-#include "../includes/ghcconfig.h"
-
module PositionIndependentCode (
cmmMakeDynamicReference,
needImportedSymbols,
CodeStub, SymbolPtr, GotSymbolPtr, GotSymbolOffset
- labelDynamic predicate
+ module Cmm
- - The CmmExpr datatype has a CmmPicBaseReg constructor
+ - The GlobalReg datatype has a PicBaseReg constructor
- The CmmLit datatype has a CmmLabelDiffOff constructor
+ codeGen & RTS
- When tablesNextToCode, no absolute addresses are stored in info tables
dynamicLinkerLabelInfo, mkPicBaseLabel,
labelDynamic, externallyVisibleCLabel )
-#if powerpc_TARGET_ARCH && linux_TARGET_OS
+#if linux_TARGET_OS
import CLabel ( mkForeignLabel )
#endif
import MachInstrs
import NCGMonad ( NatM, getNewRegNat, getNewLabelNat )
-import CmdLineOpts ( opt_PIC, opt_Static )
+import StaticFlags ( opt_PIC, opt_Static )
import Pretty
import qualified Outputable
cmmMakePicReference lbl
| opt_PIC && absoluteLabel lbl = CmmMachOp (MO_Add wordRep) [
- CmmPicBaseReg,
+ CmmReg (CmmGlobal PicBaseReg),
CmmLit $ picRelative lbl
]
where
-- Mach-O (Darwin, Mac OS X)
--
-- Indirect access is required in the following cases:
--- * things imported from a dynamic library
--- * things from a different module, if we're generating PIC code
+-- * things imported from a dynamic library
+-- * things from a different module, if we're generating PIC code
-- It is always possible to access something indirectly,
-- even when it's not necessary.
needImportedSymbols = True
--- We don't need to declare any offset tables
+-- We don't need to declare any offset tables.
+-- However, for PIC on x86, we need a small helper function.
+#if i386_TARGET_ARCH
+pprGotDeclaration
+ | opt_PIC
+ = vcat [
+ ptext SLIT(".section __TEXT,__textcoal_nt,coalesced,no_toc"),
+ ptext SLIT(".weak_definition ___i686.get_pc_thunk.ax"),
+ ptext SLIT(".private_extern ___i686.get_pc_thunk.ax"),
+ ptext SLIT("___i686.get_pc_thunk.ax:"),
+ ptext SLIT("\tmovl (%esp), %eax"),
+ ptext SLIT("\tret")
+ ]
+ | otherwise = Pretty.empty
+#else
pprGotDeclaration = Pretty.empty
+#endif
-- On Darwin, we have to generate our own stub code for lazy binding..
--- There are two versions, one for PIC and one for non-PIC.
+-- For each processor architecture, there are two versions, one for PIC
+-- and one for non-PIC.
pprImportedSymbol importedLbl
+#if powerpc_TARGET_ARCH
| Just (CodeStub, lbl) <- dynamicLinkerLabelInfo importedLbl
= case opt_PIC of
False ->
ptext SLIT("\t.indirect_symbol") <+> pprCLabel_asm lbl,
ptext SLIT("\t.long dyld_stub_binding_helper")
]
-
+#elif i386_TARGET_ARCH
+ | Just (CodeStub, lbl) <- dynamicLinkerLabelInfo importedLbl
+ = case opt_PIC of
+ False ->
+ vcat [
+ ptext SLIT(".symbol_stub"),
+ ptext SLIT("L") <> pprCLabel_asm lbl <> ptext SLIT("$stub:"),
+ ptext SLIT("\t.indirect_symbol") <+> pprCLabel_asm lbl,
+ ptext SLIT("\tjmp *L") <> pprCLabel_asm lbl
+ <> ptext SLIT("$lazy_ptr"),
+ ptext SLIT("L") <> pprCLabel_asm lbl
+ <> ptext SLIT("$stub_binder:"),
+ ptext SLIT("\tpushl $L") <> pprCLabel_asm lbl
+ <> ptext SLIT("$lazy_ptr"),
+ ptext SLIT("\tjmp dyld_stub_binding_helper")
+ ]
+ True ->
+ vcat [
+ ptext SLIT(".section __TEXT,__picsymbolstub2,")
+ <> ptext SLIT("symbol_stubs,pure_instructions,25"),
+ ptext SLIT("L") <> pprCLabel_asm lbl <> ptext SLIT("$stub:"),
+ ptext SLIT("\t.indirect_symbol") <+> pprCLabel_asm lbl,
+ ptext SLIT("\tcall ___i686.get_pc_thunk.ax"),
+ ptext SLIT("1:"),
+ ptext SLIT("\tmovl L") <> pprCLabel_asm lbl
+ <> ptext SLIT("$lazy_ptr-1b(%eax),%edx"),
+ ptext SLIT("\tjmp %edx"),
+ ptext SLIT("L") <> pprCLabel_asm lbl
+ <> ptext SLIT("$stub_binder:"),
+ ptext SLIT("\tlea L") <> pprCLabel_asm lbl
+ <> ptext SLIT("$lazy_ptr-1b(%eax),%eax"),
+ ptext SLIT("\tpushl %eax"),
+ ptext SLIT("\tjmp dyld_stub_binding_helper")
+ ]
+ $+$ vcat [ ptext SLIT(".section __DATA, __la_sym_ptr")
+ <> (if opt_PIC then int 2 else int 3)
+ <> ptext SLIT(",lazy_symbol_pointers"),
+ ptext SLIT("L") <> pprCLabel_asm lbl <> ptext SLIT("$lazy_ptr:"),
+ ptext SLIT("\t.indirect_symbol") <+> pprCLabel_asm lbl,
+ ptext SLIT("\t.long L") <> pprCLabel_asm lbl
+ <> ptext SLIT("$stub_binder")
+ ]
+#endif
-- We also have to declare our symbol pointers ourselves:
| Just (SymbolPtr, lbl) <- dynamicLinkerLabelInfo importedLbl
= vcat [
| otherwise = empty
-#elif powerpc_TARGET_ARCH && linux_TARGET_OS
+#elif linux_TARGET_OS && !powerpc64_TARGET_ARCH
--- PowerPC Linux
+-- ELF / Linux
--
--- PowerPC Linux is just plain broken.
--- While it's theoretically possible to use GOT offsets larger
--- than 16 bit, the standard crt*.o files don't, which leads to
--- linker errors as soon as the GOT size exceeds 16 bit.
--- Also, the assembler doesn't support @gotoff labels.
--- In order to be able to use a larger GOT, we circumvent the
--- entire GOT mechanism and do it ourselves (this is what GCC does).
-
--- In this scheme, we need to do _all data references_ (even refs
--- to static data) via a SymbolPtr when we are generating PIC.
-
--- We need to do this whenever we explicitly access something via
--- a symbol pointer.
+-- In theory, we don't need to generate any stubs or symbol pointers
+-- by hand for Linux.
+--
+-- Reality differs from this in two areas.
+--
+-- 1) If we just use a dynamically imported symbol directly in a read-only
+-- section of the main executable (as GCC does), ld generates R_*_COPY
+-- relocations, which are fundamentally incompatible with reversed info
+-- tables. Therefore, we need a table of imported addresses in a writable
+-- section.
+-- The "official" GOT mechanism (label@got) isn't intended to be used
+-- in position dependent code, so we have to create our own "fake GOT"
+-- when not opt_PCI && not opt_Static.
+--
+-- 2) PowerPC Linux is just plain broken.
+-- While it's theoretically possible to use GOT offsets larger
+-- than 16 bit, the standard crt*.o files don't, which leads to
+-- linker errors as soon as the GOT size exceeds 16 bit.
+-- Also, the assembler doesn't support @gotoff labels.
+-- In order to be able to use a larger GOT, we have to circumvent the
+-- entire GOT mechanism and do it ourselves (this is also what GCC does).
+
+
+-- When needImportedSymbols is defined,
+-- the NCG will keep track of all DynamicLinkerLabels it uses
+-- and output each of them using pprImportedSymbol.
+#if powerpc_TARGET_ARCH
+ -- PowerPC Linux: -fPIC or -dynamic
needImportedSymbols = opt_PIC || not opt_Static
+#else
+ -- i386 (and others?): -dynamic but not -fPIC
+needImportedSymbols = not opt_Static && not opt_PIC
+#endif
--- If we're generating PIC, we need to create our own "fake GOT".
-
+-- gotLabel
+-- The label used to refer to our "fake GOT" from
+-- position-independent code.
gotLabel = mkForeignLabel -- HACK: it's not really foreign
FSLIT(".LCTOC1") Nothing False
+-- pprGotDeclaration
+-- Output whatever needs to be output once per .s file.
-- The .LCTOC1 label is defined to point 32768 bytes into the table,
-- to make the most of the PPC's 16-bit displacements.
+-- Only needed for PIC.
-pprGotDeclaration = vcat [
+pprGotDeclaration
+ | not opt_PIC = Pretty.empty
+ | otherwise = vcat [
ptext SLIT(".section \".got2\",\"aw\""),
ptext SLIT(".LCTOC1 = .+32768")
]
-- We generate one .long literal for every symbol we import;
-- the dynamic linker will relocate those addresses.
-
+
pprImportedSymbol importedLbl
| Just (SymbolPtr, lbl) <- dynamicLinkerLabelInfo importedLbl
= vcat [
initializePicBase :: Reg -> [NatCmmTop] -> NatM [NatCmmTop]
-#if powerpc_TARGET_ARCH && darwin_TARGET_OS
+#if darwin_TARGET_OS
-- Darwin is simple: just fetch the address of a local label.
+-- The FETCHPC pseudo-instruction is expanded to multiple instructions
+-- during pretty-printing so that we don't have to deal with the
+-- local label:
+
+-- PowerPC version:
+-- bcl 20,31,1f.
+-- 1: mflr picReg
+
+-- i386 version:
+-- call 1f
+-- 1: popl %picReg
+
initializePicBase picReg (CmmProc info lab params blocks : statics)
= return (CmmProc info lab params (b':tail blocks) : statics)
where BasicBlock bID insns = head blocks
: ADD picReg picReg (RIReg tmp)
: insns)
return (CmmProc info lab params (b' : tail blocks) : gotOffset : statics)
-#else
-initializePicBase picReg proc = panic "initializePicBase"
+#elif i386_TARGET_ARCH && linux_TARGET_OS
--- TODO:
--- i386_TARGET_ARCH && linux_TARGET_OS:
--- generate something like:
+-- We cheat a bit here by defining a pseudo-instruction named FETCHGOT
+-- which pretty-prints as:
-- call 1f
-- 1: popl %picReg
-- addl __GLOBAL_OFFSET_TABLE__+.-1b, %picReg
--- It might be a good idea to use a FETCHPC pseudo-instruction (like for PowerPC)
--- in order to avoid having to create a new basic block.
--- ((FETCHPC reg) should pretty-print as call 1f; 1: popl reg)
+-- (See PprMach.lhs)
--- mingw32_TARGET_OS: not needed, won't be called
+initializePicBase picReg (CmmProc info lab params blocks : statics)
+ = return (CmmProc info lab params (b':tail blocks) : statics)
+ where BasicBlock bID insns = head blocks
+ b' = BasicBlock bID (FETCHGOT picReg : insns)
--- i386_TARGET_ARCH && darwin_TARGET_OS:
--- (just for completeness ;-)
--- call 1f
--- 1: popl %picReg
+#else
+initializePicBase picReg proc = panic "initializePicBase"
+
+-- mingw32_TARGET_OS: not needed, won't be called
#endif
projects / ghc-hetmet.git / blobdiff