Commit Graph

57 Commits

Author SHA1 Message Date
Fangrui Song 22c1bd57bf [ELF] Rename R_TLS to R_TPREL and R_NEG_TLS to R_TPREL_NEG. NFC
The scope of R_TLS (TP offset relocation types (TPREL/TPOFF) used for the
local-exec TLS model) is actually narrower than its name may imply. R_TLS_NEG
is only used by Solaris R_386_TLS_LE_32.

Rename them so that they will be less confusing.

Reviewed By: grimar, psmith, rprichard

Differential Revision: https://reviews.llvm.org/D93467
2020-12-18 08:24:42 -08:00
Fangrui Song c1a5f73a4a [ELF][ARM] Represent R_ARM_LDO32 as R_DTPREL instead of R_ABS
Follow-up to D82899. Note, we need to disable R_DTPREL relaxation
because ARM psABI does not define TLS relaxation.

Reviewed By: grimar, psmith

Differential Revision: https://reviews.llvm.org/D83138
2020-07-06 09:47:53 -07:00
Fangrui Song 07837b8f49 [ELF] Use namespace qualifiers (lld:: or elf::) instead of `namespace lld { namespace elf {`
Similar to D74882. This reverts much code from commit
bd8cfe65f5 (D68323) and fixes some
problems before D68323.

Sorry for the churn but D68323 was a mistake. Namespace qualifiers avoid
bugs where the definition does not match the declaration from the
header. See
https://llvm.org/docs/CodingStandards.html#use-namespace-qualifiers-to-implement-previously-declared-functions (D74515)

Differential Revision: https://reviews.llvm.org/D79982
2020-05-15 08:49:53 -07:00
Tobias Hieta 87383e408d [ELF][ARM] Increase default max-page-size from 4096 to 6536
See http://lists.llvm.org/pipermail/llvm-dev/2020-April/140549.html

For the record, GNU ld changed to 64k max page size in 2014
https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=7572ca8989ead4c3425a1500bc241eaaeffa2c89
"[RFC] ld/ARM: Increase maximum page size to 64kB"

Android driver forced 4k page size in AArch64 (D55029) and ARM (D77746).

A binary linked with max-page-size=4096 does not run on a system with a
higher page size configured. There are some systems out there that do
this and it leads to the binary getting `Killed!` by the kernel.

In the non-linker-script cases, when linked with -z noseparate-code
(default), the max-page-size increase should not cause any size
difference. There may be some VMA usage differences, though.

Reviewed By: psmith, MaskRay

Differential Revision: https://reviews.llvm.org/D77330
2020-04-18 08:19:45 -07:00
Peter Smith 28b172e341 [LLD][ELF][ARM] Implement ARM pc-relative relocations for ADR and LDR
The R_ARM_ALU_PC_G0 and R_ARM_LDR_PC_G0 relocations are used by the
ADR and LDR pseudo instructions, and are the basis of the group
relocations that can load an arbitrary constant via a series of add, sub
and ldr instructions.

The relocations need to be obtained via the .reloc directive.

R_ARM_ALU_PC_G0 is much more complicated as the add/sub instruction uses
a modified immediate encoding of an 8-bit immediate rotated right by an
even 4-bit field. This means that the range of representable immediates
is sparse. We extract the encoding and decoding functions for the modified
immediate from llvm/lib/Target/ARM/MCTargetDesc/ARMAddressingModes.h as
this header file is not accessible from LLD. Duplication of code isn't
ideal, but as these are well-defined mathematical functions they are
unlikely to change.

Differential Revision: https://reviews.llvm.org/D75349
2020-04-08 12:43:44 +01:00
Peter Smith 6b035b607f [LLD][ELF][ARM] Implement Thumb pc-relative relocations for adr and ldr
MC will now output the R_ARM_THM_PC8, R_ARM_THM_PC12 and
R_ARM_THM_PREL_11_0 relocations. These are short-ranged relocations that
are used to implement the adr rd, literal and ldr rd, literal pseudo
instructions.

The instructions use a new RelExpr called R_ARM_PCA in order to calculate
the required S + A - Pa expression, where Pa is AlignDown(P, 4) as the
instructions add their immediate to AlignDown(PC, 4). We also do not want
these relocations to generate or resolve against a PLT entry as the range
of these relocations is so short they would never reach.

The R_ARM_THM_PC8 has a special encoding convention for the relocation
addend, the immediate field is unsigned, yet the addend must be -4 to
account for the Thumb PC bias. The ABI (not the architecture) uses the
convention that the 8-byte immediate of 0xff represents -4.

Differential Revision: https://reviews.llvm.org/D75042
2020-02-28 11:29:29 +00:00
Tamas Petz 6e326882da [LLD][ELF][ARM] Fix support for SBREL type relocations
With this patch lld recognizes ARM SBREL relocations.
R_ARM*_MOVW_BREL relocations are not tested because they are not used.

Patch by Tamas Petz

Differential Revision: https://reviews.llvm.org/D74604
2020-02-19 10:07:46 +00:00
Peter Smith 29c1361557 [LLD][ELF][ARM] Do not substitute BL/BLX for non STT_FUNC symbols.
Recommit of 0b4a047bfb
(reverted in c29003813a) to incorporate
subsequent fix and add a warning when LLD's interworking behavior has
changed.

D73474 disabled the generation of interworking thunks for branch
relocations to non STT_FUNC symbols. This patch handles the case of BL and
BLX instructions to non STT_FUNC symbols. LLD would normally look at the
state of the caller and the callee and write a BL if the states are the
same and a BLX if the states are different.

This patch disables BL/BLX substitution when the destination symbol does
not have type STT_FUNC. This brings our behavior in line with GNU ld which
may prevent difficult to diagnose runtime errors when switching to lld.

This change does change how LLD handles interworking of symbols that do not
have type STT_FUNC from previous versions including the 10.0 release. This
brings LLD in line with ld.bfd but there may be programs that have not been
linked with ld.bfd that depend on LLD's previous behavior. We emit a warning
when the behavior changes.

A summary of the difference between 10.0 and 11.0 is that for symbols
that do not have a type of STT_FUNC LLD will not change a BL to a BLX or
vice versa. The table below enumerates the changes
| relocation     | STT_FUNC | bit(0) | in  | 10.0- out | 11.0+ out |
| R_ARM_CALL     | no       | 1      | BL  | BLX       | BL        |
| R_ARM_CALL     | no       | 0      | BLX | BL        | BLX       |
| R_ARM_THM_CALL | no       | 1      | BLX | BL        | BLX       |
| R_ARM_THM_CALL | no       | 0      | BL  | BLX       | BL        |

Differential Revision: https://reviews.llvm.org/D73542
2020-02-13 09:40:21 +00:00
Nico Weber c29003813a Revert "[LLD][ELF][ARM] Do not substitute BL/BLX for non STT_FUNC symbols."
There are still problems after the fix in
"[ELF][ARM] Fix regression of BL->BLX substitution after D73542"
so let's revert to get trunk back to green while we investigate.
See https://reviews.llvm.org/D73542

This reverts commit 5461fa2b1f.
This reverts commit 0b4a047bfb.
2020-02-07 08:55:52 -05:00
Fangrui Song 5461fa2b1f [ELF][ARM] Fix regression of BL->BLX substitution after D73542
D73542 made a typo (`rel.type == R_PLT_PC`; should be `rel.expr`) and introduced a regression:
BL->BLX substitution was disabled when the target symbol is preemptible
(expr is R_PLT_PC).

The two added bl instructions in arm-thumb-interwork-shared.s check that
we patch BL to BLX.

Fixes https://bugs.chromium.org/p/chromium/issues/detail?id=1047531
2020-02-05 14:09:14 -08:00
Peter Smith 0b4a047bfb [LLD][ELF][ARM] Do not substitute BL/BLX for non STT_FUNC symbols.
D73474 disabled the generation of interworking thunks for branch
relocations to non STT_FUNC symbols. This patch handles the case of BL and
BLX instructions to non STT_FUNC symbols. LLD would normally look at the
state of the caller and the callee and write a BL if the states are the
same and a BLX if the states are different.

This patch disables BL/BLX substitution when the destination symbol does
not have type STT_FUNC. This brings our behavior in line with GNU ld which
may prevent difficult to diagnose runtime errors when switching to lld.

Differential Revision: https://reviews.llvm.org/D73542
2020-01-29 11:42:25 +00:00
Peter Smith 4f38ab250f [LLD][ELF][ARM] Do not insert interworking thunks for non STT_FUNC symbols
ELF for the ARM architecture requires linkers to provide
interworking for symbols that are of type STT_FUNC. Interworking for
other symbols must be encoded directly in the object file. LLD was always
providing interworking, regardless of the symbol type, this breaks some
programs that have branches from Thumb state targeting STT_NOTYPE symbols
that have bit 0 clear, but they are in fact internal labels in a Thumb
function. LLD treats these symbols as ARM and inserts a transition to Arm.

This fixes the problem for in range branches, R_ARM_JUMP24,
R_ARM_THM_JUMP24 and R_ARM_THM_JUMP19. This is expected to be the vast
majority of problem cases as branching to an internal label close to the
function.

There is at least one follow up patch required.
- R_ARM_CALL and R_ARM_THM_CALL may do interworking via BL/BLX
  substitution.

In theory range-extension thunks can be altered to not change state when
the symbol type is not STT_FUNC. I will need to check with ld.bfd to see if
this is the case in practice.

Fixes (part of) https://github.com/ClangBuiltLinux/linux/issues/773

Differential Revision: https://reviews.llvm.org/D73474
2020-01-28 11:54:18 +00:00
Peter Smith 3238b03c19 [LLD][ELF][ARM] clang-format function signature [NFC]
ARM::needsThunk had gone over 80 characters, run clang-format over it to
prevent it wrapping.
2020-01-28 11:54:18 +00:00
Fangrui Song deb5819d62 [ELF] Rename relocateOne() to relocate() and pass `Relocation` to it
Symbol information can be used to improve out-of-range/misalignment diagnostics.
It also helps R_ARM_CALL/R_ARM_THM_CALL which has different behaviors with different symbol types.

There are many (67) relocateOne() call sites used in thunks, {Arm,AArch64}errata, PLT, etc.
Rename them to `relocateNoSym()` to be clearer that there is no symbol information.

Reviewed By: grimar, peter.smith

Differential Revision: https://reviews.llvm.org/D73254
2020-01-25 12:00:18 -08:00
Fangrui Song bec1b55c64 [ELF] Delete the RelExpr member R_HINT. NFC
R_HINT is ignored like R_NONE. There are no strong reasons to keep
R_HINT. The largest RelExpr member R_RISCV_PC_INDIRECT is 60 now.

Differential Revision: https://reviews.llvm.org/D71822
2020-01-14 10:56:53 -08:00
Fangrui Song 37b2808059 [ELF] writePlt, writeIplt: replace parameters gotPltEntryAddr and index with `const Symbol &`. NFC
PPC::writeIplt (IPLT code sequence, D71621) needs to access `Symbol`.

Reviewed By: grimar, ruiu

Differential Revision: https://reviews.llvm.org/D71631
2019-12-18 00:14:03 -08:00
Fangrui Song 891a8655ab [ELF] Add IpltSection
PltSection is used by both PLT and IPLT. The PLT section may have a
header while the IPLT section does not. Split off IpltSection from
PltSection to be clearer.

Unlike other targets, PPC64 cannot use the same code sequence for PLT
and IPLT. This helps make a future PPC64 patch (D71509) more isolated.

On EM_386 and EM_X86_64, when PLT is empty while IPLT is not, currently
we are inconsistent whether the PLT header is conceptually attached to
in.plt or in.iplt .  Consistently attach the header to in.plt can make
the -z retpolineplt logic simpler. It also makes `jmp` point to an
aesthetically better place for non-retpolineplt cases.

Reviewed By: grimar, ruiu

Differential Revision: https://reviews.llvm.org/D71519
2019-12-17 00:06:04 -08:00
Fangrui Song 90d195d026 [ELF] Delete relOff from TargetInfo::writePLT
This change only affects EM_386. relOff can be computed from `index`
easily, so it is unnecessarily passed as a parameter.

Both in.plt and in.iplt entries are written by writePLT. For in.iplt,
the instruction `push reloc_offset` will change because `index` is now
different. Fortunately, this does not matter because `push; jmp` is only
used by PLT. IPLT does not need the code sequence.

Reviewed By: grimar, ruiu

Differential Revision: https://reviews.llvm.org/D71518
2019-12-16 11:10:02 -08:00
Fangrui Song bf535ac4a2 [ELF][AArch64] Support R_AARCH64_{CALL26,JUMP26} range extension thunks with addends
Fixes AArch64 part of PR40438

The current range extension thunk framework does not handle a relocation
relative to a STT_SECTION symbol with a non-zero addend, which may be
used by jumps/calls to local functions on some RELA targets (AArch64,
powerpc ELFv1, powerpc64 ELFv2, etc).  See PR40438 and the following
code for examples:

  // clang -target $target a.cc
  // .text.cold may be placed in a separate output section.
  // The distance between bar in .text.cold and foo in .text may be larger than 128MiB.
  static void foo() {}
  __attribute__((section(".text.cold"))) static int bar() { foo(); return
  0; }
  __attribute__((used)) static int dummy = bar();

This patch makes such thunks with addends work for AArch64. The target
independent part can be reused by PPC in the future.

On REL targets (ARM, MIPS), jumps/calls are not represented as
STT_SECTION + non-zero addend (see
MCELFObjectTargetWriter::needsRelocateWithSymbol), so they don't need
this feature, but we need to make sure this patch does not affect them.

Reviewed By: peter.smith

Differential Revision: https://reviews.llvm.org/D70637
2019-12-02 10:07:24 -08:00
Fangrui Song bd8cfe65f5 [ELF] Wrap things in `namespace lld { namespace elf {`, NFC
This makes it clear `ELF/**/*.cpp` files define things in the `lld::elf`
namespace and simplifies `elf::foo` to `foo`.

Reviewed By: atanasyan, grimar, ruiu

Differential Revision: https://reviews.llvm.org/D68323

llvm-svn: 373885
2019-10-07 08:31:18 +00:00
Fangrui Song 47cfe8f321 [ELF] Fix variable names in comments after VariableName -> variableName change
Also fix some typos.

llvm-svn: 366181
2019-07-16 05:50:45 +00:00
Rui Ueyama 3837f4273f [Coding style change] Rename variables so that they start with a lowercase letter
This patch is mechanically generated by clang-llvm-rename tool that I wrote
using Clang Refactoring Engine just for creating this patch. You can see the
source code of the tool at https://reviews.llvm.org/D64123. There's no manual
post-processing; you can generate the same patch by re-running the tool against
lld's code base.

Here is the main discussion thread to change the LLVM coding style:
https://lists.llvm.org/pipermail/llvm-dev/2019-February/130083.html
In the discussion thread, I proposed we use lld as a testbed for variable
naming scheme change, and this patch does that.

I chose to rename variables so that they are in camelCase, just because that
is a minimal change to make variables to start with a lowercase letter.

Note to downstream patch maintainers: if you are maintaining a downstream lld
repo, just rebasing ahead of this commit would cause massive merge conflicts
because this patch essentially changes every line in the lld subdirectory. But
there's a remedy.

clang-llvm-rename tool is a batch tool, so you can rename variables in your
downstream repo with the tool. Given that, here is how to rebase your repo to
a commit after the mass renaming:

1. rebase to the commit just before the mass variable renaming,
2. apply the tool to your downstream repo to mass-rename variables locally, and
3. rebase again to the head.

Most changes made by the tool should be identical for a downstream repo and
for the head, so at the step 3, almost all changes should be merged and
disappear. I'd expect that there would be some lines that you need to merge by
hand, but that shouldn't be too many.

Differential Revision: https://reviews.llvm.org/D64121

llvm-svn: 365595
2019-07-10 05:00:37 +00:00
Fangrui Song ffed2c96d9 [ELF][ARM] Merge handleARMTlsRelocation() into handleTlsRelocation()
ARM and RISC-V do not support TLS relaxations. However, for General
Dynamic and Local Dynamic models, if we are producing an executable and
the symbol is non-preemptable, we know it must be defined and the
R_ARM_TLS_DTPMOD32/R_RISCV_TLS_DTPMOD{32,64} dynamic relocation can be
omitted because it is always 1. This may be necessary for static linking
as DTPMOD may not be expected at load time.

Merge handleARMTlsRelocation() into handleTlsRelocation(). This requires
more logic to R_TLSGD_PC and R_TLSLD_PC. Because we use SymbolicRel to
resolve the relocation at link time, R_ARM_TLS_DTPMOD32 can be deleted
from relocateOne(). It cannot be used as a static relocation type.

As a bonus, the additional logic in R_TLSGD_PC code can be shared by the
TLS support for RISC-V (D63220).

Reviewed By: ruiu

Differential Revision: https://reviews.llvm.org/D63333

llvm-svn: 363927
2019-06-20 13:53:11 +00:00
Fangrui Song 025a815d75 [ELF] Make the rule to create relative relocations in a writable section stricter
The current rule is loose: `!Sym.IsPreemptible || Expr == R_GOT`.

When the symbol is non-preemptable, this allows absolute relocation
types with smaller numbers of bits, e.g. R_X86_64_{8,16,32}. They are
disallowed by ld.bfd and gold, e.g.

    ld.bfd: a.o: relocation R_X86_64_8 against `.text' can not be used when making a shared object; recompile with -fPIC

This patch:

a) Add TargetInfo::SymbolicRel to represent relocation types that resolve to a
symbol value (e.g. R_AARCH_ABS64, R_386_32, R_X86_64_64).

  As a side benefit, we currently (ab)use GotRel (R_*_GLOB_DAT) to resolve
  GOT slots that are link-time constants. Since we now use Target->SymbolRel
  to do the job, we can remove R_*_GLOB_DAT from relocateOne() for all targets.
  R_*_GLOB_DAT cannot be used as static relocation types.
b) Change the condition to `!Sym.IsPreemptible && Type != Target->SymbolicRel || Expr == R_GOT`.

Some tests are caught by the improved error checking (ld.bfd/gold also
issue errors on them). Many misuse .long where .quad should be used
instead.

Reviewed By: ruiu

Differential Revision: https://reviews.llvm.org/D63121

llvm-svn: 363059
2019-06-11 12:59:30 +00:00
Fangrui Song e98baf8631 [ELF] Delete GotEntrySize and GotPltEntrySize
GotEntrySize and GotPltEntrySize were added in D22288. Later, with
the introduction of wordsize() (then Config->Wordsize), they become
redundant, because there is no target that sets GotEntrySize or
GotPltEntrySize to a number different from Config->Wordsize.

Reviewed By: grimar, ruiu

Differential Revision: https://reviews.llvm.org/D62727

llvm-svn: 362220
2019-05-31 10:35:45 +00:00
George Rimar 77b4f0abb8 [LLD][ELF] - Improve diagnostic about unrecognized relocations.
This is a minor improvement inspired by https://bugs.llvm.org/show_bug.cgi?id=38303.

A person reported that he observed message complaining about unsupported R_ARM_V4BX:
error: can't create dynamic relocation R_ARM_V4BX against local symbol in readonly segment; recompile object files with -fPIC

But with -z notext he only saw a relocation number, what is not convenient:
error: ../../gfx/cairo/libpixman/src/pixman-arm-neon-asm-bilinear.o:(.text+0x4F0): unrecognized reloc 40

Also, in the error messages we use relocation but not reloc.

With this patch we start to print one of the following messages:
error: file.o: unrecognized relocation Unknown(999)
error: file.o: unrecognized relocation R_X_KNOWN_BY_LLVM_BUT_UNSUPPORTED_BY_LLD_NAME

There is no way to write a test for that I believe.

Differential revision: https://reviews.llvm.org/D62237

llvm-svn: 361472
2019-05-23 09:50:18 +00:00
Chandler Carruth 2946cd7010 Update the file headers across all of the LLVM projects in the monorepo
to reflect the new license.

We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.

Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.

llvm-svn: 351636
2019-01-19 08:50:56 +00:00
Peter Smith 1811e48b7b [ELF] Fix ARM and Thumb V7PILongThunk overflow behavior.
When the range between the source and target of a V7PILongThunk exceeded an
int32 we would trigger a relocation out of range error for the
R_ARM_MOVT_PREL or R_ARM_THM_MOVT_PREL relocation. This case can happen when
linking the linux kernel as it is loaded above 0xf0000000.

There are two parts to the fix.
- Remove the overflow check for R_ARM_MOVT_PREL or R_ARM_THM_MOVT_PREL. The
ELF for the ARM Architecture document defines these relocations as having no
overflow checking so the check was spurious.
- Use int64_t for the offset calculation, in line with similar thunks so
that PC + (S - P) < 32-bits. This results in less surprising disassembly.

Differential Revision: https://reviews.llvm.org/D56396

llvm-svn: 350836
2019-01-10 16:08:23 +00:00
Peter Collingbourne ae15e7232a ELF: Handle R_ARM_V4BX correctly in PIC output files.
Previously we considered R_ARM_V4BX to be an absolute relocation,
which meant that we rejected it in read-only sections in PIC output
files. Instead, treat it as a hint relocation so that relocation
processing ignores it entirely.

Also fix a problem with the test case where it was never being run
because it has a .yaml extension and we don't run tests with that
extension.

Differential Revision: https://reviews.llvm.org/D55728

llvm-svn: 349216
2018-12-15 00:20:17 +00:00
Fangrui Song 113d868ff1 Support ARM_V4BX relocation
Summary: This patch implementation the handler for ARM_V4BX. This relocation is used by GNU runtime files and other armv4 applications.

Patch by Yin Ma

Reviewers: espindola, MaskRay, ruiu, peter.smith, pcc

Reviewed By: ruiu

Subscribers: yinma, pcc, peter.smith, MaskRay, rovka, efriedma, emaste, javed.absar, arichardson, kristof.beyls, chrib, llvm-commits

Differential Revision: https://reviews.llvm.org/D53444

llvm-svn: 347077
2018-11-16 19:24:45 +00:00
Simon Atanasyan b0486051d2 [ELF] Make TrapInstr and Filler byte arrays. NFC.
The uint32_t type does not clearly convey that these fields are interpreted
in the target endianness. Converting them to byte arrays should make this
more obvious and less error-prone.

Patch by James Clarke

Differential Revision: http://reviews.llvm.org/D54207

llvm-svn: 346893
2018-11-14 21:05:20 +00:00
Ryan Prichard e7cb0225a0 [ELF] Refactor per-target TLS layout configuration. NFC.
Summary:
There are really three different kinds of TLS layouts:

 * A fixed TLS-to-TP offset. On architectures like PowerPC, MIPS, and
   RISC-V, the thread pointer points to a fixed offset from the start
   of the executable's TLS segment. The offset is 0x7000 for PowerPC
   and MIPS, which allows a signed 16-bit offset to reach 0x1000 of
   per-thread implementation data and 0xf000 of the application's TLS
   segment. The size and layout of the TCB isn't relevant to the static
   linker and might not be known.

 * A fixed TCB size. This is the format documented as "variant 1" in
   Ulrich Drepper's TLS spec. The thread pointer points to a 2-word TCB
   followed by the executable's TLS segment. The first word is always
   the DTV pointer. Used on ARM. The thread pointer must be aligned to
   the TLS segment's alignment, possibly creating alignment padding.

 * Variant 2. This format predates variant 1 and is also documented in
   Drepper's TLS spec. It allocates the executable's TLS segment before
   the thread pointer, apparently for backwards-compatibility. It's
   used on x86 and SPARC.

Factor out an lld:🧝:getTlsTpOffset() function for use in a
follow-up patch for Android. The TcbSize/TlsTpOffset fields are only used
in getTlsTpOffset, so replace them with a switch on Config->EMachine.

Reviewers: espindola, ruiu, PkmX, jrtc27

Reviewed By: ruiu, PkmX, jrtc27

Subscribers: jyknight, emaste, sdardis, nemanjai, javed.absar, arichardson, kristof.beyls, kbarton, fedor.sergeev, atanasyan, PkmX, jsji, llvm-commits

Differential Revision: https://reviews.llvm.org/D53905

llvm-svn: 345775
2018-10-31 20:53:17 +00:00
George Rimar 95aae4c59d [ELF] - Do not fail on R_*_NONE relocations when parsing the debug info.
This is https://bugs.llvm.org//show_bug.cgi?id=38919.

Currently, LLD may report "unsupported relocation target while parsing debug info"
when parsing the debug information.

At the same time LLD does that for zeroed R_X86_64_NONE relocations,
which obviously has "invalid" targets.

The nature of R_*_NONE relocation assumes them should be ignored.
This patch teaches LLD to stop reporting the debug information parsing errors for them.

Differential revision: https://reviews.llvm.org/D52408

llvm-svn: 343078
2018-09-26 08:11:34 +00:00
Rui Ueyama 4e247522ac Reset input section pointers to null on each linker invocation.
Previously, if you invoke lld's `main` more than once in the same process,
the second invocation could fail or produce a wrong result due to a stale
pointer values of the previous run.

Differential Revision: https://reviews.llvm.org/D52506

llvm-svn: 343009
2018-09-25 19:26:58 +00:00
Peter Smith a8656c62f5 [ELF] Add support for Armv5 and Armv6 compatible Thunks
Older Arm architectures do not support the MOVT and MOVW instructions so we
must use an alternative sequence of instructions to transfer control to the
destination.

Assuming at least Armv5 this patch adds support for Thunks that load or add
to the program counter. Note that there are no Armv5 Thumb Thunks as there
is no Thumb branch instruction in Armv5 that supports Thunks. These thunks
will not work for Armv4t (arm7tdmi) as this architecture cannot change state
from using the LDR or ADD instruction.

Differential Revision: https://reviews.llvm.org/D50077

llvm-svn: 340160
2018-08-20 09:37:50 +00:00
Peter Smith d1be026ede [ELF] Add support for older Arm Architectures with smaller branch range
The Thumb BL and BLX instructions on older Arm Architectures such as v5 and
v6 have a constrained encoding J1 and J2 must equal 1, later Architectures
relaxed this restriction allowing J1 and J2 to be used to calculate a larger
immediate.

This patch adds support for the old encoding, it is used when the build
attributes for the input objects only contain older architectures.

Differential Revision: https://reviews.llvm.org/D50076

llvm-svn: 340159
2018-08-20 09:19:30 +00:00
Peter Smith 70997f9a4e [ELF][ARM] Implement support for Tag_ABI_VFP_args
The Tag_ABI_VFP_args build attribute controls the procedure call standard
used for floating point parameters on ARM. The values are:
0 - Base AAPCS (FP Parameters passed in Core (Integer) registers
1 - VFP AAPCS (FP Parameters passed in FP registers)
2 - Toolchain specific (Neither Base or VFP)
3 - Compatible with all (No use of floating point parameters)

If the Tag_ABI_VFP_args build attribute is missing it has an implicit value
of 0.
    
We use the attribute in two ways:
- Detect a clash in calling convention between Base, VFP and Toolchain.
we follow ld.bfd's lead and do not error if there is a clash between an
implicit Base AAPCS caused by a missing attribute. Many projects
including the hard-float (VFP AAPCS) version of glibc contain assembler
files that do not use floating point but do not have Tag_ABI_VFP_args.
- Set the EF_ARM_ABI_FLOAT_SOFT or EF_ARM_ABI_FLOAT_HARD ELF header flag
for Base or VFP AAPCS respectively. This flag is used by some ELF
loaders.
    
References:
- Addenda to, and Errata in, the ABI for the ARM Architecture for
Tag_ABI_VFP_args
- Elf for the ARM Architecture for ELF header flags
    
Fixes PR36009
    
Differential Revision: https://reviews.llvm.org/D49993

llvm-svn: 338377
2018-07-31 13:41:59 +00:00
George Rimar f9936e1fc9 [ELF] - Eliminate Target::isPicRel method.
As was mentioned in comments for D45158,
isPicRel's name does not make much sense,
because what this method does is checks if
we need to create the dynamic relocation or not.

Instead of renaming it to something different,
we can 'isPicRel' completely.

We can reuse the getDynRel method.
They are logically very close, getDynRel can just return
R_*_NONE in case no dynamic relocation should be produced
and that would simplify things and avoid functionality
correlation/duplication with 'isPicRel'.

The patch does this change.

Differential revision: https://reviews.llvm.org/D45248

llvm-svn: 329275
2018-04-05 12:07:20 +00:00
Rui Ueyama f001ead490 Do not use template for check{Int,UInt,IntUInt,Alignment}.
Template is just unnecessary.

Differential Revision: https://reviews.llvm.org/D45063

llvm-svn: 328843
2018-03-29 22:40:52 +00:00
Peter Smith 3d044f57d4 [ELF] Recommit 327248 with Arm using the .got for _GLOBAL_OFFSET_TABLE_
This is the same as 327248 except Arm defining _GLOBAL_OFFSET_TABLE_ to
be the base of the .got section as some existing code is relying upon it.

For most Targets the _GLOBAL_OFFSET_TABLE_ symbol is expected to be at
the start of the .got.plt section so that _GLOBAL_OFFSET_TABLE_[0] =
reserved value that is by convention the address of the dynamic section.
Previously we had defined _GLOBAL_OFFSET_TABLE_ as either the start or end
of the .got section with the intention that the .got.plt section would
follow the .got. However this does not always hold with the current
default section ordering so _GLOBAL_OFFSET_TABLE_[0] may not be consistent
with the reserved first entry of the .got.plt.

X86, X86_64 and AArch64 will use the .got.plt. Arm, Mips and Power use .got

Fixes PR36555

Differential Revision: https://reviews.llvm.org/D44259

llvm-svn: 327823
2018-03-19 06:52:51 +00:00
Rafael Espindola 1037eef8e0 Use references instead of pointers. NFC.
These values are trivially never null. While at it, also use
InputSection instead of InputSectionBase when possible.

llvm-svn: 321126
2017-12-19 23:59:35 +00:00
Shoaib Meenai 8c023a9cd9 [ELF] Fix typo in comment. NFC
llvm-svn: 321022
2017-12-18 20:33:27 +00:00
Peter Smith 3c73a41128 [ELF] Optimize Arm PLT sequences
A more efficient PLT sequence can be used when the distance between the
.plt and the end of the .plt.got is less than 128 Megabytes, which is
frequently true. We fall back to the old sequence when the offset is larger
than 128 Megabytes. This gives us an alternative to forcing the longer
entries with --long-plt as we gracefully fall back to it as needed. 

See ELF for the ARM Architecture Appendix A for details of the PLT sequence.

Differential Revision: https://reviews.llvm.org/D41246

llvm-svn: 320987
2017-12-18 14:46:27 +00:00
Peter Smith 2809926c4d [ELF][ARM] Refine check for when undefined weak needs a Thunk
When an undefined weak reference has a PLT entry we must generate a range
extension thunk for any B or BL that can't reach the PLT entry.

This change explicitly looks for whether a PLT entry exists rather than
assuming that weak references never need PLT entries unless Config->Shared
is in operation. This covers the case where we are linking an executable
with dynamic linking, hence a PLT entry will be needed for undefined weak
references. This case comes up in real programs over 32 Mb in size as there
is a B to a weak reference __gmon__start__ in the Arm crti.o for glibc.

Differential Revision: https://reviews.llvm.org/D40248

llvm-svn: 319020
2017-11-27 11:49:18 +00:00
Rui Ueyama f52496e1e0 Rename SymbolBody -> Symbol
Now that we have only SymbolBody as the symbol class. So, "SymbolBody"
is a bit strange name now. This is a mechanical change generated by

  perl -i -pe s/SymbolBody/Symbol/g $(git grep -l SymbolBody lld/ELF lld/COFF)

nd clang-format-diff.

Differential Revision: https://reviews.llvm.org/D39459

llvm-svn: 317370
2017-11-03 21:21:47 +00:00
Peter Smith 75030b6d56 [ELF] Introduce range extension thunks for ARM
This change adds initial support for range extension thunks. All thunks must
be created within the first pass so some corner cases are not supported. A
follow up patch will add support for multiple passes.

With this change the existing tests arm-branch-error.s and
arm-thumb-branch-error.s now no longer fail with an out of range branch.
These have been renamed and tests added for the range extension thunk.

Differential Revision: https://reviews.llvm.org/D34691

llvm-svn: 316752
2017-10-27 09:04:11 +00:00
Peter Smith f0c70f8d34 [ELF] Pre-create ThunkSections at Target specific intervals
When an OutputSection is larger than the branch range for a Target we
need to place thunks such that they are always in range of their caller,
and sufficiently spaced to maximise the number of callers that can use
the thunk. We use the simple heuristic of placing the
ThunkSection at intervals corresponding to a target specific branch range.
If the OutputSection is small we put the thunks at the end of the executable
sections.

Differential Revision: https://reviews.llvm.org/D34689

llvm-svn: 316751
2017-10-27 08:58:28 +00:00
Bob Haarman b8a59c8aa5 [lld] unified COFF and ELF error handling on new Common/ErrorHandler
Summary:
The COFF linker and the ELF linker have long had similar but separate
Error.h and Error.cpp files to implement error handling. This change
introduces new error handling code in Common/ErrorHandler.h, changes the
COFF and ELF linkers to use it, and removes the old, separate
implementations.

Reviewers: ruiu

Reviewed By: ruiu

Subscribers: smeenai, jyknight, emaste, sdardis, nemanjai, nhaehnle, mgorny, javed.absar, kbarton, fedor.sergeev, llvm-commits

Differential Revision: https://reviews.llvm.org/D39259

llvm-svn: 316624
2017-10-25 22:28:38 +00:00
Konstantin Zhuravlyov e7f1734f1a LLD/ELF: Allow targets to set e_flags
Differential Revision: https://reviews.llvm.org/D39139

llvm-svn: 316460
2017-10-24 17:01:40 +00:00
Rui Ueyama be85529d2b Remove one parameter from Target::getRelExpr.
A section was passed to getRelExpr just to create an error message.
But if there's an invalid relocation, we would eventually report it
in relocateOne. So we don't have to pass a section to getRelExpr.

llvm-svn: 315552
2017-10-12 03:14:06 +00:00