diff mbox series

[v8,1/6] powerpc: Allow clearing and restoring registers independent of saved breakpoint state

Message ID 20221021052238.580986-2-bgray@linux.ibm.com (mailing list archive)
State Superseded
Headers show
Series Use per-CPU temporary mappings for patching | expand

Commit Message

Benjamin Gray Oct. 21, 2022, 5:22 a.m. UTC 
From: Jordan Niethe <jniethe5@gmail.com>

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 pause_breakpoints() function which will
clear the breakpoint registers without touching the state in
current_bkr[]. Add a pair function unpause_breakpoints() which will move
the state in current_brk[] back to the registers.

Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
---
 arch/powerpc/include/asm/debug.h |  2 ++
 arch/powerpc/kernel/process.c    | 36 +++++++++++++++++++++++++++++---
 2 files changed, 35 insertions(+), 3 deletions(-)

Comments

Russell Currey Oct. 24, 2022, 3:06 a.m. UTC | #1 
On Fri, 2022-10-21 at 16:22 +1100, Benjamin Gray wrote:
> From: Jordan Niethe <jniethe5@gmail.com>

Hi Ben,

> 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 pause_breakpoints() function which
> will
> clear the breakpoint registers without touching the state in
> current_bkr[]. Add a pair function unpause_breakpoints() which will
 
typo here ^

> move
> the state in current_brk[] back to the registers.
> 
> Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
> Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
> ---
>  arch/powerpc/include/asm/debug.h |  2 ++
>  arch/powerpc/kernel/process.c    | 36 +++++++++++++++++++++++++++++-
> --
>  2 files changed, 35 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/debug.h
> b/arch/powerpc/include/asm/debug.h
> index 86a14736c76c..83f2dc3785e8 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 pause_breakpoints(void);
> +void unpause_breakpoints(void);

Nitpick, would (clear/suspend)/restore be clearer than pause/unpause?

>  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 67da147fe34d..7aee1b30e73c 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -685,6 +685,7 @@ DEFINE_INTERRUPT_HANDLER(do_break)
>  
>  static DEFINE_PER_CPU(struct arch_hw_breakpoint,
> current_brk[HBP_NUM_MAX]);
>  
> +

some bonus whitespace here

>  #ifdef CONFIG_PPC_ADV_DEBUG_REGS
>  /*
>   * Set the debug registers back to their default "safe" values.
> @@ -862,10 +863,8 @@ 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_breakpoint(int nr, struct arch_hw_breakpoint
> *brk)

Is there a way to refactor this?  The quad underscore is pretty cursed.

>  {
> -       memcpy(this_cpu_ptr(&current_brk[nr]), brk, sizeof(*brk));
> -
>         if (dawr_enabled())
>                 // Power8 or later
>                 set_dawr(nr, brk);
> @@ -879,6 +878,12 @@ 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(&current_brk[nr]), brk, sizeof(*brk));
> +       ____set_breakpoint(nr, brk);
> +}
> +
>  /* Check if we have DAWR or DABR hardware */
>  bool ppc_breakpoint_available(void)
>  {
> @@ -891,6 +896,31 @@ bool ppc_breakpoint_available(void)
>  }
>  EXPORT_SYMBOL_GPL(ppc_breakpoint_available);
>  
> +/* Disable the breakpoint in hardware without touching current_brk[]
> */
> +void pause_breakpoints(void)
> +{
> +       struct arch_hw_breakpoint brk = {0};
> +       int i;
> +
> +       if (!ppc_breakpoint_available())
> +               return;
> +
> +       for (i = 0; i < nr_wp_slots(); i++)
> +               ____set_breakpoint(i, &brk);
> +}
> +
> +/* Renable the breakpoint in hardware from current_brk[] */
> +void unpause_breakpoints(void)
> +{
> +       int i;
> +
> +       if (!ppc_breakpoint_available())
> +               return;
> +
> +       for (i = 0; i < nr_wp_slots(); i++)
> +               ____set_breakpoint(i, this_cpu_ptr(&current_brk[i]));
> +}
> +
>  #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
>  
>  static inline bool tm_enabled(struct task_struct *tsk)
diff mbox series

Patch

diff --git a/arch/powerpc/include/asm/debug.h b/arch/powerpc/include/asm/debug.h
index 86a14736c76c..83f2dc3785e8 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 pause_breakpoints(void);
+void unpause_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 67da147fe34d..7aee1b30e73c 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -685,6 +685,7 @@  DEFINE_INTERRUPT_HANDLER(do_break)
 
 static DEFINE_PER_CPU(struct arch_hw_breakpoint, current_brk[HBP_NUM_MAX]);
 
+
 #ifdef CONFIG_PPC_ADV_DEBUG_REGS
 /*
  * Set the debug registers back to their default "safe" values.
@@ -862,10 +863,8 @@  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_breakpoint(int nr, struct arch_hw_breakpoint *brk)
 {
-	memcpy(this_cpu_ptr(&current_brk[nr]), brk, sizeof(*brk));
-
 	if (dawr_enabled())
 		// Power8 or later
 		set_dawr(nr, brk);
@@ -879,6 +878,12 @@  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(&current_brk[nr]), brk, sizeof(*brk));
+	____set_breakpoint(nr, brk);
+}
+
 /* Check if we have DAWR or DABR hardware */
 bool ppc_breakpoint_available(void)
 {
@@ -891,6 +896,31 @@  bool ppc_breakpoint_available(void)
 }
 EXPORT_SYMBOL_GPL(ppc_breakpoint_available);
 
+/* Disable the breakpoint in hardware without touching current_brk[] */
+void pause_breakpoints(void)
+{
+	struct arch_hw_breakpoint brk = {0};
+	int i;
+
+	if (!ppc_breakpoint_available())
+		return;
+
+	for (i = 0; i < nr_wp_slots(); i++)
+		____set_breakpoint(i, &brk);
+}
+
+/* Renable the breakpoint in hardware from current_brk[] */
+void unpause_breakpoints(void)
+{
+	int i;
+
+	if (!ppc_breakpoint_available())
+		return;
+
+	for (i = 0; i < nr_wp_slots(); i++)
+		____set_breakpoint(i, this_cpu_ptr(&current_brk[i]));
+}
+
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 
 static inline bool tm_enabled(struct task_struct *tsk)