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* ELF v1 on powerpc64 is only barely kept on life support in a couple of Linux
distros. I don't anticipate that this will last much longer.
* Most of the Linux world has moved to powerpc64le which requires ELF v2.
* Some Linux distros have even started supporting powerpc64 with ELF v2.
* The BSD world has long since moved to ELF v2.
* We have no actual linking support for ELF v1.
* ELF v1 had confused DWARF register mappings which is becoming a problem in
our DWARF code in std.debug.
It's clear that ELF v1 is on its way out, and we never fully supported it
anyway. So let's not waste any time or energy on it going forward.
closes #5927
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FreeBSD doesn't support the same number of platforms as Linux, and even then,
only has usermode emulation for a subset of its supported platforms.
NetBSD's usermode emulation support is apparently just broken at the moment.
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std.fs.Dir: Add `walkSelectively` to provide more control over directory walking
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The DWARF code can't handle these yet.
ref https://github.com/ziglang/zig/issues/25447
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std.debug: Add unwind support for serenity
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The ABIs make this safe and reliable due to their backchain requirements.
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This just needs to do the same thing as powerpc64le. Note that the saved LR is
at the same position in both ELF v1 and v2.
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Just makes this a bit nicer to work with since those fields only have 1 intended value.
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Convenience function similar in nature to Symbol.sizeOf
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Previously, `setAlignment` would set the value to 1 fewer than it should, so if you were intending to set alignment to 8 bytes, it would actually set it to 4 bytes, etc.
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This enables depth-related use cases without any dependency on the Walker's internal stack which doesn't always pertain to the actual depth of the current entry (i.e. recursing into a directory immediately affects the stack).
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Some decision-making might depend on the level of the traversal, so
it makes sense to expose depth here since it's stable, and not in the
automatic walker where it's not.
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This is a breaking change, since the fields of Walker have changed. The function APIs are unchanged, though.
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This matches all other platforms. Even if this field is defined as 'int'
in the C definition, the expectation is that the full 32-bit unsigned
integer range can be used. In particular this Sigaction initializer in
the new std.debug code was causing a build failure:
```zig
.flags = (posix.SA.SIGINFO | posix.SA.RESTART | posix.SA.RESETHAND)
```
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Coff2: create a new linker from scratch
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rule
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The old one was correct in terms of layout but very user-hostile.
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Makes FP-based unwinding work.
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* driverkit handling missing in a few places.
* x86-solaris is a dead target.
* aarch64_be does not exist on Darwin, FreeBSD, Windows.
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It is, in fact, Windows-only.
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Implements deflate compression from scratch. A history window is kept in
the writer's buffer for matching and a chained hash table is used to
find matches. Tokens are accumulated until a threshold is reached and
then outputted as a block. Flush is used to indicate end of stream.
Additionally, two other deflate writers are provided:
* `Raw` writes only in store blocks (the uncompressed bytes). It
utilizes data vectors to efficiently send block headers and data.
* `Huffman` only performs Huffman compression on data and no matching.
The above are also able to take advantage of writer semantics since they
do not need to keep a history.
Literal and distance code parameters in `token` have also been reworked.
Their parameters are now derived mathematically, however the more
expensive ones are still obtained through a lookup table (expect on
ReleaseSmall).
Decompression bit reading has been greatly simplified, taking advantage
of the ability to peek on the underlying reader. Additionally, a few
bugs with limit handling have been fixed.
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There were only a few dozen lines of common logic, and they frankly
introduced more complexity than they eliminated. Instead, let's accept
that the implementations of `SelfInfo` are all pretty different and want
to track different state. This probably fixes some synchronization and
memory bugs by simplifying a bunch of stuff. It also improves the DWARF
unwind cache, making it around twice as fast in a debug build with the
self-hosted x86_64 backend, because we no longer have to redundantly go
through the hashmap lookup logic to find the module. Unwinding on
Windows will also see a slight performance boost from this change,
because `RtlVirtualUnwind` does not need to know the module whatsoever,
so the old `SelfInfo` implementation was doing redundant work. Lastly,
this makes it even easier to implement `SelfInfo` on freestanding
targets; there is no longer a need to emulate a real module system,
since the user controls the whole implementation!
There are various other small refactors here in the `SelfInfo`
implementations as well as in the DWARF unwinding logic. This change
turned out to make a lot of stuff simpler!
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Apparently the `__eh_frame` in Mach-O binaries doesn't include the
terminator entry, but in all other respects it acts like `.eh_frame`
rather than `.debug_frame`. I have no idea.
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By my estimation, these changes speed up DWARF unwinding when using the
self-hosted x86_64 backend by around 7x. There are two very significant
enhancements: we no longer iterate frames which don't fit in the stack
trace buffer, and we cache register rules (in a fixed buffer) to avoid
re-parsing and evaluating CFI instructions in most cases. Alongside this
are a bunch of smaller enhancements, such as pre-caching the result of
evaluating the CIE's initial instructions, avoiding re-parsing of CIEs,
and big simplifications to the `Dwarf.Unwind.VirtualMachine` logic.
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This was causing a zig2 miscomp, which emitted slightly broken debug
information, which caused extremely slow stack unwinding. We're working
on fixing or reporting this upstream, but we can use this workaround for
now, because GCC guarantees arithmetic signed shift.
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