From 3671f4ebe3eb12e7222e4d7b0f94e85cfe34253a Mon Sep 17 00:00:00 2001 From: Jordan Niethe Date: Wed, 9 Nov 2022 15:51:04 +1100 Subject: [PATCH] powerpc: Allow clearing and restoring registers independent of saved breakpoint state For the coming temporary mm used for instruction patching, the breakpoint registers need to be cleared to prevent them from accidentally being triggered. As soon as the patching is done, the breakpoints will be restored. The breakpoint state is stored in the per-cpu variable current_brk[]. Add a suspend_breakpoints() function which will clear the breakpoint registers without touching the state in current_brk[]. Add a pair function restore_breakpoints() which will move the state in current_brk[] back to the registers. Signed-off-by: Jordan Niethe Signed-off-by: Benjamin Gray Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20221109045112.187069-2-bgray@linux.ibm.com --- arch/powerpc/include/asm/debug.h | 2 ++ arch/powerpc/kernel/process.c | 38 +++++++++++++++++++++++++++++++++++--- 2 files changed, 37 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/include/asm/debug.h b/arch/powerpc/include/asm/debug.h index 86a1473..51c74460 100644 --- a/arch/powerpc/include/asm/debug.h +++ b/arch/powerpc/include/asm/debug.h @@ -46,6 +46,8 @@ static inline int debugger_fault_handler(struct pt_regs *regs) { return 0; } #endif void __set_breakpoint(int nr, struct arch_hw_breakpoint *brk); +void suspend_breakpoints(void); +void restore_breakpoints(void); bool ppc_breakpoint_available(void); #ifdef CONFIG_PPC_ADV_DEBUG_REGS extern void do_send_trap(struct pt_regs *regs, unsigned long address, diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index e3e1fea..5265da2 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -862,10 +862,8 @@ static inline int set_breakpoint_8xx(struct arch_hw_breakpoint *brk) return 0; } -void __set_breakpoint(int nr, struct arch_hw_breakpoint *brk) +static void set_hw_breakpoint(int nr, struct arch_hw_breakpoint *brk) { - memcpy(this_cpu_ptr(¤t_brk[nr]), brk, sizeof(*brk)); - if (dawr_enabled()) // Power8 or later set_dawr(nr, brk); @@ -879,6 +877,12 @@ void __set_breakpoint(int nr, struct arch_hw_breakpoint *brk) WARN_ON_ONCE(1); } +void __set_breakpoint(int nr, struct arch_hw_breakpoint *brk) +{ + memcpy(this_cpu_ptr(¤t_brk[nr]), brk, sizeof(*brk)); + set_hw_breakpoint(nr, brk); +} + /* Check if we have DAWR or DABR hardware */ bool ppc_breakpoint_available(void) { @@ -891,6 +895,34 @@ bool ppc_breakpoint_available(void) } EXPORT_SYMBOL_GPL(ppc_breakpoint_available); +/* Disable the breakpoint in hardware without touching current_brk[] */ +void suspend_breakpoints(void) +{ + struct arch_hw_breakpoint brk = {0}; + int i; + + if (!ppc_breakpoint_available()) + return; + + for (i = 0; i < nr_wp_slots(); i++) + set_hw_breakpoint(i, &brk); +} + +/* + * Re-enable breakpoints suspended by suspend_breakpoints() in hardware + * from current_brk[] + */ +void restore_breakpoints(void) +{ + int i; + + if (!ppc_breakpoint_available()) + return; + + for (i = 0; i < nr_wp_slots(); i++) + set_hw_breakpoint(i, this_cpu_ptr(¤t_brk[i])); +} + #ifdef CONFIG_PPC_TRANSACTIONAL_MEM static inline bool tm_enabled(struct task_struct *tsk) -- 2.7.4