Subject: [PATCH 2/2] powerpc/math-emu: keep track of the instructions unimplemented by FPU

From: Kevin Hao <[email-masked]>
Date: Thu, 11 Jul 2013 20:21:55 +0800

Some cores (such as Freescale BookE) don't implement all floating
point instructions in ISA. But some gcc versions do use these
instructions. So we would have to enable the math emulation in this
case. Add this to emulated instructions tracking statistics so that
the user has a way to know that its toolcahin emit these unimplemented
floating point instructions.

Signed-off-by: Kevin Hao <[email-masked]>
---
 arch/powerpc/math-emu/math.c | 50 +++++++++++++++++++++++++++-----------------
 1 file changed, 31 insertions(+), 19 deletions(-)

diff --git a/arch/powerpc/math-emu/math.c b/arch/powerpc/math-emu/math.c
index 18ce6a7..9a98b6c 100644
--- a/arch/powerpc/math-emu/math.c
+++ b/arch/powerpc/math-emu/math.c
@@ -10,6 +10,7 @@
 
 #include <asm/sfp-machine.h>
 #include <math-emu/double.h>
+#include <asm/emulated_ops.h>
 
 #define FLOATFUNC(x)	extern int x(void *, void *, void *, void *)
 
@@ -222,10 +223,17 @@ do_mathemu(struct pt_regs *regs)
 	int idx = 0;
 	int (*func)(void *, void *, void *, void *);
 	int type = 0;
-	int eflag, trap;
+	int eflag, trap, ret = -ENOSYS;
+	int has_hw_fpu = 0;
 
-	if (get_user(insn, (u32 *)pc))
-		return -EFAULT;
+#ifdef CONFIG_PPC_FPU
+	has_hw_fpu = 1;
+#endif
+
+	if (get_user(insn, (u32 *)pc)) {
+		ret = -EFAULT;
+		goto out;
+	}
 
 	switch (insn >> 26) {
 	case LFS:	func = lfs;	type = D;	break;
@@ -249,7 +257,7 @@ do_mathemu(struct pt_regs *regs)
 		case STFDUX:	func = stfd;	type = XEU;	break;
 		case STFIWX:	func = stfiwx;	type = XE;	break;
 		default:
-			goto illegal;
+			goto out;
 		}
 		break;
 
@@ -267,7 +275,7 @@ do_mathemu(struct pt_regs *regs)
 		case FNMSUBS:	func = fnmsubs;	type = ABC;	break;
 		case FNMADDS:	func = fnmadds;	type = ABC;	break;
 		default:
-			goto illegal;
+			goto out;
 		}
 		break;
 
@@ -287,7 +295,7 @@ do_mathemu(struct pt_regs *regs)
 			case FNMSUB:	func = fnmsub;	type = ABC;	break;
 			case FNMADD:	func = fnmadd;	type = ABC;	break;
 			default:
-				goto illegal;
+				goto out;
 			}
 			break;
 		}
@@ -309,12 +317,12 @@ do_mathemu(struct pt_regs *regs)
 		case MFFS:	func = mffs;	type = X;	break;
 		case MTFSF:	func = mtfsf;	type = XFLB;	break;
 		default:
-			goto illegal;
+			goto out;
 		}
 		break;
 
 	default:
-		goto illegal;
+		goto out;
 	}
 
 	switch (type) {
@@ -347,7 +355,7 @@ do_mathemu(struct pt_regs *regs)
 	case DU:
 		idx = (insn >> 16) & 0x1f;
 		if (!idx)
-			goto illegal;
+			goto out;
 
 		sdisp = (insn & 0xffff);
 		op0 = (void *)&current->thread.TS_FPR((insn >> 21) & 0x1f);
@@ -375,7 +383,7 @@ do_mathemu(struct pt_regs *regs)
 			if (((insn >> 1) & 0x3ff) == STFIWX)
 				op1 = (void *)(regs->gpr[(insn >> 11) & 0x1f]);
 			else
-				goto illegal;
+				goto out;
 		} else {
 			op1 = (void *)(regs->gpr[idx] + regs->gpr[(insn >> 11) & 0x1f]);
 		}
@@ -417,7 +425,7 @@ do_mathemu(struct pt_regs *regs)
 		break;
 
 	default:
-		goto illegal;
+		goto out;
 	}
 
 	/*
@@ -425,9 +433,8 @@ do_mathemu(struct pt_regs *regs)
 	 * if flushed into the thread_struct before attempting
 	 * emulation
 	 */
-#ifdef CONFIG_PPC_FPU
-	flush_fp_to_thread(current);
-#endif
+	if (has_hw_fpu)
+		flush_fp_to_thread(current);
 
 	eflag = func(op0, op1, op2, op3);
 
@@ -437,8 +444,10 @@ do_mathemu(struct pt_regs *regs)
 	}
 
 	trap = record_exception(regs, eflag);
-	if (trap)
-		return 1;
+	if (trap) {
+		ret = 1;
+		goto out;
+	}
 
 	switch (type) {
 	case DU:
@@ -451,8 +460,11 @@ do_mathemu(struct pt_regs *regs)
 	}
 
 	regs->nip += 4;
-	return 0;
+	ret = 0;
+
+out:
+	if (has_hw_fpu && ret >= 0)
+		PPC_WARN_EMULATED(math, regs);
 
-illegal:
-	return -ENOSYS;
+	return ret;
 }
-- 
1.8.1.4