Re: [PATCH v3 0/7] riscv: Add k/uprobe supported

From: Masami Hiramatsu
Date: Tue Jul 14 2020 - 07:23:54 EST

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 2â4 Reserved
> 1 5 Supervisor timer interrupt
> 1 6â8 Reserved
> 1 9 Supervisor external interrupt
> 1 10â15 Reserved
> 1 â16 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 10â11 Reserved
> 0 12 Instruction page fault
> 0 13 Load page fault
> 0 14 Reserved
> 0 15 Store/AMO page fault
> 0 16â23 Reserved
> 0 24â31 Available for custom use
> 0 32â47 Reserved
> 0 48â63 Available for custom use
> 0 â64 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.

Thank you,

>
> Changlog v3:
> - Add upport for function error injection
> - Fixup kprobes handler couldn't change pc
>
> Changlog v2:
> - Add Reviewed-by, Tested-by, Acked-by, thx for all of you
> - Add kprobes on ftrace feature
> - Use __always_inline as same as fix_to_virt for fixup
> BUILD_BUG_ON
> - Use const "const unsigned int" for 2th param for fixup
> BUILD_BUG_ON
>
> Guo Ren (6):
> riscv: Fixup compile error BUILD_BUG_ON failed
> riscv: Fixup kprobes handler couldn't change pc
> riscv: Add kprobes supported
> riscv: Add uprobes supported
> riscv: Add KPROBES_ON_FTRACE supported
> riscv: Add support for function error injection
>
> Patrick StÃhlin (1):
> RISC-V: Implement ptrace regs and stack API
>
> arch/riscv/Kconfig | 8 +
> arch/riscv/include/asm/kprobes.h | 40 +++
> arch/riscv/include/asm/probes.h | 24 ++
> arch/riscv/include/asm/processor.h | 1 +
> arch/riscv/include/asm/ptrace.h | 35 ++
> arch/riscv/include/asm/thread_info.h | 4 +-
> arch/riscv/include/asm/uprobes.h | 40 +++
> arch/riscv/kernel/Makefile | 1 +
> arch/riscv/kernel/mcount-dyn.S | 3 +-
> arch/riscv/kernel/patch.c | 8 +-
> arch/riscv/kernel/probes/Makefile | 6 +
> arch/riscv/kernel/probes/decode-insn.c | 48 +++
> arch/riscv/kernel/probes/decode-insn.h | 18 +
> arch/riscv/kernel/probes/ftrace.c | 52 +++
> arch/riscv/kernel/probes/kprobes.c | 471 ++++++++++++++++++++++++++
> arch/riscv/kernel/probes/kprobes_trampoline.S | 93 +++++
> arch/riscv/kernel/probes/simulate-insn.c | 85 +++++
> arch/riscv/kernel/probes/simulate-insn.h | 47 +++
> arch/riscv/kernel/probes/uprobes.c | 186 ++++++++++
> arch/riscv/kernel/ptrace.c | 99 ++++++
> arch/riscv/kernel/signal.c | 3 +
> arch/riscv/kernel/traps.c | 19 ++
> arch/riscv/lib/Makefile | 2 +
> arch/riscv/lib/error-inject.c | 10 +
> arch/riscv/mm/fault.c | 11 +
> 25 files changed, 1310 insertions(+), 4 deletions(-)
> create mode 100644 arch/riscv/include/asm/probes.h
> create mode 100644 arch/riscv/include/asm/uprobes.h
> create mode 100644 arch/riscv/kernel/probes/Makefile
> create mode 100644 arch/riscv/kernel/probes/decode-insn.c
> create mode 100644 arch/riscv/kernel/probes/decode-insn.h
> create mode 100644 arch/riscv/kernel/probes/ftrace.c
> create mode 100644 arch/riscv/kernel/probes/kprobes.c
> create mode 100644 arch/riscv/kernel/probes/kprobes_trampoline.S
> create mode 100644 arch/riscv/kernel/probes/simulate-insn.c
> create mode 100644 arch/riscv/kernel/probes/simulate-insn.h
> create mode 100644 arch/riscv/kernel/probes/uprobes.c
> create mode 100644 arch/riscv/lib/error-inject.c
>
> --
> 2.7.4
>


--
Masami Hiramatsu <mhiramat@xxxxxxxxxx>