powerpc/fsl-booke64: Add support for Debug Level exception handler

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

2 files changed, 70 insertions, 3 deletions

diff --git a/arch/powerpc/kernel/exceptions-64e.S b/arch/powerpc/kernel/exceptions-64e.S
index 4d0abb4930a1..cf27a8fa0d29 100644
--- a/arch/powerpc/kernel/exceptions-64e.S
+++ b/arch/powerpc/kernel/exceptions-64e.S
@@ -253,9 +253,6 @@ exception_marker:
         .balign 0x1000
         .globl interrupt_base_book3e
 interrupt_base_book3e:                                  /* fake trap */
-        /* Note: If real debug exceptions are supported by the HW, the vector
-         * below will have to be patched up to point to an appropriate handler
-         */
         EXCEPTION_STUB(0x000, machine_check)            /* 0x0200 */
         EXCEPTION_STUB(0x020, critical_input)           /* 0x0580 */
         EXCEPTION_STUB(0x040, debug_crit)               /* 0x0d00 */
@@ -455,6 +452,68 @@ interrupt_end_book3e:
 kernel_dbg_exc:
         b       .       /* NYI */
 
+/* Debug exception as a debug interrupt*/
+        START_EXCEPTION(debug_debug);
+        DBG_EXCEPTION_PROLOG(0xd00, PROLOG_ADDITION_2REGS)
+
+        /*
+         * If there is a single step or branch-taken exception in an
+         * exception entry sequence, it was probably meant to apply to
+         * the code where the exception occurred (since exception entry
+         * doesn't turn off DE automatically).  We simulate the effect
+         * of turning off DE on entry to an exception handler by turning
+         * off DE in the DSRR1 value and clearing the debug status.
+         */
+
+        mfspr   r14,SPRN_DBSR           /* check single-step/branch taken */
+        andis.  r15,r14,DBSR_IC@h
+        beq+    1f
+
+        LOAD_REG_IMMEDIATE(r14,interrupt_base_book3e)
+        LOAD_REG_IMMEDIATE(r15,interrupt_end_book3e)
+        cmpld   cr0,r10,r14
+        cmpld   cr1,r10,r15
+        blt+    cr0,1f
+        bge+    cr1,1f
+
+        /* here it looks like we got an inappropriate debug exception. */
+        lis     r14,DBSR_IC@h           /* clear the IC event */
+        rlwinm  r11,r11,0,~MSR_DE       /* clear DE in the DSRR1 value */
+        mtspr   SPRN_DBSR,r14
+        mtspr   SPRN_DSRR1,r11
+        lwz     r10,PACA_EXDBG+EX_CR(r13)       /* restore registers */
+        ld      r1,PACA_EXDBG+EX_R1(r13)
+        ld      r14,PACA_EXDBG+EX_R14(r13)
+        ld      r15,PACA_EXDBG+EX_R15(r13)
+        mtcr    r10
+        ld      r10,PACA_EXDBG+EX_R10(r13)      /* restore registers */
+        ld      r11,PACA_EXDBG+EX_R11(r13)
+        mfspr   r13,SPRN_SPRG_DBG_SCRATCH
+        rfdi
+
+        /* Normal debug exception */
+        /* XXX We only handle coming from userspace for now since we can't
+         *     quite save properly an interrupted kernel state yet
+         */
+1:      andi.   r14,r11,MSR_PR;         /* check for userspace again */
+        beq     kernel_dbg_exc;         /* if from kernel mode */
+
+        /* Now we mash up things to make it look like we are coming on a
+         * normal exception
+         */
+        mfspr   r15,SPRN_SPRG_DBG_SCRATCH
+        mtspr   SPRN_SPRG_GEN_SCRATCH,r15
+        mfspr   r14,SPRN_DBSR
+        EXCEPTION_COMMON(0xd00, PACA_EXDBG, INTS_DISABLE_ALL)
+        std     r14,_DSISR(r1)
+        addi    r3,r1,STACK_FRAME_OVERHEAD
+        mr      r4,r14
+        ld      r14,PACA_EXDBG+EX_R14(r13)
+        ld      r15,PACA_EXDBG+EX_R15(r13)
+        bl      .save_nvgprs
+        bl      .DebugException
+        b       .ret_from_except
+
 /* Doorbell interrupt */
         MASKABLE_EXCEPTION(0x2070, doorbell, .doorbell_exception, ACK_NONE)
 
diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index c2ec0a12e14f..a88bf2713d41 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -62,6 +62,7 @@
 #include <asm/udbg.h>
 #include <asm/kexec.h>
 #include <asm/mmu_context.h>
+#include <asm/code-patching.h>
 
 #include "setup.h"
 
@@ -477,6 +478,9 @@ static void __init irqstack_early_init(void)
 #ifdef CONFIG_PPC_BOOK3E
 static void __init exc_lvl_early_init(void)
 {
+        extern unsigned int interrupt_base_book3e;
+        extern unsigned int exc_debug_debug_book3e;
+
         unsigned int i;
 
         for_each_possible_cpu(i) {
@@ -487,6 +491,10 @@ static void __init exc_lvl_early_init(void)
                 mcheckirq_ctx[i] = (struct thread_info *)
                         __va(memblock_alloc(THREAD_SIZE, THREAD_SIZE));
         }
+
+        if (cpu_has_feature(CPU_FTR_DEBUG_LVL_EXC))
+                patch_branch(&interrupt_base_book3e + (0x040 / 4) + 1,
+                             (unsigned long)&exc_debug_debug_book3e, 0);
 }
 #else
 #define exc_lvl_early_init()