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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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19
hotspot/src/os/linux/vm/os_linux.cpp
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@ -2414,8 +2414,20 @@ static bool linux_mprotect(char* addr, size_t size, int prot) {
return ::mprotect(bottom, size, prot) == 0;
}
bool os::protect_memory(char* addr, size_t size) {
return linux_mprotect(addr, size, PROT_READ);
// 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 = PROT_NONE; break;
case MEM_PROT_READ: p = PROT_READ; break;
case MEM_PROT_RW: p = PROT_READ|PROT_WRITE; break;
case MEM_PROT_RWX: p = PROT_READ|PROT_WRITE|PROT_EXEC; break;
default:
ShouldNotReachHere();
}
// is_committed is unused.
return linux_mprotect(addr, bytes, p);
}
bool os::guard_memory(char* addr, size_t size) {
@ -3704,8 +3716,9 @@ void os::make_polling_page_unreadable(void) {
// Mark the polling page as readable
void os::make_polling_page_readable(void) {
if( !protect_memory((char *)_polling_page, Linux::page_size()) )
if( !linux_mprotect((char *)_polling_page, Linux::page_size(), PROT_READ)) {
fatal("Could not enable polling page");
}
};
int os::active_processor_count() {