Messages in this thread | | | From | Song Shuai <> | Date | Wed, 11 Jan 2023 10:11:04 +0000 | Subject | Re: [PATCH -next V6 0/7] riscv: Optimize function trace |
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<guoren@kernel.org> 于2023年1月7日周六 13:36写道: > > From: Guo Ren <guoren@linux.alibaba.com> > > The previous ftrace detour implementation fc76b8b8011 ("riscv: Using > PATCHABLE_FUNCTION_ENTRY instead of MCOUNT") contain three problems. > > - The most horrible bug is preemption panic which found by Andy [1]. > Let's disable preemption for ftrace first, and Andy could continue > the ftrace preemption work. > - The "-fpatchable-function-entry= CFLAG" wasted code size > !RISCV_ISA_C. > - The ftrace detour implementation wasted code size. > - When livepatching, the trampoline (ftrace_regs_caller) would not > return to <func_prolog+12> but would rather jump to the new function. > So, "REG_L ra, -SZREG(sp)" would not run and the original return > address would not be restored. The kernel is likely to hang or crash > as a result. (Found by Evgenii Shatokhin [4]) > > Patches 1,2,3 fixup above problems. > > Patches 4,5,6,7 are the features based on reduced detour code > patch, we include them in the series for test and maintenance. > > You can directly try it with: > https://github.com/guoren83/linux/tree/ftrace_fixup_v6 > This link is broken, maybe you forget to push the branch to remote.
And the patch ("riscv : select FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY") was folded in the PR ( https://github.com/guoren83/linux/pull/1 ) I guess you might omit it. Hope its debut in the next version.
> Make function graph use ftrace directly [2] (patch 4, 5) > ======================================================== > > In RISC-V architecture, when we enable the ftrace_graph tracer on some > functions, the function tracings on other functions will suffer extra > graph tracing work. In essence, graph_ops isn't limited by its func_hash > due to the global ftrace_graph_[regs]_call label. That should be > corrected. > > What inspires me is the commit 0c0593b45c9b ("x86/ftrace: Make function > graph use ftrace directly") that uses graph_ops::func function to > install return_hooker and makes the function called against its > func_hash. > > This series of patches makes function graph use ftrace directly for > riscv. > > If FTRACE_WITH_REGS isn't defined, ftrace_caller keeps ftrace_graph_call > so that it can be replaced with the calling of prepare_ftrace_return by > the enable/disable helper. > > As for defining FTRACE_WITH_REGS, ftrace_caller is adjusted to save the > necessary regs against the pt_regs layout, so it can reasonably call the > graph_ops::func function - ftrace_graph_func. And > ftrace_graph_[regs]_call > and its enable/disable helper aren't needed. > > Test log: > > The tests generated by CONFIG_FTRACE_STARTUP_TEST have passed in the > local > qemu-system-riscv64 virt machine. The following is the log during > startup. > > ``` > Nov 15 03:07:13 stage4 kernel: Testing tracer function: PASSED > Nov 15 03:07:13 stage4 kernel: Testing dynamic ftrace: PASSED > Nov 15 03:07:13 stage4 kernel: Testing dynamic ftrace ops #1: > Nov 15 03:07:13 stage4 kernel: (1 0 1 0 0) > Nov 15 03:07:13 stage4 kernel: (1 1 2 0 0) > Nov 15 03:07:13 stage4 kernel: (2 1 3 0 365) > Nov 15 03:07:13 stage4 kernel: (2 2 4 0 399) > Nov 15 03:07:13 stage4 kernel: (3 2 4 0 146071) > Nov 15 03:07:13 stage4 kernel: (3 3 5 0 146105) PASSED > Nov 15 03:07:13 stage4 kernel: Testing dynamic ftrace ops #2: > Nov 15 03:07:13 stage4 kernel: (1 0 1 589 0) > Nov 15 03:07:13 stage4 kernel: (1 1 2 635 0) > Nov 15 03:07:13 stage4 kernel: (2 1 3 1 2) > Nov 15 03:07:13 stage4 kernel: (2 2 4 125 126) > Nov 15 03:07:13 stage4 kernel: (3 2 4 146001 146078) > Nov 15 03:07:13 stage4 kernel: (3 3 5 146035 146112) PASSED > Nov 15 03:07:13 stage4 kernel: Testing ftrace recursion: PASSED > Nov 15 03:07:13 stage4 kernel: Testing ftrace recursion safe: PASSED > Nov 15 03:07:13 stage4 kernel: Testing ftrace regs: PASSED > Nov 15 03:07:13 stage4 kernel: Testing tracer nop: PASSED > Nov 15 03:07:13 stage4 kernel: Testing tracer irqsoff: PASSED > Nov 15 03:07:13 stage4 kernel: Testing tracer wakeup: > Nov 15 03:07:13 stage4 kernel: sched: DL replenish lagged too much > Nov 15 03:07:13 stage4 kernel: PASSED > Nov 15 03:07:13 stage4 kernel: Testing tracer wakeup_rt: PASSED > Nov 15 03:07:13 stage4 kernel: Testing tracer wakeup_dl: PASSED > Nov 15 03:07:13 stage4 kernel: Testing tracer function_graph: PASSED > ``` > > Add WITH_DIRECT_CALLS support [3] (patch 6, 7) > ============================================== > > This series adds DYNAMIC_FTRACE_WITH_DIRECT_CALLS support for RISC-V. > SAMPLE_FTRACE_DIRECT and SAMPLE_FTRACE_DIRECT_MULTI are also included > here as the samples for testing DIRECT_CALLS related interface. > > First, select the DYNAMIC_FTRACE_WITH_DIRECT_CALLS to provide > register_ftrace_direct[_multi] interfaces allowing user to register > the customed trampoline (direct_caller) as the mcount for one or > more target functions. And modify_ftrace_direct[_multi] are also > provided for modify direct_caller. > > At the same time, the samples in ./samples/ftrace/ can be built > as kerenl module for testing these interfaces with SAMPLE_FTRACE_DIRECT > and SAMPLE_FTRACE_DIRECT_MULTI selected. > > Second, to make the direct_caller and the other ftrace hooks > (eg. function/fgraph tracer, k[ret]probes) co-exist, a temporary > register > are nominated to store the address of direct_caller in > ftrace_regs_caller. > After the setting of the address direct_caller by direct_ops->func and > the RESTORE_REGS in ftrace_regs_caller, direct_caller will be jumped to > by the `jr` inst. > > The following tests have been passed in my local qemu-riscv64 virt > machine. > > 1. tests with CONFIG_FTRACE_STARTUP_TEST > 2. tests of samples/ftrace/ftrace*.ko > 3. manual tests with any combination of the following hooks > - function/function_graph tracer > - ftrace*.ko > - kprobe/kretprobe > > For your reference, here is the log when function tracer, kretprobe and > ftrace-direct-too.ko co-hooks the handle_mm_fault function. > > ``` > [root@stage4 tracing]# echo handle_mm_fault > set_ftrace_filter > [root@stage4 tracing]# echo 'r:myr handle_mm_fault' > kprobe_events > [root@stage4 tracing]# echo function > current_tracer > [root@stage4 tracing]# echo 1 > events/kprobes/myr/enable > [root@stage4 tracing]# insmod /root/ftrace-direct-too.ko > [root@stage4 tracing]# > [root@stage4 tracing]# cat trace | tail > cat-388 [000] ...1. 583.051438: myr: > (do_page_fault+0x16c/0x5f2 <- handle_mm_fault) > cat-388 [000] ...2. 583.057930: handle_mm_fault > <-do_page_fault > cat-388 [000] ..... 583.057990: my_direct_func: > handle mm fault vma=000000002d9fe19c address=ffffffae9b7000 flags=215 > cat-388 [000] ...1. 583.058284: myr: > (do_page_fault+0x16c/0x5f2 <- handle_mm_fault) > tail-389 [001] ...2. 583.059062: handle_mm_fault > <-do_page_fault > tail-389 [001] ..... 583.059104: my_direct_func: > handle mm fault vma=0000000017f3c48e address=aaaaaabebf3000 flags=215 > tail-389 [001] ...1. 583.059325: myr: > (do_page_fault+0x16c/0x5f2 <- handle_mm_fault) > tail-389 [001] ...2. 583.060371: handle_mm_fault > <-do_page_fault > tail-389 [001] ..... 583.060410: my_direct_func: > handle mm fault vma=0000000017f3c48e address=aaaaaabebf1000 flags=255 > tail-389 [001] ...1. 583.060996: myr: > (do_page_fault+0x16c/0x5f2 <- handle_mm_fault) > ``` > Note1: > > The checkpatch.pl will output some warnings on this series, like this > > ``` > WARNING: Prefer using '"%s...", __func__' to using 'my_direct_func2', > this function's name, in a string > 111: FILE: samples/ftrace/ftrace-direct-multi-modify.c:48: > +" call my_direct_func2\n" > ``` > > The reason is that checkpatch depends on patch context providing the > function name. In the above warning, my_direct_func2 has some codeline > distance with the changed trunk, so its declaration doesn't come into > the patch, and then the warning jumps out. > > You may notice the location of `my_ip` variable changes in the 2nd > patch. I did that for reducing the warnings to some extent. But killing > all the warnings will makes the patch less readable, so I stopped here. > > [1] https://lpc.events/event/16/contributions/1171/ > [2] https://lore.kernel.org/lkml/20221120084230.910152-1-suagrfillet@gmail.com/ > [3] https://lore.kernel.org/linux-riscv/20221123142025.1504030-1-suagrfillet@gmail.com/ > [4] https://lore.kernel.org/linux-riscv/d7d5730b-ebef-68e5-5046-e763e1ee6164@yadro.com/ > > Changes in v6: > - Replace 8 with MCOUNT_INSN_SIZE > - Replace "REG_L a1, PT_RA(sp)" with "mv a1, ra" > - Add Evgenii Shatokhin comment > > Changes in v5: > https://lore.kernel.org/linux-riscv/20221208091244.203407-1-guoren@kernel.org/ > - Sort Kconfig entries in alphabetical order. > > Changes in v4: > https://lore.kernel.org/linux-riscv/20221129033230.255947-1-guoren@kernel.org/ > - Include [3] for maintenance. [Song Shuai] > > Changes in V3: > https://lore.kernel.org/linux-riscv/20221123153950.2911981-1-guoren@kernel.org/ > - Include [2] for maintenance. [Song Shuai] > > Changes in V2: > https://lore.kernel.org/linux-riscv/20220921034910.3142465-1-guoren@kernel.org/ > - Add Signed-off for preemption fixup. > > Changes in V1: > https://lore.kernel.org/linux-riscv/20220916103817.9490-1-guoren@kernel.org/ > > Andy Chiu (1): > riscv: ftrace: Fixup panic by disabling preemption > > Guo Ren (2): > riscv: ftrace: Remove wasted nops for !RISCV_ISA_C > riscv: ftrace: Reduce the detour code size to half > > Song Shuai (4): > riscv: ftrace: Add ftrace_graph_func > riscv: ftrace: Make ftrace_caller call ftrace_graph_func > riscv: ftrace: Add DYNAMIC_FTRACE_WITH_DIRECT_CALLS support > samples: ftrace: Add riscv support for SAMPLE_FTRACE_DIRECT[_MULTI] > > arch/riscv/Kconfig | 3 +- > arch/riscv/Makefile | 6 +- > arch/riscv/include/asm/ftrace.h | 71 ++++++-- > arch/riscv/kernel/ftrace.c | 91 ++++------ > arch/riscv/kernel/mcount-dyn.S | 181 +++++++++++++------- > samples/ftrace/ftrace-direct-modify.c | 33 ++++ > samples/ftrace/ftrace-direct-multi-modify.c | 37 ++++ > samples/ftrace/ftrace-direct-multi.c | 22 +++ > samples/ftrace/ftrace-direct-too.c | 26 +++ > samples/ftrace/ftrace-direct.c | 22 +++ > 10 files changed, 355 insertions(+), 137 deletions(-) > > -- > 2.36.1 >
-- Thanks, Song
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