linux-kernel - [PATCH 0/1] get_nr_restart_syscall() should return __NR_ia32_restart_syscall if __USER32

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Message-ID: <20170328145413.GA3164@redhat.com>
Date:   Tue, 28 Mar 2017 16:54:13 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Denys Vlasenko <dvlasenk@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Jan Kratochvil <jan.kratochvil@...hat.com>,
        Pedro Alves <palves@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 0/1] get_nr_restart_syscall() should return
 __NR_ia32_restart_syscall if __USER32_CS

Hello,

get_nr_restart_syscall() is still buggy, TS_I386_REGS_POKED can't
really help and should probably die.

The fix just adds the __USER32_CS check, but perhaps we can avoid
these "fundamentally broken" checks altogether?

Is __NR_ia32_restart_syscall/__NR_restart_syscall the part of ABI?
OK, we probaly can't remove them, at least right now. But what if
we simply add the new syscall number,

	#define __NR_new_restart_syscall	383
	#define __NR_ia32_new_restart_syscall	383

so that it doesn't depends on bitness and we can just do

	static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
	{
		BUILD_BUG_ON(__NR_ia32_new_restart_syscall != __NR_new_restart_syscall);
	#ifdef CONFIG_X86_X32_ABI
		return __NR_new_restart_syscall | (regs->orig_ax & __X32_SYSCALL_BIT);
	#else
		return __NR_new_restart_syscall;
	#endif
	}

?

Oleg.