linux-kernel - Re: [PATCH 1/4] alpha/uapi: do not expose kernel-only stack frame structures

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Message-ID: <Z5qIqHmpxnRpXC35@minute>
Date: Wed, 29 Jan 2025 20:59:36 +0100
From: Ivan Kokshaysky <ink@...een.parts>
To: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
Cc: Richard Henderson <richard.henderson@...aro.org>,
	Matt Turner <mattst88@...il.com>, Oleg Nesterov <oleg@...hat.com>,
	Al Viro <viro@...iv.linux.org.uk>, Arnd Bergmann <arnd@...db.de>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	"Maciej W. Rozycki" <macro@...am.me.uk>,
	Magnus Lindholm <linmag7@...il.com>, linux-alpha@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] alpha/uapi: do not expose kernel-only stack frame
 structures

On Wed, Jan 29, 2025 at 07:32:11PM +0100, John Paul Adrian Glaubitz wrote:
> Hi Ivan,
> 
> On Wed, 2025-01-29 at 10:43 +0100, Ivan Kokshaysky wrote:
> > Parts of asm/ptrace.h went into UAPI with commit 96433f6ee490
> > ("UAPI: (Scripted) Disintegrate arch/alpha/include/asm") back in 2012.
> > At first glance it looked correct, as many other architectures expose
> > 'struct pt_regs' for ptrace(2) PTRACE_GETREGS/PTRACE_SETREGS requests.
> > On Alpha, however, these requests have never been implemented;
> > 'struct pt_regs' describes internal kernel stack frame which has
> > nothing to do with userspace. Same applies to 'struct switch_stack',
> > as PTRACE_GETFPREG/PTRACE_SETFPREG are not implemented either.
> > 
> > Move this stuff back into internal asm, where we can ajust it
> > without causing a lot of confusion about possible UAPI breakage.
...
> This seems to break the build for the bpf tool on alpha:
> 
> In file included from libbpf.c:36:
> /build/reproducible-path/linux-6.13~rc7/tools/include/uapi/linux/bpf_perf_event.h:14:28: error: field ‘regs’ has incomplete type
>    14 |         bpf_user_pt_regs_t regs;
>       |                            ^~~~
> 

Good catch, thanks!

I wonder if bpftool ever worked properly on Alpha. Will check...

Ivan.