linux-kernel - Re: [RFC 2/3] abi_spec: hooks into syscall to allow pre and post checking

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Date:   Mon, 21 Nov 2016 10:54:43 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     alexander.levin@...izon.com
Cc:     "dvyukov@...gle.com" <dvyukov@...gle.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "scientist@...com" <scientist@...com>,
        "glider@...gle.com" <glider@...gle.com>,
        "andreyknvl@...gle.com" <andreyknvl@...gle.com>,
        "arnd@...db.de" <arnd@...db.de>,
        "mathieu.desnoyers@...icios.com" <mathieu.desnoyers@...icios.com>,
        "daniel.vetter@...ll.ch" <daniel.vetter@...ll.ch>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC 2/3] abi_spec: hooks into syscall to allow pre and post
 checking

On Wed, 16 Nov 2016 17:37:01 +0000
alexander.levin@...izon.com wrote:

> This is a simple way to be able to verify syscall parameters before the
> call to the actual syscall, and also verify the return value after the
> call.
> 
> Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
> ---
>  include/linux/syscalls.h |  7 ++++++-
>  kernel/Makefile          |  2 ++
>  kernel/abi_spec.c        | 15 +++++++++++++++
>  3 files changed, 23 insertions(+), 1 deletion(-)
>  create mode 100644 kernel/abi_spec.c
> 
> diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
> index 91a740f..6aa3228 100644
> --- a/include/linux/syscalls.h
> +++ b/include/linux/syscalls.h
> @@ -79,6 +79,7 @@ union bpf_attr;
>  #include <linux/quota.h>
>  #include <linux/key.h>
>  #include <trace/syscall.h>
> +#include <linux/abi_spec.h>
>  
>  /*
>   * __MAP - apply a macro to syscall arguments
> @@ -192,13 +193,17 @@ extern struct trace_event_functions exit_syscall_print_funcs;
>  
>  #define __PROTECT(...) asmlinkage_protect(__VA_ARGS__)
>  #define __SYSCALL_DEFINEx(x, name, ...)					\
> +	extern const struct syscall_spec syscall_spec##name;		\
>  	asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))	\
>  		__attribute__((alias(__stringify(SyS##name))));		\
>  	static inline long SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__));	\
>  	asmlinkage long SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__));	\
>  	asmlinkage long SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__))	\
>  	{								\
> -		long ret = SYSC##name(__MAP(x,__SC_CAST,__VA_ARGS__));	\
> +		long ret;						\
> +		abispec_check_pre(&syscall_spec##name, __MAP(x,__SC_CAST,__VA_ARGS__)); \
> +		ret = SYSC##name(__MAP(x,__SC_CAST,__VA_ARGS__));	\
> +		abispec_check_post(&syscall_spec##name, ret, __MAP(x,__SC_CAST,__VA_ARGS__)); \

Do you want this for DEFINE0() too? Or does this not care about system
calls with no arguments?

-- Steve

>  		__MAP(x,__SC_TEST,__VA_ARGS__);				\
>  		__PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__));	\
>  		return ret;						\