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

[Mukesh Kumar Chaurasiya]

On Wed, Jul 22, 2026 at 09:54:43AM +0200, Florian Weimer wrote:
> * Dmitry V. Levin:
> 
> > On Fri, Jan 23, 2026 at 01:09:13PM +0530, Mukesh Kumar Chaurasiya wrote:
> >> From: Mukesh Kumar Chaurasiya <mchauras@xxxxxxxxxxxxx>
> >> 
> >> 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
> 
Hey,

Thanks for reporting this. I was unaware that this would break userspace.
I am working on a fix for this, I am trying to maintain this state
somewhere else than pt_regs. That would make the userspace work without
recompilation.

Regards,
Mukesh