Patch for shared libraries support on FreeBSD
[ghc.git] / compiler / nativeGen / PIC.hs
1 {-
2 This module handles generation of position independent code and
3 dynamic-linking related issues for the native code generator.
4
5 This depends both the architecture and OS, so we define it here
6 instead of in one of the architecture specific modules.
7
8 Things outside this module which are related to this:
9
10 + module CLabel
11 - PIC base label (pretty printed as local label 1)
12 - DynamicLinkerLabels - several kinds:
13 CodeStub, SymbolPtr, GotSymbolPtr, GotSymbolOffset
14 - labelDynamic predicate
15 + module Cmm
16 - The GlobalReg datatype has a PicBaseReg constructor
17 - The CmmLit datatype has a CmmLabelDiffOff constructor
18 + codeGen & RTS
19 - When tablesNextToCode, no absolute addresses are stored in info tables
20 any more. Instead, offsets from the info label are used.
21 - For Win32 only, SRTs might contain addresses of __imp_ symbol pointers
22 because Win32 doesn't support external references in data sections.
23 TODO: make sure this still works, it might be bitrotted
24 + NCG
25 - The cmmToCmm pass in AsmCodeGen calls cmmMakeDynamicReference for all
26 labels.
27 - nativeCodeGen calls pprImportedSymbol and pprGotDeclaration to output
28 all the necessary stuff for imported symbols.
29 - The NCG monad keeps track of a list of imported symbols.
30 - MachCodeGen invokes initializePicBase to generate code to initialize
31 the PIC base register when needed.
32 - MachCodeGen calls cmmMakeDynamicReference whenever it uses a CLabel
33 that wasn't in the original Cmm code (e.g. floating point literals).
34 + The Mangler
35 - The mangler converts absolure refs to relative refs in info tables
36 - Symbol pointers, stub code and PIC calculations that are generated
37 by GCC are left intact by the mangler (so far only on ppc-darwin
38 and ppc-linux).
39 -}
40
41 module PIC (
42 cmmMakeDynamicReference,
43 ReferenceKind(..),
44 needImportedSymbols,
45 pprImportedSymbol,
46 pprGotDeclaration,
47
48 initializePicBase_ppc,
49 initializePicBase_x86
50 )
51
52 where
53
54 import qualified PPC.Instr as PPC
55 import qualified PPC.Regs as PPC
56
57 import qualified X86.Instr as X86
58
59 import Platform
60 import Instruction
61 import Size
62 import Reg
63 import NCGMonad
64
65
66 import Cmm
67 import CLabel ( CLabel, ForeignLabelSource(..), pprCLabel,
68 mkDynamicLinkerLabel, DynamicLinkerLabelInfo(..),
69 dynamicLinkerLabelInfo, mkPicBaseLabel,
70 labelDynamic, externallyVisibleCLabel )
71
72 import CLabel ( mkForeignLabel )
73
74
75 import StaticFlags ( opt_PIC, opt_Static )
76 import BasicTypes
77
78 import Pretty
79 import qualified Outputable
80
81 import Panic ( panic )
82 import DynFlags
83 import FastString
84
85
86
87 --------------------------------------------------------------------------------
88 -- It gets called by the cmmToCmm pass for every CmmLabel in the Cmm
89 -- code. It does The Right Thing(tm) to convert the CmmLabel into a
90 -- position-independent, dynamic-linking-aware reference to the thing
91 -- in question.
92 -- Note that this also has to be called from MachCodeGen in order to
93 -- access static data like floating point literals (labels that were
94 -- created after the cmmToCmm pass).
95 -- The function must run in a monad that can keep track of imported symbols
96 -- A function for recording an imported symbol must be passed in:
97 -- - addImportCmmOpt for the CmmOptM monad
98 -- - addImportNat for the NatM monad.
99
100 data ReferenceKind
101 = DataReference
102 | CallReference
103 | JumpReference
104 deriving(Eq)
105
106
107 cmmMakeDynamicReference, cmmMakeDynamicReference'
108 :: Monad m => DynFlags
109 -> (CLabel -> m ()) -- a monad & a function
110 -- used for recording imported symbols
111 -> ReferenceKind -- whether this is the target of a jump
112 -> CLabel -- the label
113 -> m CmmExpr
114
115 cmmMakeDynamicReference = cmmMakeDynamicReference'
116
117 cmmMakeDynamicReference' dflags addImport referenceKind lbl
118 | Just _ <- dynamicLinkerLabelInfo lbl
119 = return $ CmmLit $ CmmLabel lbl -- already processed it, pass through
120
121 | otherwise
122 = case howToAccessLabel
123 dflags
124 (platformArch $ targetPlatform dflags)
125 (platformOS $ targetPlatform dflags)
126 referenceKind lbl of
127
128 AccessViaStub -> do
129 let stub = mkDynamicLinkerLabel CodeStub lbl
130 addImport stub
131 return $ CmmLit $ CmmLabel stub
132
133 AccessViaSymbolPtr -> do
134 let symbolPtr = mkDynamicLinkerLabel SymbolPtr lbl
135 addImport symbolPtr
136 return $ CmmLoad (cmmMakePicReference dflags symbolPtr) bWord
137
138 AccessDirectly -> case referenceKind of
139 -- for data, we might have to make some calculations:
140 DataReference -> return $ cmmMakePicReference dflags lbl
141 -- all currently supported processors support
142 -- PC-relative branch and call instructions,
143 -- so just jump there if it's a call or a jump
144 _ -> return $ CmmLit $ CmmLabel lbl
145
146
147 -- -----------------------------------------------------------------------------
148 -- Create a position independent reference to a label.
149 -- (but do not bother with dynamic linking).
150 -- We calculate the label's address by adding some (platform-dependent)
151 -- offset to our base register; this offset is calculated by
152 -- the function picRelative in the platform-dependent part below.
153
154 cmmMakePicReference :: DynFlags -> CLabel -> CmmExpr
155 cmmMakePicReference dflags lbl
156
157 -- Windows doesn't need PIC,
158 -- everything gets relocated at runtime
159 | OSMinGW32 <- platformOS $ targetPlatform dflags
160 = CmmLit $ CmmLabel lbl
161
162
163 | (opt_PIC || not opt_Static) && absoluteLabel lbl
164 = CmmMachOp (MO_Add wordWidth)
165 [ CmmReg (CmmGlobal PicBaseReg)
166 , CmmLit $ picRelative
167 (platformArch $ targetPlatform dflags)
168 (platformOS $ targetPlatform dflags)
169 lbl ]
170
171 | otherwise
172 = CmmLit $ CmmLabel lbl
173
174
175 absoluteLabel :: CLabel -> Bool
176 absoluteLabel lbl
177 = case dynamicLinkerLabelInfo lbl of
178 Just (GotSymbolPtr, _) -> False
179 Just (GotSymbolOffset, _) -> False
180 _ -> True
181
182
183 --------------------------------------------------------------------------------
184 -- Knowledge about how special dynamic linker labels like symbol
185 -- pointers, code stubs and GOT offsets look like is located in the
186 -- module CLabel.
187
188 -- We have to decide which labels need to be accessed
189 -- indirectly or via a piece of stub code.
190 data LabelAccessStyle
191 = AccessViaStub
192 | AccessViaSymbolPtr
193 | AccessDirectly
194
195 howToAccessLabel
196 :: DynFlags -> Arch -> OS -> ReferenceKind -> CLabel -> LabelAccessStyle
197
198
199 -- Windows
200 -- In Windows speak, a "module" is a set of objects linked into the
201 -- same Portable Exectuable (PE) file. (both .exe and .dll files are PEs).
202 --
203 -- If we're compiling a multi-module program then symbols from other modules
204 -- are accessed by a symbol pointer named __imp_SYMBOL. At runtime we have the
205 -- following.
206 --
207 -- (in the local module)
208 -- __imp_SYMBOL: addr of SYMBOL
209 --
210 -- (in the other module)
211 -- SYMBOL: the real function / data.
212 --
213 -- To access the function at SYMBOL from our local module, we just need to
214 -- dereference the local __imp_SYMBOL.
215 --
216 -- If opt_Static is set then we assume that all our code will be linked
217 -- into the same .exe file. In this case we always access symbols directly,
218 -- and never use __imp_SYMBOL.
219 --
220 howToAccessLabel dflags _ OSMinGW32 _ lbl
221
222 -- Assume all symbols will be in the same PE, so just access them directly.
223 | opt_Static
224 = AccessDirectly
225
226 -- If the target symbol is in another PE we need to access it via the
227 -- appropriate __imp_SYMBOL pointer.
228 | labelDynamic (thisPackage dflags) lbl
229 = AccessViaSymbolPtr
230
231 -- Target symbol is in the same PE as the caller, so just access it directly.
232 | otherwise
233 = AccessDirectly
234
235
236 -- Mach-O (Darwin, Mac OS X)
237 --
238 -- Indirect access is required in the following cases:
239 -- * things imported from a dynamic library
240 -- * (not on x86_64) data from a different module, if we're generating PIC code
241 -- It is always possible to access something indirectly,
242 -- even when it's not necessary.
243 --
244 howToAccessLabel dflags arch OSDarwin DataReference lbl
245 -- data access to a dynamic library goes via a symbol pointer
246 | labelDynamic (thisPackage dflags) lbl
247 = AccessViaSymbolPtr
248
249 -- when generating PIC code, all cross-module data references must
250 -- must go via a symbol pointer, too, because the assembler
251 -- cannot generate code for a label difference where one
252 -- label is undefined. Doesn't apply t x86_64.
253 -- Unfortunately, we don't know whether it's cross-module,
254 -- so we do it for all externally visible labels.
255 -- This is a slight waste of time and space, but otherwise
256 -- we'd need to pass the current Module all the way in to
257 -- this function.
258 | arch /= ArchX86_64
259 , opt_PIC && externallyVisibleCLabel lbl
260 = AccessViaSymbolPtr
261
262 | otherwise
263 = AccessDirectly
264
265 howToAccessLabel dflags arch OSDarwin JumpReference lbl
266 -- dyld code stubs don't work for tailcalls because the
267 -- stack alignment is only right for regular calls.
268 -- Therefore, we have to go via a symbol pointer:
269 | arch == ArchX86 || arch == ArchX86_64
270 , labelDynamic (thisPackage dflags) lbl
271 = AccessViaSymbolPtr
272
273
274 howToAccessLabel dflags arch OSDarwin _ lbl
275 -- Code stubs are the usual method of choice for imported code;
276 -- not needed on x86_64 because Apple's new linker, ld64, generates
277 -- them automatically.
278 | arch /= ArchX86_64
279 , labelDynamic (thisPackage dflags) lbl
280 = AccessViaStub
281
282 | otherwise
283 = AccessDirectly
284
285 -- ELF (Linux)
286 --
287 -- ELF tries to pretend to the main application code that dynamic linking does
288 -- not exist. While this may sound convenient, it tends to mess things up in
289 -- very bad ways, so we have to be careful when we generate code for the main
290 -- program (-dynamic but no -fPIC).
291 --
292 -- Indirect access is required for references to imported symbols
293 -- from position independent code. It is also required from the main program
294 -- when dynamic libraries containing Haskell code are used.
295
296 howToAccessLabel _ ArchPPC_64 os kind _
297 | osElfTarget os
298 = if kind == DataReference
299 -- ELF PPC64 (powerpc64-linux), AIX, MacOS 9, BeOS/PPC
300 then AccessViaSymbolPtr
301 -- actually, .label instead of label
302 else AccessDirectly
303
304 howToAccessLabel _ _ os _ _
305 -- no PIC -> the dynamic linker does everything for us;
306 -- if we don't dynamically link to Haskell code,
307 -- it actually manages to do so without messing thins up.
308 | osElfTarget os
309 , not opt_PIC && opt_Static
310 = AccessDirectly
311
312 howToAccessLabel dflags arch os DataReference lbl
313 | osElfTarget os
314 = case () of
315 -- A dynamic label needs to be accessed via a symbol pointer.
316 _ | labelDynamic (thisPackage dflags) lbl
317 -> AccessViaSymbolPtr
318
319 -- For PowerPC32 -fPIC, we have to access even static data
320 -- via a symbol pointer (see below for an explanation why
321 -- PowerPC32 Linux is especially broken).
322 | arch == ArchPPC
323 , opt_PIC
324 -> AccessViaSymbolPtr
325
326 | otherwise
327 -> AccessDirectly
328
329
330 -- In most cases, we have to avoid symbol stubs on ELF, for the following reasons:
331 -- on i386, the position-independent symbol stubs in the Procedure Linkage Table
332 -- require the address of the GOT to be loaded into register %ebx on entry.
333 -- The linker will take any reference to the symbol stub as a hint that
334 -- the label in question is a code label. When linking executables, this
335 -- will cause the linker to replace even data references to the label with
336 -- references to the symbol stub.
337
338 -- This leaves calling a (foreign) function from non-PIC code
339 -- (AccessDirectly, because we get an implicit symbol stub)
340 -- and calling functions from PIC code on non-i386 platforms (via a symbol stub)
341
342 howToAccessLabel dflags arch os CallReference lbl
343 | osElfTarget os
344 , labelDynamic (thisPackage dflags) lbl && not opt_PIC
345 = AccessDirectly
346
347 | osElfTarget os
348 , arch /= ArchX86
349 , labelDynamic (thisPackage dflags) lbl && opt_PIC
350 = AccessViaStub
351
352 howToAccessLabel dflags _ os _ lbl
353 | osElfTarget os
354 = if labelDynamic (thisPackage dflags) lbl
355 then AccessViaSymbolPtr
356 else AccessDirectly
357
358 -- all other platforms
359 howToAccessLabel _ _ _ _ _
360 | not opt_PIC
361 = AccessDirectly
362
363 | otherwise
364 = panic "howToAccessLabel: PIC not defined for this platform"
365
366
367
368 -- -------------------------------------------------------------------
369 -- | Says what we we have to add to our 'PIC base register' in order to
370 -- get the address of a label.
371
372 picRelative :: Arch -> OS -> CLabel -> CmmLit
373
374 -- Darwin, but not x86_64:
375 -- The PIC base register points to the PIC base label at the beginning
376 -- of the current CmmTop. We just have to use a label difference to
377 -- get the offset.
378 -- We have already made sure that all labels that are not from the current
379 -- module are accessed indirectly ('as' can't calculate differences between
380 -- undefined labels).
381 picRelative arch OSDarwin lbl
382 | arch /= ArchX86_64
383 = CmmLabelDiffOff lbl mkPicBaseLabel 0
384
385
386 -- PowerPC Linux:
387 -- The PIC base register points to our fake GOT. Use a label difference
388 -- to get the offset.
389 -- We have made sure that *everything* is accessed indirectly, so this
390 -- is only used for offsets from the GOT to symbol pointers inside the
391 -- GOT.
392 picRelative ArchPPC os lbl
393 | osElfTarget os
394 = CmmLabelDiffOff lbl gotLabel 0
395
396
397 -- Most Linux versions:
398 -- The PIC base register points to the GOT. Use foo@got for symbol
399 -- pointers, and foo@gotoff for everything else.
400 -- Linux and Darwin on x86_64:
401 -- The PIC base register is %rip, we use foo@gotpcrel for symbol pointers,
402 -- and a GotSymbolOffset label for other things.
403 -- For reasons of tradition, the symbol offset label is written as a plain label.
404 picRelative arch os lbl
405 | osElfTarget os || (os == OSDarwin && arch == ArchX86_64)
406 = let result
407 | Just (SymbolPtr, lbl') <- dynamicLinkerLabelInfo lbl
408 = CmmLabel $ mkDynamicLinkerLabel GotSymbolPtr lbl'
409
410 | otherwise
411 = CmmLabel $ mkDynamicLinkerLabel GotSymbolOffset lbl
412
413 in result
414
415 picRelative _ _ _
416 = panic "PositionIndependentCode.picRelative undefined for this platform"
417
418
419
420 --------------------------------------------------------------------------------
421
422 -- utility function for pretty-printing asm-labels,
423 -- copied from PprMach
424 --
425 asmSDoc :: Outputable.SDoc -> Doc
426 asmSDoc d
427 = Outputable.withPprStyleDoc
428 (Outputable.mkCodeStyle Outputable.AsmStyle) d
429
430 pprCLabel_asm :: CLabel -> Doc
431 pprCLabel_asm l
432 = asmSDoc (pprCLabel l)
433
434
435 needImportedSymbols :: Arch -> OS -> Bool
436 needImportedSymbols arch os
437 | os == OSDarwin
438 , arch /= ArchX86_64
439 = True
440
441 -- PowerPC Linux: -fPIC or -dynamic
442 | osElfTarget os
443 , arch == ArchPPC
444 = opt_PIC || not opt_Static
445
446 -- i386 (and others?): -dynamic but not -fPIC
447 | osElfTarget os
448 , arch /= ArchPPC_64
449 = not opt_Static && not opt_PIC
450
451 | otherwise
452 = False
453
454 -- gotLabel
455 -- The label used to refer to our "fake GOT" from
456 -- position-independent code.
457 gotLabel :: CLabel
458 gotLabel
459 -- HACK: this label isn't really foreign
460 = mkForeignLabel
461 (fsLit ".LCTOC1")
462 Nothing ForeignLabelInThisPackage IsData
463
464
465
466 --------------------------------------------------------------------------------
467 -- We don't need to declare any offset tables.
468 -- However, for PIC on x86, we need a small helper function.
469 pprGotDeclaration :: Arch -> OS -> Doc
470 pprGotDeclaration ArchX86 OSDarwin
471 | opt_PIC
472 = vcat [
473 ptext (sLit ".section __TEXT,__textcoal_nt,coalesced,no_toc"),
474 ptext (sLit ".weak_definition ___i686.get_pc_thunk.ax"),
475 ptext (sLit ".private_extern ___i686.get_pc_thunk.ax"),
476 ptext (sLit "___i686.get_pc_thunk.ax:"),
477 ptext (sLit "\tmovl (%esp), %eax"),
478 ptext (sLit "\tret") ]
479
480 pprGotDeclaration _ OSDarwin
481 = Pretty.empty
482
483 -- pprGotDeclaration
484 -- Output whatever needs to be output once per .s file.
485 -- The .LCTOC1 label is defined to point 32768 bytes into the table,
486 -- to make the most of the PPC's 16-bit displacements.
487 -- Only needed for PIC.
488 pprGotDeclaration arch os
489 | osElfTarget os
490 , arch /= ArchPPC_64
491 , not opt_PIC
492 = Pretty.empty
493
494 | osElfTarget os
495 , arch /= ArchPPC_64
496 = vcat [
497 ptext (sLit ".section \".got2\",\"aw\""),
498 ptext (sLit ".LCTOC1 = .+32768") ]
499
500 pprGotDeclaration _ _
501 = panic "pprGotDeclaration: no match"
502
503
504 --------------------------------------------------------------------------------
505 -- On Darwin, we have to generate our own stub code for lazy binding..
506 -- For each processor architecture, there are two versions, one for PIC
507 -- and one for non-PIC.
508 --
509 -- Whenever you change something in this assembler output, make sure
510 -- the splitter in driver/split/ghc-split.lprl recognizes the new output
511
512 pprImportedSymbol :: Arch -> OS -> CLabel -> Doc
513 pprImportedSymbol ArchPPC OSDarwin importedLbl
514 | Just (CodeStub, lbl) <- dynamicLinkerLabelInfo importedLbl
515 = case opt_PIC of
516 False ->
517 vcat [
518 ptext (sLit ".symbol_stub"),
519 ptext (sLit "L") <> pprCLabel_asm lbl <> ptext (sLit "$stub:"),
520 ptext (sLit "\t.indirect_symbol") <+> pprCLabel_asm lbl,
521 ptext (sLit "\tlis r11,ha16(L") <> pprCLabel_asm lbl
522 <> ptext (sLit "$lazy_ptr)"),
523 ptext (sLit "\tlwz r12,lo16(L") <> pprCLabel_asm lbl
524 <> ptext (sLit "$lazy_ptr)(r11)"),
525 ptext (sLit "\tmtctr r12"),
526 ptext (sLit "\taddi r11,r11,lo16(L") <> pprCLabel_asm lbl
527 <> ptext (sLit "$lazy_ptr)"),
528 ptext (sLit "\tbctr")
529 ]
530 True ->
531 vcat [
532 ptext (sLit ".section __TEXT,__picsymbolstub1,")
533 <> ptext (sLit "symbol_stubs,pure_instructions,32"),
534 ptext (sLit "\t.align 2"),
535 ptext (sLit "L") <> pprCLabel_asm lbl <> ptext (sLit "$stub:"),
536 ptext (sLit "\t.indirect_symbol") <+> pprCLabel_asm lbl,
537 ptext (sLit "\tmflr r0"),
538 ptext (sLit "\tbcl 20,31,L0$") <> pprCLabel_asm lbl,
539 ptext (sLit "L0$") <> pprCLabel_asm lbl <> char ':',
540 ptext (sLit "\tmflr r11"),
541 ptext (sLit "\taddis r11,r11,ha16(L") <> pprCLabel_asm lbl
542 <> ptext (sLit "$lazy_ptr-L0$") <> pprCLabel_asm lbl <> char ')',
543 ptext (sLit "\tmtlr r0"),
544 ptext (sLit "\tlwzu r12,lo16(L") <> pprCLabel_asm lbl
545 <> ptext (sLit "$lazy_ptr-L0$") <> pprCLabel_asm lbl
546 <> ptext (sLit ")(r11)"),
547 ptext (sLit "\tmtctr r12"),
548 ptext (sLit "\tbctr")
549 ]
550 $+$ vcat [
551 ptext (sLit ".lazy_symbol_pointer"),
552 ptext (sLit "L") <> pprCLabel_asm lbl <> ptext (sLit "$lazy_ptr:"),
553 ptext (sLit "\t.indirect_symbol") <+> pprCLabel_asm lbl,
554 ptext (sLit "\t.long dyld_stub_binding_helper")]
555
556 | Just (SymbolPtr, lbl) <- dynamicLinkerLabelInfo importedLbl
557 = vcat [
558 ptext (sLit ".non_lazy_symbol_pointer"),
559 char 'L' <> pprCLabel_asm lbl <> ptext (sLit "$non_lazy_ptr:"),
560 ptext (sLit "\t.indirect_symbol") <+> pprCLabel_asm lbl,
561 ptext (sLit "\t.long\t0")]
562
563 | otherwise
564 = empty
565
566
567 pprImportedSymbol ArchX86 OSDarwin importedLbl
568 | Just (CodeStub, lbl) <- dynamicLinkerLabelInfo importedLbl
569 = case opt_PIC of
570 False ->
571 vcat [
572 ptext (sLit ".symbol_stub"),
573 ptext (sLit "L") <> pprCLabel_asm lbl <> ptext (sLit "$stub:"),
574 ptext (sLit "\t.indirect_symbol") <+> pprCLabel_asm lbl,
575 ptext (sLit "\tjmp *L") <> pprCLabel_asm lbl
576 <> ptext (sLit "$lazy_ptr"),
577 ptext (sLit "L") <> pprCLabel_asm lbl
578 <> ptext (sLit "$stub_binder:"),
579 ptext (sLit "\tpushl $L") <> pprCLabel_asm lbl
580 <> ptext (sLit "$lazy_ptr"),
581 ptext (sLit "\tjmp dyld_stub_binding_helper")
582 ]
583 True ->
584 vcat [
585 ptext (sLit ".section __TEXT,__picsymbolstub2,")
586 <> ptext (sLit "symbol_stubs,pure_instructions,25"),
587 ptext (sLit "L") <> pprCLabel_asm lbl <> ptext (sLit "$stub:"),
588 ptext (sLit "\t.indirect_symbol") <+> pprCLabel_asm lbl,
589 ptext (sLit "\tcall ___i686.get_pc_thunk.ax"),
590 ptext (sLit "1:"),
591 ptext (sLit "\tmovl L") <> pprCLabel_asm lbl
592 <> ptext (sLit "$lazy_ptr-1b(%eax),%edx"),
593 ptext (sLit "\tjmp *%edx"),
594 ptext (sLit "L") <> pprCLabel_asm lbl
595 <> ptext (sLit "$stub_binder:"),
596 ptext (sLit "\tlea L") <> pprCLabel_asm lbl
597 <> ptext (sLit "$lazy_ptr-1b(%eax),%eax"),
598 ptext (sLit "\tpushl %eax"),
599 ptext (sLit "\tjmp dyld_stub_binding_helper")
600 ]
601 $+$ vcat [ ptext (sLit ".section __DATA, __la_sym_ptr")
602 <> (if opt_PIC then int 2 else int 3)
603 <> ptext (sLit ",lazy_symbol_pointers"),
604 ptext (sLit "L") <> pprCLabel_asm lbl <> ptext (sLit "$lazy_ptr:"),
605 ptext (sLit "\t.indirect_symbol") <+> pprCLabel_asm lbl,
606 ptext (sLit "\t.long L") <> pprCLabel_asm lbl
607 <> ptext (sLit "$stub_binder")]
608
609 | Just (SymbolPtr, lbl) <- dynamicLinkerLabelInfo importedLbl
610 = vcat [
611 ptext (sLit ".non_lazy_symbol_pointer"),
612 char 'L' <> pprCLabel_asm lbl <> ptext (sLit "$non_lazy_ptr:"),
613 ptext (sLit "\t.indirect_symbol") <+> pprCLabel_asm lbl,
614 ptext (sLit "\t.long\t0")]
615
616 | otherwise
617 = empty
618
619
620 pprImportedSymbol _ OSDarwin _
621 = empty
622
623
624 -- ELF / Linux
625 --
626 -- In theory, we don't need to generate any stubs or symbol pointers
627 -- by hand for Linux.
628 --
629 -- Reality differs from this in two areas.
630 --
631 -- 1) If we just use a dynamically imported symbol directly in a read-only
632 -- section of the main executable (as GCC does), ld generates R_*_COPY
633 -- relocations, which are fundamentally incompatible with reversed info
634 -- tables. Therefore, we need a table of imported addresses in a writable
635 -- section.
636 -- The "official" GOT mechanism (label@got) isn't intended to be used
637 -- in position dependent code, so we have to create our own "fake GOT"
638 -- when not opt_PCI && not opt_Static.
639 --
640 -- 2) PowerPC Linux is just plain broken.
641 -- While it's theoretically possible to use GOT offsets larger
642 -- than 16 bit, the standard crt*.o files don't, which leads to
643 -- linker errors as soon as the GOT size exceeds 16 bit.
644 -- Also, the assembler doesn't support @gotoff labels.
645 -- In order to be able to use a larger GOT, we have to circumvent the
646 -- entire GOT mechanism and do it ourselves (this is also what GCC does).
647
648
649 -- When needImportedSymbols is defined,
650 -- the NCG will keep track of all DynamicLinkerLabels it uses
651 -- and output each of them using pprImportedSymbol.
652
653 pprImportedSymbol ArchPPC_64 os _
654 | osElfTarget os
655 = empty
656
657 pprImportedSymbol _ os importedLbl
658 | osElfTarget os
659 = case dynamicLinkerLabelInfo importedLbl of
660 Just (SymbolPtr, lbl)
661 -> let symbolSize = case wordWidth of
662 W32 -> sLit "\t.long"
663 W64 -> sLit "\t.quad"
664 _ -> panic "Unknown wordRep in pprImportedSymbol"
665
666 in vcat [
667 ptext (sLit ".section \".got2\", \"aw\""),
668 ptext (sLit ".LC_") <> pprCLabel_asm lbl <> char ':',
669 ptext symbolSize <+> pprCLabel_asm lbl ]
670
671 -- PLT code stubs are generated automatically by the dynamic linker.
672 _ -> empty
673
674 pprImportedSymbol _ _ _
675 = panic "PIC.pprImportedSymbol: no match"
676
677 --------------------------------------------------------------------------------
678 -- Generate code to calculate the address that should be put in the
679 -- PIC base register.
680 -- This is called by MachCodeGen for every CmmProc that accessed the
681 -- PIC base register. It adds the appropriate instructions to the
682 -- top of the CmmProc.
683
684 -- It is assumed that the first NatCmmTop in the input list is a Proc
685 -- and the rest are CmmDatas.
686
687 -- Darwin is simple: just fetch the address of a local label.
688 -- The FETCHPC pseudo-instruction is expanded to multiple instructions
689 -- during pretty-printing so that we don't have to deal with the
690 -- local label:
691
692 -- PowerPC version:
693 -- bcl 20,31,1f.
694 -- 1: mflr picReg
695
696 -- i386 version:
697 -- call 1f
698 -- 1: popl %picReg
699
700
701
702 -- Get a pointer to our own fake GOT, which is defined on a per-module basis.
703 -- This is exactly how GCC does it, and it's quite horrible:
704 -- We first fetch the address of a local label (mkPicBaseLabel).
705 -- Then we add a 16-bit offset to that to get the address of a .long that we
706 -- define in .text space right next to the proc. This .long literal contains
707 -- the (32-bit) offset from our local label to our global offset table
708 -- (.LCTOC1 aka gotOffLabel).
709
710 initializePicBase_ppc
711 :: Arch -> OS -> Reg
712 -> [NatCmmTop PPC.Instr]
713 -> NatM [NatCmmTop PPC.Instr]
714
715 initializePicBase_ppc ArchPPC os picReg
716 (CmmProc info lab params (ListGraph blocks) : statics)
717 | osElfTarget os
718 = do
719 gotOffLabel <- getNewLabelNat
720 tmp <- getNewRegNat $ intSize wordWidth
721 let
722 gotOffset = CmmData Text [
723 CmmDataLabel gotOffLabel,
724 CmmStaticLit (CmmLabelDiffOff gotLabel
725 mkPicBaseLabel
726 0)
727 ]
728 offsetToOffset
729 = PPC.ImmConstantDiff
730 (PPC.ImmCLbl gotOffLabel)
731 (PPC.ImmCLbl mkPicBaseLabel)
732
733 BasicBlock bID insns
734 = head blocks
735
736 b' = BasicBlock bID (PPC.FETCHPC picReg
737 : PPC.LD PPC.archWordSize tmp
738 (PPC.AddrRegImm picReg offsetToOffset)
739 : PPC.ADD picReg picReg (PPC.RIReg tmp)
740 : insns)
741
742 return (CmmProc info lab params (ListGraph (b' : tail blocks)) : gotOffset : statics)
743
744 initializePicBase_ppc ArchPPC OSDarwin picReg
745 (CmmProc info lab params (ListGraph blocks) : statics)
746 = return (CmmProc info lab params (ListGraph (b':tail blocks)) : statics)
747
748 where BasicBlock bID insns = head blocks
749 b' = BasicBlock bID (PPC.FETCHPC picReg : insns)
750
751
752 initializePicBase_ppc _ _ _ _
753 = panic "initializePicBase_ppc: not needed"
754
755
756 -- We cheat a bit here by defining a pseudo-instruction named FETCHGOT
757 -- which pretty-prints as:
758 -- call 1f
759 -- 1: popl %picReg
760 -- addl __GLOBAL_OFFSET_TABLE__+.-1b, %picReg
761 -- (See PprMach.lhs)
762
763 initializePicBase_x86
764 :: Arch -> OS -> Reg
765 -> [NatCmmTop X86.Instr]
766 -> NatM [NatCmmTop X86.Instr]
767
768 initializePicBase_x86 ArchX86 os picReg
769 (CmmProc info lab params (ListGraph blocks) : statics)
770 | osElfTarget os
771 = return (CmmProc info lab params (ListGraph (b':tail blocks)) : statics)
772 where BasicBlock bID insns = head blocks
773 b' = BasicBlock bID (X86.FETCHGOT picReg : insns)
774
775 initializePicBase_x86 ArchX86 OSDarwin picReg
776 (CmmProc info lab params (ListGraph blocks) : statics)
777 = return (CmmProc info lab params (ListGraph (b':tail blocks)) : statics)
778
779 where BasicBlock bID insns = head blocks
780 b' = BasicBlock bID (X86.FETCHPC picReg : insns)
781
782 initializePicBase_x86 _ _ _ _
783 = panic "initializePicBase_x86: not needed"
784