----------------------------------------------------------------------------- -- -- GHC Extra object linking code -- -- (c) The GHC Team 2017 -- ----------------------------------------------------------------------------- module GHC.Linker.ExtraObj ( mkExtraObj , mkExtraObjToLinkIntoBinary , mkNoteObjsToLinkIntoBinary , checkLinkInfo , getLinkInfo , getCompilerInfo , ghcLinkInfoSectionName , ghcLinkInfoNoteName , platformSupportsSavingLinkOpts , haveRtsOptsFlags ) where import GHC.Prelude import GHC.Platform import GHC.Unit import GHC.Unit.Env import GHC.Unit.State import GHC.Utils.Asm import GHC.Utils.Error import GHC.Utils.Misc import GHC.Utils.Outputable as Outputable import GHC.Driver.Session import GHC.Driver.Ppr import GHC.Types.SrcLoc ( noSrcSpan ) import qualified GHC.Data.ShortText as ST import GHC.SysTools.Elf import GHC.SysTools.FileCleanup import GHC.SysTools.Tasks import GHC.SysTools.Info import GHC.Linker.Unit import Control.Monad.IO.Class import Control.Monad import Data.Maybe mkExtraObj :: DynFlags -> UnitState -> Suffix -> String -> IO FilePath mkExtraObj dflags unit_state extn xs = do cFile <- newTempName dflags TFL_CurrentModule extn oFile <- newTempName dflags TFL_GhcSession "o" writeFile cFile xs ccInfo <- liftIO $ getCompilerInfo dflags runCc Nothing dflags ([Option "-c", FileOption "" cFile, Option "-o", FileOption "" oFile] ++ if extn /= "s" then cOpts else asmOpts ccInfo) return oFile where -- Pass a different set of options to the C compiler depending one whether -- we're compiling C or assembler. When compiling C, we pass the usual -- set of include directories and PIC flags. cOpts = map Option (picCCOpts dflags) ++ map (FileOption "-I" . ST.unpack) (unitIncludeDirs $ unsafeLookupUnit unit_state rtsUnit) -- When compiling assembler code, we drop the usual C options, and if the -- compiler is Clang, we add an extra argument to tell Clang to ignore -- unused command line options. See trac #11684. asmOpts ccInfo = if any (ccInfo ==) [Clang, AppleClang, AppleClang51] then [Option "-Qunused-arguments"] else [] -- When linking a binary, we need to create a C main() function that -- starts everything off. This used to be compiled statically as part -- of the RTS, but that made it hard to change the -rtsopts setting, -- so now we generate and compile a main() stub as part of every -- binary and pass the -rtsopts setting directly to the RTS (#5373) -- -- On Windows, when making a shared library we also may need a DllMain. -- mkExtraObjToLinkIntoBinary :: DynFlags -> UnitState -> IO FilePath mkExtraObjToLinkIntoBinary dflags unit_state = do when (gopt Opt_NoHsMain dflags && haveRtsOptsFlags dflags) $ putLogMsg dflags NoReason SevInfo noSrcSpan $ withPprStyle defaultUserStyle (text "Warning: -rtsopts and -with-rtsopts have no effect with -no-hs-main." $$ text " Call hs_init_ghc() from your main() function to set these options.") mkExtraObj dflags unit_state "c" (showSDoc dflags main) where main | gopt Opt_NoHsMain dflags = Outputable.empty | otherwise = case ghcLink dflags of LinkDynLib -> if platformOS (targetPlatform dflags) == OSMinGW32 then dllMain else Outputable.empty _ -> exeMain exeMain = vcat [ text "#include ", text "extern StgClosure ZCMain_main_closure;", text "int main(int argc, char *argv[])", char '{', text " RtsConfig __conf = defaultRtsConfig;", text " __conf.rts_opts_enabled = " <> text (show (rtsOptsEnabled dflags)) <> semi, text " __conf.rts_opts_suggestions = " <> text (if rtsOptsSuggestions dflags then "true" else "false") <> semi, text "__conf.keep_cafs = " <> text (if gopt Opt_KeepCAFs dflags then "true" else "false") <> semi, case rtsOpts dflags of Nothing -> Outputable.empty Just opts -> text " __conf.rts_opts= " <> text (show opts) <> semi, text " __conf.rts_hs_main = true;", text " return hs_main(argc,argv,&ZCMain_main_closure,__conf);", char '}', char '\n' -- final newline, to keep gcc happy ] dllMain = vcat [ text "#include ", text "#include ", text "#include ", char '\n', text "bool", text "WINAPI", text "DllMain ( HINSTANCE hInstance STG_UNUSED", text " , DWORD reason STG_UNUSED", text " , LPVOID reserved STG_UNUSED", text " )", text "{", text " return true;", text "}", char '\n' -- final newline, to keep gcc happy ] -- Write out the link info section into a new assembly file. Previously -- this was included as inline assembly in the main.c file but this -- is pretty fragile. gas gets upset trying to calculate relative offsets -- that span the .note section (notably .text) when debug info is present mkNoteObjsToLinkIntoBinary :: DynFlags -> UnitEnv -> [UnitId] -> IO [FilePath] mkNoteObjsToLinkIntoBinary dflags unit_env dep_packages = do link_info <- getLinkInfo dflags unit_env dep_packages if (platformSupportsSavingLinkOpts (platformOS platform )) then fmap (:[]) $ mkExtraObj dflags unit_state "s" (showSDoc dflags (link_opts link_info)) else return [] where unit_state = ue_units unit_env platform = ue_platform unit_env link_opts info = hcat [ -- "link info" section (see Note [LinkInfo section]) makeElfNote platform ghcLinkInfoSectionName ghcLinkInfoNoteName 0 info -- ALL generated assembly must have this section to disable -- executable stacks. See also -- "GHC.CmmToAsm" for another instance -- where we need to do this. , if platformHasGnuNonexecStack platform then text ".section .note.GNU-stack,\"\"," <> sectionType platform "progbits" <> char '\n' else Outputable.empty ] -- | Return the "link info" string -- -- See Note [LinkInfo section] getLinkInfo :: DynFlags -> UnitEnv -> [UnitId] -> IO String getLinkInfo dflags unit_env dep_packages = do package_link_opts <- getUnitLinkOpts dflags unit_env dep_packages pkg_frameworks <- if not (platformUsesFrameworks (ue_platform unit_env)) then return [] else do ps <- mayThrowUnitErr (preloadUnitsInfo' unit_env dep_packages) return (collectFrameworks ps) let link_info = ( package_link_opts , pkg_frameworks , rtsOpts dflags , rtsOptsEnabled dflags , gopt Opt_NoHsMain dflags , map showOpt (ldInputs dflags) , getOpts dflags opt_l ) return (show link_info) platformSupportsSavingLinkOpts :: OS -> Bool platformSupportsSavingLinkOpts os | os == OSSolaris2 = False -- see #5382 | otherwise = osElfTarget os -- See Note [LinkInfo section] ghcLinkInfoSectionName :: String ghcLinkInfoSectionName = ".debug-ghc-link-info" -- if we use the ".debug" prefix, then strip will strip it by default -- Identifier for the note (see Note [LinkInfo section]) ghcLinkInfoNoteName :: String ghcLinkInfoNoteName = "GHC link info" -- Returns 'False' if it was, and we can avoid linking, because the -- previous binary was linked with "the same options". checkLinkInfo :: DynFlags -> UnitEnv -> [UnitId] -> FilePath -> IO Bool checkLinkInfo dflags unit_env pkg_deps exe_file | not (platformSupportsSavingLinkOpts (platformOS (ue_platform unit_env))) -- ToDo: Windows and OS X do not use the ELF binary format, so -- readelf does not work there. We need to find another way to do -- this. = return False -- conservatively we should return True, but not -- linking in this case was the behaviour for a long -- time so we leave it as-is. | otherwise = do link_info <- getLinkInfo dflags unit_env pkg_deps debugTraceMsg dflags 3 $ text ("Link info: " ++ link_info) m_exe_link_info <- readElfNoteAsString dflags exe_file ghcLinkInfoSectionName ghcLinkInfoNoteName let sameLinkInfo = (Just link_info == m_exe_link_info) debugTraceMsg dflags 3 $ case m_exe_link_info of Nothing -> text "Exe link info: Not found" Just s | sameLinkInfo -> text ("Exe link info is the same") | otherwise -> text ("Exe link info is different: " ++ s) return (not sameLinkInfo) {- Note [LinkInfo section] ~~~~~~~~~~~~~~~~~~~~~~~ The "link info" is a string representing the parameters of the link. We save this information in the binary, and the next time we link, if nothing else has changed, we use the link info stored in the existing binary to decide whether to re-link or not. The "link info" string is stored in a ELF section called ".debug-ghc-link-info" (see ghcLinkInfoSectionName) with the SHT_NOTE type. For some time, it used to not follow the specified record-based format (see #11022). -} haveRtsOptsFlags :: DynFlags -> Bool haveRtsOptsFlags dflags = isJust (rtsOpts dflags) || case rtsOptsEnabled dflags of RtsOptsSafeOnly -> False _ -> True