mirror of
https://github.com/rn10950/RetroZilla.git
synced 2024-08-30 01:20:43 +02:00
196 lines
4.8 KiB
C++
196 lines
4.8 KiB
C++
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/*
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typeinfo.cpp
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Speculatively use RTTI on a random object. If it contains a pointer at offset 0
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that is in the current process' address space, and that so on, then attempt to
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use C++ RTTI's typeid operation to obtain the name of the type.
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by Patrick C. Beard.
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*/
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#include <typeinfo>
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#include <ctype.h>
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#include "gcconfig.h"
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extern "C" const char* getTypeName(void* ptr);
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class IUnknown {
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public:
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virtual long QueryInterface() = 0;
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virtual long AddRef() = 0;
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virtual long Release() = 0;
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};
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#if defined(MACOS)
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#include <Processes.h>
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class AddressSpace {
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public:
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AddressSpace();
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Boolean contains(void* ptr);
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private:
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ProcessInfoRec mInfo;
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};
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AddressSpace::AddressSpace()
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{
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ProcessSerialNumber psn = { 0, kCurrentProcess };
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mInfo.processInfoLength = sizeof(mInfo);
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::GetProcessInformation(&psn, &mInfo);
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}
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Boolean AddressSpace::contains(void* ptr)
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{
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UInt32 start = UInt32(mInfo.processLocation);
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return (UInt32(ptr) >= start && UInt32(ptr) < (start + mInfo.processSize));
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}
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const char* getTypeName(void* ptr)
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{
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// construct only one of these per process.
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static AddressSpace space;
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// sanity check the vtable pointer, before trying to use RTTI on the object.
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void** vt = *(void***)ptr;
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if (vt && !(unsigned(vt) & 0x3) && space.contains(vt) && space.contains(*vt)) {
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IUnknown* u = static_cast<IUnknown*>(ptr);
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const char* type = typeid(*u).name();
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// make sure it looks like a C++ identifier.
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if (type && (isalnum(type[0]) || type[0] == '_'))
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return type;
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}
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return "void*";
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}
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#endif
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#if defined(LINUX)
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#include <signal.h>
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#include <setjmp.h>
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static jmp_buf context;
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static void handler(int signum)
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{
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longjmp(context, signum);
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}
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#define attempt() setjmp(context)
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class Signaller {
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public:
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Signaller(int signum);
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~Signaller();
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private:
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typedef void (*handler_t) (int signum);
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int mSignal;
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handler_t mOldHandler;
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};
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Signaller::Signaller(int signum)
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: mSignal(signum), mOldHandler(signal(signum, &handler))
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{
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}
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Signaller::~Signaller()
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{
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signal(mSignal, mOldHandler);
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}
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// The following are pointers that bamboozle our otherwise feeble
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// attempts to "safely" collect type names.
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//
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// XXX this kind of sucks because it means that anyone trying to use
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// this without NSPR will get unresolved symbols when this library
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// loads. It's also not very extensible. Oh well: FIX ME!
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extern "C" {
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// from nsprpub/pr/src/io/priometh.c (libnspr4.so)
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extern void* _pr_faulty_methods;
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};
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static inline int
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sanity_check_vtable_i386(void** vt)
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{
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// Now that we're "safe" inside the signal handler, we can
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// start poking around. If we're really an object with
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// RTTI, then the second entry in the vtable should point
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// to a function.
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//
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// Let's see if the second entry:
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//
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// 1) looks like a 4-byte aligned pointer
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//
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// 2) points to something that looks like the following
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// i386 instructions:
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//
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// 55 push %ebp
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// 89e5 mov %esp,%ebp
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// 53 push %ebx
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//
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// or
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//
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// 55 push %ebp
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// 89e5 mov %esp,%ebp
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// 56 push %esi
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//
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// (which is the standard function prologue generated
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// by egcs, plus a ``signature'' instruction that appears
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// in the typeid() function's implementation).
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unsigned char** fp1 = reinterpret_cast<unsigned char**>(vt) + 1;
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// Does it look like an address?
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unsigned char* ip = *fp1;
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if ((unsigned(ip) & 3) != 0)
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return 0;
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// Does it look like it refers to the standard prologue?
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static unsigned char prologue[] = { 0x55, 0x89, 0xE5 };
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for (unsigned i = 0; i < sizeof(prologue); ++i)
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if (*ip++ != prologue[i])
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return 0;
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// Is the next instruction a `push %ebx' or `push %esi'?
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return (*ip == 0x53 || *ip == 0x56);
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}
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static inline int
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sanity_check_vtable_ppc(void** vt)
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{
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// XXX write me!
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return 1;
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}
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#if defined(__i386)
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# define SANITY_CHECK_VTABLE(vt) (sanity_check_vtable_i386(vt))
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#elif defined(PPC)
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# define SANITY_CHECK_VTABLE(vt) (sanity_check_vtable_ppc(vt))
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#else
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# define SANITY_CHECK_VTABLE(vt) (1)
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#endif
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const char* getTypeName(void* ptr)
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{
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// sanity check the vtable pointer, before trying to use RTTI on the object.
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void** vt = *(void***)ptr;
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if (vt && !(unsigned(vt) & 3) && (vt != &_pr_faulty_methods)) {
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Signaller s1(SIGSEGV);
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if (attempt() == 0) {
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if (SANITY_CHECK_VTABLE(vt)) {
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// Looks like a function: what the hell, let's call it.
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IUnknown* u = static_cast<IUnknown*>(ptr);
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const char* type = typeid(*u).name();
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// EGCS seems to prefix a length string.
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while (isdigit(*type)) ++type;
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return type;
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}
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}
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}
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return "void*";
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}
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#endif
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