[src] cvs commit: src/include unistd.h src/lib/libc/sys readlink.2 src/sys/compat/freebsd32 syscalls.master src/sys/kern syscalls.master vfs_syscalls.c src/sys/sys syscallsubr.h

Ruslan Ermilov ru at FreeBSD.org
Wed Feb 13 11:35:38 UTC 2008


[ Replying to the list. ]

On Tue, Feb 12, 2008 at 10:48:04PM +0200, Kostik Belousov wrote:
> > -int	 readlink(const char *, char *, int);
> > +ssize_t	 readlink(const char *, char *, size_t);
> You do understand that this changes the ABI ? size_t and int have different
> sizes on 64-bit arches, and now upper-half of the register used to pass
> the third arg is used.  Amd64, fortunately, makes very hard to load a
> non-zero into the upper half, I am not so sure about IA64/sparc64.

I considered that.  I've tested locally on amd64 and sparc64, and
ia64 on pluto2.freebsd.org.  Since this is only a third argument,
it's passed in a 64-bit register, and for any meaningful value of it
(0 .. INT_MAX), there's no ABI change at all.  I compared .s files.

: // cc -S a.c ; mv a.s a.s~ ; cc -S -DNEW a.c ; diff -u a.s~ a.s
: #include <sys/types.h>
: #include <sys/limits.h>
: 
: #ifdef NEW
: ssize_t readlink(const char *, char *, size_t);
: #else
: int readlink(const char *, char *, int);
: #endif
: 
: void
: foo(void)
: {
: 	int i;
: 	char buf[1024];
: 
: 	i = readlink("foo", buf, INT_MAX);
: }

> This change, IMHO, requires symbol version compat shims.

I don't think so.


Cheers,
-- 
Ruslan Ermilov
ru at FreeBSD.org
FreeBSD committer


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