Changeset fbcdeb8 in mainline for uspace/lib/c/generic/as.c

Timestamp:

2011-12-19T17:30:39Z (12 years ago)

Author:

Martin Decky <martin@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

58f6229

Parents:

24cf31f1

Message:

Remove the two-phase way of creating virtual memory areas (first asking for a mappable address and then mapping it) which was prone to race conditions when two or more calls to as_get_mappable_page() and as_area_create() were interleaved. This for example caused the e1k driver to randomly fail.

The memory area related syscalls and IPC calls have all been altered to accept a special value (void *) -1, representing a demand to atomically search for a mappable address space "hole" and map to it.

Individual changes:

• IPC_M_SHARE_OUT: the destination address space area is supplied by the kernel, the callee only specifies the lower bound

(the address is returned to the callee via a pointer in an IPC reply argument)

• IPC_M_SHARE_IN: the destination address space ares is supplied by the kernel, the callee only specifies the lower bound

(the address is returned to the caller as usual via an IPC argument)

• SYS_AS_GET_UNMAPPED_AREA was removed
• dummy implementations of SYS_PHYSMEM_UNMAP and SYS_IOSPACE_DISABLE were added for the sake of symmetry (they do nothing yet)
• SYS_PHYSMEM_MAP and SYS_DMAMEM_MAP were altered to accept (void *) -1 as address space area base and a lower bound
• kernel as_area_create() and as_area_share() were altered to accept (void *) -1 as address space area base and a lower bound
• uspace libraries and programs were altered to reflect the new API

File:

• uspace/lib/c/generic/as.c (modified) (2 diffs)

uspace/lib/c/generic/as.c

@@ -45 +45 @@
 /** Create address space area.
  *
- * @param address Virtual address where to place new address space area.
- * @param size    Size of the area.
- * @param flags   Flags describing type of the area.
+ * @param base  Starting virtual address of the area.
+ *              If set to (void *) -1, the kernel finds
+ *              a mappable area.
+ * @param size  Size of the area.
+ * @param flags Flags describing type of the area.
  *
- * @return address on success, (void *) -1 otherwise.
+ * @return Starting virtual address of the created area on success.
+ * @return (void *) -1 otherwise.
  *
  */
-void *as_area_create(void *address, size_t size, unsigned int flags)
+void *as_area_create(void *base, size_t size, unsigned int flags)
 {
-        return (void *) __SYSCALL3(SYS_AS_AREA_CREATE, (sysarg_t) address,
-            (sysarg_t) size, (sysarg_t) flags);
+        return (void *) __SYSCALL4(SYS_AS_AREA_CREATE, (sysarg_t) base,
+            (sysarg_t) size, (sysarg_t) flags, (sysarg_t) __entry);
 }
 
@@ -102 +105 @@
 }
 
-/** Return pointer to unmapped address space area
- *
- * @param size Requested size of the allocation.
- *
- * @return Pointer to the beginning of unmapped address space area.
- *
- */
-void *as_get_mappable_page(size_t size)
-{
-        return (void *) __SYSCALL2(SYS_AS_GET_UNMAPPED_AREA,
-            (sysarg_t) __entry, (sysarg_t) size);
-}
-
 /** Find mapping to physical address.
  *