm 
missing something but I don't see why JIT code can't honor 
CONFIG_FRAME_POINTER just like any other code.

It can if there is no performance cost added. I can speak for x64 JIT, but the 
rest needs to be analyzed as well. My point was that may be it's easier to 
ignore all JITed code and just say that such call stacks may be unreliable? 
live-patching is not applicable to JITed code anyway or you want to livepatch 
the callees of it?

So the rule is that if frame pointers are enabled all kernel code should have 
correct stack frames - in case an IRQ (or NMI) hits it or it crashes.

Thanks,

	Ingo