--- support.S	2020-05-31 15:02:07.000000000 -0500
+++ sys/powerpc/powerpc/support.S	2020-05-31 22:52:49.487251000 -0500
@@ -46,6 +46,7 @@
 #ifdef __powerpc64__
 #define	LOAD	ld
 #define	STORE	std
+#define	COMPARE	cmpdi
 #define	WORD	8
 /* log_2(8 * WORD) */
 #define	LOOP_LOG	6
@@ -53,6 +54,7 @@
 #define	LOAD	lwz
 #define	STORE	stw
 #define	WORD	4
+#define	COMPARE	cmpwi
 /* log_2(8 * WORD) */
 #define	LOOP_LOG	5
 #endif
@@ -158,6 +160,35 @@
 
 #define Thresh	64	
 .text
+
+.Lfailsafe:
+	/* Dumb byte copy version */
+	cmplwi 0, %r5, 0
+	beq	.Lend
+	mtctr	rl
+#ifndef __powerpc64__
+	cmpl	0, 0, rs, rd
+#else
+	cmpl	0, 1, rs, rd
+#endif
+	bgt	2f	/* src > dst, forward copy possible */
+	add	rs, rs, rl
+	add	rd, rd, rl
+1:
+        lbz     t1, 0(rs)
+        addi    rs, rs, -1 
+        stb     t1, 0(rd)
+        addi    rd, rd, -1
+        bdnz    1b
+	b .Lend
+2:
+	lbz	t1, 0(rs)
+	addi	rs, rs, 1
+	stb	t1, 0(rd)
+	addi	rd, rd, 1
+	bdnz	2b
+	b .Lend
+
 ENTRY(bcopy_generic)
 	cmplwi	0, %r5, 0
 	beq	.Lend
@@ -166,15 +197,16 @@ ENTRY(bcopy_generic)
 	cmplwi	rl, Thresh
 	sub	t1, rs, rd
 	cmplw	cr1, t1, rl	// (dst-src) < len
+	blt-	cr1, .Lfailsafe
 	blt	.Lsmall
 	b	.Llarge
 /* memcpy */
 /* ... */
 .Lsmall:
-	mtcrf	0x3, rl
-//	blt	cr1, .Lsmallrev
+	mtcrf	0x3, rl		// load LSB 8 bits
+
 .Lsmall64:
-	bf	26, 0f
+	bf	26, .Lsmall32	// <32 bytes remain
 	LOAD	t1, 0(rs)
 	LOAD	t2, WORD*1(rs)
 	LOAD	t3, WORD*2(rs)
@@ -197,8 +229,8 @@ ENTRY(bcopy_generic)
 	STORE	t8, WORD*7(rd)
 #endif
 	addi	rd, rd, 32
-0:
-	bf	27, 1f
+.Lsmall32:
+	bf	27, 1f		// <16 bytes remain
 	LOAD	t1, 0(rs)
 	LOAD	t2, WORD*1(rs)
 #ifndef __powerpc64__
@@ -207,14 +239,14 @@ ENTRY(bcopy_generic)
 #endif
 	addi	rs, rs, 16
 	STORE	t1, 0(rd)
-	STORE	t2, 8(rd)
+	STORE	t2, WORD*1(rd)
 #ifndef __powerpc64__
 	STORE	t3, WORD*2(rd)
 	STORE	t4, WORD*3(rd)
 #endif
 	addi	rd, rd, 16
 1:
-	bf	28, 2f
+	bf	28, 2f		// <8 bytes remain
 	LOAD	t1, 0(rs)
 #ifndef __powerpc64__
 	LOAD	t2, WORD(rs)
@@ -222,23 +254,23 @@ ENTRY(bcopy_generic)
 	addi	rs, rs, 8
 	STORE	t1, 0(rd)
 #ifndef __powerpc64__
-	LOAD	t2, WORD(rd)
+	STORE	t2, WORD(rd)
 #endif
 	addi	rd, rd, 8
 2:	
-	bf	29, 3f
+	bf	29, 3f		// < 4 bytes remain
 	lwz	t1, 0(rs)
 	addi	rs, rs, 4
 	stw	t1, 0(rd)
 	addi	rd, rd, 4
 3:
-	bf	30, 4f
+	bf	30, 4f		// < 2 bytes remain
 	lhz	t1, 0(rs)
 	addi	rs, rs, 2
 	sth	t1, 0(rd)
 	addi	rd, rd, 2
 4:
-	bf	31, .Lout
+	bf	31, .Lout	// 0 bytes remain
 	lbz	t1, 0(rs)
 	addi	rs, rs, 1
 	stb	t1, 0(rd)
@@ -246,13 +278,12 @@ ENTRY(bcopy_generic)
 	b	.Lout
 
 	.align 4
-.Llarge:
-	neg	t3, rd
+.Llarge:			// Preamble - byte copy until dest dword aligned.
+	neg	t3, rd		// NOT(rd) + 1
 	andi.	t6, t3, 0x7
-//	blt	cr1, .Llargerev	
 	mtctr	t6
 	sub	rl, rl, t6
-	beq+	.Llargealigned
+	beq+	.Llargealigned	// Already aligned.
 1:
 	lbz	t1, 0(rs)
 	addi	rs, rs, 1
@@ -261,10 +292,14 @@ ENTRY(bcopy_generic)
 	bdnz	1b
 
 .Llargealigned:
-	srwi.	t2, rl, LOOP_LOG  /* length >> log_2(loop_size) => 64B iterations */
+	srwi.	t2, rl, LOOP_LOG  /* length >> log_2(loop_size) => 64B (32B) iterations */
 	mtcrf	0x3, rl
-	beq	.Lsmall64
-	mtctr	t2
+#ifndef __powerpc64__
+	beq	.Lsmall32
+#else
+	beq	.Lsmall64	/* i.e. would be on the last loop */
+#endif
+	mtctr	t2		/* 64 byte (32 byte) blocks */
 	b	1f
 
 	.align 5
@@ -289,7 +324,16 @@ ENTRY(bcopy_generic)
 	addi	rd, rd, WORD*8
 	bdnz	1b
 
+#ifndef __powerpc64__
+	/*
+	 * Ensure CR bit 26 is clear on ppc32, to ensure .Lsmall64 does not
+	 * copy more than 32 bytes.
+	 */
+	//crclr	26
+	b	.Lsmall32
+#else
 	b	.Lsmall64
+#endif
 .Lout:
 /* done */	
 .Lend:	
@@ -349,14 +393,14 @@ ENTRY_DIRECT(copyinstr)
 	stbu	%r0, 1(%r4)
 
 	// NULL byte reached ?
-	cmpdi	%r0, 0
+	COMPARE	%r0, 0
 	beq-	1f
 	b	0b
 1:
 	li	%r3, 0
 2:
 	/* skip storing length if done is NULL */
-	cmpdi	%r6, 0
+	COMPARE	%r6, 0
 	beq-	3f
 	mfctr	%r0
 	sub	%r0, %r9, %r0