Re: [PATCH v4 5/8] powerpc: add exit_flags field in pt_regs

[Florian Weimer <fweimer@redhat.com>]

* Dmitry V. Levin:

> On Fri, Jan 23, 2026 at 01:09:13PM +0530, Mukesh Kumar Chaurasiya wrote:
>> From: Mukesh Kumar Chaurasiya <mchauras@linux.ibm.com>
>> 
>> Add a new field `exit_flags` in the pt_regs structure. This field will hold
>> the flags set during interrupt or syscall execution that are required during
>> exit to user mode.
>
> Apparently, this change breaks PTRACE_GETREGS as the latter has no means
> to communicate the size of struct pt_regs being written to userspace.
>
> As result, the kernel with this patch will write to userpsace 32 more
> bytes than before, and unless the userspace is re-compiled with the latest
> ptrace.h, 32 bytes of userspace memory after struct pt_regs will be
> overwritten.
>
> This issue was detected by strace test suite, specifically, the test that
> checks whether the actual number of bytes written by
> ptrace(PTRACE_GETREGS) matches sizeof(struct pt_regs), and that test failed
> with runtime version v7.1 and headers version v7.2-rc1.

I think this needs to be reverted because it breaks existing ptrace
users.  This isn't like iptables, where kernel updates did mandate
specific versions of the userspace tools.

Thanks,
Florian