Merge remote-tracking branch 'lethosor/scan-vtables'

Author: lethosor

devel/scan-vtables.lua

@@ -0,0 +1,71 @@
+-- Scan and dump likely vtable addresses
+memscan = require('memscan')
+
+local osType = dfhack.getOSType()
+if osType ~= 'linux' then
+    qerror('unsupported OS: ' .. osType)
+end
+
+local df_ranges = {}
+for i,mem in ipairs(dfhack.internal.getMemRanges()) do
+    if mem.read and (
+        string.match(mem.name,'/dwarfort%.exe$')
+        or string.match(mem.name,'/dwarfort$')
+        or string.match(mem.name,'/Dwarf_Fortress$')
+        or string.match(mem.name,'Dwarf Fortress%.exe')
+        or string.match(mem.name,'/libg_src_lib.so$')
+    )
+    then
+        table.insert(df_ranges, mem)
+    end
+end
+
+function is_df_addr(a)
+    for _, mem in ipairs(df_ranges) do
+        if a >= mem.start_addr and a < mem.end_addr then
+            return true
+        end
+    end
+    return false
+end
+
+for _, range in ipairs(df_ranges) do
+    if (not range.read) or range.write or range.execute or range.name:match('g_src') then
+        goto next_range
+    end
+
+    local area = memscan.MemoryArea.new(range.start_addr, range.end_addr)
+    for i = 1, area.uintptr_t.count - 1 do
+        -- take every pointer-aligned value in memory mapped to the DF executable, and see if it is a valid vtable
+        -- start by following the logic in Process::doReadClassName() and ensure it doesn't crash
+        local vtable = area.uintptr_t:idx2addr(i)
+        local typeinfo = area.uintptr_t[i - 1]
+        if is_df_addr(typeinfo + 8) then
+            local typestring = df.reinterpret_cast('uintptr_t', typeinfo + 8)[0]
+            if is_df_addr(typestring) then
+                -- rule out false positives by checking that the vtable points to a table of valid pointers
+                -- TODO: check that the pointers are actually function pointers
+                local vlen = 0
+                while is_df_addr(vtable + (8*vlen)) and is_df_addr(df.reinterpret_cast('uintptr_t', vtable + (8*vlen))[0]) do
+                    vlen = vlen + 1
+                    break -- for now, any vtable with one valid pointer is valid enough
+                end
+                if vlen > 0 then
+                    -- some false positives can be ruled out if the string.char() call in read_c_string() throws an error for invalid characters
+                    local ok, name = pcall(function()
+                        return memscan.read_c_string(df.reinterpret_cast('char', typestring))
+                    end)
+                    if ok then
+                        -- GCC strips the "_Z" prefix from typeinfo names, so add it back
+                        local demangled_name = dfhack.internal.cxxDemangle('_Z' .. name)
+                        if demangled_name and not demangled_name:match('[<>]') and not demangled_name:match('^std::') then
+                            print(("<vtable-address name='%s' value='0x%x'/>"):format(demangled_name, vtable))
+                        end
+                    end
+                end
+            end
+        end
+
+    end
+    ::next_range::
+end

docs/devel/scan-vtables.rst

@@ -0,0 +1,24 @@
+devel/scan-vtables
+==================
+
+.. dfhack-tool::
+    :summary: Scan for and print likely vtable addresses.
+    :tags: dev
+
+.. warning::
+
+    THIS SCRIPT IS STRICTLY FOR DFHACK DEVELOPERS.
+
+    Running this script on a new DF version will NOT MAKE IT RUN CORRECTLY if
+    any data structures changed, thus possibly leading to CRASHES AND/OR
+    PERMANENT SAVE CORRUPTION.
+
+This script scans for likely vtables in memory pages mapped to the DF
+executable, and prints them in a format ready for inclusion in ``symbols.xml``
+
+Usage
+-----
+
+::
+
+    devel/scan-vtables