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VM: new method set_border_locked() in segment, so that you can remove 

the protection of the guard pages
db4
Björn Lindqvist 2015-08-15 00:06:59 +02:00 committed by John Benediktsson
parent 50822c1a8a
commit b8aef640f9
3 changed files with 54 additions and 27 deletions
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42
vm/os-unix.cpp
View File

@ -91,24 +91,33 @@ segment::segment(cell size_, bool executable_p) {
else
prot = PROT_READ | PROT_WRITE;
char* array = (char*)mmap(NULL, pagesize + size + pagesize, prot,
char* array = (char*)mmap(NULL, 2 * pagesize + size, prot,
MAP_ANON | MAP_PRIVATE, -1, 0);
if (array == (char*)- 1)
if (array == (char*)-1)
out_of_memory("mmap");
if (mprotect(array, pagesize, PROT_NONE) == -1) {
check_ENOMEM("mprotect low");
fatal_error("Cannot protect low guard page", (cell)array);
}
if (mprotect(array + pagesize + size, pagesize, PROT_NONE) == -1) {
check_ENOMEM("mprotect high");
fatal_error("Cannot protect high guard page", (cell)array);
}
start = (cell)(array + pagesize);
end = start + size;
set_border_locked(true);
}
void segment::set_border_locked(bool locked) {
int prot = locked ? PROT_NONE : PROT_READ | PROT_WRITE;
int pagesize = getpagesize();
cell lo = start - pagesize;
if (mprotect((char*)lo, pagesize, prot) == -1) {
check_ENOMEM("mprotect low");
fatal_error("Cannot (un)protect low guard page", lo);
}
cell hi = end;
if (mprotect((char*)hi, pagesize, prot) == -1) {
check_ENOMEM("mprotect high");
fatal_error("Cannot protect high guard page", lo);
}
}
segment::~segment() {
@ -150,10 +159,13 @@ void factor_vm::end_sampling_profiler_timer() {
}
void memory_signal_handler(int signal, siginfo_t* siginfo, void* uap) {
cell fault_addr = (cell)siginfo->si_addr;
cell fault_pc = (cell)UAP_PROGRAM_COUNTER(uap);
factor_vm* vm = current_vm();
vm->verify_memory_protection_error((cell)siginfo->si_addr);
vm->signal_fault_addr = (cell)siginfo->si_addr;
vm->signal_fault_pc = (cell)UAP_PROGRAM_COUNTER(uap);
vm->verify_memory_protection_error(fault_addr);
vm->signal_fault_addr = fault_addr;
vm->signal_fault_pc = fault_pc;
vm->dispatch_signal(uap, factor::memory_signal_handler_impl);
}

29
vm/os-windows.cpp
View File

@ -95,23 +95,34 @@ segment::segment(cell size_, bool executable_p) {
size = size_;
char* mem;
DWORD ignore;
if ((mem = (char*)VirtualAlloc(
NULL, getpagesize() * 2 + size, MEM_COMMIT,
executable_p ? PAGE_EXECUTE_READWRITE : PAGE_READWRITE)) ==
0)
0) {
out_of_memory("VirtualAlloc");
if (!VirtualProtect(mem, getpagesize(), PAGE_NOACCESS, &ignore))
fatal_error("Cannot allocate low guard page", (cell)mem);
if (!VirtualProtect(mem + size + getpagesize(), getpagesize(), PAGE_NOACCESS,
&ignore))
fatal_error("Cannot allocate high guard page", (cell)mem);
}
start = (cell)mem + getpagesize();
end = start + size;
set_border_locked(true);
}
void segment::set_border_locked(bool locked) {
int prot = locked ? PAGE_NOACCESS : PAGE_READWRITE;
int pagesize = getpagesize();
DWORD ignore;
cell lo = start - pagesize;
if (!VirtualProtect((char*)lo, pagesize, prot, &ignore)) {
fatal_error("Cannot (un)protect low guard page", lo);
}
cell hi = end;
if (!VirtualProtect((char*)hi, pagesize, prot, &ignore)) {
fatal_error("Cannot (un)protect high guard page", lo);
}
}
segment::~segment() {

10
vm/segments.hpp
View File

@ -13,14 +13,18 @@ struct segment {
~segment();
bool underflow_p(cell addr) {
return (addr >= start - getpagesize() && addr < start);
return addr >= (start - getpagesize()) && addr < start;
}
bool overflow_p(cell addr) {
return (addr >= end && addr < end + getpagesize());
return addr >= end && addr < (end + getpagesize());
}
bool in_segment_p(cell addr) { return (addr >= start && addr < end); }
bool in_segment_p(cell addr) {
return addr >= start && addr < end;
}
void set_border_locked(bool locked);
};
}