Messages in this thread | | | Date | Wed, 15 Feb 2017 09:58:14 +0530 | From | Ananth N Mavinakayanahalli <> | Subject | Re: [PATCH 1/3] powerpc: kprobes: add support for KPROBES_ON_FTRACE |
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On Wed, Feb 15, 2017 at 12:28:34AM +0530, Naveen N. Rao wrote: > Allow kprobes to be placed on ftrace _mcount() call sites. This > optimization avoids the use of a trap, by riding on ftrace > infrastructure. > > This depends on HAVE_DYNAMIC_FTRACE_WITH_REGS which depends on > MPROFILE_KERNEL, which is only currently enabled on powerpc64le with > newer toolchains. > > Based on the x86 code by Masami. > > Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> > --- > arch/powerpc/Kconfig | 1 + > arch/powerpc/include/asm/kprobes.h | 10 ++++ > arch/powerpc/kernel/Makefile | 3 ++ > arch/powerpc/kernel/kprobes-ftrace.c | 100 +++++++++++++++++++++++++++++++++++ > arch/powerpc/kernel/kprobes.c | 4 +- > arch/powerpc/kernel/optprobes.c | 3 ++ > 6 files changed, 120 insertions(+), 1 deletion(-) > create mode 100644 arch/powerpc/kernel/kprobes-ftrace.c
You'll also need to update Documentation/features/debug/kprobes-on-ftrace/arch-support.txt
> +/* Ftrace callback handler for kprobes */ > +void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip, > + struct ftrace_ops *ops, struct pt_regs *regs) > +{ > + struct kprobe *p; > + struct kprobe_ctlblk *kcb; > + unsigned long flags; > + > + /* Disable irq for emulating a breakpoint and avoiding preempt */ > + local_irq_save(flags); > + hard_irq_disable(); > + > + p = get_kprobe((kprobe_opcode_t *)nip); > + if (unlikely(!p) || kprobe_disabled(p)) > + goto end; > + > + kcb = get_kprobe_ctlblk(); > + if (kprobe_running()) { > + kprobes_inc_nmissed_count(p); > + } else { > + unsigned long orig_nip = regs->nip; > + /* Kprobe handler expects regs->nip = nip + 1 as breakpoint hit */
Can you clarify this? On powerpc, the regs->nip at the time of breakpoint hit points to the probed instruction, not the one after.
Ananth
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