This PR registers the writeout and reset functions for `gcov` for all
modules in the PGO runtime, instead of registering them
using global constructors in each module. The change is made for AIX
only, but the same mechanism works on Linux on Power.
When registering such functions using global constructors in each module
without `-ffunction-sections`, the AIX linker cannot garbage collect
unused undefined symbols, because such symbols are grouped in the same
section as the `__sinit` symbol. Keeping such undefined symbols causes
link errors (see test case
https://github.com/llvm/llvm-project/pull/108570/files#diff-500a7e1ba871e1b6b61b523700d5e30987900002add306e1b5e4972cf6d5a4f1R1
for this scenario). This PR implements the initialization in the
runtime, hence avoiding introducing `__sinit` into each module.
The implementation adds a new global variable `__llvm_covinit_functions`
to each module. This new global variable contains the function pointers
to the `Writeout` and `Reset` functions. `__llvm_covinit_functions`'s
section is the named section `__llvm_covinit`. The linker will aggregate
all the `__llvm_covinit` sections from each module
to form one single named section in the final binary. The pair of
functions
```
const __llvm_gcov_init_func_struct *__llvm_profile_begin_covinit();
const __llvm_gcov_init_func_struct *__llvm_profile_end_covinit();
```
are implemented to return the start and end address of this named
section in the final binary, and they are used in function
```
__llvm_profile_gcov_initialize()
```
(which is a constructor function in the runtime) so the runtime knows
the addresses of all the `Writeout` and `Reset` functions from all the
modules.
One noticeable implementation detail relevant to AIX is that to preserve
the `__llvm_covinit` from the linker's garbage collection, a `.ref`
pseudo instruction is inserted into them, referring to the section that
contains the `__llvm_gcov_ctr` variables, which are used in the
instrumented code. The `__llvm_gcov_ctr` variables did not belong to
named sections before, but this PR added them to the
`__llvm_gcov_ctr_section` named section, so we can add a `.ref` pseudo
instruction that refers to them in the `__llvm_covinit` section.
Currently, WebAssembly/WASI target does not provide direct support for
code coverage.
This patch set fixes several issues to unlock the feature. The main
changes are:
1. Port `compiler-rt/lib/profile` to WebAssembly/WASI.
2. Adjust profile metadata sections for Wasm object file format.
- [CodeGen] Emit `__llvm_covmap` and `__llvm_covfun` as custom sections
instead of data segments.
- [lld] Align the interval space of custom sections at link time.
- [llvm-cov] Copy misaligned custom section data if the start address is
not aligned.
- [llvm-cov] Read `__llvm_prf_names` from data segments
3. [clang] Link with profile runtime libraries if requested
See each commit message for more details and rationale.
This is part of the effort to add code coverage support in Wasm target
of Swift toolchain.
The profiling code requires GNU extensions as it uses functions such as getpagesize(), fdopen(), etc.
The problem manifests when the compiler is built to not default to the extensions mode, e.g. custom config with -std=c2x. CMake didn't support this scenario very well, but it's been fixed by CMP0128. Set the policy to NEW as we now conform to it.
If built as part of the main llvm build, via
ENABLE_LLVM_PROJECTS=compiler-rt, the code gets built with more warning
options than if built standalone. Some of these trigger warnings like:
warning: a function declaration without a prototype is deprecated in all
versions of C [-Wstrict-prototypes]
This reapplies 8fa66c6ca7 ([asan][windows]
Eliminate the static asan runtime on windows) for a second time.
That PR bounced off the tests because it caused failures in the other
sanitizer runtimes, these have been fixed by only building interception,
sanitizer_common, and asan with /MD, and continuing to build the rest of
the runtimes with /MT. This does mean that any usage of the static
ubsan/fuzzer/etc runtimes will mean you're mixing different runtime
library linkages in the same app, the interception, sanitizer_common,
and asan runtimes are designed for this, however it does result in some
linker warnings.
Additionally, it turns out when building in release-mode with
LLVM_ENABLE_PDBs the build system forced /OPT:ICF. This totally breaks
asan's "new" method of doing "weak" functions on windows, and so
/OPT:NOICF was explicitly added to asan's link flags.
---------
Co-authored-by: Amy Wishnousky <amyw@microsoft.com>
As detailed in Issue #101667, two `profile` tests `FAIL` on 32-bit
SPARC, both Linux/sparc64 and Solaris/sparcv9 (where the tests work when
enabled):
```
Profile-sparc :: ContinuousSyncMode/runtime-counter-relocation.c
Profile-sparc :: ContinuousSyncMode/set-file-object.c
```
The Solaris linker provides the crucial clue as to what's wrong:
```
ld: warning: symbol '__llvm_profile_counter_bias' has differing sizes:
(file runtime-counter-relocation-17ff25.o value=0x8; file libclang_rt.profile-sparc.a(InstrProfilingFile.c.o) value=0x4);
runtime-counter-relocation-17ff25.o definition taken
```
In fact, the types in `llvm` and `compiler-rt` differ:
- `__llvm_profile_counter_bias`/`INSTR_PROF_PROFILE_COUNTER_BIAS_VAR` is
created in `llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp`
(`InstrLowerer::getCounterAddress`) as `int64_t`, while
`compiler-rt/lib/profile/InstrProfilingFile.c` uses `intptr_t`. While
this doesn't matter in the 64-bit case, the type sizes differ for
32-bit.
- `__llvm_profile_bitmap_bias`/`INSTR_PROF_PROFILE_BITMAP_BIAS_VAR` has
the same issue: created in `InstrProfiling.cpp`
(`InstrLowerer::getBitmapAddress`) as `int64_t`, while
`InstrProfilingFile.c` again uses `intptr_t`.
This patch changes the `compiler-rt` types to match `llvm`. At the same
time, the affected testcases are enabled on Solaris, too, where they now
just `PASS`.
Tested on `sparc64-unknown-linux-gnu`, `sparcv9-sun-solaris2.11`,
`x86_64-pc-linux-gnu`, and `amd64-pc-solaris2.11.
Problem:
On AIX, functions registered by atexit in a shared library are not run
when the library is dlclosed, but instead run (and fail because the
function pointer is no longer valid) during main program exit.
The profile-rt registers some functions with atexit:
1. writeFileWithoutReturn that writes out the profile file
2. llvm_delete_reset_function_list that does some cleanup in the gcov
instrumentation library (not sure)
And so right now, we get an "Illegal instruction (core dumped)" when an
instrumented shared object is dlopen'ed and dlclosed.
Solution:
When a shared library is dlclose'd, destructors from the library are
called. So create a destructor function that iterates over all known
functions that profile-rt registers with atexit, and unregister the ones
that have been registered and execute them.
Scenarios tested:
(0) gcov dlopen/dlclose (AIX/gcov-dlopen-dlclose.test)
(1) multiple dlopen/dlclose of the same lib and multiple libs (instrprof-dlopen-dlclose.test)
(2) dlopen but no dlclose (exists: Posix/instrprof-dlopen.test)
(3) a simple fork testcase with dlopen/dlclose (instrprof-dlopen-dlclose.test)
(4) dlopen/dlclose by multiple threads. (instrprof-dlopen-dlclose.test)
(5) regular dynamic-linking of instrumented shared libs (exists: AIX/shared-bexpall-pgo.c)
(6) a simple fork testcase produces correct profile (instrprof-fork.c)
---------
Co-authored-by: Hubert Tong <hstong@ca.ibm.com>
`counter_bias` is incompatible to Bitmap. The distance between Counters
and Bitmap is different between on-memory sections and profraw image.
Reference to `__llvm_profile_bitmap_bias` is generated only if
`-fcoverge-mcdc` `-runtime-counter-relocation` are specified. The
current implementation rejected their options.
```
Runtime counter relocation is presently not supported for MC/DC bitmaps
```
In 16e74fd489 (for #82711) a duplicate definition of `IntPtrT` was
added to `InstrProfiling.h`, leading to warnings:
compiler-rt/lib/profile/InstrProfiling.h:52:15: warning: redefinition of typedef 'IntPtrT' is a C11 feature [-Wtypedef-redefinition]
52 | typedef void *IntPtrT;
| ^
compiler-rt/lib/profile/InstrProfiling.h:34:15: note: previous definition is here
34 | typedef void *IntPtrT;
| ^
Fix the warnings by removing the duplicate typedef.
Re-Apply: 246234ac70
Originally #81677
The static asan runtime on windows had various buggy hacks to ensure loaded dlls got the executable's copy of asan, these never worked all that well, so we have eliminated the static runtime altogether and made the dynamic runtime work for applications linking any flavor of the CRT.
Among other things this allows non-asan-instrumented applications to load asan-instrumented dlls that link against the static CRT.
Co-authored-by: Amy Wishnousky <amyw@microsoft.com>
This is one of the major changes we (Microsoft) have made in the version
of asan we ship with Visual Studio.
@amyw-msft wrote a blog post outlining this work at
https://devblogs.microsoft.com/cppblog/msvc-address-sanitizer-one-dll-for-all-runtime-configurations/
> With Visual Studio 2022 version 17.7 Preview 3, we have refactored the
MSVC Address Sanitizer (ASan) to depend on one runtime DLL regardless of
the runtime configuration. This simplifies project onboarding and
supports more scenarios, particularly for projects statically linked
(/MT, /MTd) to the C Runtimes. However, static configurations have a new
dependency on the ASan runtime DLL.
> Summary of the changes:
> ASan now works with /MT or /MTd built DLLs when the host EXE was not
compiled with ASan. This includes Windows services, COM components, and
plugins.
Configuring your project with ASan is now simpler, since your project
doesn’t need to uniformly specify the same [runtime
configuration](https://learn.microsoft.com/en-us/cpp/build/reference/md-mt-ld-use-run-time-library?view=msvc-170)
(/MT, /MTd, /MD, /MDd).
ASan workflows and pipelines for /MT or /MTd built projects will need to
ensure the ASan DLL (clang_rt.asan_dynamic-<arch>.dll) is available on
PATH.
The names of the ASan .lib files needed by the linker have changed (the
linker normally takes care of this if not manually specifying lib names
via /INFERASANLIBS)
You cannot mix ASan-compiled binaries from previous versions of the MSVC
Address Sanitizer (this is always true, but especially true in this
case).
Here's the description of these changes from our internal PR
1. Build one DLL that includes everything debug mode needs (not included
here, already contributed upstream).
* Remove #if _DEBUG checks everywhere.
* In some places, this needed to be replaced with a runtime check. In
asan_win.cpp, IsDebugRuntimePresent was added where we are searching for
allocations prior to ASAN initialization.
* In asan_win_runtime_functions.cpp and interception_win.cpp, we need to
be aware of debug runtime DLLs even when not built with _DEBUG.
2. Redirect statically linked functions to the ASAN DLL for /MT
* New exports for each of the C allocation APIs so that the statically
linked portion of the runtime can call them (see asan_malloc_win.cpp,
search MALLOC_DLL_EXPORT). Since we want our stack trace information to
be accurate and without noise, this means we need to capture stack frame
info from the original call and tell it to our DLL export. For this, I
have reused the __asan_win_new_delete_data used for op new/delete
support from asan_win_new_delete_thunk_common.h and moved it into
asan_win_thunk_common.h renamed as __asan_win_stack_data.
* For the C allocation APIs, a new file is included in the
statically-linked /WHOLEARCHIVE lib - asan_malloc_win_thunk.cpp. These
functions simply provide definitions for malloc/free/etc to be used
instead of the UCRT's definitions for /MT and instead call the ASAN DLL
export. /INFERASANLIBS ensures libucrt.lib will not take precedence via
/WHOLEARCHIVE.
* For other APIs, the interception code was called, so a new export is
provided: __sanitizer_override_function.
__sanitizer_override_function_by_addr is also provided to support
__except_handler4 on x86 (due to the security cookie being per-module).
3. Support weak symbols for /MD
* We have customers (CoreCLR) that rely on this behavior and would force
/MT to get it.
* There was sanitizer_win_weak_interception.cpp before, which did some
stuff for setting up the .WEAK section, but this only worked on /MT. Now
stuff registered in the .WEAK section is passed to the ASAN DLL via new
export __sanitizer_register_weak_function (impl in
sanitizer_win_interception.cpp). Unlike linux, multiple weak symbol
registrations are possible here. Current behavior is to give priority on
module load order such that whoever loads last (so priority is given to
the EXE) will have their weak symbol registered.
* Unfortunately, the registration can only occur during the user module
startup, which is after ASAN DLL startup, so any weak symbols used by
ASAN during initialization will not be picked up. This is most notable
for __asan_default_options and friends (see asan_flags.cpp). A mechanism
was made to add a callback for when a certain weak symbol was
registered, so now we process __asan_default_options during module
startup instead of ASAN startup. This is a change in behavior, but
there's no real way around this due to how DLLs are.
4. Build reorganization
* I noticed that our current build configuration is very MSVC-specific
and so did a bit of reworking. Removed a lot of
create_multiple_windows_obj_lib use since it's no longer needed and it
changed how we needed to refer to each object_lib by adding runtime
configuration to the name, conflicting with how it works for non-MSVC.
* No more Win32 static build, use /MD everywhere.
* Building with /Zl to avoid defaultlib warnings.
In addition:
* I've reapplied "[sanitizer][asan][win] Intercept _strdup on Windows
instead of strdup" which broke the previous static asan runtime. That
runtime is gone now and this change is required for the strdup tests to
work.
* I've modified the MSVC clang driver to support linking the correct
asan libraries, including via defining _DLL (which triggers different
defaultlibs and should result in the asan dll thunk being linked, along
with the dll CRT (via defaultlib directives).
* I've made passing -static-libsan an error on windows, and made
-shared-libsan the default. I'm not sure I did this correctly, or in the
best way.
* Modified the test harnesses to add substitutions for the dynamic and
static thunks and to make the library substitutions point to the dynamic
asan runtime for all test configurations on windows. Both the static and
dynamic windows test configurations remain, because they correspond to
the static and dynamic CRT, not the static and dynamic asan runtime
library.
---------
Co-authored-by: Amy Wishnousky <amyw@microsoft.com>
New change on top of [reviewed
patch](https://github.com/llvm/llvm-project/pull/81691) are [in commits
after this
one](d0757f46b3).
Previous commits are restored from the remote branch with timestamps.
1. Fix build breakage for non-ELF platforms, by defining the missing
functions {`__llvm_profile_begin_vtables`, `__llvm_profile_end_vtables`,
`__llvm_profile_begin_vtabnames `, `__llvm_profile_end_vtabnames`}
everywhere.
* Tested on mac laptop (for darwins) and Windows. Specifically,
functions in `InstrProfilingPlatformWindows.c` returns `NULL` to make it
more explicit that type prof isn't supported; see comments for the
reason.
* For the rest (AIX, other), mostly follow existing examples (like this
[one](f95b2f1acf))
2. Rename `__llvm_prf_vtabnames` -> `__llvm_prf_vns` for shorter section
name, and make returned pointers
[const](a825d2a4ec (diff-4de780ce726d76b7abc9d3353aef95013e7b21e7bda01be8940cc6574fb0b5ffR120-R121))
**Original Description**
* Raw profile format
- Header: records the byte size of compressed vtable names, and the
number of profiled vtable entries (call it `VTableProfData`). Header
also records padded bytes of each section.
- Payload: adds a section for compressed vtable names, and a section to
store `VTableProfData`. Both sections are padded so the size is a
multiple of 8.
* Indexed profile format
- Header: records the byte offset of compressed vtable names.
- Payload: adds a section to store compressed vtable names. This section
is used by `llvm-profdata` to show the list of vtables profiled for an
instrumented site.
[The originally reviewed
patch](https://github.com/llvm/llvm-project/pull/66825) will have
profile reader/write change and llvm-profdata change.
- To ensure this PR has all the necessary profile format change along
with profile version bump, created a copy of the originally reviewed
patch in https://github.com/llvm/llvm-project/pull/80761. The copy
doesn't have profile format change, but it has the set of tests which
covers type profile generation, profile read and profile merge. Tests
pass there.
rfc in
https://discourse.llvm.org/t/rfc-dynamic-type-profiling-and-optimizations-in-llvm/74600
---------
Co-authored-by: modiking <modiking213@gmail.com>
This patch inserts 1-byte counters instead of an 8-byte counters into
llvm profiles for source-based code coverage. The origial idea was
proposed as block-cov for PGO, and this patch repurposes that idea for
coverage: https://groups.google.com/g/llvm-dev/c/r03Z6JoN7d4
The current 8-byte counters mechanism add counters to minimal regions,
and infer the counters in the remaining regions via adding or
subtracting counters. For example, it infers the counter in the if.else
region by subtracting the counters between if.entry and if.then regions
in an if statement. Whenever there is a control-flow merge, it adds the
counters from all the incoming regions. However, we are not going to be
able to infer counters by subtracting two execution counts when using
single-byte counters. Therefore, this patch conservatively inserts
additional counters for the cases where we need to add or subtract
counters.
RFC:
https://discourse.llvm.org/t/rfc-single-byte-counters-for-source-based-code-coverage/75685
* Raw profile format
- Header: records the byte size of compressed vtable names, and the
number of profiled vtable entries (call it `VTableProfData`). Header
also records padded bytes of each section.
- Payload: adds a section for compressed vtable names, and a section to
store `VTableProfData`. Both sections are padded so the size is a
multiple of 8.
* Indexed profile format
- Header: records the byte offset of compressed vtable names.
- Payload: adds a section to store compressed vtable names. This section
is used by `llvm-profdata` to show the list of vtables profiled for an
instrumented site.
[The originally reviewed
patch](https://github.com/llvm/llvm-project/pull/66825) will have
profile reader/write change and llvm-profdata change.
- To ensure this PR has all the necessary profile format change along
with profile version bump, created a copy of the originally reviewed
patch in https://github.com/llvm/llvm-project/pull/80761. The copy
doesn't have profile format change, but it has the set of tests which
covers type profile generation, profile read and profile merge. Tests
pass there.
rfc in
https://discourse.llvm.org/t/rfc-dynamic-type-profiling-and-optimizations-in-llvm/74600
---------
Co-authored-by: modiking <modiking213@gmail.com>
For Windows, the compiler-rt profile library contains a polyfill
reimplementation of the mmap family of functions.
Previously, the runtime library exposed those symbols like, "mmap", in
the user symbol namespace. This could cause misdetections by configure
scripts that check for the "mmap" function just by linking, without
including headers.
Add a prefix on the symbols, and make an undeclared function static.
This fixes such an issue reported at
https://github.com/mstorsjo/llvm-mingw/issues/390.
This PR exposes four PGO functions
- `__llvm_profile_set_filename`
- `__llvm_profile_reset_counters`,
- `__llvm_profile_dump`
- `__llvm_orderfile_dump`
to user programs through the new header `instr_prof_interface.h` under
`compiler-rt/include/profile`. This way, the user can include the header
`profile/instr_prof_interface.h` to introduce these four names to their
programs.
Additionally, this PR defines macro `__LLVM_INSTR_PROFILE_GENERATE` when
the program is compiled with profile generation, and defines macro
`__LLVM_INSTR_PROFILE_USE` when the program is compiled with profile
use. `__LLVM_INSTR_PROFILE_GENERATE` together with
`instr_prof_interface.h` define the PGO functions only when the program
is compiled with profile generation. When profile generation is off,
these PGO functions are defined away and leave no trace in the user's
program.
Background:
https://discourse.llvm.org/t/pgo-are-the-llvm-profile-functions-stable-c-apis-across-llvm-releases/75832
## Motivation
Since we don't need the metadata sections at runtime, we can somehow
offload them from memory at runtime. Initially, I explored [debug info
correlation](https://discourse.llvm.org/t/instrprofiling-lightweight-instrumentation/59113),
which is used for PGO with value profiling disabled. However, it
currently only works with DWARF and it's be hard to add such artificial
debug info for every function in to CodeView which is used on Windows.
So, offloading profile metadata sections at runtime seems to be a
platform independent option.
## Design
The idea is to use new section names for profile name and data sections
and mark them as metadata sections. Under this mode, the new sections
are non-SHF_ALLOC in ELF. So, they are not loaded into memory at runtime
and can be stripped away as a post-linking step. After the process
exits, the generated raw profiles will contains only headers + counters.
llvm-profdata can be used correlate raw profiles with the unstripped
binary to generate indexed profile.
## Data
For chromium base_unittests with code coverage on linux, the binary size
overhead due to instrumentation reduced from 64M to 38.8M (39.4%) and
the raw profile files size reduce from 128M to 68M (46.9%)
```
$ bloaty out/cov/base_unittests.stripped -- out/no-cov/base_unittests.stripped
FILE SIZE VM SIZE
-------------- --------------
+121% +30.4Mi +121% +30.4Mi .text
[NEW] +14.6Mi [NEW] +14.6Mi __llvm_prf_data
[NEW] +10.6Mi [NEW] +10.6Mi __llvm_prf_names
[NEW] +5.86Mi [NEW] +5.86Mi __llvm_prf_cnts
+95% +1.75Mi +95% +1.75Mi .eh_frame
+108% +400Ki +108% +400Ki .eh_frame_hdr
+9.5% +211Ki +9.5% +211Ki .rela.dyn
+9.2% +95.0Ki +9.2% +95.0Ki .data.rel.ro
+5.0% +87.3Ki +5.0% +87.3Ki .rodata
[ = ] 0 +13% +47.0Ki .bss
+40% +1.78Ki +40% +1.78Ki .got
+12% +1.49Ki +12% +1.49Ki .gcc_except_table
[ = ] 0 +65% +1.23Ki .relro_padding
+62% +1.20Ki [ = ] 0 [Unmapped]
+13% +448 +19% +448 .init_array
+8.8% +192 [ = ] 0 [ELF Section Headers]
+0.0% +136 +0.0% +80 [7 Others]
+0.1% +96 +0.1% +96 .dynsym
+1.2% +96 +1.2% +96 .rela.plt
+1.5% +80 +1.2% +64 .plt
[ = ] 0 -99.2% -3.68Ki [LOAD #5 [RW]]
+195% +64.0Mi +194% +64.0Mi TOTAL
$ bloaty out/cov-cor/base_unittests.stripped -- out/no-cov/base_unittests.stripped
FILE SIZE VM SIZE
-------------- --------------
+121% +30.4Mi +121% +30.4Mi .text
[NEW] +5.86Mi [NEW] +5.86Mi __llvm_prf_cnts
+95% +1.75Mi +95% +1.75Mi .eh_frame
+108% +400Ki +108% +400Ki .eh_frame_hdr
+9.5% +211Ki +9.5% +211Ki .rela.dyn
+9.2% +95.0Ki +9.2% +95.0Ki .data.rel.ro
+5.0% +87.3Ki +5.0% +87.3Ki .rodata
[ = ] 0 +13% +47.0Ki .bss
+40% +1.78Ki +40% +1.78Ki .got
+12% +1.49Ki +12% +1.49Ki .gcc_except_table
+13% +448 +19% +448 .init_array
+0.1% +96 +0.1% +96 .dynsym
+1.2% +96 +1.2% +96 .rela.plt
+1.2% +64 +1.2% +64 .plt
+2.9% +64 [ = ] 0 [ELF Section Headers]
+0.0% +40 +0.0% +40 .data
+1.2% +32 +1.2% +32 .got.plt
+0.0% +24 +0.0% +8 [5 Others]
[ = ] 0 -22.9% -872 [LOAD #5 [RW]]
-74.5% -1.44Ki [ = ] 0 [Unmapped]
[ = ] 0 -76.5% -1.45Ki .relro_padding
+118% +38.8Mi +117% +38.8Mi TOTAL
```
A few things to note:
1. llvm-profdata doesn't support filter raw profiles by binary id yet,
so when a raw profile doesn't belongs to the binary being digested by
llvm-profdata, merging will fail. Once this is implemented,
llvm-profdata should be able to only merge raw profiles with the same
binary id as the binary and discard the rest (with mismatched/missing
binary id). The workflow I have in mind is to have scripts invoke
llvm-profdata to get all binary ids for all raw profiles, and
selectively choose the raw pnrofiles with matching binary id and the
binary to llvm-profdata for merging.
2. Note: In COFF, currently they are still loaded into memory but not
used. I didn't do it in this patch because I noticed that `.lcovmap` and
`.lcovfunc` are loaded into memory. A separate patch will address it.
3. This should works with PGO when value profiling is disabled as debug
info correlation currently doing, though I haven't tested this yet.
When LLVM_PROFILE_FILE is set incorrectly (e.g. multiple %c) and it
falls back to use `default.profraw` name, but continuous mode is still
set. This might cause signal bus in the following scenario.
LLVM_PROFILE_FILE is set incorrectly (with "%c%c") for process A and B.
Suppose A starts first and falls back to use `default.profraw` and
mmaped its file content to memory. Later B starts and also falls back to
use `default.profraw`, but it will truncate the file because online
merging is disable when reseting to `default.profraw`. When A tries to
update counter via mmaped memory, signal bus will occur.
This fixes it by disabling continuous mode when reset to
default.profraw.
