On Fri, Jan 02, 2015 at 06:05:23PM +0000, Oleg Nesterov wrote:
> Let me repeat once again that I know absolutely nothing about arm* ;)
>
> On 12/31, Pratyush Anand wrote:
> >
> > uprobe registers a handler at step_hook. So, single_step_handler now
> > checks for user mode as well if there is a valid hook.
> >
> > Signed-off-by: Pratyush Anand <pan...@redhat.com>
> > ---
> > arch/arm64/kernel/debug-monitors.c | 6 +++---
> > 1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/arm64/kernel/debug-monitors.c
> > b/arch/arm64/kernel/debug-monitors.c
> > index b056369fd47d..2676b8655241 100644
> > --- a/arch/arm64/kernel/debug-monitors.c
> > +++ b/arch/arm64/kernel/debug-monitors.c
> > @@ -236,6 +236,9 @@ static int single_step_handler(unsigned long addr,
> > unsigned int esr,
> > if (!reinstall_suspended_bps(regs))
> > return 0;
> >
> > + if (call_step_hook(regs, esr) == DBG_HOOK_HANDLED)
> > + return 0;
> > +
> > if (user_mode(regs)) {
> > info.si_signo = SIGTRAP;
> > info.si_errno = 0;
> > @@ -251,9 +254,6 @@ static int single_step_handler(unsigned long addr,
> > unsigned int esr,
> > */
> > user_rewind_single_step(current);
> > } else {
> > - if (call_step_hook(regs, esr) == DBG_HOOK_HANDLED)
> > - return 0;
> > -
>
> Agreed, we need something like this change...
>
> But did you verify that it can't break other users of register_step_hook() ?
> The current handlers do not check user_mode() == F, they assume that they
> can't be called otherwise.
>
> If this all is correct, please explain why in the changelog.
I think you're right, and kgdb will need fixing with this change.
Will
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