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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: 9654153158 ("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>
This commit is contained in:
Nicholas Piggin 2018-04-01 15:50:36 +10:00 committed by Michael Ellerman
parent e303c08787
commit 252988cbf0
1 changed files with 8 additions and 2 deletions
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10
arch/powerpc/kernel/process.c
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@ -718,7 +718,8 @@ static void set_debug_reg_defaults(struct thread_struct *thread)
{
thread->hw_brk.address = 0;
thread->hw_brk.type = 0;
set_breakpoint(&thread->hw_brk);
if (ppc_breakpoint_available())
set_breakpoint(&thread->hw_brk);
}
#endif /* !CONFIG_HAVE_HW_BREAKPOINT */
#endif /* CONFIG_PPC_ADV_DEBUG_REGS */
@ -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)