From 44ca02a46b6fa0a8f1181fdc08efa779c3bdce80 Mon Sep 17 00:00:00 2001
From: Joan Lledó <jlledom@member.fsf.org>
Date: Sat, 6 Nov 2021 09:13:32 +0100
Subject: vm: vm_region_get_proxy

To get a proxy to the region a given address belongs to,
with protection and range limited to the region ones.

* include/mach/mach4.defs: vm_region_get_proxy RPC declaration
* vm/vm_map.c: vm_region_get_proxy implementation
Message-Id: <20211106081333.10366-2-jlledom@mailfence.com>
---
 include/mach/mach4.defs  | 10 +++++++++
 vm/memory_object_proxy.h |  8 +++++++
 vm/vm_map.c              | 56 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 74 insertions(+)

diff --git a/include/mach/mach4.defs b/include/mach/mach4.defs
index 22bbbaec..2820bd73 100644
--- a/include/mach/mach4.defs
+++ b/include/mach/mach4.defs
@@ -111,3 +111,13 @@ routine memory_object_create_proxy(
 		start		: vm_offset_array_t;
 		len		: vm_size_array_t;
 		out proxy	: mach_port_t);
+
+/* Gets a proxy to the region that ADDRESS belongs to, starting at the region
+   start, with MAX_PROTECTION and LEN limited by the region ones, and returns
+   it in *PORT.  */
+routine vm_region_get_proxy(
+		task		: task_t;
+		address		: vm_address_t;
+		max_protection	: vm_prot_t;
+		len		: vm_size_t;
+		out proxy	: mach_port_t);
diff --git a/vm/memory_object_proxy.h b/vm/memory_object_proxy.h
index 8b3f2025..97f20b36 100644
--- a/vm/memory_object_proxy.h
+++ b/vm/memory_object_proxy.h
@@ -36,4 +36,12 @@ extern kern_return_t memory_object_proxy_lookup (ipc_port_t port,
                                                  vm_offset_t *start,
                                                  vm_offset_t *len);
 
+extern kern_return_t
+memory_object_create_proxy (ipc_space_t space, vm_prot_t max_protection,
+			    ipc_port_t *object, natural_t object_count,
+			    vm_offset_t *offset, natural_t offset_count,
+			    vm_offset_t *start, natural_t start_count,
+			    vm_size_t *len, natural_t len_count,
+			    ipc_port_t *port);
+
 #endif /* _VM_MEMORY_OBJECT_PROXY_H_ */
diff --git a/vm/vm_map.c b/vm/vm_map.c
index a687d365..900862d9 100644
--- a/vm/vm_map.c
+++ b/vm/vm_map.c
@@ -46,6 +46,7 @@
 #include <kern/list.h>
 #include <kern/rbtree.h>
 #include <kern/slab.h>
+#include <kern/mach4.server.h>
 #include <vm/pmap.h>
 #include <vm/vm_fault.h>
 #include <vm/vm_map.h>
@@ -53,6 +54,7 @@
 #include <vm/vm_page.h>
 #include <vm/vm_resident.h>
 #include <vm/vm_kern.h>
+#include <vm/memory_object_proxy.h>
 #include <ipc/ipc_port.h>
 #include <string.h>
 
@@ -4806,6 +4808,60 @@ kern_return_t	vm_region(
 	return(KERN_SUCCESS);
 }
 
+/*
+ *	vm_region_get_proxy:
+ *
+ *	Gets a proxy to the region that ADDRESS belongs to, starting at the
+ *	region start, with MAX_PROTECTION and LEN limited by the region ones,
+ *	and returns it in *PORT.
+ */
+kern_return_t
+vm_region_get_proxy (task_t task, vm_address_t address,
+		     vm_prot_t max_protection, vm_size_t len,
+		     ipc_port_t *port)
+{
+  kern_return_t ret;
+  vm_map_entry_t entry, tmp_entry;
+  vm_offset_t offset, start;
+  ipc_port_t pager;
+
+  if (task == TASK_NULL)
+    return(KERN_INVALID_ARGUMENT);
+
+  vm_map_lock_read(task->map);
+  if (!vm_map_lookup_entry(task->map, address, &tmp_entry)) {
+    if ((entry = tmp_entry->vme_next) == vm_map_to_entry(task->map)) {
+      vm_map_unlock_read(task->map);
+      return(KERN_NO_SPACE);
+    }
+  } else {
+    entry = tmp_entry;
+  }
+
+  /* Limit the allowed protection and range to the entry ones */
+  if (len > entry->vme_end - entry->vme_start) {
+    vm_map_unlock_read(task->map);
+    return(KERN_INVALID_ARGUMENT);
+  }
+
+  max_protection &= entry->max_protection;
+  pager = ipc_port_copy_send(entry->object.vm_object->pager);
+  offset = entry->offset;
+  start = 0;
+
+  vm_map_unlock_read(task->map);
+
+  ret = memory_object_create_proxy(task->itk_space, max_protection,
+				    &pager, 1,
+				    &offset, 1,
+				    &start, 1,
+				    &len, 1, port);
+  if (ret)
+    ipc_port_release_send(pager);
+
+  return ret;
+}
+
 /*
  *	Routine:	vm_map_simplify
  *
-- 
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