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* Change the way we check for enough available space when searching for spots

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to insert areas so we don't overflow.
* Consequently use the area end (base + size - 1) where appropriate which
  prevents overflows in a few places.
* Properly check for reaching the address space end.
* If we've already found a spot we don't need to recheck if we've found one.
* Simplify the B_EXACT_ADDRESS checks down to a simpler single if statement
  instead of the four seperate ones.
* Properly calculate the search end for B_EXACT_ADDRESS as well, it's also
  base + size - 1.
* Block the full last page now that this actually works without overflowing.
* Some style changes and added spacing.

This should now really fix #2550. Previously the overflow protection didn't
actually work because on allocation we overflowed and completely missed the
protecting area.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@33037 a95241bf-73f2-0310-859d-f6bbb57e9c96
This commit is contained in:
Michael Lotz 2009-09-10 17:58:19 +00:00
parent cb4a951f4c
commit e717a35b6f
1 changed files with 77 additions and 63 deletions
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140
src/system/kernel/vm/vm.cpp
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@ -1018,8 +1018,9 @@ find_reserved_area(vm_address_space* addressSpace, addr_t start,
vm_area* next;
next = addressSpace->areas;
while (next) {
if (next->base <= start && next->base + next->size >= start + size) {
while (next != NULL) {
if (next->base <= start
&& next->base + next->size > start + (size - 1)) {
// this area covers the requested range
if (next->id != RESERVED_AREA_ID) {
// but it's not reserved space, it's a real area
@ -1028,9 +1029,11 @@ find_reserved_area(vm_address_space* addressSpace, addr_t start,
break;
}
last = next;
next = next->address_space_next;
}
if (next == NULL)
return B_ENTRY_NOT_FOUND;
@ -1106,8 +1109,8 @@ find_and_insert_area_slot(vm_address_space* addressSpace, addr_t start,
// do some sanity checking
if (start < addressSpace->base || size == 0
|| (end - 1) > (addressSpace->base + (addressSpace->size - 1))
|| start + size > end)
|| end > addressSpace->base + (addressSpace->size - 1)
|| start + (size - 1) > end)
return B_BAD_ADDRESS;
if (addressSpec == B_EXACT_ADDRESS) {
@ -1133,11 +1136,12 @@ find_and_insert_area_slot(vm_address_space* addressSpace, addr_t start,
// walk up to the spot where we should start searching
second_chance:
next = addressSpace->areas;
while (next) {
if (next->base >= start + size) {
while (next != NULL) {
if (next->base > start + (size - 1)) {
// we have a winner
break;
}
last = next;
next = next->address_space_next;
}
@ -1149,34 +1153,40 @@ second_chance:
case B_ANY_ADDRESS:
case B_ANY_KERNEL_ADDRESS:
case B_ANY_KERNEL_BLOCK_ADDRESS:
{
// find a hole big enough for a new area
if (!last) {
if (last == NULL) {
// see if we can build it at the beginning of the virtual map
if (!next || (next->base >= ROUNDUP(addressSpace->base,
alignment) + size)) {
if (next == NULL || next->base > ROUNDUP(addressSpace->base,
alignment) + (size - 1)) {
foundSpot = true;
area->base = ROUNDUP(addressSpace->base, alignment);
break;
}
last = next;
next = next->address_space_next;
}
// keep walking
while (next) {
if (next->base >= ROUNDUP(last->base + last->size, alignment)
+ size) {
// we found a spot (it'll be filled up below)
break;
}
last = next;
next = next->address_space_next;
}
if ((addressSpace->base + (addressSpace->size - 1)) >= (ROUNDUP(
last->base + last->size, alignment) + (size - 1))) {
// keep walking
while (next != NULL) {
addr_t newBase = ROUNDUP(last->base + last->size, alignment);
if (next->base > newBase && next->base - newBase >= size) {
// we found a spot (it'll be filled up below)
break;
}
last = next;
next = next->address_space_next;
}
addr_t newBase = ROUNDUP(last->base + last->size, alignment);
addr_t aspaceEnd = addressSpace->base + (addressSpace->size - 1);
if (next != NULL || (aspaceEnd > newBase
&& aspaceEnd - (newBase - 1) >= size)) {
// got a spot
foundSpot = true;
area->base = ROUNDUP(last->base + last->size, alignment);
area->base = newBase;
break;
} else {
// We didn't find a free spot - if there were any reserved areas
@ -1184,8 +1194,8 @@ second_chance:
// for free space
// TODO: it would make sense to start with the biggest of them
next = addressSpace->areas;
last = NULL;
for (last = NULL; next; next = next->address_space_next) {
for (last = NULL; next != NULL;
next = next->address_space_next) {
if (next->id != RESERVED_AREA_ID) {
last = next;
continue;
@ -1207,15 +1217,28 @@ second_chance:
free(next);
break;
}
if (next->size - (ROUNDUP(next->base, alignment)
- next->base) >= size) {
addr_t newBase = ROUNDUP(next->base, alignment);
if (newBase == next->base && next->size >= size) {
// The new area will be placed at the beginning of the
// reserved area and the reserved area will be offset
// and resized
foundSpot = true;
next->base += size;
next->size -= size;
area->base = newBase;
break;
}
if (newBase <= next->base + (next->size - 1)
&& next->size - (newBase - next->base) >= size) {
// The new area will be placed at the end of the
// reserved area, and the reserved area will be resized
// to make space
foundSpot = true;
next->size -= size;
next->size = newBase - next->base;
last = next;
area->base = next->base + next->size;
area->base = newBase;
break;
}
@ -1223,31 +1246,35 @@ second_chance:
}
}
break;
}
case B_BASE_ADDRESS:
// find a hole big enough for a new area beginning with "start"
if (!last) {
if (last == NULL) {
// see if we can build it at the beginning of the specified start
if (!next || (next->base >= start + size)) {
if (next == NULL || next->base > start + (size - 1)) {
foundSpot = true;
area->base = start;
break;
}
last = next;
next = next->address_space_next;
}
// keep walking
while (next) {
if (next->base >= last->base + last->size + size) {
// we found a spot (it'll be filled up below)
break;
}
last = next;
next = next->address_space_next;
}
if ((addressSpace->base + (addressSpace->size - 1))
>= (last->base + last->size + (size - 1))) {
// keep walking
while (next != NULL) {
if (next->base - (last->base + last->size) >= size) {
// we found a spot (it'll be filled up below)
break;
}
last = next;
next = next->address_space_next;
}
if (next != NULL || addressSpace->base + (addressSpace->size - 1)
- last->base + (last->size - 1) >= size) {
// got a spot
foundSpot = true;
if (last->base + last->size <= start)
@ -1256,6 +1283,7 @@ second_chance:
area->base = last->base + last->size;
break;
}
// we didn't find a free spot in the requested range, so we'll
// try again without any restrictions
start = addressSpace->base;
@ -1265,26 +1293,11 @@ second_chance:
case B_EXACT_ADDRESS:
// see if we can create it exactly here
if (!last) {
if (!next || (next->base >= start + size)) {
foundSpot = true;
area->base = start;
break;
}
} else {
if (next) {
if (last->base + last->size <= start
&& next->base >= start + size) {
foundSpot = true;
area->base = start;
break;
}
} else {
if ((last->base + (last->size - 1)) <= start - 1) {
foundSpot = true;
area->base = start;
}
}
if ((last == NULL || last->base + (last->size - 1) < start)
&& (next == NULL || next->base > start + (size - 1))) {
foundSpot = true;
area->base = start;
break;
}
break;
default:
@ -1302,6 +1315,7 @@ second_chance:
area->address_space_next = addressSpace->areas;
addressSpace->areas = area;
}
addressSpace->change_count++;
return B_OK;
}
@ -1322,7 +1336,7 @@ insert_area(vm_address_space* addressSpace, void** _address,
switch (addressSpec) {
case B_EXACT_ADDRESS:
searchBase = (addr_t)*_address;
searchEnd = (addr_t)*_address + size;
searchEnd = (addr_t)*_address + (size - 1);
break;
case B_BASE_ADDRESS:
@ -4389,7 +4403,7 @@ vm_init(kernel_args* args)
}
void* lastPage = (void*)ROUNDDOWN(~(addr_t)0, B_PAGE_SIZE);
vm_block_address_range("overflow protection", lastPage, B_PAGE_SIZE - 1);
vm_block_address_range("overflow protection", lastPage, B_PAGE_SIZE);
#if DEBUG_CACHE_LIST
create_area("cache info table", (void**)&sCacheInfoTable,