/*
* Find and allocate an available selector, inserting an LDT entry with the
* appropriate permissions.
*/
uint16_t NaClLdtAllocateSelector(int32_t entry_number,
int size_is_in_pages,
NaClLdtDescriptorType type,
int read_exec_only,
void* base_addr,
uint32_t size_minus_one) {
struct user_desc ud;
int retval;
NaClXMutexLock(&nacl_ldt_mutex);
if (-1 == entry_number) {
/* -1 means caller did not specify -- allocate */
entry_number = NaClFindUnusedEntryNumber();
if (-1 == entry_number) {
/*
* No free entries were available.
*/
goto alloc_error;
}
}
ud.entry_number = entry_number;
switch (type) {
case NACL_LDT_DESCRIPTOR_DATA:
ud.contents = MODIFY_LDT_CONTENTS_DATA;
break;
case NACL_LDT_DESCRIPTOR_CODE:
ud.contents = MODIFY_LDT_CONTENTS_CODE;
break;
default:
goto alloc_error;
}
ud.read_exec_only = read_exec_only;
ud.seg_32bit = 1;
ud.seg_not_present = 0;
ud.useable = 1;
if (size_is_in_pages && ((unsigned long) base_addr & 0xfff)) {
/*
* The base address needs to be page aligned.
*/
goto alloc_error;
};
ud.base_addr = (unsigned long) base_addr;
if (size_minus_one > 0xfffff) {
/*
* If size is in pages, no more than 2**20 pages can be protected.
* If size is in bytes, no more than 2**20 bytes can be protected.
*/
goto alloc_error;
}
ud.limit = size_minus_one;
ud.limit_in_pages = size_is_in_pages;
/*
* Install the LDT entry.
*/
retval = modify_ldt(1, &ud, sizeof ud);
if (-1 == retval) {
goto alloc_error;
}
/*
* Return an LDT selector with a requested privilege level of 3.
*/
NaClXMutexUnlock(&nacl_ldt_mutex);
return (ud.entry_number << 3) | 0x7;
/*
* All error returns go through this epilog.
*/
alloc_error:
NaClXMutexUnlock(&nacl_ldt_mutex);
return 0;
}
/*
* Find and allocate an available selector, inserting an LDT entry with the
* appropriate permissions.
*/
uint16_t NaClLdtAllocateSelector(int entry_number,
int size_is_in_pages,
NaClLdtDescriptorType type,
int read_exec_only,
void* base_addr,
uint32_t size_minus_one) {
int retval;
struct LdtEntry ldt;
retval = 0;
NaClXMutexLock(&nacl_ldt_mutex);
if (-1 == entry_number) {
entry_number = NaClFindUnusedEntryNumber();
if (-1 == entry_number) {
/*
* No free entries were available.
*/
NaClXMutexUnlock(&nacl_ldt_mutex);
return 0;
}
}
switch (type) {
case NACL_LDT_DESCRIPTOR_DATA:
if (read_exec_only) {
ldt.type = 0x10; /* Data read only */
} else {
ldt.type = 0x12; /* Data read/write */
}
break;
case NACL_LDT_DESCRIPTOR_CODE:
if (read_exec_only) {
ldt.type = 0x18; /* Code execute */
} else {
ldt.type = 0x1a; /* Code execute/read */
}
break;
default:
NaClXMutexUnlock(&nacl_ldt_mutex);
return 0;
}
ldt.descriptor_privilege = 3;
ldt.present = 1;
ldt.available = 1; /* TODO(dcs) */
ldt.code_64_bit = 0;
ldt.op_size_32 = 1;
if (size_is_in_pages && ((unsigned long) base_addr & 0xfff)) {
/*
* The base address needs to be page aligned.
*/
NaClXMutexUnlock(&nacl_ldt_mutex);
return 0;
};
ldt.base_00to15 = ((unsigned long) base_addr) & 0xffff;
ldt.base_16to23 = (((unsigned long) base_addr) >> 16) & 0xff;
ldt.base_24to31 = (((unsigned long) base_addr) >> 24) & 0xff;
if (size_minus_one > 0xfffff) {
/*
* If the size is in pages, no more than 2**20 pages can be protected.
* If the size is in bytes, no more than 2**20 bytes can be protected.
*/
NaClXMutexUnlock(&nacl_ldt_mutex);
return 0;
}
ldt.limit_00to15 = size_minus_one & 0xffff;
ldt.limit_16to19 = (size_minus_one >> 16) & 0xf;
ldt.granularity = size_is_in_pages;
/*
* Install the LDT entry.
*/
if (NULL != set_ldt_entries) {
union {
struct LdtEntry ldt;
DWORD dwords[2];
} u;
u.ldt = ldt;
retval = (*set_ldt_entries)((entry_number << 3) | 0x7,
u.dwords[0],
u.dwords[1],
0,
0,
0);
}
if ((NULL == set_ldt_entries) || (0 != retval)) {
LdtInfo info;
info.byte_offset = entry_number << 3;
info.size = sizeof(struct LdtEntry);
info.entries[0] = ldt;
retval = (*set_information_process)((HANDLE)-1, 10, (void*)&info, 16);
}
if (0 != retval) {
NaClXMutexUnlock(&nacl_ldt_mutex);
return 0;
}
/*
* Return an LDT selector with a requested privilege level of 3.
*/
NaClXMutexUnlock(&nacl_ldt_mutex);
return (uint16_t)((entry_number << 3) | 0x7);
}
