anon memory map/unmap, without shootdown

51ace277 · Nickolai Zeldovich · 40ba7672 · 51ace277 · 51ace277 · 51ace277
--- a/Makefile
+++ b/Makefile
@@ -174,6 +174,7 @@ UPROGS=\
 	_zombie\
 	_halt\
 	_thrtest\
+	_maptest\
 fs.img: mkfs README $(UPROGS)
 	./mkfs fs.img README $(UPROGS)

--- a/defs.h
+++ b/defs.h
@@ -172,6 +172,7 @@ int             vmn_load(struct vmnode *, struct inode*, uint, uint);
 struct vmap *   vmap_alloc(void);
 void            vmap_decref(struct vmap *);
 int             vmap_insert(struct vmap *, struct vmnode *n, uint);
+int             vmap_remove(struct vmap *, uint va_start, uint len);
 struct vma *    vmap_lookup(struct vmap *, uint);
 struct vmap *   vmap_copy(struct vmap *);
 void            freevm(pde_t*);

--- a/maptest.c
+++ b/maptest.c
+#include "types.h"
+#include "stat.h"
+#include "user.h"
+#include "xv6-mtrace.h"
+#include "x86.h"
+#include "uspinlock.h"
+int
+main(void)
+{
+  volatile char *p = (char *) 0x80000;
+  if (map((void *) p, 8192) < 0) {
+    printf(1, "map failed\n");
+    exit();
+  }
+  p[0] = 'x';
+  p[4096] = 'y';
+  if (p[0] != 'x' || p[4096] != 'y') {
+    printf(1, "mismatch\n");
+    exit();
+  }
+  if (unmap((void *) p, 8192) < 0) {
+    printf(1, "unmap failed\n");
+    exit();
+  }
+  p[0] = 'z';
+  if (p[0] == 'z') {
+    printf(1, "still mapped\n");
+    exit();
+  }
+  exit();
+}
--- a/syscall.c
+++ b/syscall.c
@@ -106,6 +106,8 @@ extern int sys_unlink(void);
 extern int sys_wait(void);
 extern int sys_write(void);
 extern int sys_uptime(void);
+extern int sys_map(void);
+extern int sys_unmap(void);
 extern int sys_halt(void);
 static int (*syscalls[])(void) = {
@@ -130,6 +132,8 @@ static int (*syscalls[])(void) = {
 [SYS_wait]    sys_wait,
 [SYS_write]   sys_write,
 [SYS_uptime]  sys_uptime,
+[SYS_map]     sys_map,
+[SYS_unmap]   sys_unmap,
 [SYS_halt]    sys_halt,
 };

--- a/sysproc.c
+++ b/sysproc.c
@@ -96,6 +96,44 @@ sys_uptime(void)
 }
 int
+sys_map(void)
+{
+  uint addr;
+  uint len;
+  if (argint(0, (int*) &addr) < 0)
+    return -1;
+  if (argint(1, (int*) &len) < 0)
+    return -1;
+  struct vmnode *vmn = vmn_allocpg(PGROUNDUP(len) / PGSIZE);
+  if (vmn == 0)
+    return -1;
+  if (vmap_insert(proc->vmap, vmn, PGROUNDDOWN(addr)) < 0) {
+    vmn_free(vmn);
+    return -1;
+  }
+  return 0;
+}
+int
+sys_unmap(void)
+{
+  uint addr;
+  uint len;
+  if (argint(0, (int*) &addr) < 0)
+    return -1;
+  if (argint(1, (int*) &len) < 0)
+    return -1;
+  if (vmap_remove(proc->vmap, PGROUNDDOWN(addr), PGROUNDUP(len)) < 0)
+    return -1;
+  return 0;
+}
+int
 sys_halt(void)
 {
  int i;

--- a/user.h
+++ b/user.h
@@ -22,6 +22,8 @@ int getpid(void);
 char* sbrk(int);
 int sleep(int);
 int uptime(void);
+int map(void *addr, int len);
+int unmap(void *addr, int len);
 void halt(void);
 // ulib.c

--- a/usys.S
+++ b/usys.S
@@ -29,4 +29,6 @@ SYSCALL(getpid)
 SYSCALL(sbrk)
 SYSCALL(sleep)
 SYSCALL(uptime)
+SYSCALL(map)
+SYSCALL(unmap)
 SYSCALL(halt)
--- a/vm.c
+++ b/vm.c
@@ -322,6 +322,27 @@ vmap_insert(struct vmap *m, struct vmnode *n, uint va_start)
  return -1;
 }
+int
+vmap_remove(struct vmap *m, uint va_start, uint len)
+{
+  acquire(&m->lock);
+  uint va_end = va_start + len;
+  for(uint i = 0; i < sizeof(m->e) / sizeof(m->e[0]); i++) {
+    if(m->e[i].n && (m->e[i].va_start < va_end && m->e[i].va_end > va_start)) {
+      if(m->e[i].va_start != va_start || m->e[i].va_end != va_end) {
+	release(&m->lock);
+	cprintf("vmap_remove: partial unmap unsupported\n");
+	return -1;
+      }
+      __sync_fetch_and_sub(&m->e[i].n->ref, 1);
+      m->e[i].n = 0;
+    }
+  }
+  release(&m->lock);
+  return 0;
+}
 struct vma *
 vmap_lookup(struct vmap *m, uint va)
 {