Implement DTrace/SystemTap SDT by emitting the following:
- The probe crate's probe!() macro is used to emit a DTrace/SystemTap
SDT probe.
- Every trace event gets a corresponding trace_<name>_enabled() -> bool
generated function that Rust code can use to avoid expensive
computation when a trace event is disabled. This API works for other
trace backends too.
`#[allow(dead_code)]` additions are necessary for QEMU's dstate in
generated trace-<dir>.rs files since they are unused by the dtrace
backend. `./configure --enable-trace-backends=` can enable multiple
backends, so keep it simple and just silence the warning instead of
trying to detect the condition when generating the dstate code can be
skipped.
The tracetool tests are updated. Take a look at
tests/tracetool/dtrace.rs to see what the new generated code looks like.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Link: https://lore.kernel.org/r/20251119205200.173170-5-stefanha@redhat.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The syslog backend needs the syslog function from libc and the LOG_INFO enum
value; they are re-exported as "::trace::syslog" and "::trace::LOG_INFO"
so that device crates do not all have to add the libc dependency, but
otherwise there is nothing special.
Signed-off-by: Tanish Desai <tanishdesai37@gmail.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20250929154938.594389-17-pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Generating .rs files makes it possible to support tracing in rust.
This support comprises a new format, and common code that converts
the C expressions in trace-events to Rust. In particular, types
need to be converted, and PRI macros expanded.
As of this commit no backend generates Rust code, but it is already
possible to use tracetool to generate Rust sources; they are not
functional but they compile and contain tracepoint functions.
[Move Rust argument conversion from Event to Arguments; string
support. - Paolo]
Signed-off-by: Tanish Desai <tanishdesai37@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20250929154938.594389-9-pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Use CHECK_TRACE_EVENT_GET_STATE in log, syslog, dtrace and simple
backend, so that the "if (trace_event_get_state)" is created from common
code and unified when multiple backends are active.
When a single backend is active there is no code change (except
for the log backend, as shown in tests/tracetool/log.h), but the
code in the backends is simpler.
Signed-off-by: Tanish Desai <tanishdesai37@gmail.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-ID: <20250929154938.594389-8-pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Add a new attribute CHECK_TRACE_EVENT_GET_STATE to the backends.
When present and True, the code generated by the generate function
is wrapped in a conditional that checks whether the event is enabled;
this removes the need for repeating the same conditional in multiple
backends.
Signed-off-by: Tanish Desai <tanishdesai37@gmail.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-ID: <20250929154938.594389-7-pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
try_import returns a tuple of a boolean and the requested module or attribute.
exists() functions return tracetool.try_import("tracetool.format." + name)[1]
but they should return the boolean value instead.
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20250929154938.594389-2-pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Every generated inline probe function is wrapped with a
trivial caller that has a hard-coded condition test:
static inline void _nocheck__trace_test_wibble(void * context, int value)
{
tracepoint(qemu, test_wibble, context, value);
}
static inline void trace_test_wibble(void * context, int value)
{
if (true) {
_nocheck__trace_test_wibble(context, value);
}
}
This was introduced for TCG probes back in
864a2178: trace: [tcg] Do not generate TCG code to trace dynamically-disabled events
but is obsolete since
126d4123 tracing: excise the tcg related from tracetool
This commit removes the wrapping such that we have
static inline void trace_test_wibble(void * context, int value)
{
tracepoint(qemu, test_wibble, context, value);
}
The default build of qemu-system-x86_64 on Fedora with the
'log' backend, has its size reduced by 1 MB
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-id: 20250916081638.764020-7-berrange@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Currently the tracing 'log' back emits special code to add timestamps
to trace points sent via qemu_log(). This current impl is a bad design
for a number of reasons.
* It changes the QEMU headers, such that 'error-report.h' content
is visible to all files using tracing, but only when the 'log'
backend is enabled. This has led to build failure bugs as devs
rarely test without the (default) 'log' backend enabled, and
CI can't cover every scenario for every trace backend.
* It bloats the trace points definitions which are inlined into
every probe location due to repeated inlining of timestamp
formatting code, adding MBs of overhead to QEMU.
* The tracing subsystem should not be treated any differently
from other users of qemu_log. They all would benefit from
having timestamps present.
* The timestamp emitted with the tracepoints is in a needlessly
different format to that used by error_report() in response
to '-msg timestamp=on'.
This fixes all these issues simply by moving timestamp formatting
into qemu_log, using the same approach as for error_report.
The code before:
static inline void _nocheck__trace_qcrypto_tls_creds_get_path(void * creds, const char * filename, const char * path)
{
if (trace_event_get_state(TRACE_QCRYPTO_TLS_CREDS_GET_PATH) && qemu_loglevel_mask(LOG_TRACE)) {
if (message_with_timestamp) {
struct timeval _now;
gettimeofday(&_now, NULL);
qemu_log("%d@%zu.%06zu:qcrypto_tls_creds_get_path " "TLS creds path creds=%p filename=%s path=%s" "\n",
qemu_get_thread_id(),
(size_t)_now.tv_sec, (size_t)_now.tv_usec
, creds, filename, path);
} else {
qemu_log("qcrypto_tls_creds_get_path " "TLS creds path creds=%p filename=%s path=%s" "\n", creds, filename, path);
}
}
}
and after:
static inline void _nocheck__trace_qcrypto_tls_creds_get_path(void * creds, const char * filename, const char * path)
{
if (trace_event_get_state(TRACE_QCRYPTO_TLS_CREDS_GET_PATH) && qemu_loglevel_mask(LOG_TRACE)) {
qemu_log("qcrypto_tls_creds_get_path " "TLS creds path creds=%p filename=%s path=%s" "\n", creds, filename, path);
}
}
The log and error messages before:
$ qemu-system-x86_64 -trace qcrypto* -object tls-creds-x509,id=tls0,dir=$HOME/tls -msg timestamp=on
2986097@1753122905.917608:qcrypto_tls_creds_x509_load TLS creds x509 load creds=0x55d925bd9490 dir=/var/home/berrange/tls
2986097@1753122905.917621:qcrypto_tls_creds_get_path TLS creds path creds=0x55d925bd9490 filename=ca-cert.pem path=<none>
2025-07-21T18:35:05.917626Z qemu-system-x86_64: Unable to access credentials /var/home/berrange/tls/ca-cert.pem: No such file or directory
and after:
$ qemu-system-x86_64 -trace qcrypto* -object tls-creds-x509,id=tls0,dir=$HOME/tls -msg timestamp=on
2025-07-21T18:43:28.089797Z qcrypto_tls_creds_x509_load TLS creds x509 load creds=0x55bf5bf12380 dir=/var/home/berrange/tls
2025-07-21T18:43:28.089815Z qcrypto_tls_creds_get_path TLS creds path creds=0x55bf5bf12380 filename=ca-cert.pem path=<none>
2025-07-21T18:43:28.089819Z qemu-system-x86_64: Unable to access credentials /var/home/berrange/tls/ca-cert.pem: No such file or directory
The binary size before:
$ ls -alh qemu-system-x86_64
-rwxr-xr-x. 1 berrange berrange 87M Jul 21 19:39 qemu-system-x86_64
$ strip qemu-system-x86_64
$ ls -alh qemu-system-x86_64
-rwxr-xr-x. 1 berrange berrange 30M Jul 21 19:39 qemu-system-x86_64
and after:
$ ls -alh qemu-system-x86_64
-rwxr-xr-x. 1 berrange berrange 85M Jul 21 19:41 qemu-system-x86_64
$ strip qemu-system-x86_64
$ ls -alh qemu-system-x86_64
-rwxr-xr-x. 1 berrange berrange 29M Jul 21 19:41 qemu-system-x86_64
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Message-id: 20250721185452.3016488-1-berrange@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
The build fails on Windows. Replace calls to Unix programs like ´cat´,
´sed´ and ´true´ with calls to ´python´ and wrap calls to
´os.path.relpath´ in try-except because it can fail when the two paths
are on different drives. Make sure to convert the Windows paths to Unix
paths to prevent warnings in generated files.
Signed-off-by: oltolm <oleg.tolmatcev@gmail.com>
Message-id: 20250612221521.1109-2-oleg.tolmatcev@gmail.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This change improves performance by moving the hot path of the trace_vhost_commit()(or any other trace function) logic to the header file.
Previously, even when the trace event was disabled, the function call chain:-
trace_vhost_commit()(Or any other trace function) → _nocheck__trace_vhost_commit() → _simple_trace_vhost_commit()
incurred a significant function prologue overhead before checking the trace state.
Disassembly of _simple_trace_vhost_commit() (from the .c file) showed that 11 out of the first 14 instructions were prologue-related, including:
0x10 stp x29, x30, [sp, #-64]! Prologue: allocates 64-byte frame and saves old FP (x29) & LR (x30)
0x14 adrp x3, trace_events_enabled_count Prologue: computes page-base of the trace-enable counter
0x18 adrp x2, __stack_chk_guard Important (maybe prolog don't know?)(stack-protector): starts up the stack-canary load
0x1c mov x29, sp Prologue: sets new frame pointer
0x20 ldr x3, [x3] Prologue: loads the actual trace-enabled count
0x24 stp x19, x20, [sp, #16] Prologue: spills callee-saved regs used by this function (x19, x20)
0x28 and w20, w0, #0xff Tracepoint setup: extracts the low-8 bits of arg0 as the “event boolean”
0x2c ldr x2, [x2] Prologue (cont’d): completes loading of the stack-canary value
0x30 and w19, w1, #0xff Tracepoint setup: extracts low-8 bits of arg1
0x34 ldr w0, [x3] Important: loads the current trace-enabled flag from memory
0x38 ldr x1, [x2] Prologue (cont’d): reads the canary
0x3c str x1, [sp, #56] Prologue (cont’d): writes the canary into the new frame
0x40 mov x1, #0 Prologue (cont’d): zeroes out x1 for the upcoming branch test
0x44 cbnz w0, 0x88 Important: if tracing is disabled (w0==0) skip the heavy path entirely
The trace-enabled check happens after the prologue. This is wasteful when tracing is disabled, which is often the case in production.
To optimize this:
_nocheck__trace_vhost_commit() is now fully inlined in the .h file with
the hot path.It checks trace_event_get_state() before calling into _simple_trace_vhost_commit(), which remains in .c.
This avoids calling into the .c function altogether when the tracepoint is disabled, thereby skipping unnecessary prologue instructions.
This results in better performance by removing redundant instructions in the tracing fast path.
Signed-off-by: Tanish Desai <tanishdesai37@gmail.com>
Message-id: 20250528192528.3968-1-tanishdesai37@gmail.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This file, and a couple of uses, got left behind when the
tcg stuff was removed from tracetool.
Fixes: 126d4123c5 ("tracing: excise the tcg related from tracetool")
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
On Fedora 36, with lttng-ust 2.13.1, compilation fails with:
In file included from trace/trace-ust-all.h:49085,
from trace/trace-ust-all.c:13:
/usr/include/lttng/tracepoint-event.h:67:10: error: #include expects "FILENAME" or <FILENAME>
67 | #include LTTNG_UST_TRACEPOINT_INCLUDE
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
In lttng-ust commit 41858e2b6e8 ("Fix: don't do macro expansion in
tracepoint file name") from 2012, starting from lttng-ust 2.1, the API
was changed to expect TRACEPOINT_INCLUDE to be defined as a string.
In lttng-ust commit d2966b4b0b2 ("Remove TRACEPOINT_INCLUDE_FILE
macro"), in 2021, the compatibility macro was removed.
Use the "new" API from 2012, and bump the version requirement to 2.1 to
fix compilation with >= 2.13.
According to repology, all distributions we support have >= 2.1 (centos
8 has oldest with 2.8.1 afaict)
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20220328084717.367993-2-marcandre.lureau@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
macro is not reset after use, so the format decoded is always the
one of the first "PRI" in the format string.
For instance:
vhost_vdpa_set_config(void *dev, uint32_t offset, uint32_t size, \
uint32_t flags) "dev: %p offset: %"PRIu32" \
size: %"PRIu32" flags: 0x%"PRIx32
generates:
printf("%d@%d vhost_vdpa_set_config dev: %p offset: %u size: %u \
flags: 0x%u\n", pid(), gettimeofday_ns(), dev, offset, \
size, flags)
for the "flags" parameter, we can see a "0x%u" rather than a "0x%x"
because the first macro was "PRIu32" (for offset).
In the loop, macro becomes "PRIu32PRIu32PRIx32", and c_macro_to_format()
returns always macro[3] ('u' in this case). This patch resets macro after
the format has been decoded.
Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-id: 20210105191721.120463-3-lvivier@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
The compiler encounters trace event format strings in generated code.
Format strings are error-prone and therefore clear compiler errors are
important.
Use the #line directive to show the trace-events filename and line
number in format string errors:
https://gcc.gnu.org/onlinedocs/gcc-10.2.0/cpp/Line-Control.html
For example, if the cpu_in trace event's %u is changed to %p the
following error is reported:
trace-events:29:18: error: format ‘%p’ expects argument of type ‘void *’, but argument 7 has type ‘unsigned int’ [-Werror=format=]
Line 29 in trace-events is where cpu_in is defined. This works for any
trace-events file in the QEMU source tree and the correct path is
displayed.
Unfortunately there does not seem to be a way to set the column, so "18"
is not the right character on that line.
Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20200827142915.108730-5-stefanha@redhat.com>
The tracetool.py script writes to stdout. This means the output filename
is not available to the script. Add the output filename to the
command-line so that the script has access to the filename.
This also simplifies the tracetool.py invocation. It's no longer
necessary to use meson's custom_build(capture : true) to save output.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20200827142915.108730-2-stefanha@redhat.com>
SystemTap's dtrace(1) prints the following warning when it encounters
long long arguments:
Warning: /usr/bin/dtrace:trace/trace-dtrace-hw_virtio.dtrace:76: syntax error near:
probe vhost_vdpa_dev_start
Warning: Proceeding as if --no-pyparsing was given.
Use the uint64_t and int64_t types, respectively. This works with all
host CPU 32- and 64-bit data models (ILP32, LP64, and LLP64) that QEMU
supports.
Reported-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20201020094043.159935-1-stefanha@redhat.com
Suggested-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
dtrace on macOS complains that CPUState * is used for a few probes:
dtrace: failed to compile script trace-dtrace-root.dtrace: line 130: syntax error near "CPUState"
A comment in scripts/tracetool/__init__.py mentions that:
We only want to allow standard C types or fixed sized
integer types. We don't want QEMU specific types
as we can't assume trace backends can resolve all the
typedefs
Fixes: 3d211d9f4d ("trace: Add 'vcpu' event property to trace guest vCPU")
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
Message-id: 20200717093517.73397-3-r.bolshakov@yadro.com
Cc: Cameron Esfahani <dirty@apple.com>
Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
dtrace USDT is fully supported since OS X 10.6. There are a few
peculiarities compared to other dtrace flavors.
1. It doesn't accept empty files.
2. It doesn't recognize bool type but accepts C99 _Bool.
3. It converts int8_t * in probe points to char * in
header files and introduces [-Wpointer-sign] warning.
Cc: Cameron Esfahani <dirty@apple.com>
Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20200717093517.73397-2-r.bolshakov@yadro.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This shows how to do some "computations" in meson.build using its array
and dictionary data structures, and also a basic usage of the sourceset
module for conditional compilation.
Notice the new "if have_system" part of util/meson.build, which fixes
a bug in the old build system was buggy: util/dbus.c was built even for
non-softmmu builds, but the dependency on -lgio was lost when the linking
was done through libqemuutil.a. Because all of its users required gio
otherwise, the bug was hidden. Meson instead propagates libqemuutil's
dependencies down to its users, and shows the problem.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Meson doesn't enjoy the same flexibility we have with Make in choosing
the include path. In particular the tracing headers are using
$(build_root)/$(<D).
In order to keep the include directives unchanged,
the simplest solution is to generate headers with patterns like
"trace/trace-audio.h" and place forwarding headers in the source tree
such that for example "audio/trace.h" includes "trace/trace-audio.h".
This patch is too ugly to be applied to the Makefiles now. It's only
a way to separate the changes to the tracing header files from the
Meson rewrite of the tracing logic.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The dtrace backend defines SDT_USE_VARIADIC as a workaround for a
conflict with a LTTng UST header file, which requires SDT_USE_VARIADIC
to be defined.
LTTng UST <lttng/tracepoint.h> breaks if included after generated dtrace
headers because SDT_USE_VARIADIC will already be defined:
#ifdef LTTNG_UST_HAVE_SDT_INTEGRATION
#define SDT_USE_VARIADIC <-- error, it's already defined
#include <sys/sdt.h>
Be more careful when defining SDT_USE_VARIADIC. This fixes the build
when both the dtrace and ust tracers are enabled at the same time.
Fixes: 27e08bab94 ("tracetool: work around ust <sys/sdt.h> include conflict")
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20200729153926.127083-1-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Both the dtrace and ust backends may include <sys/sdt.h> but LTTng
Userspace Tracer 2.11 and later requires SDT_USE_VARIADIC to be defined
before including the header file.
This is a classic problem with C header files included from different
parts of a program. If the same header is included twice within the same
compilation unit then the first inclusion determines the macro
environment.
Work around this by defining SDT_USE_VARIADIC in the dtrace backend too.
It doesn't hurt and fixes a missing STAP_PROBEV() compiler error when
the ust backend is enabled together with the dtrace backend.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20200625140757.237012-1-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
We are going to re-use mem_info later for plugins and will need to
track the mmu_idx for softmmu code.
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
