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40760d12ba
darling-objc4/runtime/objc-runtime.mm
Ariel Abreu 4d6225bbe3
objc4-781.2
2020-06-09 21:50:17 -04:00

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/*
* Copyright (c) 1999-2007 Apple Inc. All Rights Reserved.
*
* @APPLE_LICENSE_HEADER_START@
*
* This file contains Original Code and/or Modifications of Original Code
* as defined in and that are subject to the Apple Public Source License
* Version 2.0 (the 'License'). You may not use this file except in
* compliance with the License. Please obtain a copy of the License at
* http://www.opensource.apple.com/apsl/ and read it before using this
* file.
*
* The Original Code and all software distributed under the License are
* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
* Please see the License for the specific language governing rights and
* limitations under the License.
*
* @APPLE_LICENSE_HEADER_END@
*/
/***********************************************************************
* objc-runtime.m
* Copyright 1988-1996, NeXT Software, Inc.
* Author: s. naroff
*
**********************************************************************/
/***********************************************************************
* Imports.
**********************************************************************/
#include "objc-private.h"
#include "objc-loadmethod.h"
#include "objc-file.h"
#include "message.h"
/***********************************************************************
* Exports.
**********************************************************************/
/* Linker metadata symbols */
// NSObject was in Foundation/CF on macOS < 10.8.
#if TARGET_OS_OSX
#if __OBJC2__
const char __objc_nsobject_class_10_5 = 0;
const char __objc_nsobject_class_10_6 = 0;
const char __objc_nsobject_class_10_7 = 0;
const char __objc_nsobject_metaclass_10_5 = 0;
const char __objc_nsobject_metaclass_10_6 = 0;
const char __objc_nsobject_metaclass_10_7 = 0;
const char __objc_nsobject_isa_10_5 = 0;
const char __objc_nsobject_isa_10_6 = 0;
const char __objc_nsobject_isa_10_7 = 0;
#else
const char __objc_nsobject_class_10_5 = 0;
const char __objc_nsobject_class_10_6 = 0;
const char __objc_nsobject_class_10_7 = 0;
#endif
#endif
// Settings from environment variables
#define OPTION(var, env, help) bool var = false;
#include "objc-env.h"
#undef OPTION
struct option_t {
bool* var;
const char *env;
const char *help;
size_t envlen;
};
const option_t Settings[] = {
#define OPTION(var, env, help) option_t{&var, #env, help, strlen(#env)},
#include "objc-env.h"
#undef OPTION
};
// objc's key for pthread_getspecific
#if SUPPORT_DIRECT_THREAD_KEYS
#define _objc_pthread_key TLS_DIRECT_KEY
#else
static tls_key_t _objc_pthread_key;
#endif
// Selectors
SEL SEL_cxx_construct = NULL;
SEL SEL_cxx_destruct = NULL;
struct objc::SafeRanges objc::dataSegmentsRanges;
header_info *FirstHeader = 0; // NULL means empty list
header_info *LastHeader = 0; // NULL means invalid; recompute it
// Set to true on the child side of fork()
// if the parent process was multithreaded when fork() was called.
bool MultithreadedForkChild = false;
/***********************************************************************
* objc_noop_imp. Used when we need to install a do-nothing method somewhere.
**********************************************************************/
id objc_noop_imp(id self, SEL _cmd __unused) {
return self;
}
/***********************************************************************
* _objc_isDebugBuild. Defined in debug builds only.
* Some test code looks for the presence of this symbol.
**********************************************************************/
#if DEBUG != OBJC_IS_DEBUG_BUILD
#error mismatch in debug-ness macros
// DEBUG is used in our code. OBJC_IS_DEBUG_BUILD is used in the
// header declaration of _objc_isDebugBuild() because that header
// is visible to other clients who might have their own DEBUG macro.
#endif
#if OBJC_IS_DEBUG_BUILD
void _objc_isDebugBuild(void) { }
#endif
/***********************************************************************
* objc_getClass. Return the id of the named class. If the class does
* not exist, call _objc_classLoader and then objc_classHandler, either of
* which may create a new class.
* Warning: doesn't work if aClassName is the name of a posed-for class's isa!
**********************************************************************/
Class objc_getClass(const char *aClassName)
{
if (!aClassName) return Nil;
// NO unconnected, YES class handler
return look_up_class(aClassName, NO, YES);
}
/***********************************************************************
* objc_getRequiredClass.
* Same as objc_getClass, but kills the process if the class is not found.
* This is used by ZeroLink, where failing to find a class would be a
* compile-time link error without ZeroLink.
**********************************************************************/
Class objc_getRequiredClass(const char *aClassName)
{
Class cls = objc_getClass(aClassName);
if (!cls) _objc_fatal("link error: class '%s' not found.", aClassName);
return cls;
}
/***********************************************************************
* objc_lookUpClass. Return the id of the named class.
* If the class does not exist, call _objc_classLoader, which may create
* a new class.
*
* Formerly objc_getClassWithoutWarning ()
**********************************************************************/
Class objc_lookUpClass(const char *aClassName)
{
if (!aClassName) return Nil;
// NO unconnected, NO class handler
return look_up_class(aClassName, NO, NO);
}
/***********************************************************************
* objc_getMetaClass. Return the id of the meta class the named class.
* Warning: doesn't work if aClassName is the name of a posed-for class's isa!
**********************************************************************/
Class objc_getMetaClass(const char *aClassName)
{
Class cls;
if (!aClassName) return Nil;
cls = objc_getClass (aClassName);
if (!cls)
{
_objc_inform ("class `%s' not linked into application", aClassName);
return Nil;
}
return cls->ISA();
}
/***********************************************************************
* objc::SafeRanges::find. Find an image data segment that contains address
**********************************************************************/
bool
objc::SafeRanges::find(uintptr_t ptr, uint32_t &pos)
{
if (!sorted) {
std::sort(ranges, ranges + count, [](const Range &s1, const Range &s2){
return s1.start < s2.start;
});
sorted = true;
}
uint32_t l = 0, r = count;
while (l < r) {
uint32_t i = (l + r) / 2;
if (ptr < ranges[i].start) {
r = i;
} else if (ptr >= ranges[i].end) {
l = i + 1;
} else {
pos = i;
return true;
}
}
pos = UINT32_MAX;
return false;
}
/***********************************************************************
* objc::SafeRanges::add. Register a new well known data segment.
**********************************************************************/
void
objc::SafeRanges::add(uintptr_t start, uintptr_t end)
{
if (count == size) {
// Have a typical malloc growth:
// - size <= 32: grow by 4
// - size <= 64: grow by 8
// - size <= 128: grow by 16
// ... etc
size += size < 16 ? 4 : 1 << (fls(size) - 3);
ranges = (Range *)realloc(ranges, sizeof(Range) * size);
}
ranges[count++] = Range{ start, end };
sorted = false;
}
/***********************************************************************
* objc::SafeRanges::remove. Remove a previously known data segment.
**********************************************************************/
void
objc::SafeRanges::remove(uintptr_t start, uintptr_t end)
{
uint32_t pos;
if (!find(start, pos) || ranges[pos].end != end) {
_objc_fatal("Cannot find range %#lx..%#lx", start, end);
}
if (pos < --count) {
ranges[pos] = ranges[count];
sorted = false;
}
}
/***********************************************************************
* appendHeader. Add a newly-constructed header_info to the list.
**********************************************************************/
void appendHeader(header_info *hi)
{
// Add the header to the header list.
// The header is appended to the list, to preserve the bottom-up order.
hi->setNext(NULL);
if (!FirstHeader) {
// list is empty
FirstHeader = LastHeader = hi;
} else {
if (!LastHeader) {
// list is not empty, but LastHeader is invalid - recompute it
LastHeader = FirstHeader;
while (LastHeader->getNext()) LastHeader = LastHeader->getNext();
}
// LastHeader is now valid
LastHeader->setNext(hi);
LastHeader = hi;
}
#if __OBJC2__
if ((hi->mhdr()->flags & MH_DYLIB_IN_CACHE) == 0) {
foreach_data_segment(hi->mhdr(), [](const segmentType *seg, intptr_t slide) {
uintptr_t start = (uintptr_t)seg->vmaddr + slide;
objc::dataSegmentsRanges.add(start, start + seg->vmsize);
});
}
#endif
}
/***********************************************************************
* removeHeader
* Remove the given header from the header list.
* FirstHeader is updated.
* LastHeader is set to NULL. Any code that uses LastHeader must
* detect this NULL and recompute LastHeader by traversing the list.
**********************************************************************/
void removeHeader(header_info *hi)
{
header_info *prev = NULL;
header_info *current = NULL;
for (current = FirstHeader; current != NULL; current = current->getNext()) {
if (current == hi) {
header_info *deadHead = current;
// Remove from the linked list.
if (prev)
prev->setNext(current->getNext());
else
FirstHeader = current->getNext(); // no prev so removing head
// Update LastHeader if necessary.
if (LastHeader == deadHead) {
LastHeader = NULL; // will be recomputed next time it's used
}
break;
}
prev = current;
}
#if __OBJC2__
if ((hi->mhdr()->flags & MH_DYLIB_IN_CACHE) == 0) {
foreach_data_segment(hi->mhdr(), [](const segmentType *seg, intptr_t slide) {
uintptr_t start = (uintptr_t)seg->vmaddr + slide;
objc::dataSegmentsRanges.remove(start, start + seg->vmsize);
});
}
#endif
}
/***********************************************************************
* environ_init
* Read environment variables that affect the runtime.
* Also print environment variable help, if requested.
**********************************************************************/
void environ_init(void)
{
if (issetugid()) {
// All environment variables are silently ignored when setuid or setgid
// This includes OBJC_HELP and OBJC_PRINT_OPTIONS themselves.
return;
}
bool PrintHelp = false;
bool PrintOptions = false;
bool maybeMallocDebugging = false;
// Scan environ[] directly instead of calling getenv() a lot.
// This optimizes the case where none are set.
for (char **p = *_NSGetEnviron(); *p != nil; p++) {
if (0 == strncmp(*p, "Malloc", 6) || 0 == strncmp(*p, "DYLD", 4) ||
0 == strncmp(*p, "NSZombiesEnabled", 16))
{
maybeMallocDebugging = true;
}
if (0 != strncmp(*p, "OBJC_", 5)) continue;
if (0 == strncmp(*p, "OBJC_HELP=", 10)) {
PrintHelp = true;
continue;
}
if (0 == strncmp(*p, "OBJC_PRINT_OPTIONS=", 19)) {
PrintOptions = true;
continue;
}
const char *value = strchr(*p, '=');
if (!*value) continue;
value++;
for (size_t i = 0; i < sizeof(Settings)/sizeof(Settings[0]); i++) {
const option_t *opt = &Settings[i];
if ((size_t)(value - *p) == 1+opt->envlen &&
0 == strncmp(*p, opt->env, opt->envlen))
{
*opt->var = (0 == strcmp(value, "YES"));
break;
}
}
}
// Special case: enable some autorelease pool debugging
// when some malloc debugging is enabled
// and OBJC_DEBUG_POOL_ALLOCATION is not set to something other than NO.
if (maybeMallocDebugging) {
const char *insert = getenv("DYLD_INSERT_LIBRARIES");
const char *zombie = getenv("NSZombiesEnabled");
const char *pooldebug = getenv("OBJC_DEBUG_POOL_ALLOCATION");
if ((getenv("MallocStackLogging")
|| getenv("MallocStackLoggingNoCompact")
|| (zombie && (*zombie == 'Y' || *zombie == 'y'))
|| (insert && strstr(insert, "libgmalloc")))
&&
(!pooldebug || 0 == strcmp(pooldebug, "YES")))
{
DebugPoolAllocation = true;
}
}
// Print OBJC_HELP and OBJC_PRINT_OPTIONS output.
if (PrintHelp || PrintOptions) {
if (PrintHelp) {
_objc_inform("Objective-C runtime debugging. Set variable=YES to enable.");
_objc_inform("OBJC_HELP: describe available environment variables");
if (PrintOptions) {
_objc_inform("OBJC_HELP is set");
}
_objc_inform("OBJC_PRINT_OPTIONS: list which options are set");
}
if (PrintOptions) {
_objc_inform("OBJC_PRINT_OPTIONS is set");
}
for (size_t i = 0; i < sizeof(Settings)/sizeof(Settings[0]); i++) {
const option_t *opt = &Settings[i];
if (PrintHelp) _objc_inform("%s: %s", opt->env, opt->help);
if (PrintOptions && *opt->var) _objc_inform("%s is set", opt->env);
}
}
}
/***********************************************************************
* logReplacedMethod
* OBJC_PRINT_REPLACED_METHODS implementation
**********************************************************************/
void
logReplacedMethod(const char *className, SEL s,
bool isMeta, const char *catName,
IMP oldImp, IMP newImp)
{
const char *oldImage = "??";
const char *newImage = "??";
// Silently ignore +load replacement because category +load is special
if (s == @selector(load)) return;
#if TARGET_OS_WIN32
// don't know dladdr()/dli_fname equivalent
#else
Dl_info dl;
if (dladdr((void*)oldImp, &dl) && dl.dli_fname) oldImage = dl.dli_fname;
if (dladdr((void*)newImp, &dl) && dl.dli_fname) newImage = dl.dli_fname;
#endif
_objc_inform("REPLACED: %c[%s %s] %s%s (IMP was %p (%s), now %p (%s))",
isMeta ? '+' : '-', className, sel_getName(s),
catName ? "by category " : "", catName ? catName : "",
oldImp, oldImage, newImp, newImage);
}
/***********************************************************************
* _objc_fetch_pthread_data
* Fetch objc's pthread data for this thread.
* If the data doesn't exist yet and create is NO, return NULL.
* If the data doesn't exist yet and create is YES, allocate and return it.
**********************************************************************/
_objc_pthread_data *_objc_fetch_pthread_data(bool create)
{
_objc_pthread_data *data;
data = (_objc_pthread_data *)tls_get(_objc_pthread_key);
if (!data && create) {
data = (_objc_pthread_data *)
calloc(1, sizeof(_objc_pthread_data));
tls_set(_objc_pthread_key, data);
}
return data;
}
/***********************************************************************
* _objc_pthread_destroyspecific
* Destructor for objc's per-thread data.
* arg shouldn't be NULL, but we check anyway.
**********************************************************************/
extern void _destroyInitializingClassList(struct _objc_initializing_classes *list);
void _objc_pthread_destroyspecific(void *arg)
{
_objc_pthread_data *data = (_objc_pthread_data *)arg;
if (data != NULL) {
_destroyInitializingClassList(data->initializingClasses);
_destroySyncCache(data->syncCache);
_destroyAltHandlerList(data->handlerList);
for (int i = 0; i < (int)countof(data->printableNames); i++) {
if (data->printableNames[i]) {
free(data->printableNames[i]);
}
}
free(data->classNameLookups);
// add further cleanup here...
free(data);
}
}
void tls_init(void)
{
#if SUPPORT_DIRECT_THREAD_KEYS
pthread_key_init_np(TLS_DIRECT_KEY, &_objc_pthread_destroyspecific);
#else
_objc_pthread_key = tls_create(&_objc_pthread_destroyspecific);
#endif
}
/***********************************************************************
* _objcInit
* Former library initializer. This function is now merely a placeholder
* for external callers. All runtime initialization has now been moved
* to map_images() and _objc_init.
**********************************************************************/
void _objcInit(void)
{
// do nothing
}
/***********************************************************************
* objc_setForwardHandler
**********************************************************************/
#if !__OBJC2__
// Default forward handler (nil) goes to forward:: dispatch.
void *_objc_forward_handler = nil;
void *_objc_forward_stret_handler = nil;
#else
// Default forward handler halts the process.
__attribute__((noreturn, cold)) void
objc_defaultForwardHandler(id self, SEL sel)
{
_objc_fatal("%c[%s %s]: unrecognized selector sent to instance %p "
"(no message forward handler is installed)",
class_isMetaClass(object_getClass(self)) ? '+' : '-',
object_getClassName(self), sel_getName(sel), self);
}
void *_objc_forward_handler = (void*)objc_defaultForwardHandler;
#if SUPPORT_STRET
struct stret { int i[100]; };
__attribute__((noreturn, cold)) struct stret
objc_defaultForwardStretHandler(id self, SEL sel)
{
objc_defaultForwardHandler(self, sel);
}
void *_objc_forward_stret_handler = (void*)objc_defaultForwardStretHandler;
#endif
#endif
void objc_setForwardHandler(void *fwd, void *fwd_stret)
{
_objc_forward_handler = fwd;
#if SUPPORT_STRET
_objc_forward_stret_handler = fwd_stret;
#endif
}
#if !__OBJC2__
// GrP fixme
extern "C" Class _objc_getOrigClass(const char *name);
#endif
static BOOL internal_class_getImageName(Class cls, const char **outName)
{
#if !__OBJC2__
cls = _objc_getOrigClass(cls->demangledName());
#endif
auto result = dyld_image_path_containing_address(cls);
*outName = result;
return (result != nil);
}
static ChainedHookFunction<objc_hook_getImageName>
GetImageNameHook{internal_class_getImageName};
void objc_setHook_getImageName(objc_hook_getImageName newValue,
objc_hook_getImageName *outOldValue)
{
GetImageNameHook.set(newValue, outOldValue);
}
const char *class_getImageName(Class cls)
{
if (!cls) return nil;
const char *name;
if (GetImageNameHook.get()(cls, &name)) return name;
else return nil;
}
/**********************************************************************
* Fast Enumeration Support
**********************************************************************/
static void (*enumerationMutationHandler)(id);
/**********************************************************************
* objc_enumerationMutation
* called by compiler when a mutation is detected during foreach iteration
**********************************************************************/
void objc_enumerationMutation(id object) {
if (enumerationMutationHandler == nil) {
_objc_fatal("mutation detected during 'for(... in ...)' enumeration of object %p.", (void*)object);
}
(*enumerationMutationHandler)(object);
}
/**********************************************************************
* objc_setEnumerationMutationHandler
* an entry point to customize mutation error handing
**********************************************************************/
void objc_setEnumerationMutationHandler(void (*handler)(id)) {
enumerationMutationHandler = handler;
}
/**********************************************************************
* Associative Reference Support
**********************************************************************/
id
objc_getAssociatedObject(id object, const void *key)
{
return _object_get_associative_reference(object, key);
}
static void
_base_objc_setAssociatedObject(id object, const void *key, id value, objc_AssociationPolicy policy)
{
_object_set_associative_reference(object, key, value, policy);
}
static ChainedHookFunction<objc_hook_setAssociatedObject> SetAssocHook{_base_objc_setAssociatedObject};
void
objc_setHook_setAssociatedObject(objc_hook_setAssociatedObject _Nonnull newValue,
objc_hook_setAssociatedObject _Nullable * _Nonnull outOldValue) {
SetAssocHook.set(newValue, outOldValue);
}
void
objc_setAssociatedObject(id object, const void *key, id value, objc_AssociationPolicy policy)
{
SetAssocHook.get()(object, key, value, policy);
}
void objc_removeAssociatedObjects(id object)
{
if (object && object->hasAssociatedObjects()) {
_object_remove_assocations(object);
}
}
#if SUPPORT_GC_COMPAT
#include <mach-o/fat.h>
// GC preflight for an app executable.
enum GCness {
WithGC = 1,
WithoutGC = 0,
Error = -1
};
// Overloaded template wrappers around clang's overflow-checked arithmetic.
template <typename T> bool uadd_overflow(T x, T y, T* sum);
template <typename T> bool usub_overflow(T x, T y, T* diff);
template <typename T> bool umul_overflow(T x, T y, T* prod);
template <typename T> bool sadd_overflow(T x, T y, T* sum);
template <typename T> bool ssub_overflow(T x, T y, T* diff);
template <typename T> bool smul_overflow(T x, T y, T* prod);
template <> bool uadd_overflow(unsigned x, unsigned y, unsigned* sum) { return __builtin_uadd_overflow(x, y, sum); }
template <> bool uadd_overflow(unsigned long x, unsigned long y, unsigned long* sum) { return __builtin_uaddl_overflow(x, y, sum); }
template <> bool uadd_overflow(unsigned long long x, unsigned long long y, unsigned long long* sum) { return __builtin_uaddll_overflow(x, y, sum); }
template <> bool usub_overflow(unsigned x, unsigned y, unsigned* diff) { return __builtin_usub_overflow(x, y, diff); }
template <> bool usub_overflow(unsigned long x, unsigned long y, unsigned long* diff) { return __builtin_usubl_overflow(x, y, diff); }
template <> bool usub_overflow(unsigned long long x, unsigned long long y, unsigned long long* diff) { return __builtin_usubll_overflow(x, y, diff); }
template <> bool umul_overflow(unsigned x, unsigned y, unsigned* prod) { return __builtin_umul_overflow(x, y, prod); }
template <> bool umul_overflow(unsigned long x, unsigned long y, unsigned long* prod) { return __builtin_umull_overflow(x, y, prod); }
template <> bool umul_overflow(unsigned long long x, unsigned long long y, unsigned long long* prod) { return __builtin_umulll_overflow(x, y, prod); }
template <> bool sadd_overflow(signed x, signed y, signed* sum) { return __builtin_sadd_overflow(x, y, sum); }
template <> bool sadd_overflow(signed long x, signed long y, signed long* sum) { return __builtin_saddl_overflow(x, y, sum); }
template <> bool sadd_overflow(signed long long x, signed long long y, signed long long* sum) { return __builtin_saddll_overflow(x, y, sum); }
template <> bool ssub_overflow(signed x, signed y, signed* diff) { return __builtin_ssub_overflow(x, y, diff); }
template <> bool ssub_overflow(signed long x, signed long y, signed long* diff) { return __builtin_ssubl_overflow(x, y, diff); }
template <> bool ssub_overflow(signed long long x, signed long long y, signed long long* diff) { return __builtin_ssubll_overflow(x, y, diff); }
template <> bool smul_overflow(signed x, signed y, signed* prod) { return __builtin_smul_overflow(x, y, prod); }
template <> bool smul_overflow(signed long x, signed long y, signed long* prod) { return __builtin_smull_overflow(x, y, prod); }
template <> bool smul_overflow(signed long long x, signed long long y, signed long long* prod) { return __builtin_smulll_overflow(x, y, prod); }
// Range-checking subview of a file.
class FileSlice {
int fd;
uint64_t sliceOffset;
uint64_t sliceSize;
public:
FileSlice() : fd(-1), sliceOffset(0), sliceSize(0) { }
FileSlice(int newfd, uint64_t newOffset, uint64_t newSize)
: fd(newfd) , sliceOffset(newOffset) , sliceSize(newSize) { }
// Read bytes from this slice.
// Returns YES if all bytes were read successfully.
bool pread(void *buf, uint64_t readSize, uint64_t readOffset = 0) {
uint64_t readEnd;
if (uadd_overflow(readOffset, readSize, &readEnd)) return NO;
if (readEnd > sliceSize) return NO;
uint64_t preadOffset;
if (uadd_overflow(sliceOffset, readOffset, &preadOffset)) return NO;
int64_t readed = ::pread(fd, buf, (size_t)readSize, preadOffset);
if (readed < 0 || (uint64_t)readed != readSize) return NO;
return YES;
}
// Create a new slice that is a subset of this slice.
// Returnes YES if successful.
bool slice(uint64_t newOffset, uint64_t newSize, FileSlice& result) {
// fixme arithmetic overflow
uint64_t newEnd;
if (uadd_overflow(newOffset, newSize, &newEnd)) return NO;
if (newEnd > sliceSize) return NO;
if (uadd_overflow(sliceOffset, newOffset, &result.sliceOffset)) {
return NO;
}
result.sliceSize = newSize;
result.fd = fd;
return YES;
}
// Shorten this slice in place by removing a range from the start.
bool advance(uint64_t distance) {
if (distance > sliceSize) return NO;
if (uadd_overflow(sliceOffset, distance, &sliceOffset)) return NO;
if (usub_overflow(sliceSize, distance, &sliceSize)) return NO;
return YES;
}
};
// Arch32 and Arch64 are used to specialize sliceRequiresGC()
// to interrogate old-ABI i386 and new-ABI x86_64 files.
struct Arch32 {
using mh_t = struct mach_header;
using segment_command_t = struct segment_command;
using section_t = struct section;
enum : cpu_type_t { cputype = CPU_TYPE_X86 };
enum : int { segment_cmd = LC_SEGMENT };
static bool isObjCSegment(const char *segname) {
return segnameEquals(segname, "__OBJC");
}
static bool isImageInfoSection(const char *sectname) {
return sectnameEquals(sectname, "__image_info");
}
static bool countClasses(FileSlice file, section_t& sect,
int& classCount, int& classrefCount)
{
if (sectnameEquals(sect.sectname, "__cls_refs")) {
classrefCount += sect.size / 4;
}
else if (sectnameEquals(sect.sectname, "__module_info")) {
struct module_t {
uint32_t version;
uint32_t size;
uint32_t name; // not bound
uint32_t symtab; // not bound
};
size_t mod_count = sect.size / sizeof(module_t);
if (mod_count == 0) {
// no classes defined
} else if (mod_count > 1) {
// AppleScriptObjC apps only have one module.
// Disqualify this app by setting classCount to non-zero.
// We don't actually need an accurate count.
classCount = 1;
} else if (mod_count == 1) {
FileSlice moduleSlice;
if (!file.slice(sect.offset, sect.size, moduleSlice)) return NO;
module_t module;
if (!moduleSlice.pread(&module, sizeof(module))) return NO;
if (module.symtab) {
// AppleScriptObjC apps only have a module with no symtab.
// Disqualify this app by setting classCount to non-zero.
// We don't actually need an accurate count.
classCount = 1;
}
}
}
return YES;
}
};
struct Arch64 {
using mh_t = struct mach_header_64;
using segment_command_t = struct segment_command_64;
using section_t = struct section_64;
enum : cpu_type_t { cputype = CPU_TYPE_X86_64 };
enum : int { segment_cmd = LC_SEGMENT_64 };
static bool isObjCSegment(const char *segname) {
return
segnameEquals(segname, "__DATA") ||
segnameEquals(segname, "__DATA_CONST") ||
segnameEquals(segname, "__DATA_DIRTY");
}
static bool isImageInfoSection(const char *sectname) {
return sectnameEquals(sectname, "__objc_imageinfo");
}
static bool countClasses(FileSlice, section_t& sect,
int& classCount, int& classrefCount)
{
if (sectnameEquals(sect.sectname, "__objc_classlist")) {
classCount += sect.size / 8;
}
else if (sectnameEquals(sect.sectname, "__objc_classrefs")) {
classrefCount += sect.size / 8;
}
return YES;
}
};
#define SANE_HEADER_SIZE (32*1024)
template <typename Arch>
static int sliceRequiresGC(typename Arch::mh_t mh, FileSlice file)
{
// We assume there is only one arch per pointer size that can support GC.
// (i386 and x86_64)
if (mh.cputype != Arch::cputype) return 0;
// We only check the main executable.
if (mh.filetype != MH_EXECUTE) return 0;
// Look for ObjC segment.
// Look for AppleScriptObjC linkage.
FileSlice cmds;
if (!file.slice(sizeof(mh), mh.sizeofcmds, cmds)) return Error;
// Exception: Some AppleScriptObjC apps built for GC can run without GC.
// 1. executable defines no classes
// 2. executable references NSBundle only
// 3. executable links to AppleScriptObjC.framework
// Note that shouldRejectGCApp() also knows about this.
bool wantsGC = NO;
bool linksToAppleScriptObjC = NO;
int classCount = 0;
int classrefCount = 0;
// Disallow abusively-large executables that could hang this checker.
// dyld performs similar checks (MAX_MACH_O_HEADER_AND_LOAD_COMMANDS_SIZE)
if (mh.sizeofcmds > SANE_HEADER_SIZE) return Error;
if (mh.ncmds > mh.sizeofcmds / sizeof(struct load_command)) return Error;
for (uint32_t cmdindex = 0; cmdindex < mh.ncmds; cmdindex++) {
struct load_command lc;
if (!cmds.pread(&lc, sizeof(lc))) return Error;
// Disallow abusively-small load commands that could hang this checker.
// dyld performs a similar check.
if (lc.cmdsize < sizeof(lc)) return Error;
if (lc.cmd == LC_LOAD_DYLIB || lc.cmd == LC_LOAD_UPWARD_DYLIB ||
lc.cmd == LC_LOAD_WEAK_DYLIB || lc.cmd == LC_REEXPORT_DYLIB)
{
// Look for AppleScriptObjC linkage.
FileSlice dylibSlice;
if (!cmds.slice(0, lc.cmdsize, dylibSlice)) return Error;
struct dylib_command dylib;
if (!dylibSlice.pread(&dylib, sizeof(dylib))) return Error;
const char *asoFramework =
"/System/Library/Frameworks/AppleScriptObjC.framework"
"/Versions/A/AppleScriptObjC";
size_t asoLen = strlen(asoFramework);
FileSlice nameSlice;
if (dylibSlice.slice(dylib.dylib.name.offset, asoLen, nameSlice)) {
char name[asoLen];
if (!nameSlice.pread(name, asoLen)) return Error;
if (0 == memcmp(name, asoFramework, asoLen)) {
linksToAppleScriptObjC = YES;
}
}
}
else if (lc.cmd == Arch::segment_cmd) {
typename Arch::segment_command_t seg;
if (!cmds.pread(&seg, sizeof(seg))) return Error;
if (Arch::isObjCSegment(seg.segname)) {
// ObjC segment.
// Look for image info section.
// Look for class implementations and class references.
FileSlice sections;
if (!cmds.slice(0, seg.cmdsize, sections)) return Error;
if (!sections.advance(sizeof(seg))) return Error;
for (uint32_t segindex = 0; segindex < seg.nsects; segindex++) {
typename Arch::section_t sect;
if (!sections.pread(&sect, sizeof(sect))) return Error;
if (!Arch::isObjCSegment(sect.segname)) return Error;
if (!Arch::countClasses(file, sect,
classCount, classrefCount))
{
return Error;
}
if ((sect.flags & SECTION_TYPE) == S_REGULAR &&
Arch::isImageInfoSection(sect.sectname))
{
// ObjC image info section.
// Check its contents.
FileSlice section;
if (!file.slice(sect.offset, sect.size, section)) {
return Error;
}
// The subset of objc_image_info that was in use for GC.
struct {
uint32_t version;
uint32_t flags;
} ii;
if (!section.pread(&ii, sizeof(ii))) return Error;
if (ii.flags & (1<<1)) {
// App wants GC.
// Don't return yet because we need to
// check the AppleScriptObjC exception.
wantsGC = YES;
}
}
if (!sections.advance(sizeof(sect))) return Error;
}
}
}
if (!cmds.advance(lc.cmdsize)) return Error;
}
if (!wantsGC) {
// No GC bit set.
return WithoutGC;
}
else if (linksToAppleScriptObjC && classCount == 0 && classrefCount == 1) {
// Has GC bit but falls under the AppleScriptObjC exception.
return WithoutGC;
}
else {
// Has GC bit and is not AppleScriptObjC.
return WithGC;
}
}
static int sliceRequiresGC(FileSlice file)
{
// Read mach-o header.
struct mach_header_64 mh;
if (!file.pread(&mh, sizeof(mh))) return Error;
// Check header magic. We assume only host-endian slices can support GC.
switch (mh.magic) {
case MH_MAGIC:
return sliceRequiresGC<Arch32>(*(struct mach_header *)&mh, file);
case MH_MAGIC_64:
return sliceRequiresGC<Arch64>(mh, file);
default:
return WithoutGC;
}
}
// Returns 1 if any slice requires GC.
// Returns 0 if no slice requires GC.
// Returns -1 on any I/O or file format error.
int objc_appRequiresGC(int fd)
{
struct stat st;
if (fstat(fd, &st) < 0) return Error;
FileSlice file(fd, 0, st.st_size);
// Read fat header, if any.
struct fat_header fh;
if (! file.pread(&fh, sizeof(fh))) return Error;
int result;
if (OSSwapBigToHostInt32(fh.magic) == FAT_MAGIC) {
// Fat header.
size_t nfat_arch = OSSwapBigToHostInt32(fh.nfat_arch);
// Disallow abusively-large files that could hang this checker.
if (nfat_arch > SANE_HEADER_SIZE/sizeof(struct fat_arch)) return Error;
size_t fat_size;
if (umul_overflow(nfat_arch, sizeof(struct fat_arch), &fat_size)) {
return Error;
}
FileSlice archlist;
if (!file.slice(sizeof(fh), fat_size, archlist)) return Error;
result = WithoutGC;
for (size_t i = 0; i < nfat_arch; i++) {
struct fat_arch fa;
if (!archlist.pread(&fa, sizeof(fa))) return Error;
if (!archlist.advance(sizeof(fa))) return Error;
FileSlice thin;
if (!file.slice(OSSwapBigToHostInt32(fa.offset),
OSSwapBigToHostInt32(fa.size), thin))
{
return Error;
}
switch (sliceRequiresGC(thin)) {
case WithoutGC: break; // no change
case WithGC: if (result != Error) result = WithGC; break;
case Error: result = Error; break;
}
}
}
else {
// Thin header or not a header.
result = sliceRequiresGC(file);
}
return result;
}
// SUPPORT_GC_COMPAT
#endif
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