Re: [PATCH] perf: Fix oops when kthread execs user process

[Peter Zijlstra]

On Wed, May 29, 2019 at 02:05:21PM +0100, Will Deacon wrote:
> On Wed, May 29, 2019 at 02:55:57PM +0200, Peter Zijlstra wrote:

> >  	if (user_mode(regs)) {
> 
> Hmm, so it just occurred to me that Mark's observation is that the regs
> can be junk in some cases. In which case, should we be checking for
> kthreads first?

task_pt_regs() can return garbage, but @regs is the exception (or
perf_arch_fetch_caller_regs()) regs, and for those user_mode() had
better be correct.