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-rw-r--r--library/VTableInterpose.cpp292
1 files changed, 263 insertions, 29 deletions
diff --git a/library/VTableInterpose.cpp b/library/VTableInterpose.cpp
index 3725ccba..583ef518 100644
--- a/library/VTableInterpose.cpp
+++ b/library/VTableInterpose.cpp
@@ -48,6 +48,26 @@ struct MSVC_MPTR {
intptr_t this_shift;
};
+static uint32_t *follow_jmp(void *ptr)
+{
+ uint8_t *p = (uint8_t*)ptr;
+
+ for (;;)
+ {
+ switch (*p)
+ {
+ case 0xE9:
+ p += 5 + *(int32_t*)(p+1);
+ break;
+ case 0xEB:
+ p += 2 + *(int8_t*)(p+1);
+ break;
+ default:
+ return (uint32_t*)p;
+ }
+ }
+}
+
bool DFHack::is_vmethod_pointer_(void *pptr)
{
auto pobj = (MSVC_MPTR*)pptr;
@@ -55,7 +75,7 @@ bool DFHack::is_vmethod_pointer_(void *pptr)
// MSVC implements pointers to vmethods via thunks.
// This expects that they all follow a very specific pattern.
- auto pval = (unsigned*)pobj->method;
+ auto pval = follow_jmp(pobj->method);
switch (pval[0]) {
case 0x20FF018BU: // mov eax, [ecx]; jmp [eax]
case 0x60FF018BU: // mov eax, [ecx]; jmp [eax+0x??]
@@ -71,7 +91,7 @@ int DFHack::vmethod_pointer_to_idx_(void *pptr)
auto pobj = (MSVC_MPTR*)pptr;
if (!pobj->method || pobj->this_shift != 0) return -1;
- auto pval = (unsigned*)pobj->method;
+ auto pval = follow_jmp(pobj->method);
switch (pval[0]) {
case 0x20FF018BU: // mov eax, [ecx]; jmp [eax]
return 0;
@@ -154,6 +174,73 @@ bool virtual_identity::set_vmethod_ptr(int idx, void *ptr)
return Core::getInstance().p->patchMemory(&vtable[idx], &ptr, sizeof(void*));
}
+/*
+ VMethod interposing data structures.
+
+ In order to properly support adding and removing hooks,
+ it is necessary to track them. This is what this class
+ is for. The task is further complicated by propagating
+ hooks to child classes that use exactly the same original
+ vmethod implementation.
+
+ Every applied link contains in the saved_chain field a
+ pointer to the next vmethod body that should be called
+ by the hook the link represents. This is the actual
+ control flow structure that needs to be maintained.
+
+ There also are connections between link objects themselves,
+ which constitute the bookkeeping for doing that. Finally,
+ every link is associated with a fixed virtual_identity host,
+ which represents the point in the class hierarchy where
+ the hook is applied.
+
+ When there are no subclasses (i.e. only one host), the
+ structures look like this:
+
+ +--------------+ +------------+
+ | link1 |-next------->| link2 |-next=NULL
+ |s_c: original |<-------prev-|s_c: $link1 |<--+
+ +--------------+ +------------+ |
+ |
+ host->interpose_list[vmethod_idx] ------+
+ vtable: $link2
+
+ The original vtable entry is stored in the saved_chain of the
+ first link. The interpose_list map points to the last one.
+ The hooks are called in order: link2 -> link1 -> original.
+
+ When there are subclasses that use the same vmethod, but don't
+ hook it, the topmost link gets a set of the child_hosts, and
+ the hosts have the link added to their interpose_list:
+
+ +--------------+ +----------------+
+ | link0 @host0 |<--+-interpose_list-| host1 |
+ | |-child_hosts-+----->| vtable: $link |
+ +--------------+ | | +----------------+
+ | |
+ | | +----------------+
+ +-interpose_list-| host2 |
+ +----->| vtable: $link |
+ +----------------+
+
+ When a child defines its own hook, the child_hosts link is
+ severed and replaced with a child_next pointer to the new
+ hook. The hook still points back the chain with prev.
+ All child links to subclasses of host2 are migrated from
+ link1 to link2.
+
+ +--------------+-next=NULL +--------------+-next=NULL
+ | link1 @host1 |-child_next------->| link2 @host2 |-child_*--->subclasses
+ | |<-------------prev-|s_c: $link1 |
+ +--------------+<-------+ +--------------+<-------+
+ | |
+ +--------------+ | +--------------+ |
+ | host1 |-i_list-+ | host2 |-i_list-+
+ |vtable: $link1| |vtable: $link2|
+ +--------------+ +--------------+
+
+ */
+
void VMethodInterposeLinkBase::set_chain(void *chain)
{
saved_chain = chain;
@@ -162,7 +249,7 @@ void VMethodInterposeLinkBase::set_chain(void *chain)
VMethodInterposeLinkBase::VMethodInterposeLinkBase(virtual_identity *host, int vmethod_idx, void *interpose_method, void *chain_mptr)
: host(host), vmethod_idx(vmethod_idx), interpose_method(interpose_method), chain_mptr(chain_mptr),
- saved_chain(NULL), next(NULL), prev(NULL)
+ applied(false), saved_chain(NULL), next(NULL), prev(NULL)
{
if (vmethod_idx < 0 || interpose_method == NULL)
{
@@ -179,8 +266,83 @@ VMethodInterposeLinkBase::~VMethodInterposeLinkBase()
remove();
}
-bool VMethodInterposeLinkBase::apply()
+VMethodInterposeLinkBase *VMethodInterposeLinkBase::get_first_interpose(virtual_identity *id)
+{
+ auto item = id->interpose_list[vmethod_idx];
+ if (!item)
+ return NULL;
+
+ if (item->host != id)
+ return NULL;
+ while (item->prev && item->prev->host == id)
+ item = item->prev;
+
+ return item;
+}
+
+void VMethodInterposeLinkBase::find_child_hosts(virtual_identity *cur, void *vmptr)
{
+ auto &children = cur->getChildren();
+
+ for (size_t i = 0; i < children.size(); i++)
+ {
+ auto child = static_cast<virtual_identity*>(children[i]);
+ auto base = get_first_interpose(child);
+
+ if (base)
+ {
+ assert(base->prev == NULL);
+
+ if (base->saved_chain != vmptr)
+ continue;
+
+ child_next.insert(base);
+ }
+ else
+ {
+ void *cptr = child->get_vmethod_ptr(vmethod_idx);
+ if (cptr != vmptr)
+ continue;
+
+ child_hosts.insert(child);
+ find_child_hosts(child, vmptr);
+ }
+ }
+}
+
+void VMethodInterposeLinkBase::on_host_delete(virtual_identity *from)
+{
+ if (from == host)
+ {
+ // When in own host, fully delete
+ remove();
+ }
+ else
+ {
+ // Otherwise, drop the link to that child:
+ assert(child_hosts.count(from) != 0 &&
+ from->interpose_list[vmethod_idx] == this);
+
+ // Find and restore the original vmethod ptr
+ auto last = this;
+ while (last->prev) last = last->prev;
+
+ from->set_vmethod_ptr(vmethod_idx, last->saved_chain);
+
+ // Unlink the chains
+ child_hosts.erase(from);
+ from->interpose_list[vmethod_idx] = NULL;
+ }
+}
+
+bool VMethodInterposeLinkBase::apply(bool enable)
+{
+ if (!enable)
+ {
+ remove();
+ return true;
+ }
+
if (is_applied())
return true;
if (!host->vtable_ptr)
@@ -188,33 +350,73 @@ bool VMethodInterposeLinkBase::apply()
// Retrieve the current vtable entry
void *old_ptr = host->get_vmethod_ptr(vmethod_idx);
- assert(old_ptr != NULL);
-
- // Check if there are other interpose entries for the same slot
- VMethodInterposeLinkBase *old_link = NULL;
+ VMethodInterposeLinkBase *old_link = host->interpose_list[vmethod_idx];
- for (int i = host->interpose_list.size()-1; i >= 0; i--)
- {
- if (host->interpose_list[i]->vmethod_idx != vmethod_idx)
- continue;
-
- old_link = host->interpose_list[i];
- assert(old_link->next == NULL && old_ptr == old_link->interpose_method);
- break;
- }
+ assert(old_ptr != NULL && (!old_link || old_link->interpose_method == old_ptr));
// Apply the new method ptr
+ set_chain(old_ptr);
+
if (!host->set_vmethod_ptr(vmethod_idx, interpose_method))
+ {
+ set_chain(NULL);
return false;
+ }
- set_chain(old_ptr);
- host->interpose_list.push_back(this);
+ // Push the current link into the home host
+ applied = true;
+ host->interpose_list[vmethod_idx] = this;
+ prev = old_link;
- // Link into the chain if any
- if (old_link)
+ child_hosts.clear();
+ child_next.clear();
+
+ if (old_link && old_link->host == host)
{
+ // If the old link is home, just push into the plain chain
+ assert(old_link->next == NULL);
old_link->next = this;
- prev = old_link;
+
+ // Child links belong to the topmost local entry
+ child_hosts.swap(old_link->child_hosts);
+ child_next.swap(old_link->child_next);
+ }
+ else
+ {
+ // If creating a new local chain, find children with same vmethod
+ find_child_hosts(host, old_ptr);
+
+ if (old_link)
+ {
+ // Enter the child chain set
+ assert(old_link->child_hosts.count(host));
+ old_link->child_hosts.erase(host);
+ old_link->child_next.insert(this);
+
+ // Subtract our own children from the parent's sets
+ for (auto it = child_next.begin(); it != child_next.end(); ++it)
+ old_link->child_next.erase(*it);
+ for (auto it = child_hosts.begin(); it != child_hosts.end(); ++it)
+ old_link->child_hosts.erase(*it);
+ }
+ }
+
+ // Chain subclass hooks
+ for (auto it = child_next.begin(); it != child_next.end(); ++it)
+ {
+ auto nlink = *it;
+ assert(nlink->saved_chain == old_ptr && nlink->prev == old_link);
+ nlink->set_chain(interpose_method);
+ nlink->prev = this;
+ }
+
+ // Chain passive subclass hosts
+ for (auto it = child_hosts.begin(); it != child_hosts.end(); ++it)
+ {
+ auto nhost = *it;
+ assert(nhost->interpose_list[vmethod_idx] == old_link);
+ nhost->set_vmethod_ptr(vmethod_idx, interpose_method);
+ nhost->interpose_list[vmethod_idx] = this;
}
return true;
@@ -225,25 +427,57 @@ void VMethodInterposeLinkBase::remove()
if (!is_applied())
return;
- // Remove from the list in the identity
- for (int i = host->interpose_list.size()-1; i >= 0; i--)
- if (host->interpose_list[i] == this)
- vector_erase_at(host->interpose_list, i);
-
- // Remove from the chain
+ // Remove the link from prev to this
if (prev)
- prev->next = next;
+ {
+ if (prev->host == host)
+ prev->next = next;
+ else
+ {
+ prev->child_next.erase(this);
+
+ if (next)
+ prev->child_next.insert(next);
+ }
+ }
if (next)
{
next->set_chain(saved_chain);
next->prev = prev;
+
+ assert(child_next.empty() && child_hosts.empty());
}
else
{
+ // Remove from the list in the identity and vtable
+ host->interpose_list[vmethod_idx] = prev;
host->set_vmethod_ptr(vmethod_idx, saved_chain);
+
+ for (auto it = child_next.begin(); it != child_next.end(); ++it)
+ {
+ auto nlink = *it;
+ assert(nlink->saved_chain == interpose_method && nlink->prev == this);
+ nlink->set_chain(saved_chain);
+ nlink->prev = prev;
+ if (prev)
+ prev->child_next.insert(nlink);
+ }
+
+ for (auto it = child_hosts.begin(); it != child_hosts.end(); ++it)
+ {
+ auto nhost = *it;
+ assert(nhost->interpose_list[vmethod_idx] == this);
+ nhost->interpose_list[vmethod_idx] = prev;
+ nhost->set_vmethod_ptr(vmethod_idx, saved_chain);
+ if (prev)
+ prev->child_hosts.insert(nhost);
+ }
}
+ applied = false;
prev = next = NULL;
+ child_next.clear();
+ child_hosts.clear();
set_chain(NULL);
}