Mercurial > hg > graal-compiler
diff src/os/windows/vm/os_windows.cpp @ 237:1fdb98a17101
6716785: implicit null checks not triggering with CompressedOops
Summary: 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
author | coleenp |
---|---|
date | Sat, 19 Jul 2008 17:38:22 -0400 |
parents | d1605aabd0a1 |
children | d95b224e9f17 |
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--- a/src/os/windows/vm/os_windows.cpp Fri Jul 11 01:14:44 2008 -0700 +++ b/src/os/windows/vm/os_windows.cpp Sat Jul 19 17:38:22 2008 -0400 @@ -2170,6 +2170,7 @@ // 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 @@ 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) {