[ELF] Support --package-metadata

This was recently introduced in GNU linkers and it makes sense for
ld.lld to have the same support. This implementation omits checking if
the input string is valid j

[ELF] Support --package-metadata

This was recently introduced in GNU linkers and it makes sense for
ld.lld to have the same support. This implementation omits checking if
the input string is valid json to reduce size bloat.

Differential Revision: https://reviews.llvm.org/D131439

(cherry picked from commit dbd04b853b680b0a383e5f58edf3643364f67bdf)

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[ELF] Optimize some non-constant alignTo with alignToPowerOf2. NFC

My x86-64 lld executable is 2KiB smaller. .eh_frame writing gets faster as there
were lots of divisions.

[ELF] Reword --no-allow-shlib-undefined diagnostic

Use a format more similar to unresolved references from regular object
files. It's probably easier to read for people who are less familiar
with th

[ELF] Reword --no-allow-shlib-undefined diagnostic

Use a format more similar to unresolved references from regular object
files. It's probably easier to read for people who are less familiar
with the linker diagnostics.

Reviewed By: ikudrin

Differential Revision: https://reviews.llvm.org/D129790

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[LLD] Two tweaks to symbol ordering scheme

When `--symbol-ordering-file` is specified, the linker today will always put
hot contributions in the middle of cold ones when targeting RISC machine, so
t

[LLD] Two tweaks to symbol ordering scheme

When `--symbol-ordering-file` is specified, the linker today will always put
hot contributions in the middle of cold ones when targeting RISC machine, so
to minimize the chances that branch thunks need be generated for hot code
calling into cold code. This is not necessary when user specifies an ordering
of read-only data (vs. function) symbols, or when output section is small such
that no branch thunk would ever be required. The latter is common for mobile
apps. For example, among all the native ARM64 libraries in Facebook Instagram
App for Android, 80% of them have text section smaller than 64KB and the
largest text section seen is less than 8MB, well below the distance that a
BRANCH26 can reach.

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D128382

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[ELF] Relax R_RISCV_ALIGN

Alternative to D125036. Implement R_RISCV_ALIGN relaxation so that we can handle
-mrelax object files (i.e. -mno-relax is no longer needed) and creates a
framework for futu

[ELF] Relax R_RISCV_ALIGN

Alternative to D125036. Implement R_RISCV_ALIGN relaxation so that we can handle
-mrelax object files (i.e. -mno-relax is no longer needed) and creates a
framework for future relaxation.

`relaxAux` is placed in a union with InputSectionBase::jumpInstrMod, storing
auxiliary information for relaxation. In the first pass, `relaxAux` is allocated.
The main data structure is `relocDeltas`: when referencing `relocations[i]`, the
actual offset is `r_offset - (i ? relocDeltas[i-1] : 0)`.

`relaxOnce` performs one relaxation pass. It computes `relocDeltas` for all text
section. Then, adjust st_value/st_size for symbols relative to this section
based on `SymbolAnchor`. `bytesDropped` is set so that `assignAddresses` knows
that the size has changed.

Run `relaxOnce` in the `finalizeAddressDependentContent` loop to wait for
convergence of text sections and other address dependent sections (e.g.
SHT_RELR). Note: extrating `relaxOnce` into a separate loop works for many cases
but has issues in some linker script edge cases.

After convergence, compute section contents: shrink the NOP sequence of each
R_RISCV_ALIGN as appropriate. Instead of deleting bytes, we run a sequence of
memcpy on the content delimitered by relocation locations. For R_RISCV_ALIGN let
the next memcpy skip the desired number of bytes. Section content computation is
parallelizable, but let's ensure the implementation is mature before
optimizations. Technically we can save a copy if we interleave some code with
`OutputSection::writeTo`, but let's not pollute the generic code (we don't have
templated relocation resolving, so using conditions can impose overhead to
non-RISCV.)

Tested:
`make ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- LLVM=1 defconfig all` built Linux kernel using -mrelax is bootable.
FreeBSD RISCV64 system using -mrelax is bootable.
bash/curl/firefox/libevent/vim/tmux using -mrelax works.

Differential Revision: https://reviews.llvm.org/D127581

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[ELF] Optimize getInputSections. NFC

In the majority of cases (e.g. orphan sections), an OutputSection has at most
one InputSectionDescription (isd). By changing the return type to
ArrayRef<InputSec

[ELF] Optimize getInputSections. NFC

In the majority of cases (e.g. orphan sections), an OutputSection has at most
one InputSectionDescription (isd). By changing the return type to
ArrayRef<InputSection *> we can just reference the isd->sections. For
OutputSections with more than one InputSectionDescription we use a caller
provided SmallVector to copy the elements as before.

Reviewed By: peter.smith

Differential Revision: https://reviews.llvm.org/D129111

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[ELF] Move InputFiles global variables (memoryBuffers, objectFiles, etc) into Ctx. NFC

Rename parallelForEachN to just parallelFor

Patch created by running:

rg -l parallelForEachN | xargs sed -i '' -c 's/parallelForEachN/parallelFor/'

No behavior change.

Differential Revision: ht

Rename parallelForEachN to just parallelFor

Patch created by running:

rg -l parallelForEachN | xargs sed -i '' -c 's/parallelForEachN/parallelFor/'

No behavior change.

Differential Revision: https://reviews.llvm.org/D128140

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Revert D125410 "[ELF] Align the end of PT_GNU_RELRO to max-page-size instead of common-page-size"

This reverts commit ebdb9d635a077274e38baa8584f5b0e631b4b1d3.

Changing p_memsz is insufficient and

Revert D125410 "[ELF] Align the end of PT_GNU_RELRO to max-page-size instead of common-page-size"

This reverts commit ebdb9d635a077274e38baa8584f5b0e631b4b1d3.

Changing p_memsz is insufficient and may make PT_GNU_RELRO extend beyond the
PT_LOAD.

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[ELF] Align the end of PT_GNU_RELRO to max-page-size instead of common-page-size

We picked common-page-size to match GNU ld. Recently, the resolution to GNU ld
https://sourceware.org/bugzilla/show_b

[ELF] Align the end of PT_GNU_RELRO to max-page-size instead of common-page-size

We picked common-page-size to match GNU ld. Recently, the resolution to GNU ld
https://sourceware.org/bugzilla/show_bug.cgi?id=28824 (milestone: 2.39) switched
to max-page-size so that the last page can be protected by RELRO in case the
system page size is larger than common-page-size.

Thanks to our two RW PT_LOAD scheme (D58892), switching to max-page-size does
not change file size (while GNU ld's scheme may increase file size).

Reviewed By: peter.smith

Differential Revision: https://reviews.llvm.org/D125410

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[ELF] Support custom sections between DATA_SEGMENT_ALIGN and DATA_SEGMENT_RELRO_END

We currently hard code RELRO sections. When a custom section is between
DATA_SEGMENT_ALIGN and DATA_SEGMENT_RELRO_

[ELF] Support custom sections between DATA_SEGMENT_ALIGN and DATA_SEGMENT_RELRO_END

We currently hard code RELRO sections. When a custom section is between
DATA_SEGMENT_ALIGN and DATA_SEGMENT_RELRO_END, we may report a spurious
`error: section: ... is not contiguous with other relro sections`. GNU ld
makes such sections RELRO.

glibc recently switched to default --with-default-link=no. This configuration
places `__libc_atexit` and others between DATA_SEGMENT_ALIGN and
DATA_SEGMENT_RELRO_END. This patch allows such a ld.bfd --verbose
linker script to be fed into lld.

Reviewed By: peter.smith

Differential Revision: https://reviews.llvm.org/D124656

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[ELF] Fix non-relocatable-non-emit-relocs --gc-sections to discard .L symbols

This reverts commit 764cd491b126318add093c7c8ba3884967d64b21, which I
incorrectly assumed NFC partly because there were

[ELF] Fix non-relocatable-non-emit-relocs --gc-sections to discard .L symbols

This reverts commit 764cd491b126318add093c7c8ba3884967d64b21, which I
incorrectly assumed NFC partly because there were no test coverage for the
non-relocatable non-emit-relocs case before 9d6d936243fe343abe89323a27c7241b395af541.

The interaction of {,-r,--emit-relocs} {,--discard-locals} {,--gc-sections} is
complex but without -r/--emit-relocs, --gc-sections does need to discard .L
symbols like --no-gc-sections. The behavior matches GNU ld.

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[ELF][MTE] Add --android-memtag-* options to synthesize ELF notes

This ELF note is aarch64 and Android-specific. It specifies to the
dynamic loader that specific work should be scheduled to enable M

[ELF][MTE] Add --android-memtag-* options to synthesize ELF notes

This ELF note is aarch64 and Android-specific. It specifies to the
dynamic loader that specific work should be scheduled to enable MTE
protection of stack and heap regions.

Current synthesis of the ".note.android.memtag" ELF note is done in the
Android build system. We'd like to move that to the compiler. This patch
adds the --memtag-stack, --memtag-heap, and --memtag-mode={async, sync,
none} flags to the linker, which synthesises the note for us.

Future changes will add -fsanitize=memtag* flags to clang which will
pass these through to lld.

Depends on D119381.

Differential Revision: https://reviews.llvm.org/D119384

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[ELF] --emit-relocs: fix missing STT_SECTION when the first input section is synthetic

addSectionSymbols suppresses the STT_SECTION symbol if the first input section
is non-SHF_MERGE synthetic. This

[ELF] --emit-relocs: fix missing STT_SECTION when the first input section is synthetic

addSectionSymbols suppresses the STT_SECTION symbol if the first input section
is non-SHF_MERGE synthetic. This is incorrect when the first input section is synthetic
while a non-synthetic input section exists:

* `.bss : { *(COMMON) *(.bss) }`
(abc388ed3cf0ef7e617ebe243d3b0b32d29e69a5 regressed the case because
COMMON symbols precede .bss in the absence of a linker script)
* Place a synthetic section in another section: `.data : { *(.got) *(.data) }`

For `%t/a1` in the new test emit-relocs-synthetic.s, ld.lld produces incorrect
relocations with symbol index 0.
```
0000000000000000 <_start>:
0: 8b 05 33 00 00 00 movl 51(%rip), %eax # 0x39 <bss>
0000000000000002: R_X86_64_PC32 *ABS*+0xd
6: 8b 05 1c 00 00 00 movl 28(%rip), %eax # 0x28 <common>
0000000000000008: R_X86_64_PC32 common-0x4
c: 8b 05 06 00 00 00 movl 6(%rip), %eax # 0x18
000000000000000e: R_X86_64_GOTPCRELX *ABS*+0x4
```

Fix the issue by checking every input section.

Reviewed By: ikudrin

Differential Revision: https://reviews.llvm.org/D122463

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[ELF] Simplify MergeInputSection::getParentOffset. NFC

and remove overly verbose comments.

[ELF] addSectionSymbols: simplify isec->getOutputSection(). NFC

[ELF] Implement --build-id={md5,sha1} with truncated BLAKE3

--build-id was introduced as "approximation of true uniqueness across all
binaries that might be used by overlapping sets of people". It d

[ELF] Implement --build-id={md5,sha1} with truncated BLAKE3

--build-id was introduced as "approximation of true uniqueness across all
binaries that might be used by overlapping sets of people". It does not require
the some resistance mentioned below. In practice, people just use --build-id=md5
for 16-byte build ID and --build-id=sha1 for 20-byte build ID.

BLAKE3 has 256-bit key length, which provides 128-bit security against
(second-)preimage, collision, and differentiability attacks. Its portable
implementation is fast. It additionally provides Arm Neon/AVX2/AVX-512. Just
implement --build-id={md5,sha1} with truncated BLAKE3.

Linking clang 14 RelWithDebInfo with --threads=8 on a Skylake CPU:

* 1.13x as fast with --build-id=md5
* 1.15x as fast with --build-id=sha1

--threads=4 on Apple m1:

* 1.25x as fast with --build-id=md5
* 1.17x as fast with --build-id=sha1

Reviewed By: ikudrin

Differential Revision: https://reviews.llvm.org/D121531

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[ELF] Don't use multiple inheritance for OutputSection. NFC

Add an OutputDesc class inheriting from SectionCommand. An OutputDesc wraps an
OutputSection. This change allows InputSection::getParent t

[ELF] Don't use multiple inheritance for OutputSection. NFC

Add an OutputDesc class inheriting from SectionCommand. An OutputDesc wraps an
OutputSection. This change allows InputSection::getParent to be inlined.

Differential Revision: https://reviews.llvm.org/D120650

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[ELF] Change some non-null pointer parameters to references. NFC

To decrease difference for D120650. Also, rename some `OutputSection *sec` (and
`cmd`) to the more common `osec`.

[ELF] Replace an unneeded dyn_cast_or_null with dyn_cast. NFC

[ELF] Move --print-archive-stats= and --why-extract= beside --warn-backrefs report

So that early errors don't suppress their output.

[ELF] Move isUsedInRegularObj assignment from ctor to call sites. NFC

This removes the tricky
`isUsedInRegularObj(!file || file->kind() == InputFile::ObjKind)`
and the copy from `Symbol::mergeProper

[ELF] Move isUsedInRegularObj assignment from ctor to call sites. NFC

This removes the tricky
`isUsedInRegularObj(!file || file->kind() == InputFile::ObjKind)`
and the copy from `Symbol::mergeProperties`.

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[ELF] Don't rely on Symbols.h's transitive inclusion of InputFiles.h. NFC

[ELF] Check COMMON symbols for PROVIDE and don't redefine COMMON symbols edata/end/etext

In GNU ld, the definition precedence is: regular symbol assignment > relocatable object definition > `PROVIDE

[ELF] Check COMMON symbols for PROVIDE and don't redefine COMMON symbols edata/end/etext

In GNU ld, the definition precedence is: regular symbol assignment > relocatable object definition > `PROVIDE` symbol assignment.

GNU ld's internal linker scripts define the non-reserved (by C and C++)
edata/end/etext with `PROVIDE` so the relocatable object definition takes
precedence. This makes sense because `int end;` is valid.

We currently redefine such symbols if they are COMMON, but not if they are
regular definitions, so `int end;` with -fcommon is essentially a UB in ld.lld.
Fix this (also improve consistency and match GNU ld) by using the
`isDefined` code path for `isCommon`. In GNU ld, reserved identifiers like
`__ehdr_start` do not use `PROVIDE`, while we treat them all as `PROVIDE`, this
seems fine.

Reviewed By: peter.smith

Differential Revision: https://reviews.llvm.org/D120389

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[ELF] Replace uncompressed InputSectionBase::data() with rawData. NFC

In many call sites we know uncompression cannot happen (non-SHF_ALLOC, or the
data (even if compressed) must have been uncompres

[ELF] Replace uncompressed InputSectionBase::data() with rawData. NFC

In many call sites we know uncompression cannot happen (non-SHF_ALLOC, or the
data (even if compressed) must have been uncompressed by a previous pass).
Prefer rawData in these cases. data() increases code size and prevents
optimization on rawData.

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