Commit Graph

4783 Commits

Author SHA1 Message Date
Sid Manning 6d0e4fce1a [ELF][HEXAGON] Set DefaultMaxPageSize to 64K
Update testcase to reflect the change.

llvm-svn: 342662
2018-09-20 16:32:19 +00:00
Zachary Turner 77bbd7b19d Fix one more test failure.
llvm-svn: 342660
2018-09-20 16:18:15 +00:00
Sean Fertile 69e09116ba [PPC64] Handle ppc64le triple in getBitcodeMachineKind.
Enables lto and thinlto with bitcode targeting ppc64le.

Differential Revision: https://reviews.llvm.org/D52265

llvm-svn: 342604
2018-09-20 00:26:49 +00:00
Sean Fertile 7f3f05e0b7 [PPC64] Optimize redundant instructions in global access sequences.
The access sequence for global variables in the medium and large code models use
2 instructions to add an offset to the toc-pointer. If the offset fits whithin
16-bits then the instruction that sets the high 16 bits is redundant.

This patch adds the --toc-optimize option, (on by default) and enables rewriting
of 2 instruction global variable accesses into 1 when the offset from the
TOC-pointer to the variable (or .got entry) fits in 16 signed bits. eg

addis %r3, %r2, 0           -->     nop
addi  %r3, %r3, -0x8000     -->     addi %r3, %r2, -0x8000

This rewriting can be disabled with the --no-toc-optimize flag

Differential Revision: https://reviews.llvm.org/D49237

llvm-svn: 342602
2018-09-20 00:26:44 +00:00
Martin Storsjo 32d21d6a2d [COFF] Add support for delay loading DLLs for ARM64
Differential Revision: https://reviews.llvm.org/D52190

llvm-svn: 342447
2018-09-18 07:22:01 +00:00
Ryan Prichard 1c33d14bcd [ELF] Set Out::TlsPhdr earlier for encoding packed reloc tables
Summary:
For --pack-dyn-relocs=android, finalizeSections calls
LinkerScript::assignAddresses and
AndroidPackedRelocationSection::updateAllocSize in a loop,
where assignAddresses lays out the ELF image, then updateAllocSize
determines the size of the Android packed relocation table by encoding it.
Encoding the table requires knowing the values of relocation addends.

To get the addend of a TLS relocation, updateAllocSize can call getSymVA
on a TLS symbol before setPhdrs has initialized Out::TlsPhdr, producing an
error:

    <file> has an STT_TLS symbol but doesn't have an SHF_TLS section

Fix the problem by initializing Out::TlsPhdr immediately after the program
headers are created. The segment's p_vaddr field isn't initialized until
setPhdrs, so use FirstSec->Addr, which is what setPhdrs would use.
FirstSec will typically refer to the .tdata or .tbss output section, whose
(tentative) address was computed by assignAddresses.

Android currently avoids this problem because it uses emutls and doesn't
support ELF TLS. This problem doesn't apply to --pack-dyn-relocs=relr
because SHR_RELR only handles relative relocations without explicit addends
or info.

Fixes https://bugs.llvm.org/show_bug.cgi?id=37841.

Reviewers: ruiu, pcc, chh, javed.absar, espindola

Subscribers: emaste, arichardson, llvm-commits, srhines

Differential Revision: https://reviews.llvm.org/D51671

llvm-svn: 342432
2018-09-18 00:24:48 +00:00
Sean Fertile 72435e5701 [PPC64] Support relaxing R_PPC64_TLSGD16 in TlsGdtoLe relaxation.
A General-dynamic tls access can be written using a R_PPC64_TLSGD16 relocation
if the target got entry is within 16 bits of the TOC-base. This patch adds
support for R_PPC64_TLSGD16 by relaxing it the same as a R_PPC64_GOT_TLSGD16_LO.

Differential Revision: https://reviews.llvm.org/D52055

llvm-svn: 342411
2018-09-17 20:27:02 +00:00
Nico Weber 5ffd8cedf4 lld-link: Also demangle undefined dllimported symbols.
dllimported symbols go through an import stub that's called __imp_ followed by
the name the stub points to. Make that work.

Differential Revision: https://reviews.llvm.org/D52145

llvm-svn: 342401
2018-09-17 16:31:20 +00:00
Nico Weber 0bd2d304e6 lld-link: Set PDB GUID to hash of PDB contents instead of to a random byte sequence.
Previously, lld-link would use a random byte sequence as the PDB GUID. Instead,
use a hash of the PDB file contents.

To not disturb llvm-pdbutil pdb2yaml, the hash generation is an opt-in feature
on InfoStreamBuilder and ldb/COFF/PDB.cpp always sets it.

Since writing the PDB computes this ID which also goes in the exe, the PDB
writing code now must be called before writeBuildId(). writeBuildId() for that
reason is no longer included in the "Code Layout" timer.

Since the PDB GUID is now a function of the PDB contents, the PDB Age is always
set to 1. There was a long comment above loadExistingBuildId (now gone) about
how not changing the GUID and only incrementing the age was important, but
according to the discussion in PR35914 that comment was incorrect.

Differential Revision: https://reviews.llvm.org/D51956

llvm-svn: 342334
2018-09-15 18:37:22 +00:00
Nico Weber da15acbd68 lld-link: print demangled symbol names for "undefined symbol" diagnostics
For this, add a few toString() calls when printing the "undefined symbol"
diagnostics; toString() already does demangling on Windows hosts.

Also make lld::demangleMSVC() (called by toString(Symbol*)) call LLVM's
microsoftDemangle() instead of UnDecorateSymbolName() so that it works on
non-Windows hosts – this makes both updating tests easier and provides a better
user experience for people doing cross-links.

This doesn't yet do the right thing for symbols starting with __imp_, but that
can be improved in a follow-up.

Differential Revision: https://reviews.llvm.org/D52104

llvm-svn: 342332
2018-09-15 18:27:09 +00:00
Martin Storsjo 7a41693898 [COFF] Provide __CTOR_LIST__ and __DTOR_LIST__ symbols for MinGW
MinGW uses these kind of list terminator symbols for traversing
the constructor/destructor lists. These list terminators are
actual pointers entries in the lists, with the values 0 and
(uintptr_t)-1 (instead of just symbols pointing to the start/end
of the list).

(This mechanism exists in both the mingw-w64 crt startup code and
in libgcc; normally the mingw-w64 one is used, but a DLL build of
libgcc uses the libgcc one. Therefore it's not trivial to change
the mechanism without lots of cross-project synchronization and
potentially invalidating some combinations of old/new versions
of them.)

When mingw-w64 has been used with lld so far, the CRT startup object
files have so far provided these symbols, ending up with different,
incompatible builds of the CRT startup object files depending on
whether binutils or lld are going to be used.

In order to avoid the need of different configuration of the CRT startup
object files depending on what linker to be used, provide these symbols
in lld instead. (Mingw-w64 checks at build time whether the linker
provides these symbols or not.) This unifies this particular detail
between the two linkers.

This does disallow the use of the very latest lld with older versions
of mingw-w64 (the configure check for the list was added recently;
earlier it simply checked whether the CRT was built with gcc or clang),
and requires rebuilding the mingw-w64 CRT. But the number of users of
lld+mingw still is low enough that such a change should be tolerable,
and unifies this aspect of the toolchains, easing interoperability
between the toolchains for the future.

The actual test for this feature is added in ctors_dtors_priority.s,
but a number of other tests that checked absolute output addresses
are updated.

Differential Revision: https://reviews.llvm.org/D52053

llvm-svn: 342294
2018-09-14 22:26:59 +00:00
Ed Maste c0b474f67a lld: add -z interpose support
-z interpose sets the DF_1_INTERPOSE flag, marking the object as an
interposer.

Via FreeBSD PR 230604, linking Valgrind with lld failed.

Differential Revision:	https://reviews.llvm.org/D52094

llvm-svn: 342239
2018-09-14 14:25:37 +00:00
Martin Storsjo 4c1b815d39 [COFF] Allow embedded directives to be separated by null bytes
The PE spec says that they will be separated by spaces, but link.exe
handles it just fine if they are separated by null bytes as well.

This adds tests to the lld repo, with the actual functional change
in LLVM in SVN r342204.

Differential Revision: https://reviews.llvm.org/D52014

llvm-svn: 342206
2018-09-14 06:08:56 +00:00
Rui Ueyama 11ca38f421 COFF: Add support for /force:multiple option
Patch by Thomas Roughton.

This patch adds support for linking with multiple definitions to LLD's
COFF driver, in line with link.exe's /force:multiple option.

Differential Revision: https://reviews.llvm.org/D50598

llvm-svn: 342191
2018-09-13 22:05:10 +00:00
Nico Weber f1828e3240 lld-link: For nonexisting inputs, omit follow-on diagnostics
For lld-link missing.obj, lld-link currently prints:

  lld-link: error: could not open foo.obj: No such file or directory
  lld-link: warning: /machine is not specified. x64 is assumed
  lld-link: error: subsystem must be defined

The 2nd and 3rd diagnostics are consequences of the input not existing and are
not interesting. If input files are missing, the best thing we can do is point
that out and then return.

Differential Revision: https://reviews.llvm.org/D51981

llvm-svn: 342158
2018-09-13 18:13:21 +00:00
Peter Smith f31f596152 [ELF] Guard --fix-cortex-a53-843419 against --just-syms
If --just-syms is used the mapping symbols from the ELF file will be
absolute symbols with no section. The code to process mapping symbols in
--fix-cortex-a53-843419 assumes that these symbols have a defining section
so a crash will result when --just-syms is used. The simple fix is to not
process the symbol when it doesn't have a section.

Fixes PR37971

Differential Revision: https://reviews.llvm.org/D52038

llvm-svn: 342146
2018-09-13 15:49:13 +00:00
Azharuddin Mohammed 4dce517c47 Add missing REQUIRES x86 to test/COFF/icf-safe.s
Reviewers: ruiu, pcc

Reviewed By: ruiu

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D51764

llvm-svn: 342145
2018-09-13 15:40:19 +00:00
Zachary Turner a1f85f8bdd [PDB] Emit old fpo data to the PDB file.
r342003 added support for emitting FPO data from the
DEBUG_S_FRAMEDATA subsection of the .debug$S section to the PDB
file.  However, that is not the end of the story.  FPO can end
up in two different destinations in a PDB, each corresponding to
a different FPO data source.

The case handled by r342003 involves copying data from the
DEBUG_S_FRAMEDATA subsection of the .debug$S section to the
"New FPO" stream in the PDB, which is then referred to by the
DBI stream.  The case handled by this patch involves copying
records from the .debug$F section of an object file to the "FPO"
stream (or perhaps more aptly, the "Old FPO" stream) in the PDB
file, which is also referred to by the DBI stream.

The formats are largely similar, and the difference is mostly
only visible in masm generated object files, such as some of the
low-level CRT object files like memcpy.  MASM doesn't appear to
support writing the DEBUG_S_FRAMEDATA subsection, and instead
just writes these records to the .debug$F section.

Although clang-cl does not emit a .debug$F section ever, lld still
needs to support it so we have good debugging for CRT functions.

Differential Revision: https://reviews.llvm.org/D51958

llvm-svn: 342080
2018-09-12 21:02:01 +00:00
Chih-Hung Hsieh 73e04847bf [ELF] Revert "Also demote lazy symbols."
This reverts commit https://reviews.llvm.org/rL330869
for a regression to link Android dex2oatds.

Differential Revision: https://reviews.llvm.org/D51892

llvm-svn: 342007
2018-09-11 23:00:36 +00:00
Zachary Turner 42e7cc1b0f [PDB] Write FPO Data to the PDB.
llvm-svn: 342003
2018-09-11 22:35:01 +00:00
Reid Kleckner a6f64265ea [codeview] Decode and dump FP regs from S_FRAMEPROC records
Summary:
There are two registers encoded in the S_FRAMEPROC flags: one for locals
and one for parameters. The encoding is described by the
ExpandEncodedBasePointerReg function in cvinfo.h. Two bits are used to
indicate one of four possible values:

  0: no register - Used when there are no variables.
  1: SP / standard - Variables are stored relative to the standard SP
     for the ISA.
  2: FP - Variables are addressed relative to the ISA frame
     pointer, i.e. EBP on x86. If realignment is required, parameters
     use this. If a dynamic alloca is used, locals will be EBP relative.
  3: Alternative - Variables are stored relative to some alternative
     third callee-saved register. This is required to address highly
     aligned locals when there are dynamic stack adjustments. In this
     case, both the incoming SP saved in the standard FP and the current
     SP are at some dynamic offset from the locals. LLVM uses ESI in
     this case, MSVC uses EBX.

Most of the changes in this patch are to pass around the CPU so that we
can decode these into real, named architectural registers.

Subscribers: hiraditya

Differential Revision: https://reviews.llvm.org/D51894

llvm-svn: 341999
2018-09-11 22:00:50 +00:00
Petr Hosek c6a233a68a [ELF] Don't emit .relr.dyn section if there are no relocs
This resolves PR38875.

Differential Revision: https://reviews.llvm.org/D51834

llvm-svn: 341870
2018-09-10 21:54:56 +00:00
Martin Storsjo db62913f28 [MinGW] Hook up the --require-defined option to -include:
Differential Revision: https://reviews.llvm.org/D51840

llvm-svn: 341846
2018-09-10 17:41:40 +00:00
Alexandre Ganea d93b07f0b0 [LLD][COFF] Cleanup error messages / add more coverage tests
- Log the reason for a PDB or precompiled-OBJ load failure
- Properly handle out-of-date PDB or precompiled-OBJ signature by displaying a corresponding error
- Slightly change behavior on PDB failure: any subsequent load attempt from another OBJ would result in the same error message being logged
- Slightly change behavior on PDB failure: retry with filename only if previous error was ENOENT ("no such file or directory")
- Tests: a. for native PDB errors; b. cover all the cases above

Differential Revision: https://reviews.llvm.org/D51559

llvm-svn: 341825
2018-09-10 13:51:21 +00:00
Fangrui Song 1fe3e8b26f [ELF] Check if LinkSec is nullptr when initializing SHF_LINK_ORDER sections
Summary: This protects lld from a null pointer dereference when a faulty input file has such invalid sh_link fields.

Reviewers: ruiu, espindola

Reviewed By: ruiu

Subscribers: emaste, arichardson, llvm-commits

Differential Revision: https://reviews.llvm.org/D51743

llvm-svn: 341611
2018-09-07 00:18:07 +00:00
Bob Haarman 2ba4d231d1 [COFF] don't mark lazy symbols as used in regular objects
Summary:
r338767 updated the COFF and wasm linker SymbolTable code to be
strutured more like the ELF linker's. That inadvertedly changed the
behavior of the COFF linker so that lazy symbols would be marked as
used in regular objects. This change adds an overload of the insert()
function, similar to the ELF linker, which does not perform that
marking.

Reviewers: ruiu, rnk, hans

Subscribers: aheejin, sunfish, llvm-commits

Differential Revision: https://reviews.llvm.org/D51720

llvm-svn: 341585
2018-09-06 20:23:56 +00:00
Nico Weber 13b55bbc2f lld-link: Write an empty "repro" debug directory entry if /Brepro is passed
If the coff timestamp is set to a hash, like lld-link does if /Brepro is
passed, the coff spec suggests that a IMAGE_DEBUG_TYPE_REPRO entry is in the
debug directory. This lets lld-link write such a section.
Fixes PR38429, see bug for details.

Differential Revision: https://reviews.llvm.org/D51652

llvm-svn: 341486
2018-09-05 18:02:43 +00:00
Martin Storsjo a47957ab13 [COFF] Allow exporting all symbols from system libraries specfied with -wholearchive:
When building a shared libc++.dll, it pulls in libc++abi.a statically
with the --wholearchive flag. If such a build is done with
--export-all-symbols, it's reasonable to assume that everything
from that library also should be exported with the same rules as normal
local object files, even though we normally avoid autoexporting things
from libc++abi.a in other cases when linking a DLL (user code).

Differential Revision: https://reviews.llvm.org/D51529

llvm-svn: 341403
2018-09-04 20:56:56 +00:00
Ben Dunbobbin d2c2c57f52 [LLD] Add test missed from r341206. NFC.
llvm-svn: 341207
2018-08-31 12:09:21 +00:00
Ben Dunbobbin df6f0ad210 [LLD] Check too large offsets into merge sections earlier
This patch moves the checking for too large offsets into merge sections
earlier.

Without this change the large offset generated in the added test-case
will cause an assert (as it happens to be a value reserved as a
"tombstone" in the DenseMap implementation) when OffsetMap is queried in
getSectionPiece().

To simplify the code and avoid future mistakes I have refactored so that
there is only one function that looks up offsets in the OffsetMap.

Differential Revision: https://reviews.llvm.org/D51180

llvm-svn: 341206
2018-08-31 11:51:51 +00:00
Martin Storsjo 802fcb4167 [COFF] When doing automatic dll imports, replace whole .refptr.<var> chunks with __imp_<var>
After fixing up the runtime pseudo relocation, the .refptr.<var>
will be a plain pointer with the same value as the IAT entry itself.
To save a little binary size and reduce the number of runtime pseudo
relocations, redirect references to the IAT entry (via the __imp_<var>
symbol) itself and discard the .refptr.<var> chunk (as long as the
same section chunk doesn't contain anything else than the single
pointer).

As there are now cases for both setting the Live variable to true
and false externally, remove the accessors and setters and just make
the variable public instead.

Differential Revision: https://reviews.llvm.org/D51456

llvm-svn: 341175
2018-08-31 07:45:20 +00:00
Fangrui Song f1126325e8 [PPC64] Improve a test ppc64_entry_point.s
Rename to ppc64-entry-point.s
Deduplicate .text dump of little-endian big-endian

llvm-svn: 341153
2018-08-31 00:33:16 +00:00
Fangrui Song 0f0f8aa2e1 Import lit.llvm after rLLD341134
llvm-svn: 341150
2018-08-31 00:23:09 +00:00
Fangrui Song d958df8324 [PPC64] Improve a test ppc64-toc-rel.s
Deduplicate dump of .text .data for little-endian and big-endian
Fix a RELOCS-NE check line typo

llvm-svn: 341148
2018-08-31 00:16:22 +00:00
Fangrui Song c799893787 [PPC64] Remove unused -z notext from a test
llvm-svn: 341139
2018-08-30 23:01:00 +00:00
Nico Weber abb8febb72 Remove LIT_SITE_CFG_IN_FOOTER, lld
It's always replaced with the same (short) static string, so just put that
there directly.

No intended behavior change.
https://reviews.llvm.org/D51357

llvm-svn: 341134
2018-08-30 22:12:16 +00:00
Martin Storsjo fcd552999f [COFF] Skip exporting artificial symbols when exporting all symbols
Differential Revision: https://reviews.llvm.org/D51457

llvm-svn: 341017
2018-08-30 05:44:41 +00:00
Martin Storsjo e5120a3bd4 [test] Adjust a test to use CHECK-NEXT instead of CHECK-NOT. NFC.
Since the order and placement of the non-wanted elements might not
be obvious, it feels more straightforward to hardcode the whole list
with -NEXT elements (and checking for the end of the output with
CHECK-EMPTY) instead of adding CHECK-NOT lines at the right places
where the unwanted elements would appear if they erroneously
were to included.

llvm-svn: 341016
2018-08-30 05:44:36 +00:00
Peter Collingbourne 6556e6b929 ELF: Don't examine values of linker script symbols during ICF.
These symbols are declared early with the same value, so they otherwise
appear identical to ICF.

Differential Revision: https://reviews.llvm.org/D51376

llvm-svn: 340998
2018-08-29 23:43:38 +00:00
Martin Storsjo bb0a3c911d [CMake] Add an lld-test-depends target
This builds all dependencies of lld-test/check-lld, without running
the tests. This matches llvm-test-depends and clang-test-depends.

Differential Revision: https://reviews.llvm.org/D51439

llvm-svn: 340943
2018-08-29 17:30:45 +00:00
Martin Storsjo cfbbb707f5 [COFF] Merge the .ctors, .dtors and .CRT sections into .rdata for MinGW
There's no point in keeping them as separate sections.

This differs from GNU ld, which places .ctors and .dtors content in
.text (implemented by a built-in linker script). But since the content
only is pointers, there's no need to have it executable.

GNU ld also leaves .CRT separate as its own standalone section.

MSVC merges .CRT into .rdata similarly, with a directive embedded in
an object file in msvcrt.lib or libcmt.lib.

Differential Revision: https://reviews.llvm.org/D51414

llvm-svn: 340940
2018-08-29 17:24:10 +00:00
Rui Ueyama 025bb56a86 Always add a .note.GNU-stack section if -r.
With this patch, lld creates a .note.GNU_stack and adds that to an
output file if it is creating a re-linkable object file (i.e. if -r
is given). If we don't do this, and if you use GNU linkers as a final
linker, they create an executable whose stack area is executable,
which is considered pretty bad these days.

Differential Revision: https://reviews.llvm.org/D51400

llvm-svn: 340902
2018-08-29 07:27:09 +00:00
Fangrui Song f9b789eaa4 [ELF] Change llvm-objdump -D to -d for check lines that only inspect text sections
Reviewers: ruiu, sfertile, syzaara, espindola

Subscribers: emaste, nemanjai, arichardson, kbarton, llvm-commits

Differential Revision: https://reviews.llvm.org/D51389

llvm-svn: 340890
2018-08-29 02:07:58 +00:00
Sean Fertile 4d354e1199 [PPC64] Fix DQ-form instruction handling and emit error for misalignment.
Relanding r340564, original commit message:

Fixes the handling of *_DS relocations used on DQ-form instructions where we
were overwriting some of the extended opcode bits. Also adds an alignment check
so that the user will receive a diagnostic error if the value we are writing
is not properly aligned.

Differential Revision: https://reviews.llvm.org/D51124

llvm-svn: 340832
2018-08-28 15:16:01 +00:00
George Rimar a46d08ebe6 [LLD][ELD] - Do not reject INFO output section type when used with a start address.
This is https://bugs.llvm.org/show_bug.cgi?id=38625

LLD accept this: 

".stack (INFO) : {", 

but not this:

".stack address_expression (INFO) :"

The patch fixes it.

Differential revision: https://reviews.llvm.org/D51027

llvm-svn: 340804
2018-08-28 08:39:21 +00:00
George Rimar 27bbe7d0b4 [LLF][ELF] - Support -z global.
-z global is a flag used on Android (see D49198).

Differential revision: https://reviews.llvm.org/D49374

llvm-svn: 340802
2018-08-28 08:24:34 +00:00
Sid Manning 569a56d6a0 [ELF][HEXAGON] Add R_HEX_11/10/9_X support
Differential Revision: https://reviews.llvm.org/D51225

llvm-svn: 340739
2018-08-27 12:55:28 +00:00
Matt Arsenault 8d6c7a63a1 Handle identifying AMDGPU bitcode files
llvm-svn: 340738
2018-08-27 12:40:00 +00:00
Martin Storsjo eac1b05f1d [COFF] Support MinGW automatic dllimport of data
Normally, in order to reference exported data symbols from a different
DLL, the declarations need to have the dllimport attribute, in order to
use the __imp_<var> symbol (which contains an address to the actual
variable) instead of the variable itself directly. This isn't an issue
in the same way for functions, since any reference to the function without
the dllimport attribute will end up as a reference to a thunk which loads
the actual target function from the import address table (IAT).

GNU ld, in MinGW environments, supports automatically importing data
symbols from DLLs, even if the references didn't have the appropriate
dllimport attribute. Since the PE/COFF format doesn't support the kind
of relocations that this would require, the MinGW's CRT startup code
has an custom framework of their own for manually fixing the missing
relocations once module is loaded and the target addresses in the IAT
are known.

For this to work, the linker (originall in GNU ld) creates a list of
remaining references needing fixup, which the runtime processes on
startup before handing over control to user code.

While this feature is rather controversial, it's one of the main features
allowing unix style libraries to be used on windows without any extra
porting effort.

Some sort of automatic fixing of data imports is also necessary for the
itanium C++ ABI on windows (as clang implements it right now) for importing
vtable pointers in certain cases, see D43184 for some discussion on that.

The runtime pseudo relocation handler supports 8/16/32/64 bit addresses,
either PC relative references (like IMAGE_REL_*_REL32*) or absolute
references (IMAGE_REL_AMD64_ADDR32, IMAGE_REL_AMD64_ADDR32,
IMAGE_REL_I386_DIR32). On linking, the relocation is handled as a
relocation against the corresponding IAT slot. For the absolute references,
a normal base relocation is created, to update the embedded address
in case the image is loaded at a different address.

The list of runtime pseudo relocations contains the RVA of the
imported symbol (the IAT slot), the RVA of the location the relocation
should be applied to, and a size of the memory location. When the
relocations are fixed at runtime, the difference between the actual
IAT slot value and the IAT slot address is added to the reference,
doing the right thing for both absolute and relative references.

With this patch alone, things work fine for i386 binaries, and mostly
for x86_64 binaries, with feature parity with GNU ld. Despite this,
there are a few gotchas:
- References to data from within code works fine on both x86 architectures,
  since their relocations consist of plain 32 or 64 bit absolute/relative
  references. On ARM and AArch64, references to data doesn't consist of
  a plain 32 or 64 bit embedded address or offset in the code. On ARMNT,
  it's usually a MOVW+MOVT instruction pair represented by a
  IMAGE_REL_ARM_MOV32T relocation, each instruction containing 16 bit of
  the target address), on AArch64, it's usually an ADRP+ADD/LDR/STR
  instruction pair with an even more complex encoding, storing a PC
  relative address (with a range of +/- 4 GB). This could theoretically
  be remedied by extending the runtime pseudo relocation handler with new
  relocation types, to support these instruction encodings. This isn't an
  issue for GCC/GNU ld since they don't support windows on ARMNT/AArch64.
- For x86_64, if references in code are encoded as 32 bit PC relative
  offsets, the runtime relocation will fail if the target turns out to be
  out of range for a 32 bit offset.
- Fixing up the relocations at runtime requires making sections writable
  if necessary, with the VirtualProtect function. In Windows Store/UWP apps,
  this function is forbidden.

These limitations are addressed by a few later patches in lld and
llvm.

Differential Revision: https://reviews.llvm.org/D50917

llvm-svn: 340726
2018-08-27 08:43:31 +00:00
Martin Storsjo c4b0061c05 [COFF] Check the instructions in ARM MOV32T relocations
For this relocation, which applies to two consecutive instructions,
it's plausible that the second instruction might not actually be
the right one.

Differential Revision: https://reviews.llvm.org/D50998

llvm-svn: 340715
2018-08-27 06:04:36 +00:00