On Thu, 2 Jan 2025 14:20:58 +0100 Jiri Olsa <olsajiri@xxxxxxxxx> wrote: > On Thu, Dec 26, 2024 at 02:11:16PM +0900, Masami Hiramatsu (Google) wrote: > > Hi, > > > > Here is the 22nd version of the series to re-implement the fprobe on > > function-graph tracer. The previous version is; > > > > https://lore.kernel.org/all/173379652547.973433.2311391879173461183.stgit@devnote2/ > > > > This version is rebased on v6.13-rc4 with fixes on [3/20] for x86-32 and > > [5/20] for build error. > > > hi, > I ran the bench and I'm seeing native_sched_clock being used > again kretprobe_multi bench: > > 5.85% bench [kernel.kallsyms] [k] native_sched_clock > | > ---native_sched_clock > sched_clock > | > --5.83%--trace_clock_local > ftrace_return_to_handler > return_to_handler > syscall > bpf_prog_test_run_opts > trigger_producer_batch > start_thread > __GI___clone3 > > I recall we tried to fix that before with [1] change, but that replaced > later with [2] changes > > When I remove the trace_clock_local call in __ftrace_return_to_handler > than the kretprobe-multi gets much faster (see last block below), so it > seems worth to make it optional > > there's some decrease in kprobe_multi benchmark compared to base numbers, > which I'm not sure yet why, but other than that it seems ok > > base: > kprobe : 12.873 ± 0.011M/s > kprobe-multi : 13.088 ± 0.052M/s > kretprobe : 6.339 ± 0.003M/s > kretprobe-multi: 7.240 ± 0.002M/s > > fprobe_on_fgraph: > kprobe : 12.816 ± 0.002M/s > kprobe-multi : 12.126 ± 0.004M/s > kretprobe : 6.305 ± 0.018M/s > kretprobe-multi: 7.740 ± 0.003M/s > > removed native_sched_clock call: > kprobe : 12.850 ± 0.006M/s > kprobe-multi : 12.115 ± 0.006M/s > kretprobe : 6.270 ± 0.017M/s > kretprobe-multi: 9.190 ± 0.005M/s Hmm, this still look good. Ok, let me move the trace_clock_local() to the function_graph. Thanks! > > > happy new year ;-) thanks, > > jirka > > > [1] https://lore.kernel.org/bpf/172615389864.133222.14452329708227900626.stgit@devnote2/ > [2] https://lore.kernel.org/all/20240914214805.779822616@xxxxxxxxxxx/ > > > > > Overview > > -------- > > This series rewrites the fprobe on this function-graph. > > The purposes of this change are; > > > > 1) Remove dependency of the rethook from fprobe so that we can reduce > > the return hook code and shadow stack. > > > > 2) Make 'ftrace_regs' the common trace interface for the function > > boundary. > > > > 1) Currently we have 2(or 3) different function return hook codes, > > the function-graph tracer and rethook (and legacy kretprobe). > > But since this is redundant and needs double maintenance cost, > > I would like to unify those. From the user's viewpoint, function- > > graph tracer is very useful to grasp the execution path. For this > > purpose, it is hard to use the rethook in the function-graph > > tracer, but the opposite is possible. (Strictly speaking, kretprobe > > can not use it because it requires 'pt_regs' for historical reasons.) > > > > 2) Now the fprobe provides the 'pt_regs' for its handler, but that is > > wrong for the function entry and exit. Moreover, depending on the > > architecture, there is no way to accurately reproduce 'pt_regs' > > outside of interrupt or exception handlers. This means fprobe should > > not use 'pt_regs' because it does not use such exceptions. > > (Conversely, kprobe should use 'pt_regs' because it is an abstract > > interface of the software breakpoint exception.) > > > > This series changes fprobe to use function-graph tracer for tracing > > function entry and exit, instead of mixture of ftrace and rethook. > > Unlike the rethook which is a per-task list of system-wide allocated > > nodes, the function graph's ret_stack is a per-task shadow stack. > > Thus it does not need to set 'nr_maxactive' (which is the number of > > pre-allocated nodes). > > Also the handlers will get the 'ftrace_regs' instead of 'pt_regs'. > > Since eBPF mulit_kprobe/multi_kretprobe events still use 'pt_regs' as > > their register interface, this changes it to convert 'ftrace_regs' to > > 'pt_regs'. Of course this conversion makes an incomplete 'pt_regs', > > so users must access only registers for function parameters or > > return value. > > > > Design > > ------ > > Instead of using ftrace's function entry hook directly, the new fprobe > > is built on top of the function-graph's entry and return callbacks > > with 'ftrace_regs'. > > > > Since the fprobe requires access to 'ftrace_regs', the architecture > > must support CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS and > > CONFIG_HAVE_FTRACE_GRAPH_FUNC, which enables to call function-graph > > entry callback with 'ftrace_regs', and also > > CONFIG_HAVE_FUNCTION_GRAPH_FREGS, which passes the ftrace_regs to > > return_to_handler. > > > > All fprobes share a single function-graph ops (means shares a common > > ftrace filter) similar to the kprobe-on-ftrace. This needs another > > layer to find corresponding fprobe in the common function-graph > > callbacks, but has much better scalability, since the number of > > registered function-graph ops is limited. > > > > In the entry callback, the fprobe runs its entry_handler and saves the > > address of 'fprobe' on the function-graph's shadow stack as data. The > > return callback decodes the data to get the 'fprobe' address, and runs > > the exit_handler. > > > > The fprobe introduces two hash-tables, one is for entry callback which > > searches fprobes related to the given function address passed by entry > > callback. The other is for a return callback which checks if the given > > 'fprobe' data structure pointer is still valid. Note that it is > > possible to unregister fprobe before the return callback runs. Thus > > the address validation must be done before using it in the return > > callback. > > > > Download > > -------- > > This series can be applied against the v6.13-rc2 kernel. > > > > This series can also be found below branch. > > > > https://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git/log/?h=topic/fprobe-on-fgraph > > > > Thank you, > > > > --- > > > > Masami Hiramatsu (Google) (19): > > fgraph: Get ftrace recursion lock in function_graph_enter > > fgraph: Pass ftrace_regs to entryfunc > > fgraph: Replace fgraph_ret_regs with ftrace_regs > > fgraph: Pass ftrace_regs to retfunc > > fprobe: Use ftrace_regs in fprobe entry handler > > fprobe: Use ftrace_regs in fprobe exit handler > > tracing: Add ftrace_partial_regs() for converting ftrace_regs to pt_regs > > tracing: Add ftrace_fill_perf_regs() for perf event > > tracing/fprobe: Enable fprobe events with CONFIG_DYNAMIC_FTRACE_WITH_ARGS > > bpf: Enable kprobe_multi feature if CONFIG_FPROBE is enabled > > ftrace: Add CONFIG_HAVE_FTRACE_GRAPH_FUNC > > fprobe: Rewrite fprobe on function-graph tracer > > fprobe: Add fprobe_header encoding feature > > tracing/fprobe: Remove nr_maxactive from fprobe > > selftests: ftrace: Remove obsolate maxactive syntax check > > selftests/ftrace: Add a test case for repeating register/unregister fprobe > > Documentation: probes: Update fprobe on function-graph tracer > > ftrace: Add ftrace_get_symaddr to convert fentry_ip to symaddr > > bpf: Use ftrace_get_symaddr() for kprobe_multi probes > > > > Sven Schnelle (1): > > s390/tracing: Enable HAVE_FTRACE_GRAPH_FUNC > > > > > > Documentation/trace/fprobe.rst | 42 + > > arch/arm64/Kconfig | 2 > > arch/arm64/include/asm/Kbuild | 1 > > arch/arm64/include/asm/ftrace.h | 51 +- > > arch/arm64/kernel/asm-offsets.c | 12 > > arch/arm64/kernel/entry-ftrace.S | 32 + > > arch/arm64/kernel/ftrace.c | 78 ++ > > arch/loongarch/Kconfig | 4 > > arch/loongarch/include/asm/fprobe.h | 12 > > arch/loongarch/include/asm/ftrace.h | 32 - > > arch/loongarch/kernel/asm-offsets.c | 12 > > arch/loongarch/kernel/ftrace_dyn.c | 10 > > arch/loongarch/kernel/mcount.S | 17 - > > arch/loongarch/kernel/mcount_dyn.S | 14 > > arch/powerpc/Kconfig | 1 > > arch/powerpc/include/asm/ftrace.h | 13 > > arch/powerpc/kernel/trace/ftrace.c | 8 > > arch/powerpc/kernel/trace/ftrace_64_pg.c | 16 > > arch/riscv/Kconfig | 3 > > arch/riscv/include/asm/Kbuild | 1 > > arch/riscv/include/asm/ftrace.h | 45 + > > arch/riscv/kernel/ftrace.c | 17 - > > arch/riscv/kernel/mcount.S | 24 - > > arch/s390/Kconfig | 4 > > arch/s390/include/asm/fprobe.h | 10 > > arch/s390/include/asm/ftrace.h | 37 + > > arch/s390/kernel/asm-offsets.c | 6 > > arch/s390/kernel/entry.h | 1 > > arch/s390/kernel/ftrace.c | 48 - > > arch/s390/kernel/mcount.S | 23 - > > arch/x86/Kconfig | 4 > > arch/x86/include/asm/Kbuild | 1 > > arch/x86/include/asm/ftrace.h | 54 +- > > arch/x86/kernel/ftrace.c | 47 + > > arch/x86/kernel/ftrace_32.S | 13 > > arch/x86/kernel/ftrace_64.S | 17 - > > include/asm-generic/fprobe.h | 46 + > > include/linux/fprobe.h | 62 +- > > include/linux/ftrace.h | 116 +++ > > include/linux/ftrace_regs.h | 2 > > kernel/trace/Kconfig | 22 - > > kernel/trace/bpf_trace.c | 28 + > > kernel/trace/fgraph.c | 65 +- > > kernel/trace/fprobe.c | 664 +++++++++++++++----- > > kernel/trace/ftrace.c | 6 > > kernel/trace/trace.h | 6 > > kernel/trace/trace_fprobe.c | 146 ++-- > > kernel/trace/trace_functions_graph.c | 10 > > kernel/trace/trace_irqsoff.c | 6 > > kernel/trace/trace_probe_tmpl.h | 2 > > kernel/trace/trace_sched_wakeup.c | 6 > > kernel/trace/trace_selftest.c | 11 > > lib/test_fprobe.c | 51 -- > > samples/fprobe/fprobe_example.c | 4 > > .../test.d/dynevent/add_remove_fprobe_repeat.tc | 19 + > > .../ftrace/test.d/dynevent/fprobe_syntax_errors.tc | 4 > > 56 files changed, 1318 insertions(+), 670 deletions(-) > > create mode 100644 arch/loongarch/include/asm/fprobe.h > > create mode 100644 arch/s390/include/asm/fprobe.h > > create mode 100644 include/asm-generic/fprobe.h > > create mode 100644 tools/testing/selftests/ftrace/test.d/dynevent/add_remove_fprobe_repeat.tc > > > > -- > > Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx> -- Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
