Re: [Xen-devel] PATCH: makes acm_setup arch independant

[Stefan Berger <stefanb@xxxxxxxxxx>]

xen-devel-bounces@xxxxxxxxxxxxxxxxxxx wrote on 09/05/2006
04:10:51 AM:

> Hi,
> 
> the acm_setup code use a multiboot descriptor to extract the policy
module.
> Because multiboot is not used on every platform, I slightly changed
the 
> interface: acm_setup now use buffer/len arguments.
> The module extraction code is moved to arch/x86/setup.c
> 
> I have just tested this code on ia64.

Does 'tested' mean that it compiles on ia64 or does
it 'work' and you can boot with an ACM policy on ia64? In the latter case
I would say that there's some ia64-specific code missing in the patch.

A minor issue is whether as much as possible of the
ACM-specific code should be kept inside the acm directory and we use #ifdefs
like

#if defined(__i386__)

#if defined(__x86_64__)

to compile architecture-specific functions there,
or whether functions like the extract_acm_policy below should be surrounded
by #ifdef ACM_SECURITY and they can stay inside the architecture-specific
code. The assumption would be that no one boots with an ACM policy if the
compile time option ACM_SECURITY was not set. Thoughts?

   Stefan

> The code compiles on x86 but I am unable to test it.
> 
> I have also fixed the alignment issue in acm_dump_policy_reference
(ia64 
> doesn't like unaligned accesses).  And yes there is a memset
to avoid 
> garbage.
> 
> 
> Tristan.

diff -r 31e9909a7221 -r 37c90a210d71
xen/arch/x86/setup.c
--- a/xen/arch/x86/setup.c    
   Tue Sep 05 07:38:00 2006 +0200
+++ b/xen/arch/x86/setup.c    
   Tue Sep 05 07:48:49 2006 +0200
@@ -203,6 +203,55 @@ static void __init
percpu_free_unused_ar
 #endif
 }
 
+/* Fecth acm policy module from multiboot
modules.  */
+static void
+extract_acm_policy(multiboot_info_t
*mbi,
+          
        unsigned int *initrdidx,
+          
        char **_policy_start, unsigned long *_policy_len)
+{
+    int i;
+    module_t *mod = (module_t
*)__va(mbi->mods_addr);
+
+    if ( mbi->mods_count
> 1 )
+        *initrdidx
= 1;
+
+    /*
+     * Try all modules and
see whichever could be the binary policy.
+     * Adjust the initrdidx
if module[1] is the binary policy.
+     */
+    for ( i = mbi->mods_count-1;
i >= 1; i-- )
+    {
+        unsigned
long start;
+        char *policy_start;
+        unsigned
long policy_len;
+
+        start
= initial_images_start + (mod[i].mod_start-mod[0].mod_start);
+#if defined(__i386__)
+        policy_start
= (char *)start;
+#elif defined(__x86_64__)
+        policy_start
= __va(start);
+#endif
+        policy_len
  = mod[i].mod_end - mod[i].mod_start;
+        if ( acm_is_policy(policy_start,
policy_len) )
+        {
+          
 printf("Policy len  0x%lx, start at %p - module %d.\n",
+          
        policy_len, policy_start, i);
+          
 *_policy_start = policy_start;
+          
 *_policy_len = policy_len;
+          
 if ( i == 1 )
+          
 {
+          
     if (mbi->mods_count > 2)
+          
         *initrdidx = 2;
+          
     else
+          
         *initrdidx = 0;
+          
 }
+          
 else
+          
     *initrdidx = 1;
+          
 break;
+        }
+    }
+}
+
 static void __init init_idle_domain(void)
 {
     struct domain *idle_domain;
@@ -225,6 +274,8 @@ void __init __start_xen(multiboot_info_t
     char __cmdline[]
= "", *cmdline = __cmdline;
     unsigned long _initrd_start
= 0, _initrd_len = 0;
     unsigned int initrdidx
= 1;
+    char *_policy_start
= NULL;
+    unsigned long _policy_len
= 0;
     module_t *mod =
(module_t *)__va(mbi->mods_addr);
     unsigned long nr_pages,
modules_length;
     paddr_t s, e;
@@ -559,8 +610,11 @@ void __init __start_xen(multiboot_info_t
     if ( opt_watchdog
) 
         watchdog_enable();
 
+    /* Extract policy from
multiboot.  */
+    extract_acm_policy(mbi,
&initrdidx, &_policy_start, &_policy_len);
+
     /* initialize access
control security module */
-    acm_init(&initrdidx,
mbi, initial_images_start);
+    acm_init(_policy_start,
_policy_len);
 
     /* Create initial
domain 0. */
     dom0 = domain_create(0);
diff -r 31e9909a7221 -r 37c90a210d71
xen/include/acm/acm_hooks.h
--- a/xen/include/acm/acm_hooks.h  
     Tue Sep 05 07:38:00 2006 +0200
+++ b/xen/include/acm/acm_hooks.h  
     Tue Sep 05 07:48:49 2006 +0200
@@ -369,9 +369,11 @@ static inline
int acm_sharing(ssidref_t 
         return
ACM_ACCESS_PERMITTED;
 }
 
-extern int acm_init(unsigned int *initrdidx,
-          
         const multiboot_info_t *mbi,
-          
         unsigned long start);
+
+extern int acm_init(char *policy_start,
unsigned long policy_len);
+
+/* Return true iff buffer has an acm
policy magic number.  */
+extern int acm_is_policy(char *buf,
unsigned long len);
 
 #endif
 
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