Re: libc6 select problems?
On 2 Jan 1998, Mark W. Eichin wrote:
> Well, at least I've figured out that it isn't a kernel problem. I
> built xntpd and rsync using libc5-altdev and alt-gcc, and aside from a
> typo (already reported) in the alt sched.h, they both work fine.
It's a kernel problem. I'll explain myself:
There are two syscalls for select:
$ grep select /usr/include/asm/unistd.h
#define __NR_select 93 /* Common */
#define __NR__newselect 230 /* Linux Specific */
`libc5' uses the first one (93), but `libc6' uses the second
(230). Both of them should work OK, but there's a little bug in the
kernel sources which makes it execute `llseek' instead of `select'
when the second syscall is used. So, `select(n,...)' is
interpreted by the kernel as `llseek(n,...)'. `llseek' returns EBADFD
if `n' isn't a valid file descriptor (and this is normally the case
when we use select). See my previous mail to debian-devel for a
> I'm not having much luck in figuring out where in glibc-sparc select
> itself is built, though (the Makefiles are a little too magic.) I'm
> about to just build it and read the logs and see hack on it from that
Yes, it's real ugly... it's defined from
sysdeps/unix/Makefile, looking at file syscalls.list which is in
sysdeps/unix/sysv/linux. It basically translates the call directly to
a system call.
> Is anyone working on gdb, or strace? Looks like we're stuck at the
> "printf" level of debugging right now, and that's kind of
> sad... strace needs actual porting (I got as far a build that did a
> fake_exec and ran the program, but didn't see any *real* syscalls),
> gdb uses the bfd it ships with, and that would need to be updated to a
> current sparc-linux-aware libbfd. It shouldn't be too hard to port,
> but still...
I'm working on `strace'... there is a working version (in .rpm
format) in ftp.nuclecu.unam.mx:/pub/Linux/Sparc-miguel (well, I cannot
remember exactly the path, but it was something like that). It
compiles and runs OK as libc5... I'm working on porting it to libc6.
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