[[e-mail]: [PATCH] Fail gracefuly when attempting to load 64-bit kFreeBSD on IA32 CPU]

[Robert Millan]

FYI

--
Robert Millan

  The DRM opt-in fallacy: "Your data belongs to us. We will decide when (and
  how) you may access your data; but nobody's threatening your freedom: we
  still allow you to remove your data and not access it at all."


--
Robert Millan

  The DRM opt-in fallacy: "Your data belongs to us. We will decide when (and
  how) you may access your data; but nobody's threatening your freedom: we
  still allow you to remove your data and not access it at all."

---

2009-10-07  Robert Millan  <rmh.grub@...>

        Fail gracefuly when attempting to load 64-bit kFreeBSD on IA32 CPU.

        * include/grub/i386/cpuid.h: New file.
        * commands/i386/cpuid.c: Include `<grub/i386/cpuid.h>'.
        (has_longmode): Rename to ...
        (grub_cpuid_has_longmode): ... this.  Update all users.  Remove
        `unsigned' attribute.
        * loader/i386/bsd.c: Include `<grub/i386/cpuid.h>'.
        (grub_bsd_load_elf): Fail if load of 64-bit kernel was requested
        on a CPU that doesn't implement AMD64 instruction set.

Index: include/grub/i386/cpuid.h
===================================================================
--- include/grub/i386/cpuid.h (revision 0)
+++ include/grub/i386/cpuid.h (revision 0)
@@ -0,0 +1,19 @@
+/*
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2009  Free Software Foundation, Inc.
+ *
+ *  GRUB is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  GRUB is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+extern unsigned char grub_cpuid_has_longmode;
Index: commands/i386/cpuid.c
===================================================================
--- commands/i386/cpuid.c (revision 2626)
+++ commands/i386/cpuid.c (working copy)
@@ -1,7 +1,7 @@
 /* cpuid.c - test for CPU features */
 /*
  *  GRUB  --  GRand Unified Bootloader
- *  Copyright (C) 2006, 2007  Free Software Foundation, Inc.
+ *  Copyright (C) 2006, 2007, 2009  Free Software Foundation, Inc.
  *  Based on gcc/gcc/config/i386/driver-i386.c
  *
  *  GRUB is free software: you can redistribute it and/or modify
@@ -24,6 +24,7 @@
 #include <grub/env.h>
 #include <grub/command.h>
 #include <grub/extcmd.h>
+#include <grub/i386/cpuid.h>
 
 #define cpuid(num,a,b,c,d) \
   asm volatile ("xchgl %%ebx, %1; cpuid; xchgl %%ebx, %1" \
@@ -38,14 +39,14 @@ static const struct grub_arg_option options[] =
 
 #define bit_LM (1 << 29)
 
-static unsigned char has_longmode = 0;
+unsigned char grub_cpuid_has_longmode = 0;
 
 static grub_err_t
 grub_cmd_cpuid (grub_extcmd_t cmd __attribute__ ((unused)),
  int argc __attribute__ ((unused)),
  char **args __attribute__ ((unused)))
 {
-  return has_longmode ? GRUB_ERR_NONE
+  return grub_cpuid_has_longmode ? GRUB_ERR_NONE
     : grub_error (GRUB_ERR_TEST_FAILURE, "false");
 }
 
@@ -55,7 +56,7 @@ GRUB_MOD_INIT(cpuid)
 {
 #ifdef __x86_64__
   /* grub-emu */
-  has_longmode = 1;
+  grub_cpuid_has_longmode = 1;
 #else
   unsigned int eax, ebx, ecx, edx;
   unsigned int max_level;
@@ -82,7 +83,7 @@ GRUB_MOD_INIT(cpuid)
     goto done;
 
   cpuid (0x80000001, eax, ebx, ecx, edx);
-  has_longmode = !!(edx & bit_LM);
+  grub_cpuid_has_longmode = !!(edx & bit_LM);
 done:
 #endif
 
Index: loader/i386/bsd.c
===================================================================
--- loader/i386/bsd.c (revision 2626)
+++ loader/i386/bsd.c (working copy)
@@ -19,6 +19,7 @@
 #include <grub/loader.h>
 #include <grub/cpu/loader.h>
 #include <grub/cpu/bsd.h>
+#include <grub/i386/cpuid.h>
 #include <grub/machine/init.h>
 #include <grub/machine/memory.h>
 #include <grub/memory.h>
@@ -871,6 +872,9 @@ grub_bsd_load_elf (grub_elf_t elf)
     {
       is_64bit = 1;
 
+      if (! grub_cpuid_has_longmode)
+ return grub_error (GRUB_ERR_BAD_OS, "Your CPU does not implement AMD64 architecture.");
+
       /* FreeBSD has 64-bit entry point.  */
       if (kernel_type == KERNEL_TYPE_FREEBSD)
  {

---

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[Robert Millan]

On Fri, Oct 09, 2009 at 08:21:49PM +0200, Robert Millan wrote:
>
> FYI

This should prevent amd64 kFreeBSD from crashing when running on ia32
CPU.  If you'd like a more user-friendly message, the cpuid command
can be used with scripting, e.g.:

  if cpuid --blah ; then
    echo "I don't like you!"
    read
    halt
  fi

either inside a menuentry or top of grub.cfg.

--
Robert Millan

  The DRM opt-in fallacy: "Your data belongs to us. We will decide when (and
  how) you may access your data; but nobody's threatening your freedom: we
  still allow you to remove your data and not access it at all."


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[Aurelien Jarno]

On Fri, Oct 09, 2009 at 08:30:41PM +0200, Robert Millan wrote:

> On Fri, Oct 09, 2009 at 08:21:49PM +0200, Robert Millan wrote:
> >
> > FYI
>
> This should prevent amd64 kFreeBSD from crashing when running on ia32
> CPU.  If you'd like a more user-friendly message, the cpuid command
> can be used with scripting, e.g.:
>
>   if cpuid --blah ; then
>     echo "I don't like you!"
>     read
>     halt
>   fi
>
> either inside a menuentry or top of grub.cfg.
>

The message looks fine for now. Thanks for adding that.

--
Aurelien Jarno                        GPG: 1024D/F1BCDB73
aurelien@...                 http://www.aurel32.net


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