[libunwind] Add missing licenses in test files

[libunwind] Fix testing with sanitizers enabled

When testing with sanitizers enabled, we need to link against a plethora
of system libraries. Using `-nodefaultlibs` like we used to breaks this,
and

[libunwind] Fix testing with sanitizers enabled

When testing with sanitizers enabled, we need to link against a plethora
of system libraries. Using `-nodefaultlibs` like we used to breaks this,
and we would have to add all these system libraries manually, which is
not portable and error prone. Instead, stop using `-nodefaultlibs` so
that we get the libraries added by default by the compiler.

The only caveat with this approach is that we are now relying on the
fact that `-L <path-to-local-libunwind>` will cause the just built
libunwind to be selected before the system implementation (either of
libunwind or libgcc_s.so), which is somewhat fragile.

This patch also turns the 32 bit multilib build into a soft failure
since we are in the process of removing it anyway, see D114473 for
details. This patch is incompatible with the 32 bit multilib build
because Ubuntu does not provide a proper libstdc++ for 32 bits, and
that is required when running with sanitizers enabled.

Differential Revision: https://reviews.llvm.org/D114385

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[libunwind] Add a from-scratch config for running libunwind tests

Running tests for libunwind is a lot simpler than running tests for
libc++, so a simple Lit config file is sufficient. The benefit i

[libunwind] Add a from-scratch config for running libunwind tests

Running tests for libunwind is a lot simpler than running tests for
libc++, so a simple Lit config file is sufficient. The benefit is that
we disentangle the libunwind test configuration from the libc++ and
libc++abi test configuration. The setup was too complicated, which led
to some bugs (notably we were running against the system libunwind on
Apple platforms).

Differential Revision: https://reviews.llvm.org/D111664

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[runtimes][ci] Run the tests for libunwind in the CI

We should arguably have always been doing that. The state of libunwind
is quite sad, so this commit adds several XFAILs to make the CI pass.
We n

[runtimes][ci] Run the tests for libunwind in the CI

We should arguably have always been doing that. The state of libunwind
is quite sad, so this commit adds several XFAILs to make the CI pass.
We need to investigate why so many tests are not passing in some
configurations, but I'll defer that to folks who actually work on
libunwind for lack of bandwidth.

Differential Revision: https://reviews.llvm.org/D110872

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[runtimes] Use int main(int, char**) consistently in tests

This is needed when running the tests in Freestanding mode, where main()
isn't treated specially. In Freestanding, main() doesn't get mangl

[runtimes] Use int main(int, char**) consistently in tests

This is needed when running the tests in Freestanding mode, where main()
isn't treated specially. In Freestanding, main() doesn't get mangled as
extern "C", so whatever runtime we're using fails to find the entry point.

One way to solve this problem is to define a symbol alias from __Z4mainiPPc
to _main, however this requires all definitions of main() to have the same
mangling. Hence this commit.

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[libunwind] Combine dl_iterate_phdr codepaths for DWARF and EHABI

dl_iterate_phdr is used to search for unwind info provided by either
PT_GNU_EH_FRAME or PT_ARM_EXIDX. Most of the code between the t

[libunwind] Combine dl_iterate_phdr codepaths for DWARF and EHABI

dl_iterate_phdr is used to search for unwind info provided by either
PT_GNU_EH_FRAME or PT_ARM_EXIDX. Most of the code between the two is
the same, so combine them, and factor out what's different into
checkForUnwindInfoSegment.

Details:
- The FrameHeaderCache can now be enabled for ARM EHABI.
- findUnwindSectionsByPhdr now finds the last PT_ARM_EXIDX rather than
the first. There should only be one segment.
- The dso_base and text_segment_length fields of UnwindInfoSections
are now needed for dl_iterate_phdr when using EHABI, to hold the
low and high PC values for a cache entry.

Reviewed By: compnerd, danielkiss, #libunwind, saugustine

Differential Revision: https://reviews.llvm.org/D87880

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[libunwind][DWARF] Fix end of .eh_frame calculation

* When .eh_frame is located using .eh_frame_hdr (PT_GNU_EH_FRAME), the
start of .eh_frame is known, but not the size. In this case, the
unw

[libunwind][DWARF] Fix end of .eh_frame calculation

* When .eh_frame is located using .eh_frame_hdr (PT_GNU_EH_FRAME), the
start of .eh_frame is known, but not the size. In this case, the
unwinder must rely on a terminator present at the end of .eh_frame.
Set dwarf_section_length to UINTPTR_MAX to indicate this.

* Add a new field, text_segment_length, that the FrameHeaderCache uses
to track the size of the PT_LOAD segment indicated by dso_base.

* Compute ehSectionEnd by adding sectionLength to ehSectionStart,
never to fdeHint.

Fixes PR46829.

Differential Revision: https://reviews.llvm.org/D87750

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[libunwind] Replace chain-of-ifdefs for dl_iterate_phdr

Define a _LIBUNWIND_USE_DL_ITERATE_PHDR macro in config.h when there is
no other unwind info lookup method. Also define a
_LIBUNWIND_USE_DL_UN

[libunwind] Replace chain-of-ifdefs for dl_iterate_phdr

Define a _LIBUNWIND_USE_DL_ITERATE_PHDR macro in config.h when there is
no other unwind info lookup method. Also define a
_LIBUNWIND_USE_DL_UNWIND_FIND_EXIDX macro to factor out
(__BIONIC__ and _LIBUNWIND_ARM_EHABI).

Differential Revision: https://reviews.llvm.org/D86768

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Default to disabling the libunwind frameheader cache.

Although it works fine with glibc, as currently implemented the
frameheader cache is incompatible with certain platforms with
slightly different

Default to disabling the libunwind frameheader cache.

Although it works fine with glibc, as currently implemented the
frameheader cache is incompatible with certain platforms with
slightly different locking semantics inside dl_iterate_phdr.

Therefore only enable it when it is turned on explicitly with
a configure-time option.

Differential Revision: https://reviews.llvm.org/D86163

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Only run frameheader_cache_test.pass.cpp on x86_64.

Although there is nothing architecturally specific, the
ifdef chains are too complicated otherwise.

Add a catch-all else case so any unanticipated configs pass this test.

Cache uwnind frame headers as they are found.

Summary:
This improves unwind performance quite substantially, and follows
a somewhat similar approach used in libgcc_s as described in the
thread here:

Cache uwnind frame headers as they are found.

Summary:
This improves unwind performance quite substantially, and follows
a somewhat similar approach used in libgcc_s as described in the
thread here:

https://gcc.gnu.org/ml/gcc/2005-02/msg00625.html

On certain extremely exception heavy internal tests, the time
drops from about 80 minutes to about five minutes.

Subscribers: libcxx-commits

Tags: #libc

Differential Revision: https://reviews.llvm.org/D75954

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