int32_t NaClSysMunmap(struct NaClAppThread *natp,
void *start,
size_t length) {
int32_t retval = -NACL_ABI_EINVAL;
uintptr_t sysaddr;
int holding_app_lock = 0;
size_t alloc_rounded_length;
NaClLog(3, "Entered NaClSysMunmap(0x%08"NACL_PRIxPTR", "
"0x%08"NACL_PRIxPTR", 0x%"NACL_PRIxS")\n",
(uintptr_t) natp, (uintptr_t) start, length);
NaClSysCommonThreadSyscallEnter(natp);
if (!NaClIsAllocPageMultiple((uintptr_t) start)) {
NaClLog(4, "start addr not allocation multiple\n");
retval = -NACL_ABI_EINVAL;
goto cleanup;
}
if (0 == length) {
/*
* linux mmap of zero length yields a failure, but osx does not, leading
* to a NaClVmmapUpdate of zero pages, which should not occur.
*/
retval = -NACL_ABI_EINVAL;
goto cleanup;
}
alloc_rounded_length = NaClRoundAllocPage(length);
if (alloc_rounded_length != length) {
length = alloc_rounded_length;
NaClLog(LOG_WARNING,
"munmap: rounded length to 0x%"NACL_PRIxS"\n", length);
}
sysaddr = NaClUserToSysAddrRange(natp->nap, (uintptr_t) start, length);
if (kNaClBadAddress == sysaddr) {
NaClLog(4, "region not user addresses\n");
retval = -NACL_ABI_EFAULT;
goto cleanup;
}
NaClXMutexLock(&natp->nap->mu);
while (0 != natp->nap->threads_launching) {
NaClXCondVarWait(&natp->nap->cv, &natp->nap->mu);
}
natp->nap->vm_hole_may_exist = 1;
holding_app_lock = 1;
/*
* NB: windows (or generic) version would use Munmap virtual
* function from the backing NaClDesc object obtained by iterating
* through the address map for the region, and those Munmap virtual
* functions may return -NACL_ABI_E_MOVE_ADDRESS_SPACE.
*
* We should hold the application lock while doing this iteration
* and unmapping, so that the address space is consistent for other
* threads.
*/
/*
* User should be unable to unmap any executable pages. We check here.
*/
if (NaClSysCommonAddrRangeContainsExecutablePages_mu(natp->nap,
(uintptr_t) start,
length)) {
NaClLog(2, "NaClSysMunmap: region contains executable pages\n");
retval = -NACL_ABI_EINVAL;
goto cleanup;
}
/*
* Overwrite current mapping with inaccessible, anonymous
* zero-filled pages, which should be copy-on-write and thus
* relatively cheap. Do not open up an address space hole.
*/
NaClLog(4,
("NaClSysMunmap: mmap(0x%08"NACL_PRIxPTR", 0x%"NACL_PRIxS","
" 0x%x, 0x%x, -1, 0)\n"),
sysaddr, length, PROT_NONE,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED);
if (MAP_FAILED == mmap((void *) sysaddr,
length,
PROT_NONE,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED,
-1,
(off_t) 0)) {
NaClLog(4, "mmap to put in anonymous memory failed, errno = %d\n", errno);
retval = -NaClXlateErrno(errno);
goto cleanup;
}
NaClVmmapUpdate(&natp->nap->mem_map,
(NaClSysToUser(natp->nap, (uintptr_t) sysaddr)
>> NACL_PAGESHIFT),
length >> NACL_PAGESHIFT,
0, /* prot */
(struct NaClMemObj *) NULL,
1); /* Delete mapping */
retval = 0;
cleanup:
if (holding_app_lock) {
natp->nap->vm_hole_may_exist = 0;
NaClXCondVarBroadcast(&natp->nap->cv);
NaClXMutexUnlock(&natp->nap->mu);
}
NaClSysCommonThreadSyscallLeave(natp);
return retval;
}
int32_t NaClSysMunmap(struct NaClAppThread *natp,
void *start,
size_t length) {
int32_t retval = -NACL_ABI_EINVAL;
uintptr_t sysaddr;
uintptr_t addr;
uintptr_t endaddr;
int holding_app_lock = 0;
size_t alloc_rounded_length;
NaClLog(3, "NaClSysMunmap(0x%08x, 0x%08x, 0x%x)\n",
natp, start, length);
NaClSysCommonThreadSyscallEnter(natp);
if (!NaClIsAllocPageMultiple((uintptr_t) start)) {
NaClLog(4, "start addr not allocation multiple\n");
retval = -NACL_ABI_EINVAL;
goto cleanup;
}
if (0 == length) {
/*
* linux mmap of zero length yields a failure, but windows code
* would just iterate through and do nothing, so does not yield a
* failure.
*/
retval = -NACL_ABI_EINVAL;
goto cleanup;
}
alloc_rounded_length = NaClRoundAllocPage(length);
if (alloc_rounded_length != length) {
length = alloc_rounded_length;
NaClLog(LOG_WARNING,
"munmap: rounded length to 0x%x\n", length);
}
sysaddr = NaClUserToSysAddrRange(natp->nap, (uintptr_t) start, length);
if (kNaClBadAddress == sysaddr) {
retval = -NACL_ABI_EFAULT;
goto cleanup;
}
NaClXMutexLock(&natp->nap->mu);
holding_app_lock = 1;
/*
* User should be unable to unmap any executable pages. We check here.
*/
if (NaClSysCommonAddrRangeContainsExecutablePages_mu(natp->nap,
(uintptr_t) start,
length)) {
NaClLog(2, "NaClSysMunmap: region contains executable pages\n");
retval = -NACL_ABI_EINVAL;
goto cleanup;
}
endaddr = sysaddr + length;
for (addr = sysaddr; addr < endaddr; addr += NACL_MAP_PAGESIZE) {
struct NaClVmmapEntry const *entry;
entry = NaClVmmapFindPage(&natp->nap->mem_map,
NaClSysToUser(natp->nap, addr)
>> NACL_PAGESHIFT);
if (NULL == entry) {
NaClLog(LOG_FATAL,
"NaClSysMunmap: could not find VM map entry for addr 0x%08x\n",
addr);
}
NaClLog(3,
("NaClSysMunmap: addr 0x%08x, nmop 0x%08x\n"),
addr, entry->nmop);
if (NULL == entry->nmop) {
/* anonymous memory; we just decommit it and thus make it inaccessible */
if (!VirtualFree((void *) addr,
NACL_MAP_PAGESIZE,
MEM_DECOMMIT)) {
int error = GetLastError();
NaClLog(LOG_FATAL,
("NaClSysMunmap: Could not VirtualFree MEM_DECOMMIT"
" addr 0x%08x, error %d (0x%x)\n"),
addr, error, error);
}
} else {
/*
* This should invoke a "safe" version of unmap that fills the
* memory hole as quickly as possible, and may return
* -NACL_ABI_E_MOVE_ADDRESS_SPACE. The "safe" version just
* minimizes the size of the timing hole for any racers, plus
* the size of the memory window is only 64KB, rather than
* whatever size the user is unmapping.
*/
retval = (*entry->nmop->ndp->vtbl->Unmap)(entry->nmop->ndp,
natp->effp,
(void*) addr,
NACL_MAP_PAGESIZE);
if (0 != retval) {
NaClLog(LOG_FATAL,
("NaClSysMunmap: Could not unmap via ndp->Unmap 0x%08x"
" and cannot handle address space move\n"),
addr);
}
}
NaClVmmapUpdate(&natp->nap->mem_map,
(NaClSysToUser(natp->nap, (uintptr_t) addr)
>> NACL_PAGESHIFT),
NACL_PAGES_PER_MAP,
0, /* prot */
(struct NaClMemObj *) NULL,
1); /* delete */
}
retval = 0;
cleanup:
if (holding_app_lock) {
NaClXMutexUnlock(&natp->nap->mu);
}
NaClSysCommonThreadSyscallLeave(natp);
return retval;
}