On Mon, Jan 24, 2022 at 10:54 AM Kenny Yu <kennyyu@xxxxxx> wrote:
>
> This adds a helper for bpf programs to read the memory of other
> tasks.
>
> As an example use case at Meta, we are using a bpf task iterator program
> and this new helper to print C++ async stack traces for all threads of
> a given process.
>
> Signed-off-by: Kenny Yu <kennyyu@xxxxxx>
> ---
LGTM.
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> include/linux/bpf.h | 1 +
> include/uapi/linux/bpf.h | 11 +++++++++++
> kernel/bpf/helpers.c | 34 ++++++++++++++++++++++++++++++++++
> kernel/trace/bpf_trace.c | 2 ++
> tools/include/uapi/linux/bpf.h | 11 +++++++++++
> 5 files changed, 59 insertions(+)
>
[...]
> + ret = access_process_vm(tsk, (unsigned long)user_ptr, dst, size, 0);
> + if (ret == size)
> + return 0;
> +
> + memset(dst, 0, size);
> + /* Return -EFAULT for partial read */
> + return (ret < 0) ? ret : -EFAULT;
nit: unnecessary ()
> +}
> +
> +const struct bpf_func_proto bpf_copy_from_user_task_proto = {
> + .func = bpf_copy_from_user_task,
> + .gpl_only = false,
> + .ret_type = RET_INTEGER,
> + .arg1_type = ARG_PTR_TO_UNINIT_MEM,
> + .arg2_type = ARG_CONST_SIZE_OR_ZERO,
> + .arg3_type = ARG_ANYTHING,
> + .arg4_type = ARG_PTR_TO_BTF_ID,
> + .arg4_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK],
> + .arg5_type = ARG_ANYTHING
> +};
> +
[...]
