On Wed, Jun 9, 2021 at 2:42 AM Yonghong Song <yhs@xxxxxx> wrote: > So your intention is to call functions in > drivers/gpu/drm/drm_gem_ttm_helper.c, right? How do you get function > parameters? What kinds of programs you intend to call > this functions? ok... sounds like my use case was not concret enough. Perhaps I can elaborate further with the following examples: In the GPU scheduler, there's a trace point "trace_drm_run_job(sched_job, entity)": https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/scheduler/sched_main.c#L813 If I want to analyze the jobs being scheduled, I can potentially attach a bpf prog with this tracepoint. Each driver has its own run_job and sched_job implementation so I was thinking the drivers can provide a bpf helper function to resolve this. Alternatively, there could be tracepoint in the driver implementation that one can attach bpf to, but tracepoints are not universally put in place (have trace: https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c#L221; not have trace: https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/etnaviv/etnaviv_sched.c#L72 .) So in cases without tracepoint, I guess I would be using kprobe or fentry? Note that all of these are in kernel modules. My understanding is that BTF will work but having helper functions from the kernel modules are not yet available? So let say I want to whitelist and call " amdgpu_device_gpu_recover" (https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c#L4521) from inside a bpf prog, or whitelist and call "drm_sched_increase_karma" https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/scheduler/sched_main.c#L362, I wouldn't be able to do so? Are there any criteria in terms of what kernel function should or should not be whitelisted (separate from the kernel module support question)? For example, would amdgpu_device_gpu_recover be not "whitelist-able" because of the hw interaction or complexity or likelihood to crash the kernel while drm_sched_increase_karma is ok because it's more or less manipulation of some data structure? A quick side question, does container_of work inside a bpf prog? > kprobe probably won't work as kernel does not capture > traced function types. fentry program might be a good > choice. Thanks for the pointer. I am not familiar with fentry but I will look into it. By function type, what do you mean by that?
