linux-kernel - Re: [PATCH v4 3/5] x86: Split syscall_trace

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Message-ID: <20140729192555.GB6308@redhat.com>
Date:	Tue, 29 Jul 2014 21:25:55 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>,
	Will Drewry <wad@...omium.org>, x86@...nel.org,
	linux-arm-kernel@...ts.infradead.org, linux-mips@...ux-mips.org,
	linux-arch@...r.kernel.org, linux-security-module@...r.kernel.org,
	Alexei Starovoitov <ast@...mgrid.com>, hpa@...or.com,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH v4 3/5] x86: Split syscall_trace_enter into two phases

On 07/28, Andy Lutomirski wrote:
>
> +long syscall_trace_enter_phase2(struct pt_regs *regs, u32 arch,
> +				unsigned long phase1_result)
> +{
> +	long ret = 0;
> +	u32 work = ACCESS_ONCE(current_thread_info()->flags) &
> +		_TIF_WORK_SYSCALL_ENTRY;
> +
> +	BUG_ON(regs != task_pt_regs(current));
>  
>  	/*
>  	 * If we stepped into a sysenter/syscall insn, it trapped in
> @@ -1463,17 +1569,20 @@ long syscall_trace_enter(struct pt_regs *regs)
>  	 * do_debug() and we need to set it again to restore the user
>  	 * state.  If we entered on the slow path, TF was already set.
>  	 */
> -	if (test_thread_flag(TIF_SINGLESTEP))
> +	if (work & _TIF_SINGLESTEP)
>  		regs->flags |= X86_EFLAGS_TF;

This is minor, I won't argue, but this can be moved into phase1(), afaics.

Oleg.

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