On Wed, Feb 27, 2019 at 11:07:23AM -0800, Philip Guenther wrote:
> On Mon, 25 Feb 2019, Falk Richter wrote:
> > >Synopsis: <OpenBSD 6.4 doesn't boot on 486 class processor anymore>
> ...
> > >Description:
> > <Just after booting the kernel the system stops with:
> > trap: 0(0) invalid opcode fault
> > cn_tab=0x5412c
> > eax 0 ecx 0 edx ff58 ebx ffc8
> > esp fe0c ebp ff40 esi 8 edi ff58
> > eip 4241c eflags 10046 cs 8 ss 10
> > ds 10 es 10 fs 10 gs 10
> >
> > I tested it with AMD / Cyrix 486DX2-66, AMD 486DX4-100 and Cyrix
> > 5x86-100GP processors on different mainboards with chipsets of UMC, SiS
> > and Winbond. I found one exception which works yet (see dmesg): AMD 5x86
> > P75 (marketing name) which was a AMD 486DX4-133 with write-back cache.
>
> The problem is that ucode_load() in sys/arch/i386/stand/libsa/exec_i386.c
> uses CPUID() without checking whether the cpuid instruction is supported.
> There are currently three places in sys/arch/i386/stand/libsa which make
> that check: cpuprobe.c, machdep.c, and random_i386.S. ucode_load() could
> copy the chunk from machdep.c...or someone could add a global and do the
> check once, early...
Index: boot/conf.c
===================================================================
RCS file: /cvs/src/sys/arch/i386/stand/boot/conf.c,v
retrieving revision 1.65
diff -u -p -r1.65 conf.c
--- boot/conf.c 23 Aug 2018 14:47:52 -0000 1.65
+++ boot/conf.c 28 Feb 2019 01:19:19 -0000
@@ -41,7 +41,7 @@
#include <dev/cons.h>
#include "debug.h"
-const char version[] = "3.34";
+const char version[] = "3.35";
int debug = 1;
Index: cdboot/conf.c
===================================================================
RCS file: /cvs/src/sys/arch/i386/stand/cdboot/conf.c,v
retrieving revision 1.33
diff -u -p -r1.33 conf.c
--- cdboot/conf.c 23 Aug 2018 14:47:52 -0000 1.33
+++ cdboot/conf.c 28 Feb 2019 01:19:31 -0000
@@ -42,7 +42,7 @@
#include <dev/cons.h>
#include "debug.h"
-const char version[] = "3.30";
+const char version[] = "3.31";
int debug = 1;
void (*sa_cleanup)(void) = NULL;
Index: libsa/exec_i386.c
===================================================================
RCS file: /cvs/src/sys/arch/i386/stand/libsa/exec_i386.c,v
retrieving revision 1.47
diff -u -p -r1.47 exec_i386.c
--- libsa/exec_i386.c 10 Dec 2018 16:52:02 -0000 1.47
+++ libsa/exec_i386.c 28 Feb 2019 00:55:07 -0000
@@ -34,6 +34,7 @@
#include <lib/libsa/loadfile.h>
#include <machine/biosvar.h>
#include <machine/specialreg.h>
+#include <machine/psl.h>
#include <stand/boot/bootarg.h>
#include "cmd.h"
@@ -163,7 +164,40 @@ ucode_load(void)
char path[128];
size_t buflen;
char *buf;
- int fd;
+ int fd, psl_check;
+
+ /*
+ * The following is a simple check to see if cpuid is supported.
+ * We try to toggle bit 21 (PSL_ID) in eflags. If it works, then
+ * cpuid is supported. If not, there's no cpuid, and we don't
+ * try it (don't want /boot to get an invalid opcode exception).
+ *
+ * XXX The NexGen Nx586 does not support this bit, so this is not
+ * a good method to detect the presence of cpuid on this
+ * processor. That's fine: the purpose here is to detect the
+ * absence of cpuid. We don't mind if the instruction's not
+ * there - this is not intended to determine exactly what
+ * processor is there, just whether it's i386 or amd64.
+ *
+ * The only thing that would cause us grief is a processor which
+ * does not support cpuid but which does allow the PSL_ID bit
+ * in eflags to be toggled.
+ */
+ __asm volatile(
+ "pushfl\n\t"
+ "popl %2\n\t"
+ "xorl %2, %0\n\t"
+ "pushl %0\n\t"
+ "popfl\n\t"
+ "pushfl\n\t"
+ "popl %0\n\t"
+ "xorl %2, %0\n\t" /* If %2 == %0, no cpuid */
+ : "=r" (psl_check)
+ : "0" (PSL_ID), "r" (0)
+ : "cc");
+
+ if (psl_check != PSL_ID)
+ return;
CPUID(0, dummy, vendor[0], vendor[2], vendor[1]);
vendor[3] = 0; /* NULL-terminate */
Index: pxeboot/conf.c
===================================================================
RCS file: /cvs/src/sys/arch/i386/stand/pxeboot/conf.c,v
retrieving revision 1.38
diff -u -p -r1.38 conf.c
--- pxeboot/conf.c 23 Aug 2018 14:47:52 -0000 1.38
+++ pxeboot/conf.c 28 Feb 2019 01:19:44 -0000
@@ -44,7 +44,7 @@
#include "pxeboot.h"
#include "pxe_net.h"
-const char version[] = "3.30";
+const char version[] = "3.31";
int debug = 1;
void (*sa_cleanup)(void) = pxe_shutdown;
