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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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93
hotspot/src/share/vm/runtime/virtualspace.cpp
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@ -28,12 +28,15 @@
// ReservedSpace
ReservedSpace::ReservedSpace(size_t size) {
initialize(size, 0, false, NULL);
initialize(size, 0, false, NULL, 0);
}
ReservedSpace::ReservedSpace(size_t size, size_t alignment,
bool large, char* requested_address) {
initialize(size, alignment, large, requested_address);
bool large,
char* requested_address,
const size_t noaccess_prefix) {
initialize(size+noaccess_prefix, alignment, large, requested_address,
noaccess_prefix);
}
char *
@ -105,7 +108,8 @@ char* ReservedSpace::reserve_and_align(const size_t reserve_size,
ReservedSpace::ReservedSpace(const size_t prefix_size,
const size_t prefix_align,
const size_t suffix_size,
const size_t suffix_align)
const size_t suffix_align,
const size_t noaccess_prefix)
{
assert(prefix_size != 0, "sanity");
assert(prefix_align != 0, "sanity");
@ -118,12 +122,16 @@ ReservedSpace::ReservedSpace(const size_t prefix_size,
assert((suffix_align & prefix_align - 1) == 0,
"suffix_align not divisible by prefix_align");
// Add in noaccess_prefix to prefix_size;
const size_t adjusted_prefix_size = prefix_size + noaccess_prefix;
const size_t size = adjusted_prefix_size + suffix_size;
// On systems where the entire region has to be reserved and committed up
// front, the compound alignment normally done by this method is unnecessary.
const bool try_reserve_special = UseLargePages &&
prefix_align == os::large_page_size();
if (!os::can_commit_large_page_memory() && try_reserve_special) {
initialize(prefix_size + suffix_size, prefix_align, true);
initialize(size, prefix_align, true, NULL, noaccess_prefix);
return;
}
@ -131,15 +139,19 @@ ReservedSpace::ReservedSpace(const size_t prefix_size,
_size = 0;
_alignment = 0;
_special = false;
_noaccess_prefix = 0;
// Assert that if noaccess_prefix is used, it is the same as prefix_align.
assert(noaccess_prefix == 0 ||
noaccess_prefix == prefix_align, "noaccess prefix wrong");
// Optimistically try to reserve the exact size needed.
const size_t size = prefix_size + suffix_size;
char* addr = os::reserve_memory(size, NULL, prefix_align);
if (addr == NULL) return;
// Check whether the result has the needed alignment (unlikely unless
// prefix_align == suffix_align).
const size_t ofs = size_t(addr) + prefix_size & suffix_align - 1;
const size_t ofs = size_t(addr) + adjusted_prefix_size & suffix_align - 1;
if (ofs != 0) {
// Wrong alignment. Release, allocate more space and do manual alignment.
//
@ -153,11 +165,11 @@ ReservedSpace::ReservedSpace(const size_t prefix_size,
}
const size_t extra = MAX2(ofs, suffix_align - ofs);
addr = reserve_and_align(size + extra, prefix_size, prefix_align,
addr = reserve_and_align(size + extra, adjusted_prefix_size, prefix_align,
suffix_size, suffix_align);
if (addr == NULL) {
// Try an even larger region. If this fails, address space is exhausted.
addr = reserve_and_align(size + suffix_align, prefix_size,
addr = reserve_and_align(size + suffix_align, adjusted_prefix_size,
prefix_align, suffix_size, suffix_align);
}
}
@ -165,10 +177,12 @@ ReservedSpace::ReservedSpace(const size_t prefix_size,
_base = addr;
_size = size;
_alignment = prefix_align;
_noaccess_prefix = noaccess_prefix;
}
void ReservedSpace::initialize(size_t size, size_t alignment, bool large,
char* requested_address) {
char* requested_address,
const size_t noaccess_prefix) {
const size_t granularity = os::vm_allocation_granularity();
assert((size & granularity - 1) == 0,
"size not aligned to os::vm_allocation_granularity()");
@ -181,6 +195,7 @@ void ReservedSpace::initialize(size_t size, size_t alignment, bool large,
_size = 0;
_special = false;
_alignment = 0;
_noaccess_prefix = 0;
if (size == 0) {
return;
}
@ -220,7 +235,8 @@ void ReservedSpace::initialize(size_t size, size_t alignment, bool large,
// important. If available space is not detected, return NULL.
if (requested_address != 0) {
base = os::attempt_reserve_memory_at(size, requested_address);
base = os::attempt_reserve_memory_at(size,
requested_address-noaccess_prefix);
} else {
base = os::reserve_memory(size, NULL, alignment);
}
@ -259,6 +275,11 @@ void ReservedSpace::initialize(size_t size, size_t alignment, bool large,
_base = base;
_size = size;
_alignment = MAX2(alignment, (size_t) os::vm_page_size());
_noaccess_prefix = noaccess_prefix;
// Assert that if noaccess_prefix is used, it is the same as alignment.
assert(noaccess_prefix == 0 ||
noaccess_prefix == _alignment, "noaccess prefix wrong");
assert(markOopDesc::encode_pointer_as_mark(_base)->decode_pointer() == _base,
"area must be distinguisable from marks for mark-sweep");
@ -274,6 +295,7 @@ ReservedSpace::ReservedSpace(char* base, size_t size, size_t alignment,
_base = base;
_size = size;
_alignment = alignment;
_noaccess_prefix = 0;
_special = special;
}
@ -320,17 +342,58 @@ size_t ReservedSpace::allocation_align_size_down(size_t size) {
void ReservedSpace::release() {
if (is_reserved()) {
char *real_base = _base - _noaccess_prefix;
const size_t real_size = _size + _noaccess_prefix;
if (special()) {
os::release_memory_special(_base, _size);
os::release_memory_special(real_base, real_size);
} else{
os::release_memory(_base, _size);
os::release_memory(real_base, real_size);
}
_base = NULL;
_size = 0;
_noaccess_prefix = 0;
_special = false;
}
}
void ReservedSpace::protect_noaccess_prefix(const size_t size) {
// If there is noaccess prefix, return.
if (_noaccess_prefix == 0) return;
assert(_noaccess_prefix >= (size_t)os::vm_page_size(),
"must be at least page size big");
// Protect memory at the base of the allocated region.
// If special, the page was committed (only matters on windows)
if (!os::protect_memory(_base, _noaccess_prefix, os::MEM_PROT_NONE,
_special)) {
fatal("cannot protect protection page");
}
_base += _noaccess_prefix;
_size -= _noaccess_prefix;
assert((size == _size) && ((uintptr_t)_base % _alignment == 0),
"must be exactly of required size and alignment");
}
ReservedHeapSpace::ReservedHeapSpace(size_t size, size_t alignment,
bool large, char* requested_address) :
ReservedSpace(size, alignment, large,
requested_address,
UseCompressedOops ? lcm(os::vm_page_size(), alignment) : 0) {
// Only reserved space for the java heap should have a noaccess_prefix
// if using compressed oops.
protect_noaccess_prefix(size);
}
ReservedHeapSpace::ReservedHeapSpace(const size_t prefix_size,
const size_t prefix_align,
const size_t suffix_size,
const size_t suffix_align) :
ReservedSpace(prefix_size, prefix_align, suffix_size, suffix_align,
UseCompressedOops ? lcm(os::vm_page_size(), prefix_align) : 0) {
protect_noaccess_prefix(prefix_size+suffix_size);
}
// VirtualSpace
@ -348,6 +411,7 @@ VirtualSpace::VirtualSpace() {
_lower_alignment = 0;
_middle_alignment = 0;
_upper_alignment = 0;
_special = false;
}
@ -402,7 +466,8 @@ VirtualSpace::~VirtualSpace() {
void VirtualSpace::release() {
(void)os::release_memory(low_boundary(), reserved_size());
// This does not release memory it never reserved.
// Caller must release via rs.release();
_low_boundary = NULL;
_high_boundary = NULL;
_low = NULL;