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From: Masami Hiramatsu <mhiramat@kernel.org>
To: James Morse <james.morse@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	Naresh Kamboju <naresh.kamboju@linaro.org>,
	Dan Rue <dan.rue@linaro.org>, Matt Hart <matthew.hart@linaro.org>,
	Anders Roxell <anders.roxell@linaro.org>,
	Daniel Diaz <daniel.diaz@linaro.org>
Subject: Re: [PATCH v2 2/4] arm64: unwind: Prohibit probing on return_address()
Date: Wed, 24 Jul 2019 16:39:14 +0900	[thread overview]
Message-ID: <20190724163914.c4a9cea2b5b9df3116e5e694@kernel.org> (raw)
In-Reply-To: <038c4b88-e7ef-aaab-0a79-5d7371719aa5@arm.com>

On Tue, 23 Jul 2019 17:04:21 +0100
James Morse <james.morse@arm.com> wrote:

> Hi,
> 
> On 22/07/2019 08:48, Masami Hiramatsu wrote:
> > Prohibit probing on return_address() and subroutines which
> > is called from return_address(), since the it is invoked from
> > trace_hardirqs_off() which is also kprobe blacklisted.
> 
> (Nits: "which are called" and "since it is")

Thanks!

> 
> 
> > diff --git a/arch/arm64/kernel/return_address.c b/arch/arm64/kernel/return_address.c
> > index b21cba90f82d..7f8a143268b0 100644
> > --- a/arch/arm64/kernel/return_address.c
> > +++ b/arch/arm64/kernel/return_address.c
> > @@ -8,6 +8,7 @@
> >  
> >  #include <linux/export.h>
> >  #include <linux/ftrace.h>
> > +#include <linux/kprobes.h>
> >  
> >  #include <asm/stack_pointer.h>
> >  #include <asm/stacktrace.h>
> > @@ -17,7 +18,7 @@ struct return_address_data {
> >  	void *addr;
> >  };
> >  
> > -static int save_return_addr(struct stackframe *frame, void *d)
> > +static nokprobe_inline int save_return_addr(struct stackframe *frame, void *d)
> 
> This nokprobe_inline ends up as __always_inline if kprobes is enabled.
> What do we expect the compiler to do with this? save_return_addr is passed as a
> function-pointer to walk_stackframe()... I don't see how the compiler can inline it!

Oops, that's my mistake. Then it should be NOKPROBE_SYMBOL.

> 
> This would be needed for on_accessible_stack().
> Should we cover ftrace_graph_get_ret_stack()?, or is that already in hand?

No, that is OK. It just covers that the functions which are involved in
the kprobe execution path. ftrace_graph_ret_stack() is out of the debug
exception handler.

Thank you,

> >  {
> >  	struct return_address_data *data = d;
> >  
> > @@ -52,3 +53,4 @@ void *return_address(unsigned int level)
> >  		return NULL;
> >  }
> >  EXPORT_SYMBOL_GPL(return_address);
> > +NOKPROBE_SYMBOL(return_address);
> 
> 
> Thanks,
> 
> James


-- 
Masami Hiramatsu <mhiramat@kernel.org>

  reply	other threads:[~2019-07-24  7:39 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-22  7:48 [PATCH v2 0/4] arm64: kprobes: Fix some bugs in arm64 kprobes Masami Hiramatsu
2019-07-22  7:48 ` [PATCH v2 1/4] arm64: kprobes: Recover pstate.D in single-step exception handler Masami Hiramatsu
2019-07-23 16:03   ` James Morse
2019-07-24 13:09     ` Masami Hiramatsu
2019-07-22  7:48 ` [PATCH v2 2/4] arm64: unwind: Prohibit probing on return_address() Masami Hiramatsu
2019-07-23 16:04   ` James Morse
2019-07-24  7:39     ` Masami Hiramatsu [this message]
2019-07-22  7:48 ` [PATCH v2 3/4] arm64: Make debug exception handlers visible from RCU Masami Hiramatsu
2019-07-22 12:07   ` Paul E. McKenney
2019-07-23 17:07   ` James Morse
2019-07-24 11:47     ` Masami Hiramatsu
2019-07-22  7:49 ` [PATCH v2 4/4] arm64: Remove unneeded rcu_read_lock from debug handlers Masami Hiramatsu
2019-07-22 12:07   ` Paul E. McKenney

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