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From: James Morse <james.morse@arm.com>
To: Masami Hiramatsu <mhiramat@kernel.org>
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: Tue, 23 Jul 2019 17:04:21 +0100	[thread overview]
Message-ID: <038c4b88-e7ef-aaab-0a79-5d7371719aa5@arm.com> (raw)
In-Reply-To: <156378172702.12011.1144595747474511323.stgit@devnote2>

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")


> 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!

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


>  {
>  	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

  reply	other threads:[~2019-07-23 16:04 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 [this message]
2019-07-24  7:39     ` Masami Hiramatsu
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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