. map text (kernel's and processes') in readonly

. map kernel in non-user
 . don't map in first pages of kernel code and data
   if possible

these first pages could actually be freed but as the
kernel isn't allowed to touch them either we can't reuse
them until VM has totally taken over page table management
and kernel doesn't rely on identity mapping any more.

servers/vm/alloc.c

@@ -426,9 +426,7 @@ PRIVATE PUBLIC phys_bytes alloc_pages(int pages, int memflags)
 #define ALLOCRETURNCHECK			\
 	availbytes(&avail2, &chunks2);		\
 	vm_assert(avail1 - bytes == avail2);	\
-	vm_assert(chunks1 == chunks2 || chunks1-1 == chunks2);	\
+	vm_assert(chunks1 == chunks2 || chunks1-1 == chunks2);
-	if(verbosealloc)					\
-		printf("memory: 0x%lx bytes in %d chunks\n", avail2, chunks2);
 #else
 #define ALLOCRETURNCHECK
 #endif
@@ -495,9 +493,7 @@ PRIVATE PUBLIC void free_pages(phys_bytes pageno, int npages)
 #define FREERETURNCHECK								\
 	availbytes(&avail2, &chunks2);					\
 	vm_assert(avail1 + origsize  == avail2);			\
-	vm_assert(chunks1 == chunks2 || chunks1+1 == chunks2 || chunks1-1 == chunks2);	\
+	vm_assert(chunks1 == chunks2 || chunks1+1 == chunks2 || chunks1-1 == chunks2);
-	if(verbosealloc)							\
-		printf("memory: 0x%lx bytes in %d chunks\n", avail2, chunks2);
 #else
 #define FREERETURNCHECK
 #endif

servers/vm/exec.c

@@ -361,7 +361,7 @@ PUBLIC int proc_new(struct vmproc *vmp,
 	vmp->vm_offset = vstart;
 
 	/* page mapping flags for code */
-#define TEXTFLAGS (PTF_PRESENT | PTF_USER | PTF_WRITE)
+#define TEXTFLAGS (PTF_PRESENT | PTF_USER)
 	SANITYCHECK(SCL_DETAIL);
 	if(text_bytes > 0) {
 		if(!map_page_region(vmp, vstart, 0, text_bytes,

servers/vm/glo.h

@@ -20,8 +20,6 @@ u32_t data1[200];
 EXTERN long vm_sanitychecklevel;
 #endif
 
-int verbosealloc;
-
 #define VMP_SYSTEM	_NR_PROCS
 
 /* vm operation mode state and values */

servers/vm/i386/pagetable.c

@@ -781,12 +781,12 @@ PUBLIC int pt_mapkernel(pt_t *pt)
 
         /* Map in text. flags: don't write, supervisor only */
         if((r=pt_writemap(pt, KERNEL_TEXT, KERNEL_TEXT, KERNEL_TEXT_LEN,
-                 I386_VM_PRESENT | I386_VM_USER | I386_VM_WRITE, 0)) != OK)
+		I386_VM_PRESENT, 0)) != OK)
 		return r;
  
         /* Map in data. flags: read-write, supervisor only */
         if((r=pt_writemap(pt, KERNEL_DATA, KERNEL_DATA, KERNEL_DATA_LEN,
-                I386_VM_PRESENT | I386_VM_USER | I386_VM_WRITE, 0)) != OK)
+		I386_VM_PRESENT|I386_VM_WRITE, 0)) != OK)
 		return r;
 
 	return OK;

servers/vm/main.c

@@ -247,6 +247,23 @@ PRIVATE void vm_init(void)
 	 */
         kernel_top_bytes = find_kernel_top();
 
+	/* Can first kernel pages of code and data be (left) mapped out?
+	 * If so, change the SYSTEM process' memory map to reflect this
+	 * (future mappings of SYSTEM into other processes will not include
+	 * first pages), and free the first pages.
+	 */
+	if(vm_paged && sys_vmctl(SELF, VMCTL_NOPAGEZERO, 0) == OK) {
+	  	struct vmproc *vmp;
+		vmp = &vmproc[VMP_SYSTEM];
+		if(vmp->vm_arch.vm_seg[T].mem_len > 0) {
+#define DIFF CLICKSPERPAGE
+			vmp->vm_arch.vm_seg[T].mem_phys += DIFF;
+			vmp->vm_arch.vm_seg[T].mem_len -= DIFF;
+		}
+		vmp->vm_arch.vm_seg[D].mem_phys += DIFF;
+		vmp->vm_arch.vm_seg[D].mem_len -= DIFF;
+	}
+
 	/* Give these processes their own page table. */
 	for (ip = &image[0]; ip < &image[NR_BOOT_PROCS]; ip++) {
 		int s;

servers/vm/vm.h

@@ -12,7 +12,7 @@
 #define ABS2CLICK(a) ((a) >> CLICK_SHIFT)
 
 /* Compile in asserts and custom sanity checks at all? */
-#define SANITYCHECKS	0
+#define SANITYCHECKS	1
 #define VMSTATS		1
 
 /* If so, this level: */