In D71281 a fix was put in to round up the size of a ThunkSection to the
nearest 4KiB when performing errata patching. This fixed a problem with a
very large instrumented program that had thunks and patches mutually
trigger each other. Unfortunately it triggers an assertion failure in an
AArch64 allyesconfig build of the kernel. There is a specific assertion
preventing an InputSectionDescription being larger than 4KiB. This will
always trigger if there is at least one Thunk needed in that
InputSectionDescription, which is possible for an allyesconfig build.
Abstractly the problem case is:
.text : {
*(.text) ;
...
. = ALIGN(SZ_4K);
__idmap_text_start = .;
*(.idmap.text)
__idmap_text_end = .;
...
}
The assertion checks that __idmap_text_end - __idmap_start is < 4 KiB.
Note that there is more than one InputSectionDescription in the
OutputSection so we can't just restrict the fix to OutputSections smaller
than 4 KiB.
The fix presented here limits the D71281 to InputSectionDescriptions that
meet the following conditions:
1.) The OutputSection is bigger than the thunkSectionSpacing so adding
thunks will affect the addresses of following code.
2.) The InputSectionDescription is larger than 4 KiB. This will prevent
any assertion failures that an InputSectionDescription is < 4 KiB
in size.
We do this at ThunkSection creation time as at this point we know that
the addresses are stable and up to date prior to adding the thunks as
assignAddresses() will have been called immediately prior to thunk
generation.
The fix reverts the two tests affected by D71281 to their original state
as they no longer need the 4KiB size roundup. I've added simpler tests to
check for D71281 when the OutputSection size is larger than the ThunkSection
spacing.
Fixes https://github.com/ClangBuiltLinux/linux/issues/812
Differential Revision: https://reviews.llvm.org/D72344
`{clang,gcc} -nostdlib -r a.c` passes --dynamic-linker to the linker,
and the expected behavior is to ignore it.
If .interp is kept in the relocatable object file, a final link will get
PT_INTERP even if --dynamic-linker is not specified. glibc ld.so expects
to see PT_DYNAMIC and the executable will likely fail to run.
Ignore --dynamic-linker in -r mode as well as -shared.
ThunkSection contains 4-byte instructions on all targets that use
thunks. Thunks should not be used in any performance sensitive places,
and locality/cache line/instruction fetching arguments should not apply.
We use 16 bytes as preferred function alignments for modern PowerPC cores.
In any case, 8 is not optimal.
Differential Revision: https://reviews.llvm.org/D72819
Moved the section name check ahead of any filename matching or
exclusion. Firstly, this reduces the need to retrieve the filename and
secondly, reduces the amount of potentially expensive filename pattern
matching if such rules are present in the linker script.
The impact of this change is particularly significant when linking
objects built with -ffunction-sections and -fstack-size-section, using a
linker script that includes non-trivial filename patterns. In a number
of such cases, the link time is halved.
Differential Revision: https://reviews.llvm.org/D72775
This assertion was added as part of D70659 but did not account for .bss
input sections. I noticed that this assert was incorrectly triggering
while building FreeBSD for MIPS64. Fixed by relaxing the assert to also
account for SHT_NOBITS input sections and adjust the test
mips-jalr-non-function.s to link a file with a .bss section first.
Reviewed By: MaskRay, grimar
Differential Revision: https://reviews.llvm.org/D72567
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
Suggested by Peter Collingbourne.
Non-VER_NDX_GLOBAL versions should not be assigned to defined symbols. --exclude-libs violates this and can cause a spurious error "cannot refer to absolute symbol" after D71795.
excludeLibs incorrectly assigns VER_NDX_LOCAL to an undefined weak symbol =>
isPreemptible is false =>
R_PLT_PC is optimized to R_PC =>
in isStaticLinkTimeConstant, an error is emitted.
Reviewed By: pcc, grimar
Differential Revision: https://reviews.llvm.org/D72681
This patch is a joint work by Rui Ueyama and me based on D58102 by Xiang Zhang.
It adds Intel CET (Control-flow Enforcement Technology) support to lld.
The implementation follows the draft version of psABI which you can
download from https://github.com/hjl-tools/x86-psABI/wiki/X86-psABI.
CET introduces a new restriction on indirect jump instructions so that
you can limit the places to which you can jump to using indirect jumps.
In order to use the feature, you need to compile source files with
-fcf-protection=full.
* IBT is enabled if all input files are compiled with the flag. To force enabling ibt, pass -z force-ibt.
* SHSTK is enabled if all input files are compiled with the flag, or if -z shstk is specified.
IBT-enabled executables/shared objects have two PLT sections, ".plt" and
".plt.sec". For the details as to why we have two sections, please read
the comments.
Reviewed By: xiangzhangllvm
Differential Revision: https://reviews.llvm.org/D59780
RELA targets don't read initial .got.plt entries.
REL targets (ARM, x86-32) write the address of the IFUNC resolver to the
entry (`write32le(buf, s.getVA())`).
The default writeIgotPlt() is not meaningful. Make it a no-op. AArch64
and x86-64 will have 0 as initial .got.plt entries associated with
IFUNC.
Reviewed By: peter.smith
Differential Revision: https://reviews.llvm.org/D72474
down to pass builder in ltobackend.
Currently CodeGenOpts like UnrollLoops/VectorizeLoop/VectorizeSLP in clang
are not passed down to pass builder in ltobackend when new pass manager is
used. This is inconsistent with the behavior when new pass manager is used
and thinlto is not used. Such inconsistency causes slp vectorization pass
not being enabled in ltobackend for O3 + thinlto right now. This patch
fixes that.
Differential Revision: https://reviews.llvm.org/D72386
An undefined weak does not fetch the lazy definition. A lazy weak symbol
should be considered undefined, and thus preemptible if .dynsym exists.
D71795 is not quite an NFC. It errors on an R_X86_64_PLT32 referencing
an undefined weak symbol. isPreemptible is false (incorrect) => R_PLT_PC
is optimized to R_PC => in isStaticLinkTimeConstant, an error is emitted
when an R_PC is applied on an undefined weak (considered absolute).
Weak undefined symbols are preemptible after D71794.
if (sym.isPreemptible)
return false;
if (!config->isPic)
return true;
// isPic means includeInDynsym is true after D71794.
...
// We can delete this if because it can never be true.
if (sym.isUndefWeak)
return true;
Differential Revision: https://reviews.llvm.org/D71795
D59275 added the following clause to Symbol::includeInDynsym()
if (isUndefWeak() && Config->Pie && SharedFiles.empty())
return false;
D59549 explored the possibility to generalize it for -no-pie.
GNU ld's rules are architecture dependent and partly controlled by -z
{,no-}dynamic-undefined-weak. Our attempts to mimic its rules are
actually half-baked and don't provide perceivable benefits (it can save
a few more weak undefined symbols in .dynsym in a -static-pie
executable). Let's just delete the rule for simplicity. We will expect
cosmetic inconsistencies with ld.bfd in certain -static-pie scenarios.
This permits a simplification in D71795.
Reviewed By: peter.smith
Differential Revision: https://reviews.llvm.org/D71794
In AArch64 a branch to an undefined weak symbol that does not have a PLT
entry should resolve to the next instruction. The thunk generation code
can prevent this from happening as a range extension thunk can be generated
if the branch is sufficiently far away from 0, the value of an undefined
weak symbol.
The fix is taken from the Arm implementation of needsThunk(), we prevent a
thunk from being generated to an undefined weak symbol.
fixes pr44451
Differential Revision: https://reviews.llvm.org/D72267
```
lld/ELF/Relocations.cpp:1622:56: warning: loop variable 'ts' of type 'const std::pair<ThunkSection *, uint32_t>' (aka 'const pair<lld:🧝:ThunkSection *, unsigned int>') creates a copy from type 'const std::pair<ThunkSection *, uint32_t>' [-Wrange-loop-analysis]
for (const std::pair<ThunkSection *, uint32_t> ts : isd->thunkSections)
```
Drop const qualifier to fix -Wrange-loop-analysis.
We can make -Wrange-loop-analysis warnings (DiagnoseForRangeConstVariableCopies) on `const A` more
permissive on more types (e.g. POD -> trivially copyable), unfortunately it will not make std::pair
good, because `constexpr pair& operator=(const pair& p);` is unfortunately user-defined.
Reviewed By: Mordante
Differential Revision: https://reviews.llvm.org/D72211
One instance looks like a false positive:
lld/ELF/Relocations.cpp:1622:14: note: use reference type 'const std::pair<ThunkSection *, uint32_t> &' (aka 'cons
t pair<lld:🧝:ThunkSection *, unsigned int> &') to prevent copying
for (const std::pair<ThunkSection *, uint32_t> ts : isd->thunkSections)
It is not changed in this commit.
GCC before r245813 (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79439)
did not emit nop after b/bl. This can happen with recursive calls.
r245813 was back ported to GCC 5.5 and GCC 6.4.
This is common, for example, libstdc++.a(locale.o) shipped with GCC 4.9
and many objects in netlib lapack can cause lld to error. gold allows
such calls to the same section. Our __plt_foo symbol's `section` field
is used for ThunkSection, so we can't implement a similar loosen rule
easily. But we can make use of its `file` field which is currently NULL.
Differential Revision: https://reviews.llvm.org/D71639
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
This restores commit 1417558e4a and its follow-up, reverted by commit c3dbd782f1.
After this commit:
clang -fuse-ld=bfd -no-pie -nostdlib a.c => .interp not created
clang -fuse-ld=bfd -pie -fPIE -nostdlib a.c => .interp created
clang -fuse-ld=gold -no-pie -nostdlib a.c => .interp not created
clang -fuse-ld=gold -pie -fPIE -nostdlib a.c => .interp created
clang -fuse-ld=lld -no-pie -nostdlib a.c => .interp created
clang -fuse-ld=lld -pie -fPIE -nostdlib a.c => .interp created
This reverts commit 1417558e4a.
Also reverts commit 019a92bb28.
This causes check-sanitizer to fail. The "-Nolib" variant of the test
crashes on startup in the loader.
Similar to rL362355, but with the `!config->shared` guard.
(1) {gcc,clang} -fuse-ld=bfd -pie -fPIE -nostdlib a.c => .interp created
(2) {gcc,clang} -fuse-ld=lld -pie -fPIE -nostdlib a.c => .interp not created
(3) {gcc,clang} -fuse-ld=lld -pie -fPIE -nostdlib a.c a.so => .interp created
The inconsistency of (2) is due to the condition `!Config->SharedFiles.empty()`.
To make lld behave more like ld.bfd, we could change the condition to:
config->hasDynSymTab && !config->dynamicLinker.empty() && script->needsInterpSection();
However, that would bring another inconsistency as can be observed with:
(4) {gcc,clang} -fuse-ld=bfd -no-pie -nostdlib a.c => .interp not created
Linux powerpc discards `*(.gnu.version*)` (arch/powerpc/kernel/vmlinux.lds.S)
to suppress --orphan-handling=warn warnings in the -pie output `.tmp_vmlinux1`
The support is simple. Just add isLive() to:
1) Fix an assertion in SectionBase::getPartition() called by VersionTableSection::isNeeded().
2) Suppress DT_VERSYM, DT_VERDEF, DT_VERNEED and DT_VERNEEDNUM, if the relevant section is discarded.
Reviewed By: grimar
Differential Revision: https://reviews.llvm.org/D71819
For undef-not-suggest.test, we currently make redundant alternative
spelling suggestions:
```
ld.lld: error: relocation refers to a discarded section: .text.foo
>>> defined in a.o
>>> section group signature: foo
>>> prevailing definition is in a.o
>>> referenced by a.o:(.rodata+0x0)
>>> did you mean:
>>> defined in: a.o
ld.lld: error: relocation refers to a symbol in a discarded section: foo
>>> defined in a.o
>>> section group signature: foo
>>> prevailing definition is in a.o
>>> referenced by a.o:(.rodata+0x8)
>>> did you mean: for
>>> defined in: a.o
```
Reviewed By: grimar, ruiu
Differential Revision: https://reviews.llvm.org/D71735
Summary:
If none of the input files are ELF object files (for example, when
generating an object file from a single binary input file via
"-b binary"), use a fallback value for the ELF header flags instead
of crashing with an assertion failure.
Reviewers: MaskRay, ruiu, espindola
Reviewed By: MaskRay, ruiu
Subscribers: kevans, grimar, emaste, arichardson, asb, rbar, johnrusso, simoncook, sabuasal, niosHD, kito-cheng, shiva0217, zzheng, edward-jones, rogfer01, MartinMosbeck, brucehoult, the_o, rkruppe, PkmX, jocewei, psnobl, benna, Jim, lenary, s.egerton, pzheng, sameer.abuasal, apazos, luismarques, llvm-commits, jrtc27
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D71101
GNU ld creates the synthetic section .iplt, and has a built-in linker
script that assigns .iplt to the output section .plt . There is no
output section named .iplt .
Making .iplt an output section actually has a benefit that makes the
tricky toolchain feature stand out. Symbolizers don't have to deal with
mixed PLT entries (e.g. llvm-objdump -d incorrectly annotates such jump
targets).
On EM_PPC{,64}, .glink contains a PLT resolver and a series of jump
instructions. The 4-byte entry size makes it unnecessary to have an
alignment of 16.
Mark ppc32-gnu-ifunc.s and ppc32-gnu-ifunc-nonpreemptable.s as `XFAIL: *`.
They test IPLT on EM_PPC, which never works.
Reviewed By: peter.smith
Differential Revision: https://reviews.llvm.org/D71520
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
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
This reverts commit 2bbd32f5e8, it was
causing UBSan failures like the following:
lld/ELF/Target.cpp:103:41: runtime error: applying non-zero offset 24 to null pointer
When a common symbol is merged with a shared symbol, increase st_size if
the shared symbol has a larger st_size. At runtime, the executable's
symbol overrides the shared symbol. The shared symbol may be created
from common symbols in a previous link. This rule makes sure we pick
the largest size among all common symbols.
This behavior matches GNU ld. See
https://sourceware.org/bugzilla/show_bug.cgi?id=25236 for discussions.
A shared symbol does not hold alignment constraints. Ignore the
alignment update.
Reviewed By: peter.smith
Differential Revision: https://reviews.llvm.org/D71161
Summary:
So far it seems like the only test affected by this change is the one I
recently added for R_MIPS_JALR relocations since the other test cases that
use this function early (unknown-relocation-*) do not have a valid input
section for the relocation offset.
Reviewers: ruiu, grimar, MaskRay, espindola
Reviewed By: ruiu, MaskRay
Subscribers: emaste, sdardis, jrtc27, atanasyan, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D70659
On some edge cases such as Chromium compiled with full instrumentation we
have a .text section over twice the size of the maximum branch range and
the instrumented code generation containing many examples of the erratum
sequence. The combination of Thunks and many erratum sequences causes
finalizeAddressDependentContent() to not converge. We end up with:
start
- Thunk Creation (disturbs addresses after thunks, creating more patches)
- Patch Creation (disturbs addresses after patches, creating more thunks)
- goto start
In most images with few thunks and patches the mutual disturbance does not
cause convergence problems. As the .text size and number of patches go up
the risk increases.
A way to prevent the thunk creation from interfering with patch creation is
to round up the size of the thunks to a 4KiB boundary when the
erratum patch is enabled. As the erratum sequence only triggers when an
instruction sequence starts at 0xff8 or 0xffc modulo (4 KiB) by making the
thunks not affect addresses modulo (4 KiB) we prevent thunks from
interfering with the patch.
The patches themselves could be aggregated in the same way that Thunks are
within ThunkSections and we could round up the size in the same way. This
would reduce the number of patches created in a .text section size >
128 MiB but would not likely help convergence problems.
Differential Revision: https://reviews.llvm.org/D71281
fixes (remaining part of) pr44071, other part in D71242
The code to insert patch section merges them with a comparison function that
uses logic of the form:
return (isa<PatchSection>(a) && !isa<PatchSection>(b));
If the PatchSections don't implement classof this check fails if b is also
a SyntheticSection. This can result in the patches being out of range if
the SyntheticSection is big, for example a ThunkSection with lots of thunks.
Differential Revision: https://reviews.llvm.org/D71242
fixes (part of) pr44071
clang/gcc -fdebug-type-sections places .debug_types and
.rela.debug_types in a section group, with a signature symbol which
represents the type signature. The section group is for deduplication
purposes.
After D70146, we will discard such section groups. Refine the rule so
that we will retain the group if no member has the SHF_ALLOC flag.
GNU ld has a similar rule to retain the group if all members have the
SEC_DEBUGGING flag. We try to be more general for future-proof purposes:
if other non-SHF_ALLOC sections have deduplication needs, they may be
placed in a section group. Don't discard them.
Reviewed By: grimar
Differential Revision: https://reviews.llvm.org/D71157
Fixes PPC64 part of PR40438
// clang -target ppc64le -c a.cc
// .text.unlikely may be placed in a separate output section (via -z keep-text-section-prefix)
// The distance between bar in .text.unlikely and foo in .text may be larger than 32MiB.
static void foo() {}
__attribute__((section(".text.unlikely"))) static int bar() { foo(); return 0; }
__attribute__((used)) static int dummy = bar();
This patch makes such thunks with addends work for PPC64.
AArch64: .text -> `__AArch64ADRPThunk_ (adrp x16, ...; add x16, x16, ...; br x16)` -> target
PPC64: .text -> `__long_branch_ (addis 12, 2, ...; ld 12, ...(12); mtctr 12; bctr)` -> target
AArch64 can leverage ADRP to jump to the target directly, but PPC64
needs to load an address from .branch_lt . Before Power ISA v3.0, the
PC-relative ADDPCIS was not available. .branch_lt was invented to work
around the limitation.
Symbol::ppc64BranchltIndex is replaced by
PPC64LongBranchTargetSection::entry_index which take addends into
consideration.
The tests are rewritten: ppc64-long-branch.s tests -no-pie and
ppc64-long-branch-pi.s tests -pie and -shared.
Reviewed By: sfertile
Differential Revision: https://reviews.llvm.org/D70937
replaceWithDefined is used by canonical PLT and copy relocations, which
imply that the symbol is preemptable. ppc64BranchltIndex is only used by
non-preemptable cases, and it can only be the default value in
replaceWithDefined.
The .note.gnu.property SHT_NOTE sections on AArch64 (a 64-bit target)
should have alignment 8 to more closely match the binutils implementation
where alignment is 4-bytes on 32-bit machines and 8-bytes on 64-bit
machines.
Previously LLD was using 4 for both 32-bit and 64-bit machines.
Differential Revision: https://reviews.llvm.org/D70962
The PT_GNU_PROPERTY program header describes the location of the
.note.gnu.property SHT_NOTES section. The linux kernel uses this program
header to find the .note.gnu.property section rather than parsing.
Executables that have properties that the kernel needs to act on that don't
have the PT_GNU_PROPERTY program header will not boot.
Differential Revision: https://reviews.llvm.org/D70961
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
ThunkCreator::getThunk and ThunkCreator::normalizeExistingThunk
currently assume that the implicit addends are -8 for ARM and -4 for
Thumb. In D70637, ThunkCreator::getThunk will need to take care of the
relocation addend explicitly.
Add the utility function getPCBias() as a prerequisite so that the getThunk change in D70637
can be more general.
Reviewed By: peter.smith
Differential Revision: https://reviews.llvm.org/D70690
D62381 introduced forEachSymbol(). It seems that many call sites cannot
be parallelized because the body shared some states. Replace
forEachSymbol with iterator_range<filter_iterator<...>> symbols() to
simplify code and improve debuggability (std::function calls take some
frames).
It also allows us to use early return to simplify code added in D69650.
Reviewed By: grimar
Differential Revision: https://reviews.llvm.org/D70505
Currently LLD always use zlib compression level 6.
This patch changes it to use 1 for -O0, -O1 and 6 for -O2.
It fixes https://bugs.llvm.org/show_bug.cgi?id=44089.
There was also a thread in llvm-dev on this topic:
https://lists.llvm.org/pipermail/llvm-dev/2018-August/125020.html
Here is a table with results of building clang mentioned there:
```
Level Time Size
0 0m17.128s 2045081496 Z_NO_COMPRESSION
1 0m31.471s 922618584 Z_BEST_SPEED
2 0m32.659s 903642376
3 0m36.749s 890805856
4 0m41.532s 876697184
5 0m48.383s 862778576
6 1m3.176s 855251640 Z_DEFAULT_COMPRESSION
7 1m15.335s 853755920
8 2m0.561s 852497560
9 2m33.972s 852397408 Z_BEST_COMPRESSION
```
It shows that it is probably not reasonable to use values greater than 6.
Differential revision: https://reviews.llvm.org/D70658
In GNU ld, -Ttext sets the address of the .text section and -Ttext-segment sets the address of the text segment (RX).
gold only supports the -Ttext-segment semantic and treats -Ttext as an alias for -Ttext-segment.
lld only supports the -Ttext semantic and treats -Ttext-segment as an
alias for -Ttext. The text segment will be assigned to an address less
than the specified -Ttext-segment value.
This patch drops the -Ttext-segment alias.
The text segment is traditionally the first segment. Users who specify
-Ttext-segment may actually want to specify --image-base, the lld way to
express this. Unfortunately currently this is supported by GNU ld's
COFF port but not by its ELF port. gold does not support this option.
With -z separate-code, the behavior of GNU ld -Ttext-segment is weird (see https://sourceware.org/bugzilla/show_bug.cgi?id=25207)
rL289827 introduced the alias for linking qemu's non-pie user mode
binaries. As explained previously, this actually assigns the text
segment to an address less than 0x60000000. I feel that a better fix is
on the qemu side:
https://lists.nongnu.org/archive/html/qemu-devel/2019-11/msg02480.html
Reviewed By: grimar, ruiu
Differential Revision: https://reviews.llvm.org/D70468
Remove the lld::enableColors function, as it just obscures which
stream it's affecting, and replace with explicit calls to the stream's
enable_colors.
Also, assign the stderrOS and stdoutOS globals first in link function,
just to ensure nothing might use them.
(Either change individually fixes the issue of using the old
stream, but both together seems best.)
Follow-up to b11386f9be.
Differential Revision: https://reviews.llvm.org/D70492
Summary:
Current versions of clang would erroneously emit this relocation not only
against functions (loaded from the GOT) but also against data symbols
(e.g. a table of function pointers). LLD was then changing this into a
branch-and-link instruction, causing the program to jump to the data
symbol at run time. I discovered this problem when attempting to boot
MIPS64 FreeBSD after updating the to the latest upstream master.
Reviewers: atanasyan, jrtc27, espindola
Reviewed By: atanasyan
Subscribers: emaste, sdardis, krytarowski, MaskRay, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D70406
Based on D70020 by serge-sans-paille.
The ELF spec says:
> Furthermore, there may be internal references among these sections that would not make sense if one of the sections were removed or replaced by a duplicate from another object. Therefore, such groups must be included or omitted from the linked object as a unit. A section cannot be a member of more than one group.
GNU ld has 2 behaviors that we don't have:
- Group members (nextInSectionGroup != nullptr) are subject to garbage collection.
This includes non-SHF_ALLOC SHT_NOTE sections.
In particular, discarding non-SHF_ALLOC SHT_NOTE sections is an expected behavior by the Annobin
project. See
https://developers.redhat.com/blog/2018/02/20/annobin-storing-information-binaries/
for more information.
- Groups members are retained or discarded as a unit.
Members may have internal references that are not expressed as
SHF_LINK_ORDER, relocations, etc. It seems that we should be more conservative here:
if a section is marked live, mark all the other member within the
group.
Both behaviors are reasonable. This patch implements them.
A new field InputSectionBase::nextInSectionGroup tracks the next member
within a group. on ELF64, this increases sizeof(InputSectionBase) froms
144 to 152.
InputSectionBase::dependentSections tracks section dependencies, which
is used by both --gc-sections and /DISCARD/. We can't overload it for
the "next member" semantic, because we should allow /DISCARD/ to discard
sections independent of --gc-sections (GNU ld behavior). This behavior
may be reasonably used by `/DISCARD/ : { *(.ARM.exidx*) }` or `/DISCARD/
: { *(.note*) }` (new test `linkerscript/discard-group.s`).
Reviewed By: ruiu
Differential Revision: https://reviews.llvm.org/D70146
This change is for those who use lld as a library. Context:
https://reviews.llvm.org/D70287
This patch adds a new parmeter to lld::*::link() so that we can pass
an raw_ostream object representing stdout. Previously, lld::*::link()
took only an stderr object.
Justification for making stdoutOS and stderrOS mandatory: I wanted to
make link() functions to take stdout and stderr in that order.
However, if we change the function signature from
bool link(ArrayRef<const char *> args, bool canExitEarly,
raw_ostream &stderrOS = llvm::errs());
to
bool link(ArrayRef<const char *> args, bool canExitEarly,
raw_ostream &stdoutOS = llvm::outs(),
raw_ostream &stderrOS = llvm::errs());
, then the meaning of existing code that passes stderrOS silently
changes (stderrOS would be interpreted as stdoutOS). So, I chose to
make existing code not to compile, so that developers can fix their
code.
Differential Revision: https://reviews.llvm.org/D70292
The patch in https://reviews.llvm.org/D64077 causes a build failure
because both the Defined and SharedSymbol classes are bigger than 80
bytes on MinGW 8.
This patch fixes this build failure by changing the type of the
bitfields. It is a similar change to the bitfield changes in
https://reviews.llvm.org/D64238, but instead of changing to bool I
decided to use uint8_t because one of the bitfields takes up two bits
instead of one.
Note: the patch is slightly different from the one reviewed in
Phabricator, but it is a trivial change to align it with LLVM master
instead of LLVM 9. Also, it passes all lld tests.
Differential Revision: https://reviews.llvm.org/D70266
The definition may be mangled while an undefined reference is not.
This may come up when (1) the reference is from a C file or (2) the definition
misses an extern "C".
(2) is more common. Suggest an arbitrary mangled name that matches the
undefined reference, if such a definition exists.
ld.lld: error: undefined symbol: foo
>>> referenced by a.o:(.text+0x1)
>>> did you mean to declare foo(int) as extern "C"?
>>> defined in: a1.o
Reviewed By: dblaikie, ruiu
Differential Revision: https://reviews.llvm.org/D69650
When missing an extern "C" declaration, an undefined reference may be
mangled while the definition is not. Suggest the missing
extern "C" and the base name.
Reviewed By: ruiu
Differential Revision: https://reviews.llvm.org/D69592
The logic added in r372781 caused ARMExidxSyntheticSection::addSection()
to return false for exidx sections without a link order dep that passed
isValidExidxSectionDep(). This included exidx sections for empty functions. As
a result, such exidx sections would end up treated like ordinary sections and
would end up being laid out before the ARMExidxSyntheticSection, most likely in
the wrong order relative to the exidx entries in the ARMExidxSyntheticSection,
breaking the orderedness invariant relied upon by unwinders. Fix this by
simply discarding such sections.
Differential Revision: https://reviews.llvm.org/D69744
Summary:
Add a flag `F_no_mmap` to `FileOutputBuffer` to support
`--[no-]mmap-output-file` in ELF LLD. LLD currently explicitly ignores
this flag for compatibility with GNU ld and gold.
We need this flag to speed up link time for large binaries in certain
scenarios. When we link some of our larger binaries we find that LLD
takes 50+ GB of memory, which causes memory pressure. The memory
pressure causes the VM to flush dirty pages of the output file to disk.
This is normally okay, since we should be flushing cold pages. However,
when using BtrFS with compression we need to write 128KB at a time when
we flush a page. If any page in that 128KB block is written again, then
it must be flushed a second time, and so on. Since LLD doesn't write
sequentially this causes write amplification. The same 128KB block will
end up being flushed multiple times, causing the linker to many times
more IO than necessary. We've observed 3-5x faster builds with
-no-mmap-output-file when we hit this scenario.
The bad scenario only applies to compressed filesystems, which group
together multiple pages into a single compressed block. I've tested
BtrFS, but the problem will be present for any compressed filesystem
on Linux, since it is caused by the VM.
Silently ignoring --no-mmap-output-file caused a silent regression when
we switched from gold to lld. We pass --no-mmap-output-file to fix this
edge case, but since lld silently ignored the flag we didn't realize it
wasn't being respected.
Benchmark building a 9 GB binary that exposes this edge case. I linked 3
times with --mmap-output-file and 3 times with --no-mmap-output-file and
took the average. The machine has 24 cores @ 2.4 GHz, 112 GB of RAM,
BtrFS mounted with -compress-force=zstd, and an 80% full disk.
| Mode | Time |
|---------|-------|
| mmap | 894 s |
| no mmap | 126 s |
When compression is disabled, BtrFS performs just as well with and
without mmap on this benchmark.
I was unable to reproduce the regression with any binaries in
lld-speed-test.
Reviewed By: ruiu, MaskRay
Differential Revision: https://reviews.llvm.org/D69294
Add a new '-z nognustack' option that suppresses emitting PT_GNU_STACK
segment. This segment is not supported at all on NetBSD (stack is
always non-executable), and the option is meant to be used to disable
emitting it.
Differential Revision: https://reviews.llvm.org/D56554
sections, but the current code misses certain variants. In particular, those
named when clang takes the code path in
clang/lib/Driver/ToolChain.cpp:416, where crtfiles are named:
clang_rt.<component>-<arch>-<env>.<suffix>
Previously, the code only handled:
clang_rt.<component>.<suffix>
<component>.<suffix>
This revision fixes that.
Fix PR43767
In -r mode, when processing a SHT_REL[A] that relocates a SHF_MERGE, sec->getRelocatedSection() is a
MergeInputSection and its parent is an OutputSection but is asserted to
be a SyntheticSection (MergeSyntheticSection) in LinkerScript.cpp:addInputSec().
##
The code path is not exercised in non -r mode because the relocated
section changed from MergeInputSection to InputSection.
Reorder the code to make the non -r logic apply to -r as well, thus fix
the crash.
Reviewed By: peter.smith
Differential Revision: https://reviews.llvm.org/D69364
The only condition that isecLoc becomes null is
Out::bufferStart == nullptr,
isec->getParent()->offset == 0, and
isec->outSecOff == 0.
We can check the first condition only once.
llvm-svn: 374332
isecLoc there can be null, but at the same time isec->getSize() may
be non-null. It is UB to offset a nullptr.The most straight-forward fix
here appears to perform casts+normal integral arithmetics.
FAIL: lld :: ELF/invalid/invalid-relocation-aarch64.test (1158 of 2217)
******************** TEST 'lld :: ELF/invalid/invalid-relocation-aarch64.test' FAILED ********************
Script:
--
: 'RUN: at line 2'; /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm_build_ubsan/bin/yaml2obj /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm-project/lld/test/ELF/invalid/invalid-relocation-aarch64.test -o /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm_build_ubsan/tools/lld/test/ELF/invalid/Output/invalid-relocation-aarch64.test.tmp.o
: 'RUN: at line 3'; not /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm_build_ubsan/bin/ld.lld /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm_build_ubsan/tools/lld/test/ELF/invalid/Output/invalid-relocation-aarch64.test.tmp.o -o /dev/null 2>&1 | /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm_build_ubsan/bin/FileCheck /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm-project/lld/test/ELF/invalid/invalid-relocation-aarch64.test
--
Exit Code: 1
Command Output (stderr):
--
/b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm-project/lld/test/ELF/invalid/invalid-relocation-aarch64.test:4:10: error: CHECK: expected string not found in input
# CHECK: error: unknown relocation (1024) against symbol foo
^
<stdin>:1:1: note: scanning from here
/b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm-project/lld/ELF/Target.cpp💯41: runtime error: applying non-zero offset 24 to null pointer
^
<stdin>:1:118: note: possible intended match here
/b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm-project/lld/ELF/Target.cpp💯41: runtime error: applying non-zero offset 24 to null pointer
^
--
********************
Testing: 0.. 10.. 20.. 30.. 40.. 50.
FAIL: lld :: ELF/invalid/invalid-relocation-x64.test (1270 of 2217)
******************** TEST 'lld :: ELF/invalid/invalid-relocation-x64.test' FAILED ********************
Script:
--
: 'RUN: at line 2'; /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm_build_ubsan/bin/yaml2obj /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm-project/lld/test/ELF/invalid/invalid-relocation-x64.test -o /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm_build_ubsan/tools/lld/test/ELF/invalid/Output/invalid-relocation-x64.test.tmp1.o
: 'RUN: at line 3'; echo ".global foo; foo:" > /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm_build_ubsan/tools/lld/test/ELF/invalid/Output/invalid-relocation-x64.test.tmp2.s
: 'RUN: at line 4'; /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm_build_ubsan/bin/llvm-mc /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm_build_ubsan/tools/lld/test/ELF/invalid/Output/invalid-relocation-x64.test.tmp2.s -o /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm_build_ubsan/tools/lld/test/ELF/invalid/Output/invalid-relocation-x64.test.tmp2.o -filetype=obj -triple x86_64-pc-linux
: 'RUN: at line 5'; not /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm_build_ubsan/bin/ld.lld /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm_build_ubsan/tools/lld/test/ELF/invalid/Output/invalid-relocation-x64.test.tmp1.o /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm_build_ubsan/tools/lld/test/ELF/invalid/Output/invalid-relocation-x64.test.tmp2.o -o /dev/null 2>&1 | /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm_build_ubsan/bin/FileCheck /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm-project/lld/test/ELF/invalid/invalid-relocation-x64.test
--
Exit Code: 1
Command Output (stderr):
--
/b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm-project/lld/test/ELF/invalid/invalid-relocation-x64.test:6:10: error: CHECK: expected string not found in input
# CHECK: error: unknown relocation (152) against symbol foo
^
<stdin>:1:1: note: scanning from here
/b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm-project/lld/ELF/Target.cpp💯41: runtime error: applying non-zero offset 24 to null pointer
^
<stdin>:1:118: note: possible intended match here
/b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm-project/lld/ELF/Target.cpp💯41: runtime error: applying non-zero offset 24 to null pointer
^
--
********************
Testing: 0.. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80.. 90..
Testing Time: 20.73s
********************
Failing Tests (2):
lld :: ELF/invalid/invalid-relocation-aarch64.test
lld :: ELF/invalid/invalid-relocation-x64.test
llvm-svn: 374329
The combination of the two flags doesn't make sense. And other linkers
seem to just ignore --export-dynamic if --relocatable is given, but
we probably should report it as an error to let users know that is
an invalid combination.
Fixes https://bugs.llvm.org/show_bug.cgi?id=43552
Differential Revision: https://reviews.llvm.org/D68441
llvm-svn: 374022
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
This allows us to delete `using namespace llvm::support::endian` and
simplify D68323. This change adds runtime config->endianness check but
the overhead should be negligible.
Reviewed By: ruiu
Differential Revision: https://reviews.llvm.org/D68561
llvm-svn: 373884
Before, SecToClusters[*] was used to track the belonged cluster.
During a merge (From -> Into), every element of From has to be updated.
Use a union-find set to speed up this use case.
Also, replace `std::vector<int> Sections;` with a doubly-linked
pointers: int Next, Prev;
Reviewed By: Bigcheese
Differential Revision: https://reviews.llvm.org/D46228
llvm-svn: 373708
Our .interp section is not a SyntheticSection. As a result, it terminates the
loop in removeUnusedSyntheticSections(). This has at least two consequences:
- The synthetic .bss and .bss.rel.ro sections are always present in
dynamically linked executables, even when they are not needed.
- The synthetic .ARM.exidx (and possibly other) sections are always present
in partitions other than the last one, even when not needed.
.ARM.exidx in particular is problematic because it assumes that its
list of code sections is non-empty in getLinkOrderDep(), which can
lead to a crash if the partition does not have any code sections.
Fix these problems by moving the creation of the .interp sections to the
top of createSyntheticSections(). While here, make the code a little less
error-prone by changing the add() lambdas to take a SyntheticSection instead
of an InputSectionBase.
Differential Revision: https://reviews.llvm.org/D68256
llvm-svn: 373347
Merging SHF_LINK_ORDER sections can affect semantics if the sh_link
fields point to different sections.
Specifically, for SHF_LINK_ORDER sections, the sh_link field acts as a reverse
dependency from the linked section, causing the SHF_LINK_ORDER section to
be included if the linked section is included. Merging sections with different
sh_link fields will cause the entire contents of the SHF_LINK_ORDER section
to be associated with a single (arbitrarily chosen) output section, whereas the
correct semantics are for the individual pieces of the SHF_LINK_ORDER section
to be associated with their linked output sections. As a result we can end up
incorrectly dropping SHF_LINK_ORDER section contents or including the wrong
section contents, depending on which linked sections were chosen.
Differential Revision: https://reviews.llvm.org/D68094
llvm-svn: 373255
Instead of returning an optional, just return the input string if
demangling fails, as that's what all callers use anyway.
Differential Revision: https://reviews.llvm.org/D68015
llvm-svn: 373077
Fixes PR43461 (regression caused by D67504)
The partition field of a SECTIONS-specified section is not set after
D67504. The 0 value affects findSection() which checks if the partition
field is 1.
So `Out::initArray = findSection(".init_array")` is null, and
DT_INIT_ARRAYSZ is not set.
Reviewed By: peter.smith
Differential Revision: https://reviews.llvm.org/D68087
llvm-svn: 372996
The R_MIPS_JALR relocation denotes jalr/jr instructions in position
independent code. Both these instructions take a target's address from
the $25 register. If offset to the target symbol fits into the 18-bits,
it's more efficient to replace jalr/jr by bal/b instructions.
Differential Revision: https://reviews.llvm.org/D68057
llvm-svn: 372951
D64906 allows PT_LOAD to have overlapping p_offset ranges. In the
default R RX RW RW layout + -z noseparate-code case, we do not tail pad
segments when transiting to another segment. This can save at most
3*maxPageSize bytes.
a) Before D64906, we tail pad R, RX and the first RW.
b) With -z separate-code, we tail pad R and RX, but not the first RW (RELRO).
In some cases, b) saves one file page. In some cases, b) wastes one
virtual memory page. The waste is a concern on Fuchsia. Because it uses
compressed binaries, it doesn't benefit from the saved file page.
This patch adds -z separate-loadable-segments to restore the behavior before
D64906. It can affect section addresses and can thus be used as a
debugging mechanism (see PR43214 and ld.so partition bug in
crbug.com/998712).
Reviewed By: jakehehrlich, ruiu
Differential Revision: https://reviews.llvm.org/D67481
llvm-svn: 372807
Summary:
When support for ThinLTO was first added to lld, the options that
control it were prefixed with --plugin-opt= for compatibility with
an existing implementation as a linker plugin. This change enables
shorter versions of the options to be used, as follows:
New Existing
-thinlto-emit-imports-files --plugin-opt=thinlto-emit-imports-files
-thinlto-index-only --plugin-opt=thinlto-index-only
-thinlto-index-only= --plugin-opt=thinlto-index-only=
-thinlto-object-suffix-replace= --plugin-opt=thinlto-object-suffix-replace=
-thinlto-prefix-replace= --plugin-opt=thinlto-prefix-replace=
-lto-obj-path= --plugin-opt=obj-path=
The options with the --plugin-opt= prefix have been retained as aliases
for the shorter variants so that they continue to be accepted.
Reviewers: tejohnson, ruiu, espindola
Reviewed By: ruiu
Subscribers: emaste, arichardson, MaskRay, steven_wu, dexonsmith, arphaman, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D67782
llvm-svn: 372798
When /DISCARD/ is used on an input section, that input section may have
a .ARM.exidx metadata section that depends on it. As the discard handling
comes after the .ARM.exidx synthetic section is created we need to make
sure that we account for the case where the .ARM.exidx output section
should be removed because there are no more live input sections.
Differential Revision: https://reviews.llvm.org/D67848
llvm-svn: 372781
D67504 removed uses of `assigned` from OutputSection::addSection, which
makes `assigned` purely used in processSectionCommands() and its
callees. By replacing its references with `parent`, we can remove
`assigned`.
Reviewed By: grimar
Differential Revision: https://reviews.llvm.org/D67531
llvm-svn: 372735
Fixes PR38748
mergeSections() calls getOutputSectionName() to get output section
names. Two MergeInputSections may be merged even if they are made
different by SECTIONS commands.
This patch moves mergeSections() after processSectionCommands() and
addOrphanSections() to fix the issue. The new pass is renamed to
OutputSection::finalizeInputSections().
processSectionCommands() and addorphanSections() are changed to add
sections to InputSectionDescription::sectionBases.
finalizeInputSections() merges MergeInputSections and migrates
`sectionBases` to `sections`.
For the -r case, we drop an optimization that tries keeping sh_entsize
non-zero. This is for the simplicity of addOrphanSections(). The
updated merge-entsize2.s reflects the change.
Reviewed By: grimar
Differential Revision: https://reviews.llvm.org/D67504
llvm-svn: 372734
In case of linking binary blobs which do not have any ELF headers, we can
deduce MIPS ABI ELF header flags from an `emulation` option.
Patch by Kyle Evans.
llvm-svn: 372513
Summary:
If st_link(A)=B, and A has the SHF_LINK_ORDER flag, we may dereference
a null pointer if B is garbage collected (PR43147):
1. In Wrter.cpp:compareByFilePosition, `aOut->sectionIndex` or `bOut->sectionIndex`
2. In OutputSections::finalize, `d->getParent()->sectionIndex`
Simply error and bail out to avoid null pointer dereferences. ld.bfd has
a similar error:
sh_link of section `.bar' points to discarded section `.foo0' of `a.o'
ld.bfd is more permissive in that it just checks whether the linked-to
section of the first input section is discarded. This is likely because
it sets sh_link of the output section according to the first input
section.
Reviewed By: grimar
Differential Revision: https://reviews.llvm.org/D67761
llvm-svn: 372400
D67284 introduced ARMErrataFix.cpp which was derived from
AArch64ErrataFix.cpp. There were some useful refactoring changes made to
ARMErrataFix.cpp made as part of the review. This change applies the
relevant changes back to AArch64ErrataFix.cpp.
Main changes are:
- Old style variable names in comments like IS, are now new style isec.
- Simplify init() collection of mappingSymbols to always start with a code
mapping symbol.
- Simplify logic in mergeCmp().
- Fix one 80 column overflow caused by IS -> isec transformation.
Differential Revision: https://reviews.llvm.org/D67622
llvm-svn: 372094
Provide a missing initializer to get rid of warning provoking buildbot
failures.
error: missing field 'rel' initializer
[-Werror,-Wmissing-field-initializers]
llvm-svn: 371970
The --fix-cortex-a8 option implements a linker workaround for the
coretex-a8 erratum 657417. A summary of the erratum conditions is:
- A 32-bit Thumb-2 branch instruction B.w, Bcc.w, BL, BLX spans two
4KiB regions.
- The destination of the branch is to the first 4KiB region.
- The instruction before the branch is a 32-bit Thumb-2 non-branch
instruction.
The linker fix is to redirect the branch to a patch not in the first
4KiB region. The patch forwards the branch on to its target.
The cortex-a8, is an old CPU, with the first implementation of this
workaround in ld.bfd appearing in 2009. The cortex-a8 has been used in
early Android Phones and there are some critical applications that still
need to run on a cortex-a8 that have the erratum. The patch is applied
roughly 10 times on LLD and 20 on Clang when they are built with
--fix-cortex-a8 on an Arm system.
The formal erratum description is avaliable in the ARM Core Cortex-A8
(AT400/AT401) Errata Notice document. This is available from Arm on
request but it seems to be findable via a web search.
Differential Revision: https://reviews.llvm.org/D67284
llvm-svn: 371965
If there is no readonly section, we map:
* The ELF header at imageBase+maxPageSize
* Program headers at imageBase+maxPageSize+sizeof(Ehdr)
* The first section .text at imageBase+maxPageSize+sizeof(Ehdr)+sizeof(program headers)
Due to the interaction between Writer<ELFT>::fixSectionAlignments and
LinkerScript::allocateHeaders,
`alignDown(p_vaddr(R PT_LOAD)) = alignDown(p_vaddr(RX PT_LOAD))`.
The RX PT_LOAD will override the R PT_LOAD at runtime, which is not ideal:
```
// PHDR at 0x401034, should be 0x400034
PHDR 0x000034 0x00401034 0x00401034 0x000a0 0x000a0 R 0x4
// R PT_LOAD contains just Ehdr and program headers.
// At 0x401000, should be 0x400000
LOAD 0x000000 0x00401000 0x00401000 0x000d4 0x000d4 R 0x1000
LOAD 0x0000d4 0x004010d4 0x004010d4 0x00001 0x00001 R E 0x1000
```
* createPhdrs allocates the headers to the R PT_LOAD.
* fixSectionAlignments assigns `imageBase+maxPageSize+sizeof(Ehdr)+sizeof(program headers)` (formula: `alignTo(dot, maxPageSize) + dot % config->maxPageSize`) to addrExpr of .text
* allocateHeaders computes the minimum address among SHF_ALLOC sections, i.e. addr(.text)
* allocateHeaders sets address of ELF header to `addr(.text)-sizeof(Ehdr)-sizeof(program headers) = imageBase+maxPageSize`
The main observation is that when the SECTIONS command is not used, we
don't have to call allocateHeaders. This requires an assumption that
the presence of PT_PHDR and addresses of headers can be decided
regardless of address information.
This may seem natural because dot is not manipulated by a linker script.
The other thing is that we have to drop the special rule for -T<section>
in `getInitialDot`. If -Ttext is smaller than the image base, the headers
will not be allocated with the old behavior (allocateHeaders is called)
but always allocated with the new behavior.
The behavior change is not a problem. Whether and where headers are
allocated can vary among linkers, or ld.bfd across different versions
(--enable-separate-code or not). It is thus advised to use a linker
script with the PHDRS command to have a consistent behavior across
linkers. If PT_PHDR is needed, an explicit --image-base can be a simpler
alternative.
Differential Revision: https://reviews.llvm.org/D67325
llvm-svn: 371957
ICF is performed after EhInputSections and MergeInputSections were
eliminated from inputSections. Every element of inputSections is an
InputSection.
llvm-svn: 371744
-z undefs is the inverse of -z defs. It allows unresolved references
from object files. This can be used to cancel --no-undefined or -z defs.
Reviewed By: ruiu
Differential Revision: https://reviews.llvm.org/D67479
llvm-svn: 371715
```
part.phdrs = script->hasPhdrsCommands() ? script->createPhdrs() : createPhdrs(part);
```
createPhdrs() allocates a PT_PHDR and a PF_R PT_LOAD, which will be
deleted later in LinkerScript::allocateHeaders, but leave a gap between
the program headers and the first section. Don't allocate the segments
to avoid the gap. PT_INTERP is likely not needed as well.
Reviewed By: ruiu
Differential Revision: https://reviews.llvm.org/D67324
llvm-svn: 371398
Summary:
ld.bfd produces an output with --noinhibit-exec when an ASSERT fails.
Use errorOrWarn() so that we can produce an output as well.
An interesting case is that symbol assignments may execute multiple
times, so we probably want to suppress errors for non-final runs.
Reviewed By: peter.smith
Differential Revision: https://reviews.llvm.org/D67285
llvm-svn: 371225
Recommit r370635 (reverted by r371202), with one change: move addOrphanSections() before ICF.
Before, orphan sections in two different partitions may be folded and
moved to the main partition.
Now, InputSection->OutputSection assignment for orphans happens before
ICF. ICF does not fold input sections with different output sections.
With the PR43241 reproduce,
`llvm-objcopy --extract-partition libvr.so libchrome__combined.so libvr.so` => no error
Updated description:
Fixes PR39418. Complements D47241 (the non-linker-script case).
processSectionCommands() assigns input sections to output sections.
ICF is called before it, so .text.foo and .text.bar may be folded even if
their output sections are made different by SECTIONS commands.
```
markLive<ELFT>()
doIcf<ELFT>() // During ICF, we don't know the output sections
writeResult()
combineEhSections<ELFT>()
script->processSectionCommands() // InputSection -> OutputSection assignment
```
This patch splits processSectionCommands() into processSectionCommands()
and processSymbolAssignments(), and moves
processSectionCommands()/addOrphanSections() before ICF:
```
markLive<ELFT>()
combineEhSections<ELFT>()
script->processSectionCommands()
script->addOrphanSections();
doIcf<ELFT>() // should remove folded input sections
writeResult()
script->processSymbolAssignments()
```
An alternative approach is to unfold a section `sec` in
processSectionCommands() when we find `sec` and `sec->repl` belong to
different output sections. I feel this patch is superior because this
can fold more sections and the decouple of
SectionCommand/SymbolAssignment gives flexibility:
* An ExprValue can't be evaluated before its section is assigned to an
output section -> we can delete getOutputSectionVA and simplify
another place where we had to check if the output section is null.
Moreover, a case in linkerscript/early-assign-symbol.s can be handled
now.
* processSectionCommands/processSymbolAssignments can be freely moved
around.
llvm-svn: 371216
```
Writer<ELFT>::run
assignFileOffsets
setFileOffset
computeFileOffset
os->ptLoad->p_align may be smaller than config->maxPageSize
setPhdrs
p_align = max(p_align, config->maxPageSize)
```
If we move the config->maxPageSize logic to the constructor of
PhdrEntry, computeFileOffset can be simplified.
Reviewed By: ruiu
Differential Revision: https://reviews.llvm.org/D67211
llvm-svn: 371085
Previously, segments were aligned according to their first section's
alignment requirements. That was not correct, but segments are also
aligned to a page boundary, and a page boundary is usually much larger
than a section alignment requirement, so no one noticed this bug before.
Now, lld has --nmagic option which sets maxPageSize to 1 to effectively
disable page alignment, which reveals the issue.
Fixes https://bugs.llvm.org/show_bug.cgi?id=43212
Differential Revision: https://reviews.llvm.org/D67152
llvm-svn: 371013
Fixes PR43214.
The size of SHT_RELR may oscillate between 2 numbers (see D53003 for a
similar --pack-dyn-relocs=android issue). This can happen if the shrink
of SHT_RELR causes it to take more words to encode relocation offsets
(this can happen with thunks or segments with overlapping p_offset
ranges), and the expansion of SHT_RELR causes it to take fewer words to
encode relocation offsets.
To avoid the issue, add padding 1s to the end of the relocation section
if its size would decrease. Trailing 1s do not decode to more relocations.
Reviewed By: peter.smith
Differential Revision: https://reviews.llvm.org/D67164
llvm-svn: 370923
Non-undefined symbols with Levenshtein distance 1 or a transposition are
suggestion candidates. This is probably good enough and it can suggest
some missing/superfluous qualifiers: const, restrict, volatile, & and &&
ref-qualifier, e.g.
error: undefined symbol: foo(int*)
>>> referenced by b.o:(.text+0x1)
+>>> did you mean: foo(int const*)
+>>> defined in: a.o
error: undefined symbol: foo(int*&)
>>> referenced by b.o:(.text+0x1)
+>>> did you mean: foo(int*)
+>>> defined in: b.o
Reviewed By: ruiu
Differential Revision: https://reviews.llvm.org/D67039
llvm-svn: 370853
Fixes PR39418. Complements D47241 (the non-linker-script case).
processSectionCommands() assigns input sections to output sections.
ICF is called before it, so .text.foo and .text.bar may be folded even if
their output sections are made different by SECTIONS commands.
```
markLive<ELFT>()
doIcf<ELFT>() // During ICF, we don't know the output sections
writeResult()
combineEhSections<ELFT>()
script->processSectionCommands() // InputSection -> OutputSection assignment
```
This patch splits processSectionCommands() into processSectionCommands() and
processSymbolAssignments(), and moves processSectionCommands() before ICF:
```
markLive<ELFT>()
combineEhSections<ELFT>()
script->processSectionCommands()
doIcf<ELFT>() // should remove folded input sections
writeResult()
script->processSymbolAssignments()
```
An alternative approach is to unfold a section `sec` in
processSectionCommands() when we find `sec` and `sec->repl` belong to
different output sections. I feel this patch is superior because this
can fold more sections and the decouple of
SectionCommand/SymbolAssignment gives flexibility:
* An ExprValue can't be evaluated before its section is assigned to an
output section -> we can delete getOutputSectionVA and simplify
another place where we had to check if the output section is null.
Moreover, a case in linkerscript/early-assign-symbol.s can be handled
now.
* processSectionCommands/processSymbolAssignments can be freely moved
around.
Reviewed By: ruiu
Differential Revision: https://reviews.llvm.org/D66717
llvm-svn: 370635
Fixes https://bugs.chromium.org/p/chromium/issues/detail?id=998712
SHT_LLVM_PART_EHDR marks the start of a partition. The partition
sections will be extracted to a separate file. Align to the next maximum
page size boundary so that we can find the ELF header at the start. We
cannot benefit from overlapping p_offset ranges with the previous
segment anyway.
It seems we lack some llvm-objcopy --extract-main-partition and
--extract-partition sanity checks. It may place EHDR at the start
even if p_offset if non zero. Anyway, the lld change is justified for
the reasons above.
Reviewed By: ruiu
Differential Revision: https://reviews.llvm.org/D67032
llvm-svn: 370629
D64136 and D65584, while fixing STB_WEAK issues and improving our
compatibility with ld.bfd, can cause another STB_WEAK problem related to
LTO:
If %tundef.o has an undefined reference on f,
and %tweakundef.o has a weak undefined reference on f,
%tdef.o has a definition of f
```
ld.lld %tundef.o %tweakundef.o --start-lib %tdef.o --end-lib
```
1) `%tundef.o` doesn't set the `referenced` bit.
2) `%weakundef.o` changes the binding from STB_GLOBAL to STB_WEAK
3) `%tdef.o` is not fetched because the binding is weak.
Step (1) is incorrect. This patch sets the `referenced` bit of Undefined
created by bitcode files.
Reviewed By: ruiu
Differential Revision: https://reviews.llvm.org/D66992
llvm-svn: 370437
Port the D64906 technique to RISC-V. It deletes 3 alignments at
PT_LOAD boundaries for the default case: the size of a RISC-V binary
decreases by at most 12kb.
llvm-svn: 370192
This essentially reverts the code change of D63132 and switches to a simpler approach.
In an executable/shared object, st_shndx of a symbol can be:
1) SHN_UNDEF: undefined symbol (or canonical PLT)
2) SHN_ABS: absolute symbol
3) any other value (usually a regular section index) represents a relative symbol.
The actual value does not matter.
Many ld.so (musl, all archs except MIPS of FreeBSD rtld-elf) even treat 2) and 3)
the same. If .sdata does not exist, it does not matter what value/section
__global_pointer$ has, as long as it is relative (otherwise there will be a pedantic
lld error. See D63132). Just set the st_shndx arbitrarily to 1.
Dummy st_shndx=1 may be used by __rela_iplt_start, linker-script-defined symbols outside a section, __dso_handle, etc.
Reviewed By: ruiu
Differential Revision: https://reviews.llvm.org/D66798
llvm-svn: 370172
Port the D64906 technique to ARM. It deletes 3 alignments at
PT_LOAD boundaries for the default case: the size of an arm binary
decreases by at most 12kb.
Reviewed By: grimar
Differential Revision: https://reviews.llvm.org/D66749
llvm-svn: 370049
EhFrameSection::addSection checks liveness of FDE early. This makes it
infeasible to move combineEhSections() before ICF.
Postpone the check to EhFrameSection::finalizeContents(). This is what
ARMExidxSyntheticSection does and it will make a subsequent patch D66717
simpler.
Reviewed By: ruiu
Differential Revision: https://reviews.llvm.org/D66727
llvm-svn: 369890
PR42990. For `SECTIONS { b = a; . = 0xff00 + (a >> 8); a = .; }`,
we currently set st_value(a)=0xff00 while st_value(b)=0xffff.
The following call tree demonstrates the problem:
```
link<ELF64LE>(Args);
Script->declareSymbols(); // insert a and b as absolute Defined
Writer<ELFT>().run();
Script->processSectionCommands();
addSymbol(cmd); // a and b are re-inserted. LinkerScript::getSymbolValue
// is lazily called by subsequent evaluation
finalizeSections();
forEachRelSec(scanRelocations<ELFT>);
processRelocAux // another problem PR42506, not affected by this patch
finalizeAddressDependentContent(); // loop executed once
script->assignAddresses(); // a = 0, b = 0xff00
script->assignAddresses(); // a = 0xff00, _end = 0xffff
```
We need another assignAddresses() to finalize the value of `a`.
This patch
1) modifies assignAddress() to track the original section/value of each
symbol and return a symbol whose section/value has changed.
2) moves the post-finalizeSections assignAddress() inside the loop
of finalizeAddressDependentContent() and makes it iterative.
Symbol assignment may not converge so we make a few attempts before
bailing out.
Note, assignAddresses() must be called at least twice. The penultimate
call finalized section addresses while the last finalized symbol values.
It is somewhat obscure and there was no comment.
linkerscript/addr-zero.test tests this.
Reviewed By: ruiu
Differential Revision: https://reviews.llvm.org/D66279
llvm-svn: 369889
--strip-all suppresses the creation of in.symtab
This can cause a null pointer dereference in OutputSection::finalize()
// --emit-relocs => copyRelocs is true
if (!config->copyRelocs || (type != SHT_RELA && type != SHT_REL))
return;
...
link = in.symTab->getParent()->sectionIndex; // in.symTab is null
Let's just disallow the combination. In some cases the combination can
cause GNU linkers to fail:
* ld.bfd: final link failed: invalid operation
* gold: internal error in set_no_output_symtab_entry, at ../../gold/object.h:1814
Reviewed By: ruiu
Differential Revision: https://reviews.llvm.org/D66704
llvm-svn: 369878
Reported at https://reviews.llvm.org/D64930#1642223
If the only section of a PT_LOAD is a SHT_NOBITS section (e.g. .bss), we
may not align its sh_offset. p_offset of the PT_LOAD will be set to
sh_offset, and we will get p_offset!=p_vaddr (mod p_align). If such
executable is mapped by the Linux kernel, it will segfault.
After D64906, this may happen the non-linker script case.
The linker script case has had this issue for a long time.
This was fixed by rL321657 (but the test linkerscript/nobits-offset.s
failed to test a SHT_NOBITS section), but broken by rL345154.
Reviewed By: peter.smith
Differential Revision: https://reviews.llvm.org/D66658
llvm-svn: 369828
Building on D60557 mention the name of the linker generated contents of
the reproduce archive, response.txt and version.txt.
Also write a shorter description in the ld.lld --help that is closer to
the documentation.
Differential Revision: https://reviews.llvm.org/D66641
llvm-svn: 369762
Peter Smith