Re: [PATCH] bpf: Support shadow stack

[Yonghong Song <yonghong.song@linux.dev>]

Please ignore this patch and the next one shadow stack patch as well.
These patches are my prototype before lsfmmbpf conference.
Alexei has suggested a better approach which I will implement and post
soon.

On 6/4/24 10:55 AM, Yonghong Song wrote:
> Try to add 3rd argument to bpf program where the 3rd argument
> is the frame pointer to bpf program stack.
>
> There are a few issues here:
>    - Currently, only main bpf program is using shadow stack.
>      other sub programs (static or global) still use stack.
>      It is POSSIBLE to a hidden register to pass
>      frame pointer (derived from main program) to those static
>      or global functions.
>    - But tail call and ext programs are not working now we
>      we do not know at jit time what programs will be used
>      in tail call and ext. It is possible to do some jit
>      during text_poke time. But that will need additional
>      stack allocation at jit time and that will be complicated.
>    - For xdp program, need to patch jit for xdp dispatcher.
>
> Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
> ---
>   arch/x86/net/bpf_jit_comp.c | 105 +++++++++++++++++++++++++++++-------
>   include/linux/bpf-cgroup.h  |   9 ++--
>   include/linux/bpf.h         |  29 ++++++----
>   include/linux/filter.h      |  25 +++++++--
>   kernel/bpf/cgroup.c         |   9 ++--
>   kernel/bpf/core.c           |  36 +++++++++++--
>   kernel/bpf/offload.c        |   3 +-
>   7 files changed, 173 insertions(+), 43 deletions(-)
[...]