Add support for dtrace:fbt on modules for PowerPC

Summary:
Revert the initial FBT-with-KDB changes for trap_subr*.S, and instead use the
db_trap filter function to handle dtrace trap filtering.  With this, the MMU is
enabled by the support code, simplifying the codepath altogether.

Test Plan: Tested on my G4 PowerBook

Reviewers: #powerpc, nwhitehorn

Reviewed By: nwhitehorn

Differential Revision: https://reviews.freebsd.org/D1207

MFC after:	3 weeks

4 files changed, 11 insertions, 32 deletions

diff --git a/sys/powerpc/aim/machdep.c b/sys/powerpc/aim/machdep.c
index 5864a02..d1413a2 100644
--- a/sys/powerpc/aim/machdep.c
+++ b/sys/powerpc/aim/machdep.c
@@ -757,6 +757,10 @@ db_trap_glue(struct trapframe *frame)
 		|| frame->exc == EXC_BPT
 		|| frame->exc == EXC_DSI)) {
 		int type = frame->exc;
+
+		/* Ignore DTrace traps. */
+		if (*(uint32_t *)frame->srr0 == EXC_DTRACE) 
+			return (0);
 		if (type == EXC_PGM && (frame->srr1 & 0x20000)) {
 			type = T_BREAKPOINT;
 		}
diff --git a/sys/powerpc/aim/trap.c b/sys/powerpc/aim/trap.c
index cc54e59..8276e96 100644
--- a/sys/powerpc/aim/trap.c
+++ b/sys/powerpc/aim/trap.c
@@ -258,7 +258,8 @@ trap(struct trapframe *frame)
 			if (frame->srr1 & EXC_PGM_TRAP) {
 #ifdef KDTRACE_HOOKS
 				inst = fuword32((const void *)frame->srr0);
-				if (inst == 0x0FFFDDDD && dtrace_pid_probe_ptr != NULL) {
+				if (inst == 0x0FFFDDDD &&
+				    dtrace_pid_probe_ptr != NULL) {
 					struct reg regs;
 					fill_regs(td, &regs);
 					(*dtrace_pid_probe_ptr)(&regs);
@@ -301,7 +302,7 @@ trap(struct trapframe *frame)
 #ifdef KDTRACE_HOOKS
 		case EXC_PGM:
 			if (frame->srr1 & EXC_PGM_TRAP) {
-				if (*(uint32_t *)frame->srr0 == 0x7c810808) {
+				if (*(uint32_t *)frame->srr0 == EXC_DTRACE) {
 					if (dtrace_invop_jump_addr != NULL) {
 						dtrace_invop_jump_addr(frame);
 						return;
diff --git a/sys/powerpc/aim/trap_subr32.S b/sys/powerpc/aim/trap_subr32.S
index 56ca715..2aae2a0 100644
--- a/sys/powerpc/aim/trap_subr32.S
+++ b/sys/powerpc/aim/trap_subr32.S
@@ -890,8 +890,7 @@ CNAME(dblow):
 	mfcr	%r29			/* save CR in r29 */
 	mfsrr1	%r1
 	mtcr	%r1
-	bf	17,2f			/* branch if privileged */
-1:
+	bf	17,1f			/* branch if privileged */
 	/* Unprivileged case */
 	mtcr	%r29			/* put the condition register back */
         mfsprg2	%r29			/* ... and r29 */
@@ -900,19 +899,7 @@ CNAME(dblow):
 	li	%r1, 0	 		/* How to get the vector from LR */
 
         bla     generictrap		/* and we look like a generic trap */
-2:
-#ifdef KDTRACE_HOOKS
-	/* Privileged, so drop to KDB */
-	mfsrr0	%r1
-	mtsprg3	%r3
-	lwz	%r1,0(%r1)
-	/* Check if it's a DTrace trap. */
-	li	%r3,0x0808
-	addis	%r3,%r3,0x7c81
-	cmplw	%cr0,%r3,%r1
-	mfsprg3	%r3
-	beq	%cr0,1b
-#endif
+1:
 	/* Privileged, so drop to KDB */
 	GET_CPUINFO(%r1)
 	stw	%r28,(PC_DBSAVE+CPUSAVE_R28)(%r1)	/* free r28 */
diff --git a/sys/powerpc/aim/trap_subr64.S b/sys/powerpc/aim/trap_subr64.S
index bedf1f1..0dc46b3 100644
--- a/sys/powerpc/aim/trap_subr64.S
+++ b/sys/powerpc/aim/trap_subr64.S
@@ -799,9 +799,8 @@ CNAME(dblow):
 	mfcr	%r29			/* save CR in r29 */
 	mfsrr1	%r1
 	mtcr	%r1
-	bf	17,2f			/* branch if privileged */
+	bf	17,1f			/* branch if privileged */
 
-1:
 	/* Unprivileged case */
 	mtcr	%r29			/* put the condition register back */
         mfsprg2	%r29			/* ... and r29 */
@@ -810,19 +809,7 @@ CNAME(dblow):
 	li	%r1, 0	 		/* How to get the vector from LR */
 
         bla     generictrap		/* and we look like a generic trap */
-2:
-#ifdef KDTRACE_HOOKS
-	/* Privileged, so drop to KDB */
-	mfsrr0	%r1
-	mtsprg3	%r3
-	lwz	%r1,0(%r1)
-	/* Check if it's a DTrace trap. */
-	li	%r3,0x0808
-	addis	%r3,%r3,0x7c81
-	cmplw	%cr0,%r3,%r1
-	mfsprg3	%r3
-	beq	%cr0,1b
-#endif
+1:
 	GET_CPUINFO(%r1)
 	std	%r27,(PC_DBSAVE+CPUSAVE_R27)(%r1)	/* free r27 */
 	std	%r28,(PC_DBSAVE+CPUSAVE_R28)(%r1)	/* free r28 */