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branch: pathscale

fixed bug in restoring context for aarch64

latest commit 5bd62d69c8
Alexander Esilevich authored


-*- mode: Outline -*-

This is version 1.0 of the unwind library.  This library supports
several architecture/operating-system combinations:

 Linux/x86-64:	Works well.
 Linux/x86:	Works well.
 Linux/ARM:	Works well.
 Linux/IA-64:	Fully tested and supported.
 Linux/PARISC:	Works well, but C library missing unwind-info.
 HP-UX/IA-64:	Mostly works but known to have some serious limitations.
 Linux/AArch64:	Newly added.
 Linux/PPC64:	Newly added.
 Linux/SuperH:	Newly added.
 FreeBSD/i386:	Newly added.
 FreeBSD/x86-64: Newly added (FreeBSD architecture is known as amd64).
 Linux/Tilegx:  Newly added (64-bit mode only).

* General Build Instructions

In general, this library can be built and installed with the following

	$ autoreconf -i # Needed only for building from git. Depends on libtool.
	$ ./configure
	$ make
	$ make install prefix=PREFIX

where PREFIX is the installation prefix.  By default, a prefix of
/usr/local is used, such that libunwind.a is installed in
/usr/local/lib and unwind.h is installed in /usr/local/include.  For
testing, you may want to use a prefix of /usr/local instead.

* Building with Intel compiler

** Version 8 and later

Starting with version 8, the preferred name for the IA-64 Intel
compiler is "icc" (same name as on x86).  Thus, the configure-line
should look like this:

    $ ./configure CC=icc CFLAGS="-g -O3 -ip" CXX=icc CCAS=gcc CCASFLAGS=-g \

* Building on HP-UX

For the time being, libunwind must be built with GCC on HP-UX.

libunwind should be configured and installed on HP-UX like this:

    $ ./configure CFLAGS="-g -O2 -mlp64" CXXFLAGS="-g -O2 -mlp64"

Caveat: Unwinding of 32-bit (ILP32) binaries is not supported
	at the moment.

** Workaround for older versions of GCC

GCC v3.0 and GCC v3.2 ship with a bad version of sys/types.h.  The
workaround is to issue the following commands before running

    $ mkdir $top_dir/include/sys
    $ cp /usr/include/sys/types.h $top_dir/include/sys

GCC v3.3.2 or later have been fixed and do not require this

* Building for PowerPC64 / Linux

For building for power64 you should use:

  $ ./configure CFLAGS="-g -O2 -m64" CXXFLAGS="-g -O2 -m64"

If your power support altivec registers:
  $ ./configure CFLAGS="-g -O2 -m64 -maltivec" CXXFLAGS="-g -O2 -m64 -maltivec"

To check if your processor has support for vector registers (altivec):
    cat /proc/cpuinfo | grep altivec
and should have something like this:
    cpu             : PPC970, altivec supported

If libunwind seems to not work (backtracing failing), try to compile
it with -O0, without optimizations. There are some compiler problems
depending on the version of your gcc.

* Building on FreeBSD

General building instructions apply. To build and execute several tests,
you need libexecinfo library available in ports as devel/libexecinfo.

Development of the port was done of FreeBSD 8.0-STABLE. The library
was build with the system compiler that is modified version of gcc 4.2.1,
as well as the gcc 4.4.3.

* Regression Testing

After building the library, you can run a set of regression tests with:

	$ make check

** Expected results on IA-64 Linux

Unless you have a very recent C library and compiler installed, it is
currently expected to have the following tests fail on IA-64 Linux:

	Gtest-init		(should pass starting with glibc-2.3.x/gcc-3.4)
	Ltest-init		(should pass starting with glibc-2.3.x/gcc-3.4)
	test-ptrace		(should pass starting with glibc-2.3.x/gcc-3.4)
	run-ia64-test-dyn1	(should pass starting with glibc-2.3.x)

This does not mean that libunwind cannot be used with older compilers
or C libraries, it just means that for certain corner cases, unwinding
will fail.  Since they're corner cases, it is not likely for
applications to trigger them.

Note: If you get lots of errors in Gia64-test-nat and Lia64-test-nat, it's
      almost certainly a sign of an old assembler.  The GNU assembler used
      to encode previous-stack-pointer-relative offsets incorrectly.
      This bug was fixed on 21-Sep-2004 so any later assembler will be

** Expected results on x86 Linux

The following tests are expected to fail on x86 Linux:

	Gtest-resume-sig	(fails to get SIGUSR2)
	Ltest-resume-sig	(likewise)
	Gtest-dyn1		(no dynamic unwind info support yet)
	Ltest-dyn1		(no dynamic unwind info support yet)
	test-setjmp		(longjmp() not implemented yet)
	run-check-namespace	(no _Ux86_getcontext yet)

** Expected results on x86-64 Linux

The following tests are expected to fail on x86-64 Linux:

	Gtest-dyn1		(no dynamic unwind info support yet)
	Ltest-dyn1		(no dynamic unwind info support yet)
	Gtest-init (see
	Ltest-init		(likewise)
	test-async-sig		(crashes due to bad unwind-info?)
	test-setjmp		(longjmp() not implemented yet)
	run-check-namespace	(no _Ux86_64_getcontext yet)
	run-ptrace-mapper	(??? investigate)
	run-ptrace-misc	(see

** Expected results on PARISC Linux

Caveat: GCC v3.4 or newer is needed on PA-RISC Linux.  Earlier
versions of the compiler failed to generate the exception-handling
program header (GNU_EH_FRAME) needed for unwinding.

The following tests are expected to fail on x86-64 Linux:

	Gtest-bt   (backtrace truncated at kill() due to lack of unwind-info)
	Ltest-bt   (likewise)
	Gtest-resume-sig  (Gresume.c:my_rt_sigreturn() is wrong somehow)
	Ltest-resume-sig  (likewise)
	Gtest-init (likewise)
	Ltest-init (likewise)
	Gtest-dyn1 (no dynamic unwind info support yet)
	Ltest-dyn1 (no dynamic unwind info support yet)
	test-setjmp		(longjmp() not implemented yet)
	run-check-namespace	(toolchain doesn't support HIDDEN yet)

** Expected results on HP-UX

"make check" is currently unsupported for HP-UX.  You can try to run
it, but most tests will fail (and some may fail to terminate).  The
only test programs that are known to work at this time are:


** Expected results on PPC64 Linux

"make check" should run with no more than 10 out of 24 tests failed.

* Performance Testing

This distribution includes a few simple performance tests which give
some idea of the basic cost of various libunwind operations.  After
building the library, you can run these tests with the following

 $ cd tests
 $ make perf

* Contacting the Developers

Please direct all questions regarding this library to:

You can do this by sending a mail to with
a body of:

	subscribe libunwind-devel

or you can subscribe and manage your subscription via the
web-interface at:
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