From 6c14ba0dbafacc1338d77d071f16b70f5f60c6b0 Mon Sep 17 00:00:00 2001
From: danw <danw@NetBSD.org>
Date: Wed, 19 Jan 2000 03:30:12 +0000
Subject: [PATCH] Fill in the alignment trap handler a bit: now it can fix
 unaligned floating point loads and stores (to work around a gcc bug), but
 will still cause a bus error on other sorts of unaligned accesses.

---
 sys/arch/powerpc/include/trap.h | 20 ++++++++++-
 sys/arch/powerpc/powerpc/trap.c | 59 +++++++++++++++++++++++++++++++--
 2 files changed, 75 insertions(+), 4 deletions(-)

diff --git a/sys/arch/powerpc/include/trap.h b/sys/arch/powerpc/include/trap.h
index 3087a3ff90e0..5b0d4bf48924 100644
--- a/sys/arch/powerpc/include/trap.h
+++ b/sys/arch/powerpc/include/trap.h
@@ -1,4 +1,4 @@
-/*	$NetBSD: trap.h,v 1.1 1996/09/30 16:34:35 ws Exp $	*/
+/*	$NetBSD: trap.h,v 1.2 2000/01/19 03:30:12 danw Exp $	*/
 
 /*
  * Copyright (C) 1995, 1996 Wolfgang Solfrank.
@@ -64,4 +64,22 @@
 /* Trap was in user mode */
 #define	EXC_USER	0x10000
 
+
+/*
+ * EXC_ALI sets bits in the DSISR and DAR to provide enough
+ * information to recover from the unaligned access without needing to
+ * parse the offending instruction. This includes certain bits of the
+ * opcode, and information about what registers are used. The opcode
+ * indicator values below come from Appendix F of Book III of "The
+ * PowerPC Architecture".
+ */
+
+#define EXC_ALI_OPCODE_INDICATOR(dsisr) ((dsisr >> 10) & 0x7f)
+#define EXC_ALI_LFD	0x09
+#define EXC_ALI_STFD	0x0b
+
+/* Macros to extract register information */
+#define EXC_ALI_RST(dsisr) ((dsisr >> 5) & 0x1f)   /* source or target */
+#define EXC_ALI_RA(dsisr) (dsisr & 0x1f)
+
 #endif	/* _MACHINE_TRAP_H_ */
diff --git a/sys/arch/powerpc/powerpc/trap.c b/sys/arch/powerpc/powerpc/trap.c
index 684a352eeea5..08d5e3a79045 100644
--- a/sys/arch/powerpc/powerpc/trap.c
+++ b/sys/arch/powerpc/powerpc/trap.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: trap.c,v 1.22 1999/05/03 10:02:20 tsubai Exp $	*/
+/*	$NetBSD: trap.c,v 1.23 2000/01/19 03:30:13 danw Exp $	*/
 
 /*
  * Copyright (C) 1995, 1996 Wolfgang Solfrank.
@@ -62,6 +62,8 @@
 volatile int astpending;
 volatile int want_resched;
 
+static int fix_unaligned __P((struct proc *p, struct trapframe *frame));
+
 void
 trap(frame)
 	struct trapframe *frame;
@@ -262,8 +264,10 @@ syscall_bad:
 		break;
 
 	case EXC_ALI|EXC_USER:
-/* XXX temporarily */
-		trapsignal(p, SIGBUS, EXC_ALI);
+		if (fix_unaligned(p, frame) != 0)
+			trapsignal(p, SIGBUS, EXC_ALI);
+		else
+			frame->srr0 += 4;
 		break;
 
 	case EXC_PGM|EXC_USER:
@@ -531,3 +535,52 @@ badaddr_read(addr, size, rptr)
 
 	return 0;
 }
+
+/*
+ * For now, this only deals with the particular unaligned access case
+ * that gcc tends to generate.  Eventually it should handle all of the
+ * possibilities that can happen on a 32-bit PowerPC in big-endian mode.
+ */
+
+static int
+fix_unaligned(p, frame)
+	struct proc *p;
+	struct trapframe *frame;
+{
+	int indicator = EXC_ALI_OPCODE_INDICATOR(frame->dsisr);
+
+	switch (indicator) {
+	case EXC_ALI_LFD:
+	case EXC_ALI_STFD:
+		{
+			int reg = EXC_ALI_RST(frame->dsisr);
+			double *fpr = &p->p_addr->u_pcb.pcb_fpu.fpr[reg];
+
+			/* Juggle the FPU to ensure that we've initialized
+			 * the FPRs, and that their current state is in
+			 * the PCB.
+			 */
+			if (fpuproc != p) {
+				if (fpuproc)
+					save_fpu(fpuproc);
+				enable_fpu(p);
+			}
+			save_fpu(p);
+
+			if (indicator == EXC_ALI_LFD) {
+				if (copyin((void *)frame->dar, fpr,
+				    sizeof(double)) != 0)
+					return -1;
+				enable_fpu(p);
+			} else {
+				if (copyout(fpr, (void *)frame->dar,
+				    sizeof(double)) != 0)
+					return -1;
+			}
+			return 0;
+		}
+		break;
+	}
+
+	return -1;
+}