private void zeroBlock(Address block) {
// FIXME: efficiency check here!
if (VM.VERIFY_ASSERTIONS)
VM.assertions._assert(
block.toWord().and(Word.fromIntSignExtend(BYTES_IN_BLOCK - 1)).isZero());
VM.memory.zero(block, Extent.fromIntZeroExtend(BYTES_IN_BLOCK));
}
/**
* Allows access to an area of virtual memory.
*
* @param start the address of the start of the area to be mapped
* @param size the size, in bytes, of the area to be mapped
* @return <code>true</code> if successful, otherwise <code>false</code>
*/
public final boolean munprotect(Address start, int size) {
return org.jikesrvm.runtime.Memory.mprotect(
start,
Extent.fromIntZeroExtend(size),
org.jikesrvm.runtime.Memory.PROT_READ
| org.jikesrvm.runtime.Memory.PROT_WRITE
| org.jikesrvm.runtime.Memory.PROT_EXEC);
}
/**
* Zero a region of memory
*
* @param start The start of the region to be zeroed (must be 4-byte aligned)
* @param bytes The number of bytes to be zeroed (must be 4-byte aligned)
*/
public static void zero(Address start, Extent bytes) throws InlinePragma {
if (Assert.VERIFY_ASSERTIONS) {
assertAligned(start);
assertAligned(bytes);
}
if (bytes.GT(Extent.fromIntZeroExtend(SMALL_REGION_THRESHOLD)))
org.mmtk.vm.Memory.zero(start, bytes);
else zeroSmall(start, bytes);
}
/**
* Demand zero mmaps an area of virtual memory.
*
* @param start the address of the start of the area to be mapped
* @param size the size, in bytes, of the area to be mapped
* @return 0 if successful, otherwise the system errno
*/
public final int dzmmap(Address start, int size) {
Address result = org.jikesrvm.runtime.Memory.dzmmap(start, Extent.fromIntZeroExtend(size));
if (result.EQ(start)) return 0;
if (result.GT(Address.fromIntZeroExtend(127))) {
VM.sysWrite("demand zero mmap with MAP_FIXED on ", start);
VM.sysWriteln(" returned some other address", result);
VM.sysFail("mmap with MAP_FIXED has unexpected behavior");
}
return result.toInt();
}
/**
* Protects access to an area of virtual memory.
*
* @param start the address of the start of the area to be mapped
* @param size the size, in bytes, of the area to be mapped
* @return <code>true</code> if successful, otherwise <code>false</code>
*/
public final boolean mprotect(Address start, int size) {
return org.jikesrvm.runtime.Memory.mprotect(
start, Extent.fromIntZeroExtend(size), org.jikesrvm.runtime.Memory.PROT_NONE);
}