[PATCH v6 2/2] powerpc/32: Handle bookE debugging in C in syscall entry/exit

From: Christophe Leroy
Date: Tue Feb 09 2021 - 18:11:01 EST

The handling of SPRN_DBCR0 and other registers can easily
be done in C instead of ASM.

For that, create booke_load_dbcr0() and booke_restore_dbcr0().

Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
---
v5: New
v6: Refactor into helpers
---
arch/powerpc/include/asm/interrupt.h | 12 ++++++++
arch/powerpc/include/asm/reg_booke.h | 3 ++
arch/powerpc/kernel/entry_32.S | 7 -----
arch/powerpc/kernel/head_32.h | 15 ----------
arch/powerpc/kernel/head_booke.h | 19 -------------
arch/powerpc/kernel/interrupt.c | 41 ++++++++++++++++++----------
6 files changed, 42 insertions(+), 55 deletions(-)

diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h
index 4badb3e51c19..e62c37915bbe 100644
--- a/arch/powerpc/include/asm/interrupt.h
+++ b/arch/powerpc/include/asm/interrupt.h
@@ -14,6 +14,18 @@ struct interrupt_state {
#endif
};

+static inline void booke_restore_dbcr0(void)
+{
+#ifdef CONFIG_PPC_ADV_DEBUG_REGS
+ unsigned long dbcr0 = current->thread.debug.dbcr0;
+
+ if (IS_ENABLED(CONFIG_PPC32) && unlikely(dbcr0 & DBCR0_IDM)) {
+ mtspr(SPRN_DBSR, -1);
+ mtspr(SPRN_DBCR0, global_dbcr0[smp_processor_id()]);
+ }
+#endif
+}
+
static inline void interrupt_enter_prepare(struct pt_regs *regs, struct interrupt_state *state)
{
/*
diff --git a/arch/powerpc/include/asm/reg_booke.h b/arch/powerpc/include/asm/reg_booke.h
index 262782f08fd4..17b8dcd9a40d 100644
--- a/arch/powerpc/include/asm/reg_booke.h
+++ b/arch/powerpc/include/asm/reg_booke.h
@@ -691,6 +691,9 @@
#define mttmr(rn, v) asm volatile(MTTMR(rn, %0) : \
: "r" ((unsigned long)(v)) \
: "memory")
+
+extern unsigned long global_dbcr0[];
+
#endif /* !__ASSEMBLY__ */

#endif /* __ASM_POWERPC_REG_BOOKE_H__ */
diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 9dd90be9f8a5..78c430b7f9d9 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -343,13 +343,6 @@ ret_from_syscall:
addi r4,r1,STACK_FRAME_OVERHEAD
li r5,0
bl syscall_exit_prepare
-#if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
- /* If the process has its own DBCR0 value, load it up. The internal
- debug mode bit tells us that dbcr0 should be loaded. */
- lwz r0,THREAD+THREAD_DBCR0(r2)
- andis. r10,r0,DBCR0_IDM@h
- bnel- load_dbcr0
-#endif
#ifdef CONFIG_PPC_47x
lis r4,icache_44x_need_flush@ha
lwz r5,icache_44x_need_flush@l(r4)
diff --git a/arch/powerpc/kernel/head_32.h b/arch/powerpc/kernel/head_32.h
index 1afad7bc3395..5d4706c14572 100644
--- a/arch/powerpc/kernel/head_32.h
+++ b/arch/powerpc/kernel/head_32.h
@@ -153,21 +153,6 @@
SAVE_4GPRS(3, r11)
SAVE_2GPRS(7, r11)
addi r2,r12,-THREAD
-#if defined(CONFIG_40x)
- /* Check to see if the dbcr0 register is set up to debug. Use the
- internal debug mode bit to do this. */
- lwz r12,THREAD_DBCR0(r12)
- andis. r12,r12,DBCR0_IDM@h
- beq+ 3f
- /* From user and task is ptraced - load up global dbcr0 */
- li r12,-1 /* clear all pending debug events */
- mtspr SPRN_DBSR,r12
- lis r11,global_dbcr0@ha
- addi r11,r11,global_dbcr0@l
- lwz r12,0(r11)
- mtspr SPRN_DBCR0,r12
-3:
-#endif
b transfer_to_syscall /* jump to handler */
.endm

diff --git a/arch/powerpc/kernel/head_booke.h b/arch/powerpc/kernel/head_booke.h
index 5f565232b99d..47857795f50a 100644
--- a/arch/powerpc/kernel/head_booke.h
+++ b/arch/powerpc/kernel/head_booke.h
@@ -130,25 +130,6 @@ ALT_FTR_SECTION_END_IFSET(CPU_FTR_EMB_HV)
SAVE_2GPRS(7, r11)

addi r2,r10,-THREAD
- /* Check to see if the dbcr0 register is set up to debug. Use the
- internal debug mode bit to do this. */
- lwz r12,THREAD_DBCR0(r10)
- andis. r12,r12,DBCR0_IDM@h
- beq+ 3f
- /* From user and task is ptraced - load up global dbcr0 */
- li r12,-1 /* clear all pending debug events */
- mtspr SPRN_DBSR,r12
- lis r11,global_dbcr0@ha
- addi r11,r11,global_dbcr0@l
-#ifdef CONFIG_SMP
- lwz r10, TASK_CPU(r2)
- slwi r10, r10, 2
- add r11, r11, r10
-#endif
- lwz r12,0(r11)
- mtspr SPRN_DBCR0,r12
-
-3:
b transfer_to_syscall /* jump to handler */
.endm

diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
index 75d657b63332..f93664ad4a5e 100644
--- a/arch/powerpc/kernel/interrupt.c
+++ b/arch/powerpc/kernel/interrupt.c
@@ -73,6 +73,8 @@ notrace long system_call_exception(long r3, long r4, long r5,
kuap_check_amr();
#endif

+ booke_restore_dbcr0();
+
account_cpu_user_entry();

account_stolen_time();
@@ -204,6 +206,28 @@ static notrace inline bool prep_irq_for_enabled_exit(bool clear_ri, bool irqs_en
return false;
}

+static notrace void booke_load_dbcr0(void)
+{
+#ifdef CONFIG_PPC_ADV_DEBUG_REGS
+ unsigned long dbcr0 = current->thread.debug.dbcr0;
+
+ if (likely(!(dbcr0 & DBCR0_IDM)))
+ return;
+
+ /*
+ * Check to see if the dbcr0 register is set up to debug.
+ * Use the internal debug mode bit to do this.
+ */
+ mtmsr(mfmsr() & ~MSR_DE);
+ if (IS_ENABLED(CONFIG_PPC32)) {
+ isync();
+ global_dbcr0[smp_processor_id()] = mfspr(SPRN_DBCR0);
+ }
+ mtspr(SPRN_DBCR0, dbcr0);
+ mtspr(SPRN_DBSR, -1);
+#endif
+}
+
/*
* This should be called after a syscall returns, with r3 the return value
* from the syscall. If this function returns non-zero, the system call
@@ -317,6 +341,8 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
local_paca->tm_scratch = regs->msr;
#endif

+ booke_load_dbcr0();
+
account_cpu_user_exit();

#ifdef CONFIG_PPC_BOOK3S_64 /* BOOK3E and ppc32 not using this */
@@ -331,9 +357,6 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
#ifndef CONFIG_PPC_BOOK3E_64 /* BOOK3E not yet using this */
notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned long msr)
{
-#ifdef CONFIG_PPC_BOOK3E
- struct thread_struct *ts = &current->thread;
-#endif
unsigned long *ti_flagsp = &current_thread_info()->flags;
unsigned long ti_flags;
unsigned long flags;
@@ -398,17 +421,7 @@ notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned
goto again;
}

-#ifdef CONFIG_PPC_BOOK3E
- if (unlikely(ts->debug.dbcr0 & DBCR0_IDM)) {
- /*
- * Check to see if the dbcr0 register is set up to debug.
- * Use the internal debug mode bit to do this.
- */
- mtmsr(mfmsr() & ~MSR_DE);
- mtspr(SPRN_DBCR0, ts->debug.dbcr0);
- mtspr(SPRN_DBSR, -1);
- }
-#endif
+ booke_load_dbcr0();

#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
local_paca->tm_scratch = regs->msr;
--
2.25.0