Re: [RFC 6/8] ARM64: Handle TRAP_HWBRKPT for user mode as well

[Pratyush Anand]

On Thursday 08 January 2015 10:31 PM, Will Deacon wrote:
> 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 <panand@xxxxxxxxxx>
> > > ---
> > >   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.

OK, I will fix kgdb  too when I will send next revision.

~Pratyush

> Will
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