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F0 0F Workaround

To: Blair Sadewitz <blair@nac.net>
Subject: F0 0F Workaround
From: Tobias Weingartner <weingart@natasha.brandonu.ca>
Date: Mon, 08 Dec 1997 17:23:52 -0600
Cc: tech@openbsd.org
On Sunday, December 7, Blair Sadewitz wrote:
> 
> Theo told me to ask you for an F0 0F workaround patch.  Could you help me?

I can try.  Attached to the end of this message is my current workaround.
I would like people to test, and tell me if it works for them.  The patches
should apply to a current system, but they might have some "fluff" in them,
as I have other changes to the files in question.

I'd appreciate it if someone with a clean system could apply & test this
patch, and if it works, to commit it to the repo.

Thanks,

--Toby.
*----------------------------------------------------------------------------*
| Tobias Weingartner | Email: weingart@BrandonU.Ca | Need a Unix sys-admin?  |
| 6B-1137 Lorne Ave. |-----------------------------| Send E-Mail for resume, |
| Brandon, Canada    | Unix Guru? Admin, Sys-Prgmr | and other details...    |
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Index: i386/genassym.cf
===================================================================
RCS file: /cvs/src/sys/arch/i386/i386/genassym.cf,v
retrieving revision 1.5
diff -u -r1.5 genassym.cf
--- genassym.cf	1997/10/19 06:34:23	1.5
+++ genassym.cf	1997/12/08 21:31:32
@@ -108,6 +108,8 @@
 define	TF_CS		offsetof(struct trapframe, tf_cs)
 define	TF_TRAPNO	offsetof(struct trapframe, tf_trapno)
 define	TF_EFLAGS	offsetof(struct trapframe, tf_eflags)
+define	TF_EIP		offsetof(struct trapframe, tf_eip)
+define	TF_ERR		offsetof(struct trapframe, tf_err)
 
 define	FRAMESIZE	sizeof(struct trapframe)
 
Index: i386/locore.s
===================================================================
RCS file: /cvs/src/sys/arch/i386/i386/locore.s,v
retrieving revision 1.36
diff -u -r1.36 locore.s
--- locore.s	1997/10/22 23:37:12	1.36
+++ locore.s	1997/12/08 21:31:43
@@ -1931,6 +1931,19 @@
 	TRAP(T_STKFLT)
 IDTVEC(prot)
 	TRAP(T_PROTFLT)
+#ifdef I586_CPU
+IDTVEC(f00f_redirect)
+	pushl	$T_PAGEFLT
+	INTRENTRY
+	testb	$PGEX_U,TF_ERR(%esp)
+	jnz	calltrap
+	movl	%cr2,%eax
+	subl	_idt,%eax
+	cmpl	$(6*8),%eax
+	jne	calltrap
+	movb	$T_PRIVINFLT,TF_TRAPNO(%esp)
+	jmp	calltrap
+#endif
 IDTVEC(page)
 	TRAP(T_PAGEFLT)
 IDTVEC(rsvd)
Index: i386/machdep.c
===================================================================
RCS file: /cvs/src/sys/arch/i386/i386/machdep.c,v
retrieving revision 1.66
diff -u -r1.66 machdep.c
--- machdep.c	1997/12/02 05:06:41	1.66
+++ machdep.c	1997/12/08 21:31:51
@@ -489,6 +474,10 @@
 		calibrate_cyclecounter();
 		printf(" %d MHz", pentium_mhz);
 	}
+	if(!strcmp(cpu_model, "Pentium (GenuineIntel 586-class CPU)")){
+		fix_f00f();
+		printf("\nCPU: F00F bug workaround installed");
+	}
 #endif
 	printf("\n");
 
@@ -1079,7 +1068,8 @@
 
 union descriptor gdt[NGDT];
 union descriptor ldt[NLDT];
-struct gate_descriptor idt[NIDT];
+struct gate_descriptor idt_region[NIDT];
+struct gate_descriptor *idt = idt_region;
 
 extern  struct user *proc0paddr;
 
@@ -1139,6 +1129,45 @@
 	IDTVEC(fpu),     IDTVEC(align),
 	IDTVEC(syscall), IDTVEC(osyscall);
 
+#if defined(I586_CPU)
+extern IDTVEC(f00f_redirect);
+pt_entry_t *pmap_pte __P((pmap_t, vm_offset_t));
+
+int cpu_f00f_bug = 0;
+
+void
+fix_f00f()
+{
+	struct region_descriptor region;
+	vm_offset_t va;
+	pt_entry_t *pte;
+	void *p;
+
+	/* Allocate two new pages */
+	va = kmem_alloc(kernel_map, NBPG*2);
+	p = (void *)(va + NBPG - 7*sizeof(*idt));
+
+	/* Copy over old IDT */
+	bcopy(idt, p, sizeof(idt_region));
+	idt = p;
+
+	/* Fix up paging redirect */
+	setgate(&idt[ 14], &IDTVEC(f00f_redirect), 0, SDT_SYS386TGT,
+		SEL_KPL, GCODE_SEL);
+
+	/* Map first page RO */
+	pte = pmap_pte(pmap_kernel(), va);
+	*pte &= ~PG_RW;
+
+	/* Reload idtr */
+	setregion(&region, idt, sizeof(idt_region) - 1);
+	lidt(&region);
+
+	/* Tell the rest of the world */
+	cpu_f00f_bug = 1;
+}
+#endif
+
 void
 init386(first_avail)
 	vm_offset_t first_avail;
@@ -1214,7 +1227,7 @@
 
 	setregion(&region, gdt, sizeof(gdt) - 1);
 	lgdt(&region);
-	setregion(&region, idt, sizeof(idt) - 1);
+	setregion(&region, idt, sizeof(idt_region) - 1);
 	lidt(&region);
 
 #if NISA > 0
@@ -1414,8 +1418,8 @@
 	 * Try to cause a triple fault and watchdog reset by setting the
 	 * IDT to point to nothing.
 	 */
-	bzero((caddr_t)idt, sizeof(idt));
-	setregion(&region, idt, sizeof(idt) - 1);
+	bzero((caddr_t)idt, sizeof(idt_region));
+	setregion(&region, idt, sizeof(idt_region) - 1);
 	lidt(&region);
 	__asm __volatile("divl %0,%1" : : "q" (0), "a" (0));
 
Index: include/cpu.h
===================================================================
RCS file: /cvs/src/sys/arch/i386/include/cpu.h,v
retrieving revision 1.17
diff -u -r1.17 cpu.h
--- cpu.h	1997/10/25 21:47:27	1.17
+++ cpu.h	1997/12/08 21:31:52
@@ -140,6 +140,10 @@
 extern struct cpu_nameclass i386_cpus[];
 #ifdef I586_CPU
 extern int pentium_mhz;
+
+/* F00F bug fix stuff for pentium cpu */
+extern int cpu_f00f_bug;
+void fix_f00f __P((void));
 #endif
 
 /* autoconf.c */
Index: include/segments.h
===================================================================
RCS file: /cvs/src/sys/arch/i386/include/segments.h,v
retrieving revision 1.5
diff -u -r1.5 segments.h
--- segments.h	1997/04/17 03:44:51	1.5
+++ segments.h	1997/12/08 21:31:53
@@ -128,7 +128,8 @@
 
 #ifdef _KERNEL
 extern union descriptor gdt[], ldt[];
-extern struct gate_descriptor idt[];
+extern struct gate_descriptor idt_region[];
+extern struct gate_descriptor *idt;
 
 void setgate __P((struct gate_descriptor *, void *, int, int, int, int));
 void setregion __P((struct region_descriptor *, void *, size_t));
Index: isa/isa_machdep.c
===================================================================
RCS file: /cvs/src/sys/arch/i386/isa/isa_machdep.c,v
retrieving revision 1.22
diff -u -r1.22 isa_machdep.c
--- isa_machdep.c	1997/09/24 22:28:16	1.22
+++ isa_machdep.c	1997/12/08 21:31:55
@@ -62,7 +62,6 @@
 /* default interrupt vector table entries */
 typedef (*vector) __P((void));
 extern vector IDTVEC(intr)[], IDTVEC(fast)[];
-extern struct gate_descriptor idt[];
 void isa_strayintr __P((int));
 void intr_calculatemasks __P((void));
 int fakeintr __P((void *));
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