Bug#790560: udev fails to start on sparc boot, breaking boot

[Richard Mortimer]

On 06/08/2015 12:48, Artyom Tarasenko wrote:
> Here is the correspondinf part of the gdb session with symbols from
> systemd-dbg_224-1_sparc64.deb:
> 

Many thanks.

The log below pretty much does confirm that it is taking the suspected
path through the code. Some steps are not visible to the debugger due to
optimisation but otherwise are running.

I wonder if the optimiser has somehow generated bad code and this is
causing things to fail.

Specifically it does look like it is only producing output of "ine,
ignoring: Invalid argument". The "ine" starts 32 characters into the string.

Looking at a dump of the binary you can see this

050ce0 N : h V \0 \0 \0 \0 f a i l e d t
4e 3a 68 56 00 00 00 00 66 61 69 6c 65 64 20 74
050cf0 o p a r s e k e r n e l c
6f 20 70 61 72 73 65 20 6b 65 72 6e 65 6c 20 63
050d00 o m m a n d l i n e , i g n
6f 6d 6d 61 6e 64 20 6c 69 6e 65 2c 20 69 67 6e
050d10 o r i n g : % m \0 \0 \0 \0 \0 \0 \0


Later in the binary we see a similar thing the "/" for the chdir appears
exactly 32 characters before the "/: %m" in the error message

050d50 t o % u \0 \0 / \0 \0 \0 \0 \0 \0 \0
20 74 6f 20 25 75 00 00 2f 00 00 00 00 00 00 00
050d60 c o u l d n o t c h a n g e
63 6f 75 6c 64 20 6e 6f 74 20 63 68 61 6e 67 65
050d70 d i r t o / : % m \0 \0 \0
20 64 69 72 20 74 6f 20 2f 3a 20 25 6d 00 00 00

So maybe the code is trying to use the wrong string as input to chdir
and hence failing.

I do not have easy access to a disassembler to attempt to confirm what
the bad code is doing. I guess it is likely to be a compiler toolchain
issue. Either bad code generation or maybe a linker script is getting
alignments wrong on when compiled as a 64 bit binary as opposed to a 32
bit binary.


>  (gdb) run
> Starting program: /lib/systemd/systemd-udevd
> [Thread debugging using libthread_db enabled]
> Using host libthread_db library "/lib/sparc64-linux-gnu/libthread_db.so.1".
> 
> Breakpoint 3, main (argc=<optimized out>, argv=0x7fefffffc98) at
> ../src/udev/udevd.c:1662
> 1662            r = parse_proc_cmdline(parse_proc_cmdline_item);
> (gdb) next
> 1663            if (r < 0)
> (gdb)
> 1664                    log_warning_errno(r, "failed to parse kernel
> command line, ignoring: %m");
> (gdb)
> ine, ignoring: Invalid argumentu1666            if (arg_debug) {
> (gdb)
> 1671            if (getuid() != 0) {
> (gdb)
> 1676            if (arg_children_max == 0) {
> (gdb)
> 1679                    arg_children_max = 8;
> (gdb)
> 1681                    if (sched_getaffinity(0, sizeof (cpu_set),
> &cpu_set) == 0) {
> (gdb)
> 1682                            arg_children_max += CPU_COUNT(&cpu_set) * 2;
> (gdb)
> 1685                    log_debug("set children_max to %u", arg_children_max);
> (gdb)
> 1690            if (r < 0) {
> (gdb)
> 1691                    r = log_error_errno(errno, "could not change
> dir to /: %m");
> (gdb)
> /devu1760               mac_selinux_finish();
> (gdb)
> 1761            log_close();
> (gdb)
> 1651            _cleanup_free_ char *cgroup = NULL;
> (gdb)
> 1763    }
> (gdb)
>