Re: 2.6.10-rc3, i386: fpu handling on sigreturn

[Andi Kleen]

Bodo Stroesser <bstroesser@xxxxxxxxxxxxxxxxxxx> writes:
> 
> Now, the interrupted processes fpu no longer is cleared!

I agree it's a bug, although it's probably pretty obscure so people
didn't notice it.  The right fix would be to just clear_fpu again
in this case.  The problem has been in Linux forever.

Here's an untested patch for i386 and x86-64. 

-Andi

diff -u linux-2.6.10rc2-time/arch/i386/kernel/signal.c-o linux-2.6.10rc2-time/arch/i386/kernel/signal.c
--- linux-2.6.10rc2-time/arch/i386/kernel/signal.c-o	2004-11-15 12:34:25.000000000 +0100
+++ linux-2.6.10rc2-time/arch/i386/kernel/signal.c	2004-12-23 00:07:18.000000000 +0100
@@ -190,7 +190,8 @@
 			if (verify_area(VERIFY_READ, buf, sizeof(*buf)))
 				goto badframe;
 			err |= restore_i387(buf);
-		}
+		} else if (current->used_math) 
+			clear_fpu(current); 
 	}
 
 	err |= __get_user(*peax, &sc->eax);
diff -u linux-2.6.10rc2-time/arch/x86_64/kernel/signal.c-o linux-2.6.10rc2-time/arch/x86_64/kernel/signal.c
--- linux-2.6.10rc2-time/arch/x86_64/kernel/signal.c-o	2004-10-19 01:55:08.000000000 +0200
+++ linux-2.6.10rc2-time/arch/x86_64/kernel/signal.c	2004-12-23 00:07:19.000000000 +0100
@@ -125,7 +125,8 @@
 			if (verify_area(VERIFY_READ, buf, sizeof(*buf)))
 				goto badframe;
 			err |= restore_i387(buf);
-		}
+		} else if (current->used_math) 
+			clear_fpu(current); 
 	}
 
 	err |= __get_user(*prax, &sc->rax);
diff -u linux-2.6.10rc2-time/arch/x86_64/ia32/ia32_signal.c-o linux-2.6.10rc2-time/arch/x86_64/ia32/ia32_signal.c
--- linux-2.6.10rc2-time/arch/x86_64/ia32/ia32_signal.c-o	2004-10-19 01:55:08.000000000 +0200
+++ linux-2.6.10rc2-time/arch/x86_64/ia32/ia32_signal.c	2004-12-23 00:07:17.000000000 +0100
@@ -261,7 +261,8 @@
 			if (verify_area(VERIFY_READ, buf, sizeof(*buf)))
 				goto badframe;
 			err |= restore_i387_ia32(current, buf, 0);
-		}
+		} else if (current->used_math) 
+			clear_fpu(current); 
 	}
 
 	{ 

-
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