486 lines
14 KiB
C++
486 lines
14 KiB
C++
/*
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https://github.com/peterix/dfhack
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Copyright (c) 2009-2011 Petr Mrázek (peterix@gmail.com)
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This software is provided 'as-is', without any express or implied
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warranty. In no event will the authors be held liable for any
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damages arising from the use of this software.
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Permission is granted to anyone to use this software for any
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purpose, including commercial applications, and to alter it and
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redistribute it freely, subject to the following restrictions:
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1. The origin of this software must not be misrepresented; you must
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not claim that you wrote the original software. If you use this
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software in a product, an acknowledgment in the product documentation
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would be appreciated but is not required.
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2. Altered source versions must be plainly marked as such, and
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must not be misrepresented as being the original software.
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3. This notice may not be removed or altered from any source
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distribution.
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*/
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#include "Internal.h"
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#include <string>
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#include <vector>
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#include <map>
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#include "MemAccess.h"
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#include "Core.h"
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#include "VersionInfo.h"
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#include "VTableInterpose.h"
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#include "MiscUtils.h"
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using namespace DFHack;
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/*
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* Code for accessing method pointers directly. Very compiler-specific.
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*/
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#if defined(_MSC_VER)
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struct MSVC_MPTR {
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void *method;
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intptr_t this_shift;
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};
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static uint32_t *follow_jmp(void *ptr)
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{
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uint8_t *p = (uint8_t*)ptr;
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for (;;)
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{
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switch (*p)
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{
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case 0xE9:
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p += 5 + *(int32_t*)(p+1);
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break;
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case 0xEB:
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p += 2 + *(int8_t*)(p+1);
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break;
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default:
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return (uint32_t*)p;
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}
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}
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}
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bool DFHack::is_vmethod_pointer_(void *pptr)
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{
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auto pobj = (MSVC_MPTR*)pptr;
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if (!pobj->method) return false;
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// MSVC implements pointers to vmethods via thunks.
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// This expects that they all follow a very specific pattern.
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auto pval = follow_jmp(pobj->method);
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switch (pval[0]) {
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case 0x20FF018BU: // mov eax, [ecx]; jmp [eax]
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case 0x60FF018BU: // mov eax, [ecx]; jmp [eax+0x??]
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case 0xA0FF018BU: // mov eax, [ecx]; jmp [eax+0x????????]
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return true;
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default:
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return false;
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}
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}
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int DFHack::vmethod_pointer_to_idx_(void *pptr)
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{
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auto pobj = (MSVC_MPTR*)pptr;
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if (!pobj->method || pobj->this_shift != 0) return -1;
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auto pval = follow_jmp(pobj->method);
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switch (pval[0]) {
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case 0x20FF018BU: // mov eax, [ecx]; jmp [eax]
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return 0;
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case 0x60FF018BU: // mov eax, [ecx]; jmp [eax+0x??]
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return ((int8_t)pval[1])/sizeof(void*);
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case 0xA0FF018BU: // mov eax, [ecx]; jmp [eax+0x????????]
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return ((int32_t)pval[1])/sizeof(void*);
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default:
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return -1;
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}
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}
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void* DFHack::method_pointer_to_addr_(void *pptr)
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{
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if (is_vmethod_pointer_(pptr)) return NULL;
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auto pobj = (MSVC_MPTR*)pptr;
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return pobj->method;
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}
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void DFHack::addr_to_method_pointer_(void *pptr, void *addr)
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{
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auto pobj = (MSVC_MPTR*)pptr;
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pobj->method = addr;
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pobj->this_shift = 0;
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}
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#elif defined(__GXX_ABI_VERSION)
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struct GCC_MPTR {
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intptr_t method;
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intptr_t this_shift;
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};
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bool DFHack::is_vmethod_pointer_(void *pptr)
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{
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auto pobj = (GCC_MPTR*)pptr;
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return (pobj->method & 1) != 0;
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}
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int DFHack::vmethod_pointer_to_idx_(void *pptr)
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{
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auto pobj = (GCC_MPTR*)pptr;
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if ((pobj->method & 1) == 0 || pobj->this_shift != 0)
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return -1;
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return (pobj->method-1)/sizeof(void*);
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}
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void* DFHack::method_pointer_to_addr_(void *pptr)
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{
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auto pobj = (GCC_MPTR*)pptr;
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if ((pobj->method & 1) != 0 || pobj->this_shift != 0)
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return NULL;
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return (void*)pobj->method;
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}
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void DFHack::addr_to_method_pointer_(void *pptr, void *addr)
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{
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auto pobj = (GCC_MPTR*)pptr;
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pobj->method = (intptr_t)addr;
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pobj->this_shift = 0;
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}
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#else
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#error Unknown compiler type
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#endif
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void *virtual_identity::get_vmethod_ptr(int idx)
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{
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assert(idx >= 0);
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void **vtable = (void**)vtable_ptr;
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if (!vtable) return NULL;
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return vtable[idx];
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}
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bool virtual_identity::set_vmethod_ptr(int idx, void *ptr)
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{
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assert(idx >= 0);
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void **vtable = (void**)vtable_ptr;
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if (!vtable) return NULL;
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return Core::getInstance().p->patchMemory(&vtable[idx], &ptr, sizeof(void*));
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}
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/*
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VMethod interposing data structures.
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In order to properly support adding and removing hooks,
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it is necessary to track them. This is what this class
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is for. The task is further complicated by propagating
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hooks to child classes that use exactly the same original
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vmethod implementation.
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Every applied link contains in the saved_chain field a
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pointer to the next vmethod body that should be called
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by the hook the link represents. This is the actual
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control flow structure that needs to be maintained.
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There also are connections between link objects themselves,
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which constitute the bookkeeping for doing that. Finally,
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every link is associated with a fixed virtual_identity host,
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which represents the point in the class hierarchy where
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the hook is applied.
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When there are no subclasses (i.e. only one host), the
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structures look like this:
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+--------------+ +------------+
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| link1 |-next------->| link2 |-next=NULL
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|s_c: original |<-------prev-|s_c: $link1 |<--+
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+--------------+ +------------+ |
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host->interpose_list[vmethod_idx] ------+
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vtable: $link2
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The original vtable entry is stored in the saved_chain of the
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first link. The interpose_list map points to the last one.
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The hooks are called in order: link2 -> link1 -> original.
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When there are subclasses that use the same vmethod, but don't
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hook it, the topmost link gets a set of the child_hosts, and
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the hosts have the link added to their interpose_list:
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+--------------+ +----------------+
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| link0 @host0 |<--+-interpose_list-| host1 |
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| |-child_hosts-+----->| vtable: $link |
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+--------------+ | | +----------------+
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| |
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+-interpose_list-| host2 |
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+----->| vtable: $link |
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+----------------+
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When a child defines its own hook, the child_hosts link is
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severed and replaced with a child_next pointer to the new
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hook. The hook still points back the chain with prev.
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All child links to subclasses of host2 are migrated from
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link1 to link2.
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+--------------+-next=NULL +--------------+-next=NULL
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| link1 @host1 |-child_next------->| link2 @host2 |-child_*--->subclasses
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| |<-------------prev-|s_c: $link1 |
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+--------------+<-------+ +--------------+<-------+
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+--------------+ | +--------------+ |
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| host1 |-i_list-+ | host2 |-i_list-+
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|vtable: $link1| |vtable: $link2|
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+--------------+ +--------------+
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*/
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void VMethodInterposeLinkBase::set_chain(void *chain)
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{
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saved_chain = chain;
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addr_to_method_pointer_(chain_mptr, chain);
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}
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VMethodInterposeLinkBase::VMethodInterposeLinkBase(virtual_identity *host, int vmethod_idx, void *interpose_method, void *chain_mptr)
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: host(host), vmethod_idx(vmethod_idx), interpose_method(interpose_method), chain_mptr(chain_mptr),
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applied(false), saved_chain(NULL), next(NULL), prev(NULL)
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{
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if (vmethod_idx < 0 || interpose_method == NULL)
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{
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fprintf(stderr, "Bad VMethodInterposeLinkBase arguments: %d %08x\n",
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vmethod_idx, unsigned(interpose_method));
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fflush(stderr);
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abort();
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}
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}
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VMethodInterposeLinkBase::~VMethodInterposeLinkBase()
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{
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if (is_applied())
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remove();
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}
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VMethodInterposeLinkBase *VMethodInterposeLinkBase::get_first_interpose(virtual_identity *id)
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{
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auto item = id->interpose_list[vmethod_idx];
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if (!item)
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return NULL;
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if (item->host != id)
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return NULL;
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while (item->prev && item->prev->host == id)
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item = item->prev;
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return item;
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}
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void VMethodInterposeLinkBase::find_child_hosts(virtual_identity *cur, void *vmptr)
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{
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auto &children = cur->getChildren();
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for (size_t i = 0; i < children.size(); i++)
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{
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auto child = static_cast<virtual_identity*>(children[i]);
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auto base = get_first_interpose(child);
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if (base)
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{
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assert(base->prev == NULL);
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if (base->saved_chain != vmptr)
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continue;
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child_next.insert(base);
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}
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else
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{
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void *cptr = child->get_vmethod_ptr(vmethod_idx);
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if (cptr != vmptr)
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continue;
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child_hosts.insert(child);
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find_child_hosts(child, vmptr);
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}
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}
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}
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void VMethodInterposeLinkBase::on_host_delete(virtual_identity *from)
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{
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if (from == host)
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{
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// When in own host, fully delete
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remove();
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}
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else
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{
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// Otherwise, drop the link to that child:
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assert(child_hosts.count(from) != 0 &&
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from->interpose_list[vmethod_idx] == this);
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// Find and restore the original vmethod ptr
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auto last = this;
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while (last->prev) last = last->prev;
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from->set_vmethod_ptr(vmethod_idx, last->saved_chain);
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// Unlink the chains
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child_hosts.erase(from);
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from->interpose_list[vmethod_idx] = NULL;
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}
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}
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bool VMethodInterposeLinkBase::apply(bool enable)
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{
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if (!enable)
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{
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remove();
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return true;
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}
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if (is_applied())
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return true;
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if (!host->vtable_ptr)
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return false;
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// Retrieve the current vtable entry
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void *old_ptr = host->get_vmethod_ptr(vmethod_idx);
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VMethodInterposeLinkBase *old_link = host->interpose_list[vmethod_idx];
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assert(old_ptr != NULL && (!old_link || old_link->interpose_method == old_ptr));
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// Apply the new method ptr
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set_chain(old_ptr);
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if (!host->set_vmethod_ptr(vmethod_idx, interpose_method))
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{
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set_chain(NULL);
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return false;
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}
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// Push the current link into the home host
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applied = true;
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host->interpose_list[vmethod_idx] = this;
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prev = old_link;
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child_hosts.clear();
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child_next.clear();
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if (old_link && old_link->host == host)
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{
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// If the old link is home, just push into the plain chain
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assert(old_link->next == NULL);
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old_link->next = this;
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// Child links belong to the topmost local entry
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child_hosts.swap(old_link->child_hosts);
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child_next.swap(old_link->child_next);
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}
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else
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{
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// If creating a new local chain, find children with same vmethod
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find_child_hosts(host, old_ptr);
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if (old_link)
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{
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// Enter the child chain set
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assert(old_link->child_hosts.count(host));
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old_link->child_hosts.erase(host);
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old_link->child_next.insert(this);
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// Subtract our own children from the parent's sets
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for (auto it = child_next.begin(); it != child_next.end(); ++it)
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old_link->child_next.erase(*it);
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for (auto it = child_hosts.begin(); it != child_hosts.end(); ++it)
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old_link->child_hosts.erase(*it);
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}
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}
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// Chain subclass hooks
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for (auto it = child_next.begin(); it != child_next.end(); ++it)
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{
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auto nlink = *it;
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assert(nlink->saved_chain == old_ptr && nlink->prev == old_link);
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nlink->set_chain(interpose_method);
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nlink->prev = this;
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}
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// Chain passive subclass hosts
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for (auto it = child_hosts.begin(); it != child_hosts.end(); ++it)
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{
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auto nhost = *it;
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assert(nhost->interpose_list[vmethod_idx] == old_link);
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nhost->set_vmethod_ptr(vmethod_idx, interpose_method);
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nhost->interpose_list[vmethod_idx] = this;
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}
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return true;
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}
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void VMethodInterposeLinkBase::remove()
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{
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if (!is_applied())
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return;
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// Remove the link from prev to this
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if (prev)
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{
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if (prev->host == host)
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prev->next = next;
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else
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{
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prev->child_next.erase(this);
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if (next)
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prev->child_next.insert(next);
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else
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prev->child_hosts.insert(host);
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}
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}
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if (next)
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{
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next->set_chain(saved_chain);
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next->prev = prev;
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assert(child_next.empty() && child_hosts.empty());
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}
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else
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{
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// Remove from the list in the identity and vtable
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host->interpose_list[vmethod_idx] = prev;
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host->set_vmethod_ptr(vmethod_idx, saved_chain);
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for (auto it = child_next.begin(); it != child_next.end(); ++it)
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{
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auto nlink = *it;
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assert(nlink->saved_chain == interpose_method && nlink->prev == this);
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nlink->set_chain(saved_chain);
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nlink->prev = prev;
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if (prev)
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prev->child_next.insert(nlink);
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}
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for (auto it = child_hosts.begin(); it != child_hosts.end(); ++it)
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{
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auto nhost = *it;
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assert(nhost->interpose_list[vmethod_idx] == this);
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nhost->interpose_list[vmethod_idx] = prev;
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nhost->set_vmethod_ptr(vmethod_idx, saved_chain);
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if (prev)
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prev->child_hosts.insert(nhost);
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}
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}
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applied = false;
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prev = next = NULL;
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child_next.clear();
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child_hosts.clear();
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set_chain(NULL);
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}
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