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Date: Mon, 26 Mar 2012 21:49:46 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Vaibhav Nagarnaik <vnagarnaik@google.com>
CC: Steven Rostedt <rostedt@goodmis.org>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        David Sharp <dhsharp@google.com>,
        Justin Teravest <teravest@google.com>,
        Laurent Chavey <chavey@google.com>, x86@kernel.org,
        linux-kernel@vger.kernel.org, Michael Davidson <md@google.com>
Subject: Re: [PATCH 2/6] trace: add support for 32 bit compat syscalls on
 x86_64
References: <1332787168-20457-1-git-send-email-vnagarnaik@google.com> <1332787168-20457-3-git-send-email-vnagarnaik@google.com>
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On 03/26/2012 11:39 AM, Vaibhav Nagarnaik wrote:
> +/*
> + * syscall metadata for 32 bit compatible system calls
> + *
> + * The metadata entries are in the same order as the system call table
> + * but this is just to make it easier to check them for completeness
> + * and correctness.
> + */
> +
> +COMPAT_SYSCALL_METADATA0(restart_syscall)
> +COMPAT_SYSCALL_METADATA1(exit, int, error_code)
   [...]
> +COMPAT_SYSCALL_METADATA5(recvmmsg, int, fd, struct mmsghdr __user *, mmsg, unsigned int, vlen, unsigned int, flags, struct timespec __user *, timeout)

> +/*
> + * This is truly horrible.

Yes, it is.  How on Earth do you expect the above to ever be maintained?

> + *
> + * There is no header file that defines a *complete* set of 32 bit system
> + * call numbers (unistd_32.h only defines ones that are currently exported
> + * to user space and omits lots of old system calls that are still implemented
> + * by the kernel.

> + * There is also no table that can be used to map a system call number into
> + * the canonical name of that system call.

arch/x86/syscalls has all of those.  If it's not in there, it doesn't
exist, because that's where the system call table comes from.

	-hpa