Similar to D71509 (EM_PPC64), on EM_PPC, the IPLT code sequence should
be similar to a PLT call stub. Unlike EM_PPC64, EM_PPC -msecure-plt has
small/large PIC model differences.
* -fpic/-fpie: R_PPC_PLTREL24 r_addend=0. The call stub loads an address relative to `_GLOBAL_OFFSET_TABLE_`.
* -fPIC/-fPIE: R_PPC_PLTREL24 r_addend=0x8000. (A partial linked object
file may have an addend larger than 0x8000.) The call stub loads an address relative to .got2+0x8000.
Just assume large PIC model for now. This patch makes:
// clang -fuse-ld=lld -msecure-plt -fno-pie -no-pie a.c
// clang -fuse-ld=lld -msecure-plt -fPIE -pie a.c
#include <stdio.h>
static void impl(void) { puts("meow"); }
void thefunc(void) __attribute__((ifunc("resolver")));
void *resolver(void) { return &impl; }
int main(void) {
thefunc();
void (*theptr)(void) = &thefunc;
theptr();
}
work on Linux glibc. -fpie will crash because the compiler and the
linker do not agree on the value which r30 stores (_GLOBAL_OFFSET_TABLE_
vs .got2+0x8000).
Differential Revision: https://reviews.llvm.org/D71621
Non-preemptible IFUNC are placed in in.iplt (.glink on EM_PPC64). If
there is a non-GOT non-PLT relocation, for pointer equality, we change
the type of the symbol from STT_IFUNC and STT_FUNC and bind it to the
.glink entry.
On EM_386, EM_X86_64, EM_ARM, and EM_AARCH64, the PLT code sequence
loads the address from its associated .got.plt slot. An IPLT also has an
associated .got.plt slot and can use the same code sequence.
On EM_PPC64, the PLT code sequence is actually a bl instruction in
.glink . It jumps to `__glink_PLTresolve` (the PLT header). and
`__glink_PLTresolve` computes the .plt slot (relocated by
R_PPC64_JUMP_SLOT).
An IPLT does not have an associated R_PPC64_JUMP_SLOT, so we cannot use
`bl` in .iplt . Instead, create a call stub which has a similar code
sequence as PPC64PltCallStub. We don't save the TOC pointer, so such
scenarios will not work: a function pointer to a non-preemptible ifunc,
which resolves to a function defined in another DSO. This is the
restriction described by https://sourceware.org/glibc/wiki/GNU_IFUNC
(though on many architectures it works in practice):
Requirement (a): Resolver must be defined in the same translation unit as the implementations.
If an ifunc is taken address but not called, technically we don't need
an entry for it, but we currently do that.
This patch makes
// clang -fuse-ld=lld -fno-pie -no-pie a.c
// clang -fuse-ld=lld -fPIE -pie a.c
#include <stdio.h>
static void impl(void) { puts("meow"); }
void thefunc(void) __attribute__((ifunc("resolver")));
void *resolver(void) { return &impl; }
int main(void) {
thefunc();
void (*theptr)(void) = &thefunc;
theptr();
}
work on Linux glibc and FreeBSD. Calling a function pointer pointing to
a Non-preemptible IFUNC never worked before.
Differential Revision: https://reviews.llvm.org/D71509
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
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
Many -static/-no-pie/-shared/-pie applications linked against glibc or musl
should work with this patch. This also helps FreeBSD PowerPC64 to migrate
their lib32 (PR40888).
* Fix default image base and max page size.
* Support new-style Secure PLT (see below). Old-style BSS PLT is not
implemented, so it is not suitable for FreeBSD rtld now because it doesn't
support Secure PLT yet.
* Support more initial relocation types:
R_PPC_ADDR32, R_PPC_REL16*, R_PPC_LOCAL24PC, R_PPC_PLTREL24, and R_PPC_GOT16.
The addend of R_PPC_PLTREL24 is special: it decides the call stub PLT type
but it should be ignored for the computation of target symbol VA.
* Support GNU ifunc
* Support .glink used for lazy PLT resolution in glibc
* Add a new thunk type: PPC32PltCallStub that is similar to PPC64PltCallStub.
It is used by R_PPC_REL24 and R_PPC_PLTREL24.
A PLT stub used in -fPIE/-fPIC usually loads an address relative to
.got2+0x8000 (-fpie/-fpic code uses _GLOBAL_OFFSET_TABLE_ relative
addresses).
Two .got2 sections in two object files have different addresses, thus a PLT stub
can't be shared by two object files. To handle this incompatibility,
change the parameters of Thunk::isCompatibleWith to
`const InputSection &, const Relocation &`.
PowerPC psABI specified an old-style .plt (BSS PLT) that is both
writable and executable. Linkers don't make separate RW- and RWE segments,
which causes all initially writable memory (think .data) executable.
This is a big security concern so a new PLT scheme (secure PLT) was developed to
address the security issue.
TLS will be implemented in D62940.
glibc older than ~2012 requires .rela.dyn to include .rela.plt, it can
not handle the DT_RELA+DT_RELASZ == DT_JMPREL case correctly. A hack
(not included in this patch) in LinkerScript.cpp addOrphanSections() to
work around the issue:
if (Config->EMachine == EM_PPC) {
// Older glibc assumes .rela.dyn includes .rela.plt
Add(In.RelaDyn);
if (In.RelaPlt->isLive() && !In.RelaPlt->Parent)
In.RelaDyn->getParent()->addSection(In.RelaPlt);
}
Reviewed By: ruiu
Differential Revision: https://reviews.llvm.org/D62464
llvm-svn: 362721
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
Also make certain Thunk methods non-const as this will be required for
an upcoming change.
Differential Revision: https://reviews.llvm.org/D44961
llvm-svn: 328732
Now that DefinedRegular is the only remaining derived class of
Defined, we can merge the two classes.
Differential Revision: https://reviews.llvm.org/D39667
llvm-svn: 317448
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
This change allows Thunks to be added on multiple passes. To do this we must
merge only the thunks added in each pass, and deal with thunks that have
drifted out of range of their callers.
A thunk may end out of range of its caller if enough thunks are added in
between the caller and the thunk. To handle this we create another thunk.
Differential Revision: https://reviews.llvm.org/D34692
llvm-svn: 316754
We were using uint32_t as the type of relocation kind. It has a
readability issue because what Type really means in `uint32_t Type`
is not obvious. It could be a section type, a symbol type or a
relocation type.
Since we do not do any arithemetic operations on relocation types
(e.g. adding one to R_X86_64_PC32 doesn't make sense), it would be
more natural if they are represented as enums. Unfortunately, that
is not doable because relocation type definitions are spread into
multiple header files.
So I decided to use typedef. This still should be better than the
plain uint32_t because the intended type is now obvious.
llvm-svn: 315525
On ARM the interworking thunks are only produced for branch instructions
that can't be changed into a blx instruction so only Thumb callers would
call Thumb thunks and only ARM callers would call ARM thunks. With range
extension thunks branch and link instructions may need a Thunk. These
instructions can be rewritten as a blx and can use either ARM or Thumb
thunks.
We introduce an isCompatibleWith() function so that a caller can check if
an existing Thunk is compatible before reusing it.
Differential Revision: https://reviews.llvm.org/D34035
llvm-svn: 307132
Nothing special here, just detemplates code that became possible
to detemplate after recent commits in a straghtforward way.
Differential revision: https://reviews.llvm.org/D33234
llvm-svn: 303237
With the current design an InputSection is basically anything that
goes directly in a OutputSection. That includes plain input section
but also synthetic sections, so this should probably not be a
template.
llvm-svn: 295993
Thunks are now implemented by redirecting the relocation to the
symbol S, to a symbol TS in a Thunk. The Thunk will transfer control
to S. This has the following implications:
- All the side-effects of Thunks happen within createThunks()
- Thunks are no longer stored in InputSections and Symbols no longer
need to hold a pointer to a Thunk
- The synthetic Thunk sections need to be merged into OutputSections
This implementation is almost a direct conversion of the existing
Thunks with the following exceptions:
- Mips LA25 Thunks are placed before the InputSection that defines
the symbol that needs a Thunk.
- All ARM Thunks are placed at the end of the OutputSection of the
first caller to the Thunk.
Range extension Thunks are not supported yet so it is optimistically
assumed that all Thunks can be reused.
This is a recommit of r293283 with a fixed comparison predicate as
std::merge requires a strict weak ordering.
Differential revision: https://reviews.llvm.org/D29327
llvm-svn: 293757
Thunks are now implemented by redirecting the relocation to the
symbol S, to a symbol TS in a Thunk. The Thunk will transfer control
to S. This has the following implications:
- All the side-effects of Thunks happen within createThunks()
- Thunks are no longer stored in InputSections and Symbols no longer
need to hold a pointer to a Thunk
- The synthetic Thunk sections need to be merged into OutputSections
This implementation is almost a direct conversion of the existing
Thunks with the following exceptions:
- Mips LA25 Thunks are placed before the InputSection that defines
the symbol that needs a Thunk.
- All ARM Thunks are placed at the end of the OutputSection of the
first caller to the Thunk.
Range extension Thunks are not supported yet so it is optimistically
assumed that all Thunks can be reused.
Differential Revision: https://reviews.llvm.org/D29129
llvm-svn: 293283
Although they are in the same .cpp file, the way they were written
were slightly different, so they looked more different than they were.
This patch makes their styles consistent.
llvm-svn: 274996
The TinyPtrVector of const Thunk<ELFT>* in InputSections.h can cause
build failures on certain compiler/library combinations when Thunk<ELFT>
is not a complete type or is an abstract class. Fixed by making Thunk<ELFT>
non Abstract.
type or is an abstract class
llvm-svn: 274863
Generalise the Mips LA25 Thunk code and implement ARM and Thumb
interworking Thunks.
- Introduce a new module Thunks.cpp to store the Target Specific Thunk
implementations.
- DefinedRegular and Shared have a ThunkData field to record Thunk.
- A Target can have more than one type of Thunk.
- Support PC-relative calls to Thunks.
- Support Thunks to PLT entries.
- Existing Mips LA25 Thunk code integrated.
- Support for ARMv7A interworking Thunks.
Limitations:
- Only one Thunk per SymbolBody, this is sufficient for all currently
implemented Thunks.
- ARM thunks assume presence of V6T2 MOVT and MOVW instructions.
Differential revision: http://reviews.llvm.org/D21891
llvm-svn: 274836
Fangrui Song