make kernel leave a page-sized gap in its code and data to not be

mapped in if so configured.

diff --git a/include/minix/com.h b/include/minix/com.h
index 5358c1784890153ae2b3312ae0b85068b1479633..4e93a76d465028281611dceebb7929384f171a67 100755 (executable)
--- a/include/minix/com.h
+++ b/include/minix/com.h
@@ -593,6 +593,7 @@
 #define VMCTL_MEMREQ_REPLY     15
 #define VMCTL_INCSP            16
 #define VMCTL_STACKTRACE       17
+#define VMCTL_NOPAGEZERO       18
 
 /*===========================================================================*
  *                Messages for the Reincarnation Server                     *

diff --git a/include/minix/config.h b/include/minix/config.h
index 8bac14ba4d968535de8a9488097cc3413d4e1504..dcfeb432670d0529d19b7e9d5072963f0047b043 100755 (executable)
--- a/include/minix/config.h
+++ b/include/minix/config.h
@@ -95,4 +95,7 @@
 #define SPROFILE          1    /* statistical profiling */
 #define CPROFILE          0    /* call profiling */
 
+/* Compile kernel so that first page of code and data can be unmapped. */
+#define VM_KERN_NOPAGEZERO      1       
+
 #endif /* _CONFIG_H */

diff --git a/kernel/arch/i386/memory.c b/kernel/arch/i386/memory.c
index e020088681584c7b5d062243a718cbc67feb1dda..16c6cb2943bc4607fd59c307bea2c689dc19bc07 100644 (file)
--- a/kernel/arch/i386/memory.c
+++ b/kernel/arch/i386/memory.c
@@ -45,6 +45,7 @@ PUBLIC void vm_init(void)
        u32_t entry;
        unsigned pages;
        struct proc* rp;
+       struct proc *sys = proc_addr(SYSTEM);
 
        if (!vm_size)
                minix_panic("i386_vm_init: no space for page tables", NO_NUM);
@@ -77,6 +78,12 @@ PUBLIC void vm_init(void)
                        I386_VM_PRESENT;
                if (phys_mem >= vm_mem_high)
                        entry= 0;
+#if VM_KERN_NOPAGEZERO
+               if (phys_mem == (sys->p_memmap[T].mem_phys << CLICK_SHIFT) ||
+                   phys_mem == (sys->p_memmap[D].mem_phys << CLICK_SHIFT)) {
+                       entry = 0;
+               }
+#endif
                phys_put32(vm_pt_base + p*I386_VM_PT_ENT_SIZE, entry);
        }
 
@@ -471,6 +478,7 @@ PUBLIC int vm_checkrange(struct proc *caller, struct proc *target,
 
        vmassert(vm_running);
 
+
        /* If caller has had a reply to this request, return it. */
        if(RTS_ISSET(caller, VMREQUEST)) {
                if(caller->p_vmrequest.who == target->p_endpoint) {
@@ -522,8 +530,9 @@ PUBLIC int vm_checkrange(struct proc *caller, struct proc *target,
                        target->p_name, target->p_endpoint, v, wrfl, flags, phys);
                }
 
-               if(checkonly)
+               if(checkonly) {
                        return VMSUSPEND;
+               }
 
                /* This range is not OK for this process. Set parameters
                 * of the request and notify VM about the pending request.
@@ -544,7 +553,19 @@ PUBLIC int vm_checkrange(struct proc *caller, struct proc *target,
                /* Connect caller on vmrequest wait queue. */
                caller->p_vmrequest.nextrequestor = vmrequest;
                vmrequest = caller;
-               soft_notify(VM_PROC_NR);
+               if(!caller->p_vmrequest.nextrequestor) {
+                       int n = 0;
+                       struct proc *vmr;
+                       for(vmr = vmrequest; vmr; vmr = vmr->p_vmrequest.nextrequestor)
+                               n++;
+                       soft_notify(VM_PROC_NR);
+#if 0
+                       kprintf("(%d) ", n);
+                       kprintf("%d/%d ",
+                               caller->p_endpoint, target->p_endpoint);
+                       util_stacktrace();
+#endif
+               }
 
 #if 0
                kprintf("SYSTEM: vm_checkrange: range bad for "

diff --git a/kernel/system/do_vmctl.c b/kernel/system/do_vmctl.c
index bceeed639b128a7a7cc4b81a55f6914d511b701b..2628f1e2a8b69b58d2219f6b640b8b35be27e75f 100644 (file)
--- a/kernel/system/do_vmctl.c
+++ b/kernel/system/do_vmctl.c
@@ -11,6 +11,7 @@
 #include "../vm.h"
 #include "../debug.h"
 #include <minix/type.h>
+#include <minix/config.h>
 
 /*===========================================================================*
  *                             do_vmctl                                     *
@@ -92,6 +93,10 @@ kprintf("SYSTEM: request %d:0x%lx-0x%lx, wrflag %d, failed\n",
                }
 #endif
                return OK;
+#if VM_KERN_NOPAGEZERO
+       case VMCTL_NOPAGEZERO:
+               return OK;
+#endif
        case VMCTL_STACKTRACE:
                kprintf("vmctl stacktrace ");
                proc_stacktrace(p);