A "signal frame" is a function or block of code where execution arrives via a signal or interrupt, rather than via a normal call instruction. In fact, a particular instruction is interrupted by the signal and needs to be restarted. Therefore, when the signal handler is complete, execution needs to return to the interrupted instruction, rather than the instruction immediately following the call instruction, as in a normal call.
Stack unwinders need to know this to correctly unwind signal frames. Dwarf handily provides an "S" in the CIE augmentation string to describe this case, and the libunwind API provides various functions to for unwinders to determine it,.
The llvm libunwind implementation correctly sets it's internal variable "isSignalFrame" when initializing an unwind context. However, upon stepping up the stack, the current implementation correctly reads the augmentation string and sets it in the CIE info (which it then discards), libunwind doesn't update it's internal unwind context data structure.
This change fixes that, and provides compatibility with both the canonical libunwind and the libgcc implementation.
Reviewers: jfb
Subscribers: christof, libcxx-commits
Tags: #libc
Differential Revision: https://reviews.llvm.org/D69677
Have CMake treat the unwind libraries as C libraries rather than C++.
There is no C++ runtime dependency at runtime. This ensures that we do
not accidentally end up with a link against the C++ runtime.
We need to explicitly reset the implicitly linked libraries for C++ to
ensure that we do not have CMake force the link against the C++ runtime.
This adjustment should enable the NetBSD bots to be happy with this
change.
Disable the type information emission for libunwind. libunwind does not
use `dynamic_cast`. This results in a smaller binary, and more
importantly, avoids the dependency on libc++abi. This ensures that we
have complete symbol resolution of symbols on ELF targets without
linking to the C++ runtime support library. This change avoids the
emission of a reference to `__si_class_type_info`.
The unwinder should not depend on libc++. In fact, we do not end up
with a link against libc++ as we do not have a dependency on libc++ at
runtime. This ensures that we link with `clang` rather than `clang++`.
Summary:
Fix the arm_section_length count. The meaning of the arm_section_length
field changed from num-of-elements to num-of-bytes when the
dl_unwind_find_exidx special case was removed (D30306 and D30681). The
special case was restored in D39468, but that patch didn't account for the
change in arm_section_length's meaning.
That patch worked when it was applied to the NDK's fork of libunwind,
because it never removed the special case in the first place, and the
special case is probably disabled in the Android platform's copy of
libunwind, because __ANDROID_API__ is greater than 21.
Turn the dl_unwind_find_exidx special case on unconditionally for Bionic.
Bionic's dl_unwind_find_exidx is much faster than using dl_iterate_phdr.
(e.g. Bionic stores exidx info on an internal soinfo object.)
Reviewers: thomasanderson, srhines, danalbert, ed, keith.walker.arm, mclow.lists, compnerd
Reviewed By: srhines, danalbert
Subscribers: srhines, kristof.beyls, christof, libcxx-commits
Tags: #libc
Differential Revision: https://reviews.llvm.org/D68972
llvm-svn: 375275
Summary:
The workaround added in https://reviews.llvm.org/rL299575 appears to be
working around a bug in Android JB 4.1.x and 4.2.x (API 16 and 17).
Starting in API 16, Android added support for PIE binaries, but the
dynamic linker failed to initialize dlpi_addr to the address that the
executable was loaded at. The bug was fixed in Android JB 4.3.x (API 18).
Improve the true load bias calculation:
* The code was assuming that the first segment would be the PT_PHDR
segment. I think it's better to be explicit and search for PT_PHDR. (It
will be almost as fast in practice.)
* It's more correct to use p_vaddr rather than p_offset. If a PIE
executable is linked with a non-zero image base (e.g. lld's
-Wl,--image-base=xxxx), then we must use p_vaddr here.
The "phdr->p_vaddr < image_base" condition seems unnecessary and maybe
slightly wrong. If the OS were to load a binary at an address smaller than
a vaddr in the binary, we would still want to do this workaround.
The workaround is safe when the linker bug isn't present, because it
should calculate an image_base equal to dlpi_addr. Note that with API 21
and up, this workaround should never activate for dynamically-linked
objects, because non-PIE executables aren't allowed.
Consolidate the fix into a single block of code that calculates the true
image base, and make it clear that the fix no longer applies after API 18.
See https://github.com/android/ndk/issues/505 for details.
Reviewers: mclow.lists, srhines, danalbert, compnerd
Reviewed By: compnerd
Subscribers: srhines, krytarowski, christof, libcxx-commits
Tags: #libc
Differential Revision: https://reviews.llvm.org/D68971
llvm-svn: 374969
There are few differences in compile flags introduced in r374606
which are causing libcxx-libcxxabi-libunwind-armv8-linux to fail.
This change should address all of those, I've compared the generated
build file from before r374606 and with this change and the set of
flags is the same modulo order.
llvm-svn: 374624
libunwind was using its own set of macros/functions for flag checking
which was similar but different from libc++ and libc++abi. This made
it difficult to replicate the same checks across projects, in fact
there were some checks that appear to have been copy & pasted from
another project and that were broken in the standalone libunwind build.
This change refactors flag checks to match libc++ and libc++abi using
a copy of HandleLibunwindFlags.cmake which is derived from the versions
used by the other projects. This also paves a road to deduplicating and
unifying HandleLibunwindFlags.cmake, HandleLibcxxabiFlags.cmake and
HandleLibcxxFlags.cmake post monorepo switch.
Differential Revision: https://reviews.llvm.org/D68855
llvm-svn: 374606
ARM EHABI unwinding tables only store the start address of each function, so the
last function is assumed to cover the entire address space after it. The test
picks an address on the stack assuming that it's in no function, but because of
the above it's actually resolved to the last function. Fix this by using address
0 instead.
Differential Revision: https://reviews.llvm.org/D68387
llvm-svn: 373628
Move the definition of Elf_Addr typedef to the only place it is used, to avoid:
```
llvm-project/libunwind/src/AddressSpace.hpp:501:28: warning: unused typedef 'Elf_Addr' [-Wunused-local-typedef]
```
when compiling for Android with _LIBUNWIND_ARM_EHABI defined and
_LIBUNWIND_SUPPORT_DWARF_UNWIND not defined.
Patch by Joel Klinghed!
llvm-svn: 372427
If unwind info is not available at the current IP, unw_get_proc_info should
return a zero-filled structure rather than the info of the previous IP.
This change also makes unw_get_proc_info return UNW_ENOINFO instead of
UNW_ESUCCESS.
Patch by Amanieu d'Antras!
llvm-svn: 372407
r362048 added support for ELF dependent libraries, but broke Android
build since Android does not have libpthread. Remove the dependency on
the Android build.
Differential Revision: https://reviews.llvm.org/D65098
llvm-svn: 366734
This is a small fix for https://reviews.llvm.org/D64996. The types of
w0 and w1 in _Unwind_VRS_Get must be uint64_t, not uint32_t.
Committing as obvious.
llvm-svn: 366701
Summary:
The function Unwind-EHABI.cpp:_Unwind_VRS_Pop loads the saved values of
64-bit FP registers as two 32-bit words because they might not be
8-byte aligned. Combining these words into a 64-bit value has to be
done differently on big-endian platforms.
Reviewers: ostannard, john.brawn, dmgreen
Reviewed By: ostannard
Subscribers: kristof.beyls, christof, libcxx-commits
Tags: #libc
Differential Revision: https://reviews.llvm.org/D64996
llvm-svn: 366587
Summary:
The function getByte is dependent on endianness and the current
behavior is incorrect on big-endian targets.
This patch fixes the issue.
Reviewers: phosek, ostannard, dmgreen, christof, chill
Reviewed By: ostannard, chill
Subscribers: chill, christof, libcxx-commits
Tags: #libc
Differential Revision: https://reviews.llvm.org/D64402
llvm-svn: 365505
Summary:
The AArch64 version of the libunwind function which restores the
CPU state and resumes execution is not interrupt-safe. It restores
the target value of SP before loading the floating-point registers
from the context struct, but that struct is allocated on the stack
which is being deallocated. This means that if an interrupt occurs
during this function, and uses a lot of stack space, it could
overwrite the values about to be loaded into the floating-point
registers.
This patch fixes the issue.
Patch by Oliver Stannard.
Reviewers: phosek, chill
Reviewed By: chill
Subscribers: chill, javed.absar, kristof.beyls, christof, LukeCheeseman, pbarrio, olista01, libcxx-commits
Tags: #libc
Differential Revision: https://reviews.llvm.org/D63006
llvm-svn: 363545
Summary:
This updates all places in documentation that refer to "Mac OS X", "OS X", etc.
to instead use the modern name "macOS" when no specific version number is
mentioned.
If a specific version is mentioned, this attempts to use the OS name at the time
of that version:
* Mac OS X for 10.0 - 10.7
* OS X for 10.8 - 10.11
* macOS for 10.12 - present
Reviewers: JDevlieghere
Subscribers: mgorny, christof, arphaman, cfe-commits, lldb-commits, libcxx-commits, llvm-commits
Tags: #clang, #lldb, #libc, #llvm
Differential Revision: https://reviews.llvm.org/D62654
llvm-svn: 362113
This fixes the issue introduced by r362048 where we always use
pragma comment(lib, ...) for dependent libraries when the compiler
is Clang, but older Clang versions don't support this pragma so
we need to check first if it's supported before using it.
llvm-svn: 362055
As of r360984, LLD supports dependent libraries feature for ELF.
libunwind, libc++abi and libc++ have library dependencies: libdl librt
and libpthread, which means that when libunwind and libc++ are being
statically linked (using -static-libstdc++ flag), user has to manually
specify -ldl -lpthread which is onerous.
This change includes the lib pragma to specify the library dependencies
directly in the source that uses those libraries. This doesn't make any
difference when using linkers that don't support dependent libraries.
However, when using LLD that has dependent libraries feature, users no
longer have to manually specifying library dependencies when using
static linking, linker will pick the library automatically.
Differential Revision: https://reviews.llvm.org/D62090
llvm-svn: 362048
Fix two issues that caused libcxx source path not to be inferred
correctly when not specified explicitly:
1. get_lit_conf() uses default value only if the lit variable is set
to None. Due to the mehod of substituting lit.site.cfg, they were
"" rather than None when unset, effectively causing the default never
to apply. Instead, use 'or' construct to use the default whenever
get_lit_conf() returns a false value.
2. If os.path.join() is given a component starting with '/', it takes
it to be an absolute path and ignores everything preceding it.
Remove the slash to correctly append subdirectory.
With these two fixes, libunwind tests start working on NetBSD buildbot
again.
Differential Revision: https://reviews.llvm.org/D62005
llvm-svn: 361931
This change is a consequence of the discussion in "RFC: Place libs in
Clang-dedicated directories", specifically the suggestion that
libunwind, libc++abi and libc++ shouldn't be using Clang resource
directory. Tools like clangd make this assumption, but this is
currently not true for the LLVM_ENABLE_PER_TARGET_RUNTIME_DIR build.
This change addresses that by moving the output of these libraries to
lib/$target/c++ and include/c++ directories, leaving resource directory
only for compiler-rt runtimes and Clang builtin headers.
Differential Revision: https://reviews.llvm.org/D59168
llvm-svn: 361432
Clang integrated assembler was unable to build libunwind PPC32 assembly code,
present in functions used to save/restore register context.
This change consists in replacing the assembly style used in libunwind source,
to one that is compatible with both Clang integrated assembler as well as
GNU assembler.
Patch by Leandro Lupori!
Differential Revision: https://reviews.llvm.org/D61792
llvm-svn: 360862
This change makes each unwind step inspect the instruction at the
return address and, if needed, read r2 from its saved location and
modify the context appropriately.
The unwind logic is able to handle both ELFv1 and ELFv2 stacks.
Reported by Bug 41050
Patch by Leandro Lupori!
Differential Revision: https://reviews.llvm.org/D59694
llvm-svn: 360861
calls into the pthread library use weak symbols.
This option allows libpthread to be a weak dependency rather
than a hard one.
Differential Revision: https://reviews.llvm.org/D60285
llvm-svn: 360610
This change introduces support for building libuwind. The library
build should be complete, but not all CMake options have been
replicated in GN. We also don't support tests yet.
We only support two stage build at the moment.
Differential Revision: https://reviews.llvm.org/D60370
llvm-svn: 359804
For builds with SJLJ, there is no __unw_getcontext symbol. On Windows,
the weak alias macro also expands to a dllexport directive, which fails
if the symbol doesn't exist.
Differential Revision: https://reviews.llvm.org/D60251
llvm-svn: 357711
This is not necessary for ELF since .globl and .weak are mutually
exclusive, but is necessary for Mach-O otherwise the symbol isn't
visible externally.
Differential Revision: https://reviews.llvm.org/D60245
llvm-svn: 357671
libunwind defines the _Unwind_* ABI used by libc++abi. This ABI is a
stable quasi-standard common between multiple implementations such as
LLVM and GNU. The _U* symbol name space is also safely within the symbol
name space that standard C & C++ reserve for the implementation.
Futhermore, libunwind also defines several unw_* symbols, and references
these from the _Unwind_* entry points so the standard/reserved part of
the ABI is dependent on the unw_* part of the ABI. This is not OK for a
C or C++ implementation. The unw_* symbols are reserved for C and extern
"C" used by application code.
This change renames each unw_* function to __unw* and adds a weak alias
unw_* to keep the public <libunwind.h> ABI unchanged for backwards
compatibility. Every reference to unw_* in the implementation has been
changed to use __unw* so that if other unw_* definitions are in force
because nothing uses <libunwind.h> in a particular program, no _Unwind*
code path depends on any unw_* symbol. Furthemore, __unw_* symbols are
hidden, which saves PLT overhead in the shared library case.
In the future, we should cconsider untangling the unw_* API/ABI from the
_Unwind_* API/ABI. The internal API backing the _Unwind_* ABI
implementation should not rely on any nonstandard symbols not in the
implementation-reserved name space. This would then allow separating the
_Unwind_* API/ABI from unw_* entirely, but that's a more substantial
change that's going to require more significant refactoring.
Differential Revision: https://reviews.llvm.org/D59921
llvm-svn: 357640
This change is a consequence of the discussion in "RFC: Place libs in
Clang-dedicated directories", specifically the suggestion that
libunwind, libc++abi and libc++ shouldn't be using Clang resource
directory. Tools like clangd make this assumption, but this is
currently not true for the LLVM_ENABLE_PER_TARGET_RUNTIME_DIR build.
This change addresses that by moving the output of these libraries to
lib/<target> and include/ directories, leaving resource directory only
for compiler-rt runtimes and Clang builtin headers.
Differential Revision: https://reviews.llvm.org/D59013
llvm-svn: 355665
If we're not in a standalone build, this variable should be already
set, so there's no need to set it again or to cache it.
Differential Revision: https://reviews.llvm.org/D57993
llvm-svn: 353915
We're building tests with -nostdlib which means that we need to
explicitly include the builtins library. When using libgcc (default)
we can simply include -lgcc_s on the link line, but when using
compiler-rt builtins we need a complete path to the builtins library.
This path is already available in CMake as <PROJECT>_BUILTINS_LIBRARY,
so we just need to pass that path to lit and if config.compiler_rt is
true, link it to the test.
Prior to this patch, running tests when compiler-rt is being used as
the builtins library was broken as all tests would fail to link, but
with this change running tests when compiler-rt bultins library is
being used should be supported.
Differential Revision: https://reviews.llvm.org/D56701
llvm-svn: 353208
There are several changes:
- Don't stringify Pythonized bools (that's why we're Pythonizing them)
- Support specifying target and sysroot via CMake variables
- Use consistent spelling for --target, --sysroot, --gcc-toolchain
llvm-svn: 353137
CMake has a standard way of setting target triple, sysroot and external
toolchain through CMAKE_<LANG>_COMPILER_TARGET, CMAKE_SYSROOT and
CMAKE_<LANG>_COMPILER_EXTERNAL_TOOLCHAIN. These are turned into
corresponding --target=, --sysroot= and --gcc-toolchain= variables add
included appended to CMAKE_<LANG>_FLAGS.
libunwind, libc++abi, libc++ provides their own mechanism through
<PROJECT>_TARGET_TRIPLE, <PROJECT>_SYSROOT and <PROJECT>_GCC_TOOLCHAIN
variables. These are also passed to lit via lit.site.cfg, and lit config
uses these to set the corresponding compiler flags when building tessts.
This means that there are two different ways of setting target, sysroot
and toolchain, but only one is properly supported in lit. This change
extends CMake build for libunwind, libc++abi and libc++ to also support
the CMake variables in addition to project specific ones in lit.
Differential Revision: https://reviews.llvm.org/D57670
llvm-svn: 353084
Nick Desaulniers