/*
* Allocates a selector whose size is specified in bytes.
*/
uint16_t NaClLdtAllocateByteSelector(NaClLdtDescriptorType type,
int read_exec_only,
void* base_addr,
uint32_t size_in_bytes) {
return NaClLdtAllocateSelector(-1, 0, type, read_exec_only, base_addr,
size_in_bytes - 1);
}
/*
* Change a selector whose size is specified in bytes.
*/
uint16_t NaClLdtChangeByteSelector(int32_t entry_number,
NaClLdtDescriptorType type,
int read_exec_only,
void* base_addr,
uint32_t size_in_bytes) {
if ((uint32_t) entry_number >= LDT_ENTRIES) {
return 0;
}
return NaClLdtAllocateSelector(entry_number, 0, type, read_exec_only,
base_addr, size_in_bytes - 1);
}
int NaClLdtInitPlatformSpecific(void) {
HMODULE hmod = GetModuleHandleA("ntdll.dll");
/*
* query_information_process is used to examine LDT entries to find a free
* selector, etc.
*/
query_information_process =
(NTQUERY)(GetProcAddress(hmod, "NtQueryInformationProcess"));
if (query_information_process == 0) {
/*
* Unable to get query_information_process, which is needed for querying
* the LDT.
*/
return 0;
}
/*
* set_information_process is one of the methods used to update an LDT
* entry for a given selector.
*/
set_information_process =
(NTSETINFO)(GetProcAddress(hmod, "ZwSetInformationProcess"));
/*
* set_ldt_entries is the other method used to update an LDT entry for a
* given selector.
*/
set_ldt_entries = (NTSETLDT)(GetProcAddress(hmod, "NtSetLdtEntries"));
if (NULL == set_ldt_entries) {
set_ldt_entries = (NTSETLDT)(GetProcAddress(hmod, "ZwSetLdtEntries"));
}
if ((NULL == set_ldt_entries) && (NULL == set_information_process)) {
/*
* Unable to locate either method for setting the LDT.
*/
return 0;
}
if (!NaClMutexCtor(&nacl_ldt_mutex)) {
return 0;
}
/*
* Allocate the last LDT entry to force the LDT to grow to its maximum size.
*/
return NaClLdtAllocateSelector(LDT_ENTRIES - 1, 0,
NACL_LDT_DESCRIPTOR_DATA, 0, 0, 0);
}
