[rvm-commits] code: RVM-1050 : Use memmove() instead of memcpy() when memory r...

[<jik...@li...>]

details:   http://hg.code.sourceforge.net/p/jikesrvm/code/rev/f8c062ff106b
changeset: 10661:f8c062ff106b
user:      Erik Brangs <eri...@gm...>
date:      Mon Aug 19 20:38:11 2013 +0200
description:
RVM-1050 : Use memmove() instead of memcpy() when memory regions overlap in org.jikesrvm.runtime.Memory.memcopy(Address, Address, Extent).


diffstat:

 rvm/src/org/jikesrvm/runtime/BootRecord.java |   1 +
 rvm/src/org/jikesrvm/runtime/Memory.java     |  23 ++++++++++++++++++-----
 rvm/src/org/jikesrvm/runtime/SysCall.java    |  20 ++++++++++++++++++++
 tools/bootImageRunner/sys.C                  |  12 +++++++++++-
 4 files changed, 50 insertions(+), 6 deletions(-)

diffs (117 lines):

diff --git a/rvm/src/org/jikesrvm/runtime/BootRecord.java b/rvm/src/org/jikesrvm/runtime/BootRecord.java
--- a/rvm/src/org/jikesrvm/runtime/BootRecord.java
+++ b/rvm/src/org/jikesrvm/runtime/BootRecord.java
@@ -226,6 +226,7 @@
 
   // memory
   public Address sysCopyIP;
+  public Address sysMemmoveIP;
   public Address sysMallocIP;
   public Address sysCallocIP;
   public Address sysFreeIP;
diff --git a/rvm/src/org/jikesrvm/runtime/Memory.java b/rvm/src/org/jikesrvm/runtime/Memory.java
--- a/rvm/src/org/jikesrvm/runtime/Memory.java
+++ b/rvm/src/org/jikesrvm/runtime/Memory.java
@@ -424,22 +424,35 @@
   }
 
   /**
-   * Copy a region of memory.
-   * <p>
-   * Assumption: source and destination regions do not overlap
+   * Copies a region of memory.
    *
    * @param dst   Destination address
    * @param src   Source address
    * @param cnt   Number of bytes to copy
    */
   public static void memcopy(Address dst, Address src, Extent cnt) {
-    SysCall.sysCall.sysCopy(dst, src, cnt);
+    Address srcEnd = src.plus(cnt);
+    Address dstEnd = dst.plus(cnt);
+    boolean overlap = !srcEnd.LE(dst) && !dstEnd.LE(src);
+    if (overlap) {
+      SysCall.sysCall.sysMemmove(dst, src, cnt);
+    } else {
+      SysCall.sysCall.sysCopy(dst, src, cnt);
+    }
   }
 
+  /**
+   * Wrapper method for {@link #memcopy(Address, Address, Extent)}.
+   *
+   * @param dst   Destination address
+   * @param src   Source address
+   * @param cnt   Number of bytes to copy
+   */
   public static void memcopy(Address dst, Address src, int cnt) {
-    SysCall.sysCall.sysCopy(dst, src, Extent.fromIntSignExtend(cnt));
+    memcopy(dst, src, Extent.fromIntSignExtend(cnt));
   }
 
+
   /**
    * Zero a region of memory.
    *
diff --git a/rvm/src/org/jikesrvm/runtime/SysCall.java b/rvm/src/org/jikesrvm/runtime/SysCall.java
--- a/rvm/src/org/jikesrvm/runtime/SysCall.java
+++ b/rvm/src/org/jikesrvm/runtime/SysCall.java
@@ -80,9 +80,29 @@
   public abstract int sysGetenv(byte[] varName, byte[] buf, int limit);
 
   // memory
+
+  /**
+   * Copies memory.<p>
+   *
+   * Assumption: the memory regions do not overlap. Use
+   * {@link #sysMemmove(Address, Address, Extent)} if the regions might overlap.
+   * @param dst destination address
+   * @param src source address
+   * @param cnt number of bytes to copy
+   */
   @SysCallTemplate
   public abstract void sysCopy(Address dst, Address src, Extent cnt);
 
+  /**
+   * Copies memory without making any assumptions about the memory areas.
+   *
+   * @param dst destination address
+   * @param src source address
+   * @param cnt number of bytes to copy
+   */
+  @SysCallTemplate
+  public abstract void sysMemmove(Address dst, Address src, Extent cnt);
+
   @SysCallTemplate
   public abstract Address sysMalloc(int length);
 
diff --git a/tools/bootImageRunner/sys.C b/tools/bootImageRunner/sys.C
--- a/tools/bootImageRunner/sys.C
+++ b/tools/bootImageRunner/sys.C
@@ -1664,7 +1664,7 @@
 // Memory operations //
 //-------------------//
 
-// Memory to memory copy.
+// Memory to memory copy. Memory regions must not overlap.
 //
 extern "C" void
 sysCopy(void *dst, const void *src, Extent cnt)
@@ -1672,6 +1672,16 @@
     memcpy(dst, src, cnt);
 }
 
+// Memory to memory copy. Memory regions may overlap.
+//
+extern "C" void
+sysMemmove(void *dst, const void *src, Extent cnt)
+{
+    memmove(dst, src, cnt);
+}
+
+
+
 int inRVMAddressSpace(Address a);
 
 // Allocate memory.