Messages in this thread Patch in this message | | | From | Ian Rogers <> | Date | Tue, 28 Mar 2023 10:42:37 -0700 | Subject | Re: [PATCH v1 0/6] Simplify linking against tools/perf code |
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On Tue, Mar 28, 2023 at 10:12 AM Adrian Hunter <adrian.hunter@intel.com> wrote: > > On 28/03/23 19:14, Ian Rogers wrote: > > On Tue, Mar 28, 2023 at 6:24 AM Adrian Hunter <adrian.hunter@intel.com> wrote: > >> > >> On 28/03/23 04:40, Ian Rogers wrote: > >>> When fuzzing something like parse-events, having the main function in > >>> perf.c alongside global variables like input_name means that > >>> input_name must be redeclared with the fuzzer function's > >>> main. However, as the fuzzer is using the tools/perf code as a library > >>> this causes backward linking reference that the linker may warn > >>> about. Reorganize perf.c and perf.h to avoid potential backward > >>> references, or so that the declaration/definition locations are more > >>> consistent. > >>> > >> > >> Seems like it could be a pain to maintain. > >> > >> Did you consider just adding: > >> > >> diff --git a/tools/perf/perf.c b/tools/perf/perf.c > >> index 82bbe0ca858b..a75dd47d68ee 100644 > >> --- a/tools/perf/perf.c > >> +++ b/tools/perf/perf.c > >> @@ -456,6 +456,7 @@ static int libperf_print(enum libperf_print_level level, > >> return veprintf(level, verbose, fmt, ap); > >> } > >> > >> +#ifndef CUSTOM_MAIN > >> int main(int argc, const char **argv) > >> { > >> int err; > >> @@ -576,3 +577,4 @@ int main(int argc, const char **argv) > >> out: > >> return 1; > >> } > >> +#endif > >> > > > > It's possible. Would need to make the static functions not warn about > > being declared and not used. I still think that just aligning > > definitions and declarations yields the most expected code and will > > lead to fewer problems in the long run. > > Making perf source dependent on an unknown derivative makes > things more complicated. > > If you are not going to contribute it to perf, then a > suggestion is along the lines of the following:
There's not an issue with contribution, most of the fuzzers are very simple. For example, here is the coresight fuzzer we run:
``` #include <fuzzer/FuzzedDataProvider.h>
extern "C" { #include "tools/perf/util/cs-etm-decoder/cs-etm-decoder.h" }
static void null_packet_dump(const char *) {}
extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) { FuzzedDataProvider fdp(data, size); int num_cpu = fdp.ConsumeIntegralInRange(1, 1024); struct cs_etm_decoder_params d_params; std::unique_ptr<struct cs_etm_trace_params[]> t_params(new cs_etm_trace_params[num_cpu]);
for(int i=0; i < num_cpu; ++i) { t_params[i].protocol = fdp.ConsumeIntegralInRange(static_cast<int>(CS_ETM_PROTO_ETMV3) ,
static_cast<int>(CS_ETM_PROTO_PTM)); fdp.ConsumeData(&t_params[i].etmv4, sizeof(struct cs_etmv4_trace_params)); }
d_params.packet_printer = null_packet_dump; d_params.operation = CS_ETM_OPERATION_DECODE; d_params.data = NULL; d_params.formatted = true; d_params.fsyncs = false; d_params.hsyncs = false; d_params.frame_aligned = true;
std::unique_ptr<struct cs_etm_decoder, decltype(&cs_etm_decoder__free)> decoder(cs_etm_decoder__new(num_cpu, &d_params, t_params.get()), cs_etm_decoder__free);
if (decoder == nullptr) return 0;
do { size_t consumed; uint8_t buf[1024]; size_t len = fdp.ConsumeData(buf, sizeof(buf));
int ret = cs_etm_decoder__process_data_block( decoder.get(), 0, buf, len, &consumed); if (ret) return 0;
} while (fdp.remaining_bytes() > 0);
return 0; } ``` Most of the code is boiler plate around a single function call. The issues are build support, where to put the fuzzer generated test corpus, the code is C++, etc.
> diff --git a/tools/perf/perf.c b/tools/perf/perf.c > index 82bbe0ca858b..6a7fe1534664 100644 > --- a/tools/perf/perf.c > +++ b/tools/perf/perf.c > @@ -456,7 +456,18 @@ static int libperf_print(enum libperf_print_level level, > return veprintf(level, verbose, fmt, ap); > } > > $ git diff > +#ifdef CUSTOM_MAIN > +int main(void) > +{ > + printf("This is not perf\n"); > + return 0; > +} > + > +int perf_main(int argc, const char **argv); > +int perf_main(int argc, const char **argv) > +#else > int main(int argc, const char **argv) > +#endif > { > int err; > const char *cmd; > $ make EXTRA_CFLAGS="-DCUSTOM_MAIN" NO_BPF_SKEL=1 -C tools/perf >/dev/null > Warning: Kernel ABI header at 'tools/include/uapi/linux/in.h' differs from latest version at 'include/uapi/linux/in.h' > Warning: Kernel ABI header at 'tools/arch/x86/include/asm/cpufeatures.h' differs from latest version at 'arch/x86/include/asm/cpufeatures.h' > Warning: Kernel ABI header at 'tools/arch/arm64/include/uapi/asm/perf_regs.h' differs from latest version at 'arch/arm64/include/uapi/asm/perf_regs.h' > Warning: Kernel ABI header at 'tools/include/linux/coresight-pmu.h' differs from latest version at 'include/linux/coresight-pmu.h' > Makefile.config:587: No sys/sdt.h found, no SDT events are defined, please install systemtap-sdt-devel or systemtap-sdt-dev > Makefile.config:805: Missing perl devel files. Disabling perl scripting support, please install perl-ExtUtils-Embed/libperl-dev > Makefile.config:1046: No libbabeltrace found, disables 'perf data' CTF format support, please install libbabeltrace-dev[el]/libbabeltrace-ctf-dev > Makefile.config:1075: No alternatives command found, you need to set JDIR= to point to the root of your Java directory > Makefile.config:1137: libpfm4 not found, disables libpfm4 support. Please install libpfm4-dev > $ tools/perf/perf version > This is not perf >
Sure, I'm aware of how the #ifdef would function. What I'm saying is that even with a CUSTOM_MAIN ifdef, which wouldn't be necessary with my patches as you can drop the object file, the refactoring in the patches still makes sense.
perf ui: Move window resize signal functions
It isn't clear why these UI functions should be in perf.c given window resizing is a UI issue.
perf usage: Move usage strings
The usage strings were in builtin.h and not perf.h, so the declaration/definition didn't align. util.h declares usage(), although the definition is in usage.c, the variables are moved to match this. perf header: Move perf_version_string declaration
perf_version_string is defined in header.c and so declaring it in header.h rather than perf.h is consistent.
perf version: Use regular verbose flag
Just remove an unnecessary global by repurposing the existing global for the job.
perf util: Move input_name to util
There's no reference to input_name in perf.c and so util.c is as sensible a location. Having this be a global is something of an encapsulation fail, but cleaning that up wasn't the point of these patches. The variable is used in util, so reaching up a directory to get it feels somewhat unnatural.
perf util: Move perf_guest/host declarations
As with input_name.
Thanks, Ian
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