linux-kernel - Re: [RFC v2 2/7] tables.h: add linker table support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <56C77C17.7030208@zytor.com>
Date:	Fri, 19 Feb 2016 12:33:27 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"Luis R. Rodriguez" <mcgrof@...nel.org>, tglx@...utronix.de,
	mingo@...hat.com, bp@...en8.de
Cc:	x86@...nel.org, linux-kernel@...r.kernel.org, luto@...capital.net,
	boris.ostrovsky@...cle.com, rusty@...tcorp.com.au,
	david.vrabel@...rix.com, konrad.wilk@...cle.com, mcb30@...e.org,
	jgross@...e.com, ming.lei@...onical.com,
	gregkh@...uxfoundation.org, arnd@...db.de,
	linux-arch@...r.kernel.org, linux@....linux.org.uk,
	benh@...nel.crashing.org, jbaron@...mai.com, ananth@...ibm.com,
	anil.s.keshavamurthy@...el.com, davem@...emloft.net,
	masami.hiramatsu.pt@...achi.com, andriy.shevchenko@...ux.intel.com,
	dwmw2@...radead.org, xen-devel@...ts.xensource.com
Subject: Re: [RFC v2 2/7] tables.h: add linker table support

On 02/19/2016 05:45 AM, Luis R. Rodriguez wrote:
> +/**
> + * LINKTABLE_RUN_ERR - run each linker table entry func and return error if any
> + *
> + * @tbl: linker table
> + * @func: structure name for the function name we want to call.
> + * @args...: arguments to pass to func
> + *
> + * Example usage:
> + *
> + *   unsigned int err = LINKTABLE_RUN_ERR(frobnicator_fns, some_run,);
> + */
> +#define LINKTABLE_RUN_ERR(tbl, func, args...)				\
> +({									\
> +	size_t i;							\
> +	int err = 0;							\
> +	for (i = 0; !err && i < LINKTABLE_SIZE(tbl); i++)		\
> +		err = (tbl[i]).func (args);				\
> +		err; \
> +})

This is wrong and pointless.  As written it returns the error code of
the last instance.

What I suggested for this macro was that we ought to exit the loop on error.

Furthermore:

1. Using an advancing pointer would make more sense than a counter.
2. .func doesn't make any sense -- it ought to be "func"; otherwise you
    can't call into either a table containing pure function pointers,
    nor into a field of table *pointed to* by the table; which is
    likely to be quite common.

    So the idea is to use something like:

    /* Array of function pointers */
    LINKTABLE_RUN_ALL(frobnicator_fns, , arg1, arg2);

    /* Array of structures */
    LINKTABLE_RUN_ALL(frobnicator_fns, .some_run, arg1, arg2);

    /* Array of structure pointers */
    LINKTABLE_RUN_ALL(frobnicator_fns, ->some_run, arg1, arg2);