Re: [PATCH 2/6] trace: add support for 32 bit compat syscalls on x86_64

H. Peter Anvin
2012-03-27T04:50:35Z

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