On Tue, Jul 14, 2020 at 7:23 PM Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote: > > Hi Guo, > > On Mon, 13 Jul 2020 23:39:15 +0000 > guoren@xxxxxxxxxx wrote: > > > From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx> > > > > The patchset includes kprobe/uprobe support and some related fixups. > > Patrick provides HAVE_REGS_AND_STACK_ACCESS_API support and some > > kprobe's code. The framework of k/uprobe is from csky but also refers > > to other arches'. kprobes on ftrace is also supported in the patchset. > > > > There is no single step exception in riscv ISA, only single-step > > facility for jtag. See riscv-Privileged spec: > > > > Interrupt Exception Code-Description > > 1 0 Reserved > > 1 1 Supervisor software interrupt > > 1 2–4 Reserved > > 1 5 Supervisor timer interrupt > > 1 6–8 Reserved > > 1 9 Supervisor external interrupt > > 1 10–15 Reserved > > 1 ≥16 Available for platform use > > 0 0 Instruction address misaligned > > 0 1 Instruction access fault > > 0 2 Illegal instruction > > 0 3 Breakpoint > > 0 4 Load address misaligned > > 0 5 Load access fault > > 0 6 Store/AMO address misaligned > > 0 7 Store/AMO access fault > > 0 8 Environment call from U-mode > > 0 9 Environment call from S-mode > > 0 10–11 Reserved > > 0 12 Instruction page fault > > 0 13 Load page fault > > 0 14 Reserved > > 0 15 Store/AMO page fault > > 0 16–23 Reserved > > 0 24–31 Available for custom use > > 0 32–47 Reserved > > 0 48–63 Available for custom use > > 0 ≥64 Reserved > > > > No single step! > > > > Other arches use hardware single-step exception for k/uprobe, eg: > > - powerpc: regs->msr |= MSR_SINGLESTEP > > - arm/arm64: PSTATE.D for enabling software step exceptions > > - s390: Set PER control regs, turns on single step for the given address > > - x86: regs->flags |= X86_EFLAGS_TF > > - csky: of course use hw single step :) > > > > All the above arches use a hardware single-step exception > > mechanism to execute the instruction that was replaced with a probe > > breakpoint. So utilize ebreak to simulate. > > > > Some pc related instructions couldn't be executed out of line and some > > system/fence instructions couldn't be a trace site at all. So we give > > out a reject list and simulate list in decode-insn.c. > > > > You could use uprobe to test simulate code like this: > > > > echo 'p:enter_current_state_one /hello:0x6e4 a0=%a0 a1=%a1' >> /sys/kernel/debug/tracing/uprobe_events > > echo 1 > /sys/kernel/debug/tracing/events/uprobes/enable > > /hello > > ^C > > cat /sys/kernel/debug/tracing/trace > > tracer: nop > > > > entries-in-buffer/entries-written: 1/1 #P:1 > > > > _-----=> irqs-off > > / _----=> need-resched > > | / _---=> hardirq/softirq > > || / _--=> preempt-depth > > ||| / delay > > TASK-PID CPU# |||| TIMESTAMP FUNCTION > > | | | |||| | | > > hello-94 [000] d... 55.404242: enter_current_state_one: (0x106e4) a0=0x1 a1=0x3fffa8ada8 > > > > Be care /hello:0x6e4 is the file offset in elf and it relate to 0x106e4 > > in memory and hello is your target elf program. > > > > Try kprobe like this: > > > > echo 'p:myprobe _do_fork dfd=%a0 filename=%a1 flags=%a2 mode=+4($stack)' > /sys/kernel/debug/tracing/kprobe_events > > echo 'r:myretprobe _do_fork $retval' >> /sys/kernel/debug/tracing/kprobe_event > > > > echo 1 >/sys/kernel/debug/tracing/events/kprobes/enable > > cat /sys/kernel/debug/tracing/trace > > tracer: nop > > > > entries-in-buffer/entries-written: 2/2 #P:1 > > > > _-----=> irqs-off > > / _----=> need-resched > > | / _---=> hardirq/softirq > > || / _--=> preempt-depth > > ||| / delay > > TASK-PID CPU# |||| TIMESTAMP FUNCTION > > | | | |||| | | > > sh-92 [000] .n.. 131.804230: myprobe: (_do_fork+0x0/0x2e6) dfd=0xffffffe03929fdf8 filename=0x0 flags=0x101000 mode=0x1200000ffffffe0 > > sh-92 [000] d... 131.806607: myretprobe: (__do_sys_clone+0x70/0x82 <- _do_fork) arg1=0x5f > > cat /sys/kernel/debug/tracing/trace > > Thank you for your great work! > > BTW, could you also run the ftracetest and boot-time smoke test on it? > You can find it under tools/testing/selftests/ftrace, and > CONFIG_KPROBES_SANITY_TEST. > It will ensure that your patch is correctly ported. CONFIG_KPROBES_SANITY_TEST passed: [ 0.078274] NET: Registered protocol family 16 [ 0.162015] Kprobe smoke test: started [ 0.456900] Kprobe smoke test: passed successfully The tools/testing/selftests/ftrace cover a lot of stuff not only kprobe, and I'll try them later to fixup in another patchset. -- Best Regards Guo Ren ML: https://lore.kernel.org/linux-csky/
