From: Chuck Ebbert <76306.1226@compuserve.com>
Date: Tue, 13 Sep 2005 08:55:41 +0000 (-0400)
Subject: [PATCH] i386: Ignore masked FPU exceptions
X-Git-Tag: v2.6.14-rc2~47
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=33333373c40633cec8791a284e84e4b116522c8f;p=linux-2.6

[PATCH] i386: Ignore masked FPU exceptions

Masked FPU exceptions should obviously not happen in the first place,
but if they do, ignoring them seems to be the right thing to do.

Although there is no documentation available for Cyrix MII, I did find
erratum F-7 for Winchip C6, "FPU instruction may result in spurious
exception under certain conditions" which seems to indicate that this
can happen.

That would also explain the behaviour Ondrej Zary reported on the MII.

Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

diff --git a/arch/i386/kernel/traps.c b/arch/i386/kernel/traps.c
index 09a58cb6da..431a551e46 100644
--- a/arch/i386/kernel/traps.c
+++ b/arch/i386/kernel/traps.c
@@ -807,8 +807,9 @@ void math_error(void __user *eip)
 	cwd = get_fpu_cwd(task);
 	swd = get_fpu_swd(task);
 	switch (swd & ~cwd & 0x3f) {
-		case 0x000:
-		default:
+		case 0x000: /* No unmasked exception */
+			return;
+		default:    /* Multiple exceptions */
 			break;
 		case 0x001: /* Invalid Op */
 			/*