From: Alex Hornung <ahornung@gmail.com>
Date: Wed, 29 Feb 2012 15:46:48 +0000 (+0000)
Subject: boot/loader - test if CPU supports long mode
X-Git-Tag: v3.2.0~1295
X-Git-Url: https://gitweb.dragonflybsd.org/dragonfly.git/commitdiff_plain/71920ddbfafa6ebd2812dc32ea61f7d69c05175b

boot/loader - test if CPU supports long mode

 * Test if the CPU supports long mode (64 bits) before trying to load an
   x86_64 kernel.

Obtained-from: FreeBSD
Dragonfly-bug: http://bugs.dragonflybsd.org/issue1624
---

diff --git a/sys/boot/pc32/libi386/bootinfo64.c b/sys/boot/pc32/libi386/bootinfo64.c
index 39b85be813..f31ad4420e 100644
--- a/sys/boot/pc32/libi386/bootinfo64.c
+++ b/sys/boot/pc32/libi386/bootinfo64.c
@@ -32,6 +32,9 @@
 #include <sys/reboot.h>
 #include <sys/linker.h>
 #include <machine/bootinfo.h>
+#include <machine/cpufunc.h>
+#include <machine/psl.h>
+#include <machine/specialreg.h>
 #include "bootstrap.h"
 #include "libi386.h"
 #include "btxv86.h"
@@ -124,7 +127,45 @@ bi_copymodules64(vm_offset_t addr)
 }
 
 /*
- * Load the information expected by an i386 kernel.
+ * Check to see if this CPU supports long mode.
+ */
+static int
+bi_checkcpu(void)
+{
+    char *cpu_vendor;
+    int vendor[3];
+    int eflags, regs[4];
+
+    /* Check for presence of "cpuid". */
+    eflags = read_eflags();
+    write_eflags(eflags ^ PSL_ID);
+    if (!((eflags ^ read_eflags()) & PSL_ID))
+	return (0);
+
+    /* Fetch the vendor string. */
+    do_cpuid(0, regs);
+    vendor[0] = regs[1];
+    vendor[1] = regs[3];
+    vendor[2] = regs[2];
+    cpu_vendor = (char *)vendor;
+
+    /* Check for vendors that support AMD features. */
+    if (strncmp(cpu_vendor, "GenuineIntel", 12) != 0 &&
+	strncmp(cpu_vendor, "AuthenticAMD", 12) != 0)
+	return (0);
+
+    /* Has to support AMD features. */
+    do_cpuid(0x80000000, regs);
+    if (!(regs[0] >= 0x80000001))
+	return (0);
+
+    /* Check for long mode. */
+    do_cpuid(0x80000001, regs);
+    return (regs[3] & AMDID_LM);
+}
+
+/*
+ * Load the information expected by an amd64 kernel.
  *
  * - The 'boothowto' argument is constructed
  * - The 'bootdev' argument is constructed
@@ -145,6 +186,11 @@ bi_load64(char *args, vm_offset_t *modulep, vm_offset_t *kernendp)
     char			*rootdevname;
     int				howto;
 
+    if (!bi_checkcpu()) {
+	printf("CPU doesn't support long mode\n");
+	return (EINVAL);
+    }
+
     howto = bi_getboothowto(args);
 
     /*