From: will.deacon@arm.com (Will Deacon) Date: Thu, 8 Jan 2015 17:01:52 +0000 Subject: [RFC 6/8] ARM64: Handle TRAP_HWBRKPT for user mode as well In-Reply-To: <20150102180523.GC6761@redhat.com> References: <1e0a9e778669bb2a2e40bf101eff8ae85110ce54.1420038188.git.panand@redhat.com> <20150102180523.GC6761@redhat.com> Message-ID: <20150108170152.GS11583@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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 > > --- > > 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