svn commit: r338930 - head/libexec/rtld-elf/powerpc

Thu Sep 27 23:13:12 UTC 2018

On Thu, Sep 27, 2018 at 09:37:31PM +0200, Andreas Tobler wrote:
> On 27.09.18 20:48, Michael Tuexen wrote:
> >> On 25. Sep 2018, at 21:29, Andreas Tobler <andreast at FreeBSD.org> wrote:
> >>
> >> Author: andreast
> >> Date: Tue Sep 25 19:29:35 2018
> >> New Revision: 338930
> >> URL: https://svnweb.freebsd.org/changeset/base/338930
> >>
> >> Log:
> >>   Bring the 32-bit powerpc (PowerMac) back to live. The commit 338486 reworked
> >>   some TLS bits. This broke operation on the PowerMac. Namely one could not login.
> >>   At login the screen/shell was giving back lots of backslashes and the login
> >>   shell dumped core.
> >>
> >>   The fix to this issue is to revert the powerpc commit from 338486 and to
> >>   increase the TLS_TCB_SIZE to 16.
> >>   Reverting only did not help, login was possible but userland applications
> >>   aborted with strange messages.
> >>
> >>   I tested this patch with world/kernel builds and with port upgrades.
> >>   Additionally a full gcc8 bootstrap was successfully completed.
> >>
> >>   Reviewed by: jhibbits@
> >>   Approved by: re (Glen)
> >>
> >> Modified:
> >>   head/libexec/rtld-elf/powerpc/rtld_machdep.h
> >>
> >> Modified: head/libexec/rtld-elf/powerpc/rtld_machdep.h
> >> ==============================================================================
> >> --- head/libexec/rtld-elf/powerpc/rtld_machdep.h	Tue Sep 25 18:54:18 2018	(r338929)
> >> +++ head/libexec/rtld-elf/powerpc/rtld_machdep.h	Tue Sep 25 19:29:35 2018	(r338930)
> >> @@ -69,12 +69,12 @@ void _rtld_powerpc_pltcall(void);
> >>
> >> #define TLS_TP_OFFSET	0x7000
> >> #define TLS_DTV_OFFSET	0x8000
> >> -#define TLS_TCB_SIZE	8
> >> +#define TLS_TCB_SIZE	16
> >>
> >> #define round(size, align) \
> >>      (((size) + (align) - 1) & ~((align) - 1))
> >> #define calculate_first_tls_offset(size, align) \
> >> -    TLS_TCB_SIZE
> >> +    round(8, align)
> >> #define calculate_tls_offset(prev_offset, prev_size, size, align) \
> >>      round(prev_offset + prev_size, align)
> >> #define calculate_tls_end(off, size)    ((off) + (size))
> >>
> > After performing a buildworld/buildkernel and running r338956 on a 32-bit powerpc machine (G4 Mac Mini),
> > the following program:
> > 
> > #include <pthread.h>
> > #include <stdio.h>
> > #include <string.h>
> > 
> > void *
> > f(void * arg)
> > {
> > 	return (arg);
> > }
> > 
> > int
> > main(void)
> > {
> > 	void *res;
> > 	pthread_t tid;
> > 	int err;
> > 
> > 	if ((err = pthread_create(&tid, NULL, f, NULL)) != 0) {
> > 		fprintf(stderr, "pthread_create: %s\n", strerror(err));
> > 	}
> > 	if ((err = pthread_join(tid, &res)) != 0) {
> > 		fprintf(stderr, "pthread_join: %s\n", strerror(err));
> > 	}
> > 	return (0);
> > }
> > 
> > is killed:
> > 
> > tuexen at bsd5:~ % ./test
> > ld-elf.so.1: assert failed: /usr/home/tuexen/head/libexec/rtld-elf/rtld.c:4753
> > Abort (core dumped)
> > 
> > gdb shows:
> > 
> > tuexen at bsd5:~ % gdb -c test.core test
> > GNU gdb (GDB) 8.1 [GDB v8.1 for FreeBSD]
> > Copyright (C) 2018 Free Software Foundation, Inc.
> > License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
> > This is free software: you are free to change and redistribute it.
> > There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
> > and "show warranty" for details.
> > This GDB was configured as "powerpc-portbld-freebsd12.0".
> > Type "show configuration" for configuration details.
> > For bug reporting instructions, please see:
> > <http://www.gnu.org/software/gdb/bugs/>.
> > Find the GDB manual and other documentation resources online at:
> > <http://www.gnu.org/software/gdb/documentation/>.
> > For help, type "help".
> > Type "apropos word" to search for commands related to "word"...
> > Reading symbols from test...done.
> > [New LWP 100112]
> > Core was generated by `./test'.
> > Program terminated with signal SIGABRT, Aborted.
> > #0  0x41829a58 in thr_kill () at thr_kill.S:3
> > 3	RSYSCALL(thr_kill)
> > (gdb) bt
> > #0  0x41829a58 in thr_kill () at thr_kill.S:3
> > #1  0x41829378 in __raise (s=6)
> >      at /usr/home/tuexen/head/lib/libc/gen/raise.c:52
> > #2  0x41823b84 in abort () at /usr/home/tuexen/head/lib/libc/stdlib/abort.c:67
> > #3  0x41813f58 in allocate_tls (objs=0x41843000, oldtcb=<optimized out>,
> >      tcbsize=8, tcbalign=<optimized out>)
> >      at /usr/home/tuexen/head/libexec/rtld-elf/rtld.c:4753
> > #4  0x41813fc0 in _rtld_allocate_tls (oldtls=0x0, tcbsize=8, tcbalign=16)
> >      at /usr/home/tuexen/head/libexec/rtld-elf/rtld.c:5030
> > #5  0x41877438 in _tcb_ctor (thread=0x41a8d300, initial=<optimized out>)
> >      at /usr/home/tuexen/head/lib/libthr/thread/thr_ctrdtr.c:45
> > #6  0x41876ebc in _thr_alloc (curthread=0x41a8d000)
> >      at /usr/home/tuexen/head/lib/libthr/thread/thr_list.c:172
> > #7  0x41867118 in _pthread_create (thread=0xffffdc10, attr=0x0,
> >      start_routine=0x180073c <f>, arg=0x0)
> >      at /usr/home/tuexen/head/lib/libthr/thread/thr_create.c:81
> > #8  0x01800798 in main ()
> > (gdb) quit
> > 
> > Any idea what is wrong?
> 
> TLS is broken on powerpc ;)
> 
> I see the same.
> 
> Would you mind reverting my commit and see if it is better/different and 
> how different?
> 
> For me the commit was an improvement, but I agree this is not enough.
> 
> I try to analyze what is going on. Any help is appreciated.

The cause is quite clear, sizeof(struct tcb) is 8 on power 32bit, see
lib/libthread/arch/powerpc/include/pthread_md.h.  I do not think that
you can change this because it is part of the ABI assumed by the
compilers.