Re: [PATCH v2 0/1] alpha: add support for SECCOMP and SECCOMP_FILTER

[Michael Cree <mcree@orcon.net.nz>]

On Fri, Feb 20, 2026 at 11:50:09AM +0100, Magnus Lindholm wrote:
> This patch adds SECCOMP and SECCOMP_FILTER support to the Alpha
> architecture.
> 
> The seccomp-bpf selftests exercise syscall tracing, restart, and signal
> interaction paths that were previously untested on Alpha. To support
> these, the ptrace/strace syscall path is updated to reliably distinguish
> internal skip-dispatch from userspace invalid syscall numbers, ensuring
> that syscall(-1) continues to return -ENOSYS with correct r0/a3
> semantics.
> 
> Supporting seccomp also requires correct syscall restart handling when
> ptrace and signal delivery are involved. The traced syscall entry path
> now consistently tracks syscall state using r0, r1, and r2 while
> preserving Alpha's a3-based error reporting ABI:
> 
>   - r1 holds the mutable "current" syscall number
>   - r2 preserves the original syscall number for restart
>   - r0 and r19 (a3) retain their traditional roles as return value and
>     error indicator
> 
> This separation allows syscall restarts to be gated strictly on valid
> ERESTART* return codes in the ptrace/strace paths and prevents
> kernel-internal restart values from leaking into userspace.
> 
> Alpha also lacked support for PTRACE_GETREGSET(NT_PRSTATUS), causing
> ptrace-based seccomp tests to fail with -EIO. Minimal GETREGSET and
> SETREGSET support is added to export struct pt_regs directly.
> 
> With these changes applied, the seccomp-bpf and ptrace syscall selftests
> (seccomp_bpf, extended for Alpha) pass reliably on Alpha systems.
> 
> ---
> Changes since v1:
>  - Update features documentation for seccomp-filter/alpha
> Link: https://lore.kernel.org/linux-alpha/20260205133049.526-1-linmag7@gmail.com/T/#t
> 
> Magnus Lindholm (1):
>   alpha: add support for SECCOMP and SECCOMP_FILTER
> 

Passes the seccomp-bpf selftests and the live tests of Adrian's
alpha-support branch of libseccomp on my ES45.

Tested-by: Michael Cree <mcree@orcon.net.nz>

Cheers,
Michael.