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8354922: ZGC: Use MAP_FIXED_NOREPLACE when reserving memory #2475

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8354922: ZGC: Use MAP_FIXED_NOREPLACE when reserving memory #2475

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4 changes: 4 additions & 0 deletions src/hotspot/os/linux/gc/x/xSyscall_linux.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,10 @@
#define MPOL_F_ADDR (1<<1)
#endif

#ifndef MAP_FIXED_NOREPLACE
#define MAP_FIXED_NOREPLACE 0x100000
#endif

class XSyscall : public AllStatic {
public:
static int memfd_create(const char* name, unsigned int flags);
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4 changes: 4 additions & 0 deletions src/hotspot/os/linux/gc/z/zSyscall_linux.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,10 @@
#define MPOL_F_ADDR (1<<1)
#endif

#ifndef MAP_FIXED_NOREPLACE
#define MAP_FIXED_NOREPLACE 0x100000
#endif

class ZSyscall : public AllStatic {
public:
static int memfd_create(const char* name, unsigned int flags);
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7 changes: 6 additions & 1 deletion src/hotspot/os/posix/gc/x/xVirtualMemory_posix.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,9 @@
#include "gc/x/xAddress.inline.hpp"
#include "gc/x/xVirtualMemory.hpp"
#include "logging/log.hpp"
#ifdef LINUX
#include "gc/x/xSyscall_linux.hpp"
#endif

#include <sys/mman.h>
#include <sys/types.h>
Expand All @@ -38,7 +41,9 @@ void XVirtualMemoryManager::pd_initialize_after_reserve() {
}

bool XVirtualMemoryManager::pd_reserve(uintptr_t addr, size_t size) {
const uintptr_t res = (uintptr_t)mmap((void*)addr, size, PROT_NONE, MAP_ANONYMOUS|MAP_PRIVATE|MAP_NORESERVE, -1, 0);
const int flags = MAP_ANONYMOUS|MAP_PRIVATE|MAP_NORESERVE LINUX_ONLY(|MAP_FIXED_NOREPLACE);

const uintptr_t res = (uintptr_t)mmap((void*)addr, size, PROT_NONE, flags, -1, 0);
if (res == (uintptr_t)MAP_FAILED) {
// Failed to reserve memory
return false;
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7 changes: 6 additions & 1 deletion src/hotspot/os/posix/gc/z/zVirtualMemory_posix.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,9 @@
#include "gc/z/zAddress.inline.hpp"
#include "gc/z/zVirtualMemory.hpp"
#include "logging/log.hpp"
#ifdef LINUX
#include "gc/z/zSyscall_linux.hpp"
#endif

#include <sys/mman.h>
#include <sys/types.h>
Expand All @@ -38,7 +41,9 @@ void ZVirtualMemoryManager::pd_initialize_after_reserve() {
}

bool ZVirtualMemoryManager::pd_reserve(zaddress_unsafe addr, size_t size) {
void* const res = mmap((void*)untype(addr), size, PROT_NONE, MAP_ANONYMOUS|MAP_PRIVATE|MAP_NORESERVE, -1, 0);
const int flags = MAP_ANONYMOUS|MAP_PRIVATE|MAP_NORESERVE LINUX_ONLY(|MAP_FIXED_NOREPLACE);

void* const res = mmap((void*)untype(addr), size, PROT_NONE, flags, -1, 0);
if (res == MAP_FAILED) {
// Failed to reserve memory
return false;
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