Commit 252988cb authored Apr 01, 2018 by Nicholas Piggin Committed by Michael Ellerman Apr 03, 2018

powerpc: Don't write to DABR on >= Power8 if DAWR is disabled



flush_thread() calls __set_breakpoint() via set_debug_reg_defaults()
without checking ppc_breakpoint_available(). On Power8 or later CPUs
which have the DAWR feature disabled that will cause a write to the
DABR which is incorrect as those CPUs don't have a DABR.

Fix it two ways, by checking ppc_breakpoint_available() in
set_debug_reg_defaults(), and also by reworking __set_breakpoint() to
only write to DABR on Power7 or earlier.

Fixes: 96541531 ("powerpc: Disable DAWR in the base POWER9 CPU features")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Rework the logic in __set_breakpoint()]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

parent e303c087

arch/powerpc/kernel/process.c

+8 −2

Original line number	Diff line number	Diff line
		@@ -718,6 +718,7 @@ static void set_debug_reg_defaults(struct thread_struct *thread)
		{
		thread->hw_brk.address = 0;
		thread->hw_brk.type = 0;
		if (ppc_breakpoint_available())
		set_breakpoint(&thread->hw_brk);
		}
		#endif /* !CONFIG_HAVE_HW_BREAKPOINT */
		@@ -815,9 +816,14 @@ void __set_breakpoint(struct arch_hw_breakpoint *brk)
		memcpy(this_cpu_ptr(&current_brk), brk, sizeof(*brk));

		if (cpu_has_feature(CPU_FTR_DAWR))
		// Power8 or later
		set_dawr(brk);
		else
		else if (!cpu_has_feature(CPU_FTR_ARCH_207S))
		// Power7 or earlier
		set_dabr(brk);
		else
		// Shouldn't happen due to higher level checks
		WARN_ON_ONCE(1);
		}

		void set_breakpoint(struct arch_hw_breakpoint *brk)