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6716785: implicit null checks not triggering with CompressedOops

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Allocate alignment-sized page(s) below java heap so that memory accesses at heap_base+1page give signal and cause an implicit null check

Reviewed-by: kvn, jmasa, phh, jcoomes
This commit is contained in:
Coleen Phillimore 2008-07-19 17:38:22 -04:00
parent 575988272e
commit 20dba03e99
23 changed files with 197 additions and 133 deletions
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29
hotspot/src/os/windows/vm/os_windows.cpp
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@ -2170,6 +2170,7 @@ LONG WINAPI topLevelExceptionFilter(struct _EXCEPTION_POINTERS* exceptionInfo) {
// Windows 98 reports faulting addresses incorrectly
if (!MacroAssembler::needs_explicit_null_check((intptr_t)addr) ||
!os::win32::is_nt()) {
return Handle_Exception(exceptionInfo,
SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_NULL));
}
@ -2563,9 +2564,33 @@ bool os::release_memory(char* addr, size_t bytes) {
return VirtualFree(addr, 0, MEM_RELEASE) != 0;
}
bool os::protect_memory(char* addr, size_t bytes) {
// Set protections specified
bool os::protect_memory(char* addr, size_t bytes, ProtType prot,
bool is_committed) {
unsigned int p = 0;
switch (prot) {
case MEM_PROT_NONE: p = PAGE_NOACCESS; break;
case MEM_PROT_READ: p = PAGE_READONLY; break;
case MEM_PROT_RW: p = PAGE_READWRITE; break;
case MEM_PROT_RWX: p = PAGE_EXECUTE_READWRITE; break;
default:
ShouldNotReachHere();
}
DWORD old_status;
return VirtualProtect(addr, bytes, PAGE_READONLY, &old_status) != 0;
// Strange enough, but on Win32 one can change protection only for committed
// memory, not a big deal anyway, as bytes less or equal than 64K
if (!is_committed && !commit_memory(addr, bytes)) {
fatal("cannot commit protection page");
}
// One cannot use os::guard_memory() here, as on Win32 guard page
// have different (one-shot) semantics, from MSDN on PAGE_GUARD:
//
// Pages in the region become guard pages. Any attempt to access a guard page
// causes the system to raise a STATUS_GUARD_PAGE exception and turn off
// the guard page status. Guard pages thus act as a one-time access alarm.
return VirtualProtect(addr, bytes, p, &old_status) != 0;
}
bool os::guard_memory(char* addr, size_t bytes) {