This fixes remaining issues in my previous PR #90959.
Changes:
- Removed dependency on LLVM header in `xray_interface.cpp`
- Fixed XRay patching for some targets due to missing changes in
architecture-specific patching functions
- Addressed some remaining compiler warnings that I missed in the
previous patch
- Formatting
I have tested these changes on `x86_64` (natively), as well as
`ppc64le`, `aarch64` and `arm32` (cross-compiled and emulated using
qemu).
**Original description:**
This PR introduces shared library (DSO) support for XRay based on a
revised version of the implementation outlined in [this
RFC](https://discourse.llvm.org/t/rfc-upstreaming-dso-instrumentation-support-for-xray/73000).
The feature enables the patching and handling of events from DSOs,
supporting both libraries linked at startup or explicitly loaded, e.g.
via `dlopen`.
This patch adds the following:
- The `-fxray-shared` flag to enable the feature (turned off by default)
- A small runtime library that is linked into every instrumented DSO,
providing position-independent trampolines and code to register with the
main XRay runtime
- Changes to the XRay runtime to support management and patching of
multiple objects
These changes are fully backward compatible, i.e. running without
instrumented DSOs will produce identical traces (in terms of recorded
function IDs) to the previous implementation.
Due to my limited ability to test on other architectures, this feature
is only implemented and tested with x86_64. Extending support to other
architectures is fairly straightforward, requiring only a
position-independent implementation of the architecture-specific
trampoline implementation (see
`compiler-rt/lib/xray/xray_trampoline_x86_64.S` for reference).
This patch does not include any functionality to resolve function IDs
from DSOs for the provided logging/tracing modes. These modes still work
and will record calls from DSOs, but symbol resolution for these
functions in not available. Getting this to work properly requires
recording information about the loaded DSOs and should IMO be discussed
in a separate RFC, as there are mulitple feasible approaches.
---------
Co-authored-by: Sebastian Kreutzer <sebastian.kreutzer@tu-darmstadt.de>
Removes a dependency on LLVM in `xray_interface.cpp` by replacing
`llvm_unreachable` with compiler-rt's `UNREACHABLE`.
Applies clang-format to some unformatted changes.
Original PR: #90959
This PR introduces shared library (DSO) support for XRay based on a
revised version of the implementation outlined in [this
RFC](https://discourse.llvm.org/t/rfc-upstreaming-dso-instrumentation-support-for-xray/73000).
The feature enables the patching and handling of events from DSOs,
supporting both libraries linked at startup or explicitly loaded, e.g.
via `dlopen`.
This patch adds the following:
- The `-fxray-shared` flag to enable the feature (turned off by default)
- A small runtime library that is linked into every instrumented DSO,
providing position-independent trampolines and code to register with the
main XRay runtime
- Changes to the XRay runtime to support management and patching of
multiple objects
These changes are fully backward compatible, i.e. running without
instrumented DSOs will produce identical traces (in terms of recorded
function IDs) to the previous implementation.
Due to my limited ability to test on other architectures, this feature
is only implemented and tested with x86_64. Extending support to other
architectures is fairly straightforward, requiring only a
position-independent implementation of the architecture-specific
trampoline implementation (see
`compiler-rt/lib/xray/xray_trampoline_x86_64.S` for reference).
This patch does not include any functionality to resolve function IDs
from DSOs for the provided logging/tracing modes. These modes still work
and will record calls from DSOs, but symbol resolution for these
functions in not available. Getting this to work properly requires
recording information about the loaded DSOs and should IMO be discussed
in a separate RFC, as there are mulitple feasible approaches.
@petrhosek @jplehr
As mentioned by commit c5d38924dc6688c15b3fa133abeb3626e8f0767c (Apr 2020),
PC-relative entries avoid dynamic relocations and can therefore make the
section read-only.
This is similar to D78082 and D78590. We cannot commit to support
compiler/runtime built at different versions, so just don't play with versions.
For Mach-O support (incomplete yet), we use non-temporary `lxray_fn_idx[0-9]+`
symbols. Label differences are represented as a pair of UNSIGNED and SUBTRACTOR
relocations. The SUBTRACTOR external relocation requires r_extern==1 (needs to
reference a symbol table entry) which can be satisfied by `lxray_fn_idx[0-9]+`.
A `lxray_fn_idx[0-9]+` symbol also serves as the atom for this dead-strippable
section (follow-up to commit b9a134aa629de23a1dcf4be32e946e4e308fc64d).
Differential Revision: https://reviews.llvm.org/D152661
The Clang built-in function is void __xray_typedevent(size_t, const void *, size_t),
but the LLVM intrinsics has smaller integer types. Since we only allow
64-bit ELF/Mach-O targets, we can change llvm.xray.typedevent to
i64/ptr/i64.
This allows encoding more information and avoids i16 legalization for
many non-X86 targets.
fdrLoggingHandleTypedEvent only supports uint16_t event type.
Adds x-ray support for hexagon to llvm codegen, clang driver,
compiler-rt libs.
Differential Revision: https://reviews.llvm.org/D113638
Reapplying this after 543a9ad7c460bb8d641b1b7c67bbc032c9bfdb45,
which fixes the leak introduced there.
Building xray with recent clang on a 64-bit system results in a number
of -Wformat warnings:
compiler-rt/lib/xray/xray_allocator.h:70:11: warning: format specifies type 'int' but the argument has type '__sanitizer::uptr' (aka 'unsigned long') [-Wformat]
RoundedSize, B);
^~~~~~~~~~~
compiler-rt/lib/xray/xray_allocator.h:119:11: warning: format specifies type 'int' but the argument has type '__sanitizer::uptr' (aka 'unsigned long') [-Wformat]
RoundedSize, B);
^~~~~~~~~~~
Since `__sanitizer::uptr` has the same size as `size_t`, these can be
fixed by using the printf specifier `%zu`.
compiler-rt/lib/xray/xray_basic_logging.cpp:348:46: warning: format specifies type 'int' but the argument has type '__sanitizer::tid_t' (aka 'unsigned long long') [-Wformat]
Report("Cleaned up log for TID: %d\n", GetTid());
~~ ^~~~~~~~
%llu
compiler-rt/lib/xray/xray_basic_logging.cpp:353:62: warning: format specifies type 'int' but the argument has type '__sanitizer::tid_t' (aka 'unsigned long long') [-Wformat]
Report("Skipping buffer for TID: %d; Offset = %llu\n", GetTid(),
~~ ^~~~~~~~
%llu
Since `__sanitizer::tid_t` is effectively declared as `unsigned long
long`, these can be fixed by using the printf specifier `%llu`.
compiler-rt/lib/xray/xray_basic_logging.cpp:354:14: warning: format specifies type 'unsigned long long' but the argument has type 'size_t' (aka 'unsigned long') [-Wformat]
TLD.BufferOffset);
^~~~~~~~~~~~~~~~
Since `BufferOffset` is declared as `size_t`, this one can be fixed by
using `%zu` as a printf specifier.
compiler-rt/lib/xray/xray_interface.cpp:172:50: warning: format specifies type 'int' but the argument has type 'uint64_t' (aka 'unsigned long') [-Wformat]
Report("Unsupported sled kind '%d' @%04x\n", Sled.Address, int(Sled.Kind));
~~ ^~~~~~~~~~~~
%lu
Since ``xray::SledEntry::Address` is declared as `uint64_t`, this one
can be fixed by using `PRIu64`, and adding `<cinttypes>`.
compiler-rt/lib/xray/xray_interface.cpp:308:62: warning: format specifies type 'long long' but the argument has type 'size_t' (aka 'unsigned long') [-Wformat]
Report("System page size is not a power of two: %lld\n", PageSize);
~~~~ ^~~~~~~~
%zu
compiler-rt/lib/xray/xray_interface.cpp:359:64: warning: format specifies type 'long long' but the argument has type 'size_t' (aka 'unsigned long') [-Wformat]
Report("Provided page size is not a power of two: %lld\n", PageSize);
~~~~ ^~~~~~~~
%zu
Since `PageSize` is declared as `size_t`, these can be fixed by using
`%zu` as a printf specifier.
Reviewed By: vitalybuka
Differential Revision: https://reviews.llvm.org/D114469
Summary:
Add a flag to omit the xray_fn_idx to cut size overhead and relocations
roughly in half at the cost of reduced performance for single function
patching. Minor additions to compiler-rt support per-function patching
without the index.
Reviewers: dberris, MaskRay, johnislarry
Subscribers: hiraditya, arphaman, cfe-commits, #sanitizers, llvm-commits
Tags: #clang, #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D81995
Follow-up of D78082 and D78590.
Otherwise, because xray_instr_map is now read-only, the absolute
relocation used for Sled.Function will cause a text relocation.
xray_instr_map contains absolute addresses of sleds, which are relocated
by `R_*_RELATIVE` when linked in -pie or -shared mode.
By making these addresses relative to PC, we can avoid the dynamic
relocations and remove the SHF_WRITE flag from xray_instr_map. We can
thus save VM pages containg xray_instr_map (because they are not
modified).
This patch changes x86-64 and bumps the sled version to 2. Subsequent
changes will change powerpc64le and AArch64.
Reviewed By: dberris, ianlevesque
Differential Revision: https://reviews.llvm.org/D78082
