The existing malloc implementation effectively uses a stack - all new allocations come from the top of the stack. When allocating memory with a large alignment, the pad used to align the new memory is unavailable to other users. Also, memory released by calling free() is only available to other users when all memory allocated after it is also freed.
This new malloc scheme uses a first fit approach to finding available memory. It makes it possible to use alignment padding and freed space for new allocations.
This helps reduce the required memory in the permanent memory zones (ZoneHigh and ZoneLow) where users have the need to allocate structures with high alignment (eg, virtio and usb). --- src/memmap.c | 17 -- src/memmap.h | 1 - src/pmm.c | 532 ++++++++++++++++++++++++++++++++++------------------------ 3 files changed, 314 insertions(+), 236 deletions(-)
diff --git a/src/memmap.c b/src/memmap.c index 8770bbc..84bc4fa 100644 --- a/src/memmap.c +++ b/src/memmap.c @@ -119,23 +119,6 @@ add_e820(u64 start, u64 size, u32 type) //dump_map(); }
-// Find highest area of 32bit memory that can hold the given size. -struct e820entry * -find_high_area(u32 size) -{ - int i; - for (i=e820_count-1; i>=0; i--) { - struct e820entry *e = &e820_list[i]; - u64 end = e->start + e->size; - if (e->type != E820_RAM || end > 0xffffffff || e->size < size) - continue; - if (end < 1024*1024 + size) - break; - return e; - } - return NULL; -} - // Prep for memmap stuff - init bios table locations. void memmap_setup(void) diff --git a/src/memmap.h b/src/memmap.h index 68eb6ac..d4154c1 100644 --- a/src/memmap.h +++ b/src/memmap.h @@ -19,7 +19,6 @@ struct e820entry { void add_e820(u64 start, u64 size, u32 type); void memmap_setup(void); void memmap_finalize(void); -struct e820entry *find_high_area(u32 size);
// A typical OS page size #define PAGE_SIZE 4096 diff --git a/src/pmm.c b/src/pmm.c index 58c0e8b..228bc36 100644 --- a/src/pmm.c +++ b/src/pmm.c @@ -6,7 +6,7 @@
#include "util.h" // checksum #include "config.h" // BUILD_BIOS_ADDR -#include "memmap.h" // find_high_area +#include "memmap.h" // struct e820entry #include "farptr.h" // GET_FARVAR #include "biosvar.h" // GET_BDA
@@ -26,14 +26,29 @@ #define SET_PMMVAR(var, val) do { (var) = (val); } while (0) #endif
-// Zone definitions +// Information on a reserved area. +struct allocinfo_s { + struct allocinfo_s *next, **pprev; + void *data, *dataend, *allocend; +}; + +// Information on a tracked memory allocation. +struct allocdetail_s { + struct allocinfo_s detailinfo; + struct allocinfo_s datainfo; + u32 handle; +}; + +// The various memory zones. struct zone_s { - u32 top, bottom, cur; + struct allocinfo_s *info; };
-struct zone_s ZoneLow VAR32FLATVISIBLE, ZoneHigh VAR32FLATVISIBLE; +struct zone_s ZoneLow VAR32FLATVISIBLE; +struct zone_s ZoneHigh VAR32FLATVISIBLE; struct zone_s ZoneFSeg VAR32FLATVISIBLE; -struct zone_s ZoneTmpLow VAR32FLATVISIBLE, ZoneTmpHigh VAR32FLATVISIBLE; +struct zone_s ZoneTmpLow VAR32FLATVISIBLE; +struct zone_s ZoneTmpHigh VAR32FLATVISIBLE;
struct zone_s *Zones[] VAR32FLATVISIBLE = { &ZoneTmpLow, &ZoneLow, &ZoneFSeg, &ZoneTmpHigh, &ZoneHigh @@ -41,6 +56,213 @@ struct zone_s *Zones[] VAR32FLATVISIBLE = {
/**************************************************************** + * low-level memory reservations + ****************************************************************/ + +// Find and reserve space from a given zone +static void * +allocSpace(struct zone_s *zone, u32 size, u32 align, struct allocinfo_s *fill) +{ + struct allocinfo_s *info; + for (info = GET_PMMVAR(zone->info); info; info = GET_PMMVAR(info->next)) { + void *dataend = GET_PMMVAR(info->dataend); + void *allocend = GET_PMMVAR(info->allocend); + void *newallocend = (void*)ALIGN_DOWN((u32)allocend - size, align); + if (newallocend >= dataend && newallocend <= allocend) { + // Found space - now reserve it. + struct allocinfo_s **pprev = GET_PMMVAR(info->pprev); + if (!fill) + fill = newallocend; + SET_PMMVAR(fill->next, info); + SET_PMMVAR(fill->pprev, pprev); + SET_PMMVAR(fill->data, newallocend); + SET_PMMVAR(fill->dataend, newallocend + size); + SET_PMMVAR(fill->allocend, allocend); + + SET_PMMVAR(info->allocend, newallocend); + SET_PMMVAR(info->pprev, &fill->next); + SET_PMMVAR(*pprev, fill); + return newallocend; + } + } + return NULL; +} + +// Release space allocated with allocSpace() +static void +freeSpace(struct allocinfo_s *info) +{ + struct allocinfo_s *next = GET_PMMVAR(info->next); + struct allocinfo_s **pprev = GET_PMMVAR(info->pprev); + SET_PMMVAR(*pprev, next); + if (next) { + if (GET_PMMVAR(next->allocend) == GET_PMMVAR(info->data)) + SET_PMMVAR(next->allocend, GET_PMMVAR(info->allocend)); + SET_PMMVAR(next->pprev, pprev); + } +} + +// Add new memory to a zone +static void +addSpace(struct zone_s *zone, void *start, void *end) +{ + // Find position to add space + struct allocinfo_s **pprev = &zone->info, *info; + for (;;) { + info = GET_PMMVAR(*pprev); + if (!info || GET_PMMVAR(info->data) < start) + break; + pprev = &info->next; + } + + // Add space using temporary allocation info. + struct allocdetail_s tempdetail; + tempdetail.datainfo.next = info; + tempdetail.datainfo.pprev = pprev; + tempdetail.datainfo.data = tempdetail.datainfo.dataend = start; + tempdetail.datainfo.allocend = end; + tempdetail.handle = PMM_DEFAULT_HANDLE; + struct allocdetail_s *tempdetailp = MAKE_FLATPTR(GET_SEG(SS), &tempdetail); + SET_PMMVAR(*pprev, &tempdetailp->datainfo); + if (info) + SET_PMMVAR(info->pprev, &tempdetailp->datainfo.next); + + // Allocate final allocation info. + struct allocdetail_s *detail = allocSpace( + &ZoneTmpHigh, sizeof(*detail), MALLOC_MIN_ALIGN, NULL); + if (!detail) { + detail = allocSpace(&ZoneTmpLow, sizeof(*detail) + , MALLOC_MIN_ALIGN, NULL); + if (!detail) { + SET_PMMVAR(*tempdetail.datainfo.pprev, tempdetail.datainfo.next); + if (tempdetail.datainfo.next) + SET_PMMVAR(tempdetail.datainfo.next->pprev + , tempdetail.datainfo.pprev); + warn_noalloc(); + return; + } + } + + // Replace temp alloc space with final alloc space + SET_PMMVAR(detail->datainfo.next, tempdetail.datainfo.next); + SET_PMMVAR(detail->datainfo.pprev, tempdetail.datainfo.pprev); + SET_PMMVAR(detail->datainfo.data, tempdetail.datainfo.data); + SET_PMMVAR(detail->datainfo.dataend, tempdetail.datainfo.dataend); + SET_PMMVAR(detail->datainfo.allocend, tempdetail.datainfo.allocend); + SET_PMMVAR(detail->handle, PMM_DEFAULT_HANDLE); + + SET_PMMVAR(*tempdetail.datainfo.pprev, &detail->datainfo); + if (tempdetail.datainfo.next) + SET_PMMVAR(tempdetail.datainfo.next->pprev, &detail->datainfo.next); +} + +// Search all zones for an allocation obtained from allocSpace() +static struct allocinfo_s * +findAlloc(void *data) +{ + int i; + for (i=0; i<ARRAY_SIZE(Zones); i++) { + struct zone_s *zone = GET_PMMVAR(Zones[i]); + struct allocinfo_s *info; + for (info = GET_PMMVAR(zone->info); info; info = GET_PMMVAR(info->next)) + if (GET_PMMVAR(info->data) == data) + return info; + } + return NULL; +} + +// Return the last sentinal node of a zone +static struct allocinfo_s * +findLast(struct zone_s *zone) +{ + struct allocinfo_s *info = GET_PMMVAR(zone->info); + if (!info) + return NULL; + for (;;) { + struct allocinfo_s *next = GET_PMMVAR(info->next); + if (!next) + return info; + info = next; + } +} + + +/**************************************************************** + * Setup + ****************************************************************/ + +void +malloc_setup(void) +{ + ASSERT32FLAT(); + dprintf(3, "malloc setup\n"); + + ZoneLow.info = ZoneHigh.info = ZoneFSeg.info = NULL; + ZoneTmpLow.info = ZoneTmpHigh.info = NULL; + + // Clear memory in 0xf0000 area. + extern u8 code32flat_start[]; + if ((u32)code32flat_start > BUILD_BIOS_ADDR) + // Clear unused parts of f-segment + memset((void*)BUILD_BIOS_ADDR, 0 + , (u32)code32flat_start - BUILD_BIOS_ADDR); + memset(BiosTableSpace, 0, CONFIG_MAX_BIOSTABLE); + + // Populate temp high ram + u32 highram = 0; + int i; + for (i=e820_count-1; i>=0; i--) { + struct e820entry *en = &e820_list[i]; + u64 end = en->start + en->size; + if (end < 1024*1024) + break; + if (en->type != E820_RAM || end > 0xffffffff) + continue; + u32 s = en->start, e = end; + if (!highram) { + u32 newe = ALIGN_DOWN(e - CONFIG_MAX_HIGHTABLE, MALLOC_MIN_ALIGN); + if (newe <= e && newe >= s) { + highram = newe; + e = newe; + } + } + addSpace(&ZoneTmpHigh, (void*)s, (void*)e); + } + + // Populate other regions + addSpace(&ZoneTmpLow, (void*)BUILD_STACK_ADDR, (void*)BUILD_EBDA_MINIMUM); + addSpace(&ZoneFSeg, BiosTableSpace, &BiosTableSpace[CONFIG_MAX_BIOSTABLE]); + addSpace(&ZoneLow, (void*)BUILD_LOWRAM_END, (void*)BUILD_LOWRAM_END); + if (highram) { + addSpace(&ZoneHigh, (void*)highram + , (void*)highram + CONFIG_MAX_HIGHTABLE); + add_e820(highram, CONFIG_MAX_HIGHTABLE, E820_RESERVED); + } +} + +void +malloc_finalize(void) +{ + dprintf(3, "malloc finalize\n"); + + // Reserve more low-mem if needed. + u32 endlow = GET_BDA(mem_size_kb)*1024; + add_e820(endlow, BUILD_LOWRAM_END-endlow, E820_RESERVED); + + // Give back unused high ram. + struct allocinfo_s *info = findLast(&ZoneHigh); + if (info) { + u32 giveback = ALIGN_DOWN(info->allocend - info->dataend, PAGE_SIZE); + add_e820((u32)info->dataend, giveback, E820_RAM); + dprintf(1, "Returned %d bytes of ZoneHigh\n", giveback); + } + + // Clear low-memory allocations. + memset((void*)BUILD_STACK_ADDR, 0, BUILD_EBDA_MINIMUM - BUILD_STACK_ADDR); +} + + +/**************************************************************** * ebda movement ****************************************************************/
@@ -74,27 +296,22 @@ relocate_ebda(u32 newebda, u32 oldebda, u8 ebda_size) static void zonelow_expand(u32 size, u32 align) { - u32 oldpos, newpos, bottom; - for (;;) { - oldpos = GET_PMMVAR(ZoneLow.cur); - newpos = ALIGN_DOWN(oldpos - size, align); - bottom = GET_PMMVAR(ZoneLow.bottom); - if (newpos >= bottom && newpos <= oldpos) - // Space already present. - return; - // Make sure to not move ebda while an optionrom is running. - if (likely(!wait_preempt())) - break; - } + struct allocinfo_s *info = findLast(&ZoneLow); + if (!info) + return; + u32 oldpos = (u32)GET_PMMVAR(info->allocend); + u32 newpos = ALIGN_DOWN(oldpos - size, align); + u32 bottom = (u32)GET_PMMVAR(info->dataend); + if (newpos >= bottom && newpos <= oldpos) + // Space already present. + return; u16 ebda_seg = get_ebda_seg(); u32 ebda_pos = (u32)MAKE_FLATPTR(ebda_seg, 0); u8 ebda_size = GET_EBDA2(ebda_seg, size); u32 ebda_end = ebda_pos + ebda_size * 1024; - if (ebda_end != bottom) { + if (ebda_end != bottom) // Something else is after ebda - can't use any existing space. - oldpos = ebda_end; - newpos = ALIGN_DOWN(oldpos - size, align); - } + newpos = ALIGN_DOWN(ebda_end - size, align); u32 newbottom = ALIGN_DOWN(newpos, 1024); u32 newebda = ALIGN_DOWN(newbottom - ebda_size * 1024, 1024); if (newebda < BUILD_EBDA_MINIMUM) @@ -107,66 +324,31 @@ zonelow_expand(u32 size, u32 align) return;
// Update zone - SET_PMMVAR(ZoneLow.cur, oldpos); - SET_PMMVAR(ZoneLow.bottom, newbottom); + if (ebda_end == bottom) { + SET_PMMVAR(info->data, (void*)newbottom); + SET_PMMVAR(info->dataend, (void*)newbottom); + } else + addSpace(&ZoneLow, (void*)newbottom, (void*)ebda_end); }
- -/**************************************************************** - * zone allocations - ****************************************************************/ - -// Obtain memory from a given zone. -static void * __malloc -zone_malloc(struct zone_s *zone, u32 size, u32 align) +// Check if can expand the given zone to fulfill an allocation +static void * +allocExpandSpace(struct zone_s *zone, u32 size, u32 align + , struct allocinfo_s *fill) { - u32 oldpos = GET_PMMVAR(zone->cur); - u32 newpos = ALIGN_DOWN(oldpos - size, align); - if (newpos < GET_PMMVAR(zone->bottom) || newpos > oldpos) - // No space - return NULL; - SET_PMMVAR(zone->cur, newpos); - return (void*)newpos; -} + void *data = allocSpace(zone, size, align, fill); + if (data || zone != &ZoneLow) + return data;
-// Find the zone that contains the given data block. -static struct zone_s * -zone_find(void *data) -{ - int i; - for (i=0; i<ARRAY_SIZE(Zones); i++) { - struct zone_s *zone = GET_PMMVAR(Zones[i]); - if ((u32)data >= GET_PMMVAR(zone->cur) - && (u32)data < GET_PMMVAR(zone->top)) - return zone; + // Make sure to not move ebda while an optionrom is running. + if (unlikely(wait_preempt())) { + data = allocSpace(zone, size, align, fill); + if (data) + return data; } - return NULL; -}
-// Return memory to a zone (if it was the last to be allocated). -static int -zone_free(void *data, u32 olddata) -{ - struct zone_s *zone = zone_find(data); - if (!zone || !data || GET_PMMVAR(zone->cur) != (u32)data) - return -1; - SET_PMMVAR(zone->cur, olddata); - return 0; -} - -// Report the status of all the zones. -static void -dumpZones(void) -{ - int i; - for (i=0; i<ARRAY_SIZE(Zones); i++) { - struct zone_s *zone = Zones[i]; - u32 used = zone->top - zone->cur; - u32 avail = zone->top - zone->bottom; - u32 pct = avail ? ((100 * used) / avail) : 0; - dprintf(2, "zone %d: %08x-%08x used=%d (%d%%)\n" - , i, zone->bottom, zone->top, used, pct); - } + zonelow_expand(size, align); + return allocSpace(zone, size, align, fill); }
@@ -174,91 +356,52 @@ dumpZones(void) * tracked memory allocations ****************************************************************/
-// Information on PMM tracked allocations -struct pmmalloc_s { - void *data; - u32 olddata; - u32 handle; - u32 oldallocdata; - struct pmmalloc_s *next; -}; - -struct pmmalloc_s *PMMAllocs VAR32FLATVISIBLE; - // Allocate memory from the given zone and track it as a PMM allocation void * __malloc pmm_malloc(struct zone_s *zone, u32 handle, u32 size, u32 align) { - u32 oldallocdata = GET_PMMVAR(ZoneTmpHigh.cur); - struct pmmalloc_s *info = zone_malloc(&ZoneTmpHigh, sizeof(*info) - , MALLOC_MIN_ALIGN); - if (!info) { - oldallocdata = GET_PMMVAR(ZoneTmpLow.cur); - info = zone_malloc(&ZoneTmpLow, sizeof(*info), MALLOC_MIN_ALIGN); - if (!info) + if (!size) + return NULL; + + // Find and reserve space for bookkeeping. + struct allocdetail_s *detail = allocSpace( + &ZoneTmpHigh, sizeof(*detail), MALLOC_MIN_ALIGN, NULL); + if (!detail) { + detail = allocSpace(&ZoneTmpLow, sizeof(*detail) + , MALLOC_MIN_ALIGN, NULL); + if (!detail) return NULL; } - if (zone == &ZoneLow) - zonelow_expand(size, align); - u32 olddata = GET_PMMVAR(zone->cur); - void *data = zone_malloc(zone, size, align); - if (! data) { - zone_free(info, oldallocdata); + + // Find and reserve space for main allocation + void *data = allocExpandSpace(zone, size, align, &detail->datainfo); + if (!data) { + freeSpace(&detail->detailinfo); return NULL; } + dprintf(8, "pmm_malloc zone=%p handle=%x size=%d align=%x" - " ret=%p (info=%p)\n" + " ret=%p (detail=%p)\n" , zone, handle, size, align - , data, info); - SET_PMMVAR(info->data, data); - SET_PMMVAR(info->olddata, olddata); - SET_PMMVAR(info->handle, handle); - SET_PMMVAR(info->oldallocdata, oldallocdata); - SET_PMMVAR(info->next, GET_PMMVAR(PMMAllocs)); - SET_PMMVAR(PMMAllocs, info); - return data; -} + , data, detail); + SET_PMMVAR(detail->handle, handle);
-// Free a raw data block (either from a zone or from pmm alloc list). -static void -pmm_free_data(void *data, u32 olddata) -{ - int ret = zone_free(data, olddata); - if (!ret) - // Success - done. - return; - struct pmmalloc_s *info; - for (info=GET_PMMVAR(PMMAllocs); info; info = GET_PMMVAR(info->next)) - if (GET_PMMVAR(info->olddata) == (u32)data) { - SET_PMMVAR(info->olddata, olddata); - return; - } else if (GET_PMMVAR(info->oldallocdata) == (u32)data) { - SET_PMMVAR(info->oldallocdata, olddata); - return; - } + return data; }
// Free a data block allocated with pmm_malloc int pmm_free(void *data) { - struct pmmalloc_s **pinfo = &PMMAllocs; - for (;;) { - struct pmmalloc_s *info = GET_PMMVAR(*pinfo); - if (!info) - return -1; - if (GET_PMMVAR(info->data) == data) { - SET_PMMVAR(*pinfo, GET_PMMVAR(info->next)); - u32 oldallocdata = GET_PMMVAR(info->oldallocdata); - u32 olddata = GET_PMMVAR(info->olddata); - pmm_free_data(data, olddata); - pmm_free_data(info, oldallocdata); - dprintf(8, "pmm_free data=%p olddata=%p oldallocdata=%p info=%p\n" - , data, (void*)olddata, (void*)oldallocdata, info); - return 0; - } - pinfo = &info->next; - } + struct allocinfo_s *info = findAlloc(data); + if (!info || data == (void*)info || data == GET_PMMVAR(info->dataend)) + return -1; + struct allocdetail_s *detail = container_of( + info, struct allocdetail_s, datainfo); + dprintf(8, "pmm_free %p (detail=%p)\n", data, detail); + freeSpace(info); + freeSpace(&detail->detailinfo); + return 0; }
// Find the amount of free space in a given zone. @@ -266,90 +409,43 @@ static u32 pmm_getspace(struct zone_s *zone) { // XXX - doesn't account for ZoneLow being able to grow. - u32 space = GET_PMMVAR(zone->cur) - GET_PMMVAR(zone->bottom); + // XXX - results not reliable when CONFIG_THREAD_OPTIONROMS + u32 maxspace = 0; + struct allocinfo_s *info; + for (info = GET_PMMVAR(zone->info); info; info = GET_PMMVAR(info->next)) { + u32 space = GET_PMMVAR(info->allocend) - GET_PMMVAR(info->dataend); + if (space > maxspace) + maxspace = space; + } + if (zone != &ZoneTmpHigh && zone != &ZoneTmpLow) - return space; + return maxspace; // Account for space needed for PMM tracking. - u32 reserve = ALIGN(sizeof(struct pmmalloc_s), MALLOC_MIN_ALIGN); - if (space <= reserve) + u32 reserve = ALIGN(sizeof(struct allocdetail_s), MALLOC_MIN_ALIGN); + if (maxspace <= reserve) return 0; - return space - reserve; + return maxspace - reserve; }
// Find the data block allocated with pmm_malloc with a given handle. static void * pmm_find(u32 handle) { - struct pmmalloc_s *info; - for (info=GET_PMMVAR(PMMAllocs); info; info = GET_PMMVAR(info->next)) - if (GET_PMMVAR(info->handle) == handle) - return GET_PMMVAR(info->data); - return NULL; -} - -void -malloc_setup(void) -{ - ASSERT32FLAT(); - dprintf(3, "malloc setup\n"); - - PMMAllocs = NULL; - - // Memory in 0xf0000 area. - extern u8 code32flat_start[]; - if ((u32)code32flat_start > BUILD_BIOS_ADDR) - // Clear unused parts of f-segment - memset((void*)BUILD_BIOS_ADDR, 0 - , (u32)code32flat_start - BUILD_BIOS_ADDR); - memset(BiosTableSpace, 0, CONFIG_MAX_BIOSTABLE); - ZoneFSeg.bottom = (u32)BiosTableSpace; - ZoneFSeg.top = ZoneFSeg.cur = ZoneFSeg.bottom + CONFIG_MAX_BIOSTABLE; - - // Memory under 1Meg. - ZoneTmpLow.bottom = BUILD_STACK_ADDR; - ZoneTmpLow.top = ZoneTmpLow.cur = BUILD_EBDA_MINIMUM; - - // Permanent memory under 1Meg. - ZoneLow.bottom = ZoneLow.top = ZoneLow.cur = BUILD_LOWRAM_END; - - // Find memory at the top of ram. - struct e820entry *e = find_high_area(CONFIG_MAX_HIGHTABLE+MALLOC_MIN_ALIGN); - if (!e) { - // No memory above 1Meg - memset(&ZoneHigh, 0, sizeof(ZoneHigh)); - memset(&ZoneTmpHigh, 0, sizeof(ZoneTmpHigh)); - return; + int i; + for (i=0; i<ARRAY_SIZE(Zones); i++) { + struct zone_s *zone = GET_PMMVAR(Zones[i]); + struct allocinfo_s *info; + for (info = GET_PMMVAR(zone->info); info + ; info = GET_PMMVAR(info->next)) { + if (GET_PMMVAR(info->data) != (void*)info) + continue; + struct allocdetail_s *detail = container_of( + info, struct allocdetail_s, detailinfo); + if (GET_PMMVAR(detail->handle) == handle) + return GET_PMMVAR(detail->datainfo.data); + } } - u32 top = e->start + e->size, bottom = e->start; - - // Memory at top of ram. - ZoneHigh.bottom = ALIGN(top - CONFIG_MAX_HIGHTABLE, MALLOC_MIN_ALIGN); - ZoneHigh.top = ZoneHigh.cur = ZoneHigh.bottom + CONFIG_MAX_HIGHTABLE; - add_e820(ZoneHigh.bottom, CONFIG_MAX_HIGHTABLE, E820_RESERVED); - - // Memory above 1Meg - ZoneTmpHigh.bottom = ALIGN(bottom, MALLOC_MIN_ALIGN); - ZoneTmpHigh.top = ZoneTmpHigh.cur = ZoneHigh.bottom; -} - -void -malloc_finalize(void) -{ - dprintf(3, "malloc finalize\n"); - - dumpZones(); - - // Reserve more low-mem if needed. - u32 endlow = GET_BDA(mem_size_kb)*1024; - add_e820(endlow, BUILD_LOWRAM_END-endlow, E820_RESERVED); - - // Give back unused high ram. - u32 giveback = ALIGN_DOWN(ZoneHigh.cur - ZoneHigh.bottom, PAGE_SIZE); - add_e820(ZoneHigh.bottom, giveback, E820_RAM); - dprintf(1, "Returned %d bytes of ZoneHigh\n", giveback); - - // Clear low-memory allocations. - memset((void*)ZoneTmpLow.bottom, 0, ZoneTmpLow.top - ZoneTmpLow.bottom); + return NULL; }