powerpc/8xx: Implement hw_breakpoint

This patch implements HW breakpoint on the 8xx. The 8xx has
capability to manage HW breakpoints, which is slightly different
than BOOK3S:
1/ The breakpoint match doesn't trigger a DSI exception but a
dedicated data breakpoint exception.
2/ The breakpoint happens after the instruction has completed,
no need to single step or emulate the instruction,
3/ Matched address is not set in DAR but in BAR,
4/ DABR register doesn't exist, instead we have registers
LCTRL1, LCTRL2 and CMPx registers,
5/ The match on one comparator is not on a double word but
on a single word.

The patch does:
1/ Prepare the dedicated registers in call to __set_dabr(). In order
to emulate the double word handling of BOOK3S, comparator E is set to
DABR address value and comparator F to address + 4. Then breakpoint 1
is set to match comparator E or F,
2/ Skip the singlestepping stage when compiled for CONFIG_PPC_8xx,
3/ Implement the exception. In that exception, the matched address
is taken from SPRN_BAR and manage as if it was from SPRN_DAR.
4/ I/D TLB error exception routines perform a tlbie on bad TLBs. That
tlbie triggers the breakpoint exception when performed on the
breakpoint address. For this reason, the routine returns if the match
is from one of those two tlbie.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Scott Wood <oss@buserror.net>

5 files changed, 62 insertions, 3 deletions

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 1971ed4e0336..8b201eefdeaa 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -113,7 +113,7 @@ config PPC
         select HAVE_PERF_REGS
         select HAVE_PERF_USER_STACK_DUMP
         select HAVE_REGS_AND_STACK_ACCESS_API
-        select HAVE_HW_BREAKPOINT if PERF_EVENTS && PPC_BOOK3S
+        select HAVE_HW_BREAKPOINT if PERF_EVENTS && (PPC_BOOK3S || PPC_8xx)
         select ARCH_WANT_IPC_PARSE_VERSION
         select SPARSE_IRQ
         select IRQ_DOMAIN
diff --git a/arch/powerpc/include/asm/reg_8xx.h b/arch/powerpc/include/asm/reg_8xx.h
index 1f1636124a04..c52725b7085d 100644
--- a/arch/powerpc/include/asm/reg_8xx.h
+++ b/arch/powerpc/include/asm/reg_8xx.h
@@ -29,6 +29,13 @@
 #define SPRN_EIE        80      /* External interrupt enable (EE=1, RI=1) */
 #define SPRN_EID        81      /* External interrupt disable (EE=0, RI=1) */
 
+/* Debug registers */
+#define SPRN_CMPE       152
+#define SPRN_CMPF       153
+#define SPRN_LCTRL1     156
+#define SPRN_LCTRL2     157
+#define SPRN_BAR        159
+
 /* Commands.  Only the first few are available to the instruction cache.
 */
 #define IDC_ENABLE      0x02000000      /* Cache enable */
diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 1a9c99d3e5d8..5fcbd79a121d 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -561,6 +561,7 @@ InstructionTLBError:
         andis.  r10,r5,0x4000
         beq+    1f
         tlbie   r4
+itlbie:
         /* 0x400 is InstructionAccess exception, needed by bad_page_fault() */
 1:      EXC_XFER_LITE(0x400, handle_page_fault)
 
@@ -585,6 +586,7 @@ DARFixed:/* Return from dcbx instruction bug workaround */
         andis.  r10,r5,0x4000
         beq+    1f
         tlbie   r4
+dtlbie:
 1:      li      r10,RPN_PATTERN
         mtspr   SPRN_DAR,r10    /* Tag DAR, to be used in DTLB Error */
         /* 0x300 is DataAccess exception, needed by bad_page_fault() */
@@ -602,7 +604,27 @@ DARFixed:/* Return from dcbx instruction bug workaround */
  * support of breakpoints and such.  Someday I will get around to
  * using them.
  */
-        EXCEPTION(0x1c00, Trap_1c, unknown_exception, EXC_XFER_EE)
+        . = 0x1c00
+DataBreakpoint:
+        EXCEPTION_PROLOG_0
+        mfcr    r10
+        mfspr   r11, SPRN_SRR0
+        cmplwi  cr0, r11, (dtlbie - PAGE_OFFSET)@l
+        cmplwi  cr7, r11, (itlbie - PAGE_OFFSET)@l
+        beq-    cr0, 11f
+        beq-    cr7, 11f
+        EXCEPTION_PROLOG_1
+        EXCEPTION_PROLOG_2
+        addi    r3,r1,STACK_FRAME_OVERHEAD
+        mfspr   r4,SPRN_BAR
+        stw     r4,_DAR(r11)
+        mfspr   r5,SPRN_DSISR
+        EXC_XFER_EE(0x1c00, do_break)
+11:
+        mtcr    r10
+        EXCEPTION_EPILOG_0
+        rfi
+
         EXCEPTION(0x1d00, Trap_1d, unknown_exception, EXC_XFER_EE)
         EXCEPTION(0x1e00, Trap_1e, unknown_exception, EXC_XFER_EE)
         EXCEPTION(0x1f00, Trap_1f, unknown_exception, EXC_XFER_EE)
@@ -977,6 +999,10 @@ initial_mmu:
         lis     r8, IDC_ENABLE@h
         mtspr   SPRN_DC_CST, r8
 #endif
+        /* Disable debug mode entry on data breakpoints */
+        mfspr   r8, SPRN_DER
+        rlwinm  r8, r8, 0, ~0x8
+        mtspr   SPRN_DER, r8
         blr
 
 
diff --git a/arch/powerpc/kernel/hw_breakpoint.c b/arch/powerpc/kernel/hw_breakpoint.c
index 4d3aa05e28be..146eaa9b350e 100644
--- a/arch/powerpc/kernel/hw_breakpoint.c
+++ b/arch/powerpc/kernel/hw_breakpoint.c
@@ -211,9 +211,11 @@ int hw_breakpoint_handler(struct die_args *args)
         int rc = NOTIFY_STOP;
         struct perf_event *bp;
         struct pt_regs *regs = args->regs;
+#ifndef CONFIG_PPC_8xx
         int stepped = 1;
-        struct arch_hw_breakpoint *info;
         unsigned int instr;
+#endif
+        struct arch_hw_breakpoint *info;
         unsigned long dar = regs->dar;
 
         /* Disable breakpoints during exception handling */
@@ -255,6 +257,7 @@ int hw_breakpoint_handler(struct die_args *args)
               (dar - bp->attr.bp_addr < bp->attr.bp_len)))
                 info->type |= HW_BRK_TYPE_EXTRANEOUS_IRQ;
 
+#ifndef CONFIG_PPC_8xx
         /* Do not emulate user-space instructions, instead single-step them */
         if (user_mode(regs)) {
                 current->thread.last_hit_ubp = bp;
@@ -278,6 +281,7 @@ int hw_breakpoint_handler(struct die_args *args)
                 perf_event_disable_inatomic(bp);
                 goto out;
         }
+#endif
         /*
          * As a policy, the callback is invoked in a 'trigger-after-execute'
          * fashion
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 04885cec24df..2dcb65fee638 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -736,6 +736,28 @@ static inline int __set_dabr(unsigned long dabr, unsigned long dabrx)
                 mtspr(SPRN_DABRX, dabrx);
         return 0;
 }
+#elif defined(CONFIG_PPC_8xx)
+static inline int __set_dabr(unsigned long dabr, unsigned long dabrx)
+{
+        unsigned long addr = dabr & ~HW_BRK_TYPE_DABR;
+        unsigned long lctrl1 = 0x90000000; /* compare type: equal on E & F */
+        unsigned long lctrl2 = 0x8e000002; /* watchpoint 1 on cmp E | F */
+
+        if ((dabr & HW_BRK_TYPE_RDWR) == HW_BRK_TYPE_READ)
+                lctrl1 |= 0xa0000;
+        else if ((dabr & HW_BRK_TYPE_RDWR) == HW_BRK_TYPE_WRITE)
+                lctrl1 |= 0xf0000;
+        else if ((dabr & HW_BRK_TYPE_RDWR) == 0)
+                lctrl2 = 0;
+
+        mtspr(SPRN_LCTRL2, 0);
+        mtspr(SPRN_CMPE, addr);
+        mtspr(SPRN_CMPF, addr + 4);
+        mtspr(SPRN_LCTRL1, lctrl1);
+        mtspr(SPRN_LCTRL2, lctrl2);
+
+        return 0;
+}
 #else
 static inline int __set_dabr(unsigned long dabr, unsigned long dabrx)
 {