arm64: init a var in _bootstrap()

[Artturi Alm]

Hi,

spotted this while looking at how deep the hole suggested by mpi@ is.
memhook is used by mmrw minor case 0, and the diff below fixes that.
rest of it should be logically solid improvement, but given the state
of arm64 internals w/all the "// XXXshit", and how sacred these arch-md
bootstraps are to be above all cleanup, i guess i'll come up w/minimal
diff later.

-Artturi


diff --git a/sys/arch/arm64/arm64/machdep.c b/sys/arch/arm64/arm64/machdep.c
index d1d5a673849..505fa4e1510 100644
--- a/sys/arch/arm64/arm64/machdep.c
+++ b/sys/arch/arm64/arm64/machdep.c
@@ -833,13 +833,6 @@ initarm(struct arm64_bootparams *abp)
        msgbufphys = pmap_steal_avail(round_page(MSGBUFSIZE), PAGE_SIZE, NULL);
        vstart += round_page(MSGBUFSIZE);
 
-       zero_page = vstart;
-       vstart += PAGE_SIZE;
-       copy_src_page = vstart;
-       vstart += PAGE_SIZE;
-       copy_dst_page = vstart;
-       vstart += PAGE_SIZE;
-
        /* Relocate the FDT to safe memory. */
        if (fdt_get_size(config) != 0) {
                uint32_t csize, size = round_page(fdt_get_size(config));
diff --git a/sys/arch/arm64/arm64/pmap.c b/sys/arch/arm64/arm64/pmap.c
index 067b1ea2a53..61cfc279a74 100644
--- a/sys/arch/arm64/arm64/pmap.c
+++ b/sys/arch/arm64/arm64/pmap.c
@@ -155,6 +155,11 @@ struct mem_region *pmap_allocated = 
&pmap_allocated_regions[0];
 int pmap_cnt_avail, pmap_cnt_allocated;
 uint64_t pmap_avail_kvo;
 
+/* static free VAs setup during bootstrap */
+char *memhook;
+vaddr_t zero_page;
+vaddr_t copy_src_page;
+vaddr_t copy_dst_page;
 
 /* virtual to physical helpers */
 static inline int
@@ -1201,6 +1206,16 @@ pmap_bootstrap(long kvo, paddr_t lpt1,  long 
kernelstart, long kernelend,
 
        printf("all mapped\n");
 
+       /* claim some static KVAs used by mmrw/pmap_zero_page/pmap_copy_page */
+       memhook = (char *)vstart;
+       vstart += PAGE_SIZE;
+       zero_page = vstart;
+       vstart += PAGE_SIZE;
+       copy_src_page = vstart;
+       vstart += PAGE_SIZE;
+       copy_dst_page = vstart;
+       vstart += PAGE_SIZE;
+
        return vstart;
 }
 
@@ -1650,11 +1665,6 @@ pmap_update(pmap_t pm)
 {
 }
 
-char *memhook;
-vaddr_t zero_page;
-vaddr_t copy_src_page;
-vaddr_t copy_dst_page;
-
 int
 pmap_is_referenced(struct vm_page *pg)
 {