Re: [Qemu-devel] qemu-system-ppc regression booting MacOS 9.2.1 image

[aNikunj A Dadhania]

Hi Mark,

Mark Cave-Ayland <address@hidden> writes:
> Hi Nikunj,
>
> Testing git master locally I see the following segfault when trying to
> boot my test MacOS 9.2.1 image:
>
>
> $ gdb --args ./qemu-system-ppc -bios
> /home/build/src/openbios/openbios.git/openbios/obj-ppc/openbios-qemu.elf.nostrip
> -cdrom /home/build/src/qemu/image/ppc/MacOS921.iso -boot d -m 512 -M mac99

Is it possible for you to share the iso image for MAC ?

> GNU gdb (GDB) 7.4.1-debian
> Copyright (C) 2012 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 "x86_64-linux-gnu".
> For bug reporting instructions, please see:
> <http://www.gnu.org/software/gdb/bugs/>...
> Reading symbols from /home/build/rel-qemu-git/bin/qemu-system-ppc...done.
> (gdb) r
> Starting program: /home/build/rel-qemu-git/bin/qemu-system-ppc -bios
> /home/build/src/openbios/openbios.git/openbios/obj-ppc/openbios-qemu.elf.nostrip
> -cdrom /home/build/src/qemu/image/ppc/MacOS921.iso -boot d -m 512 -M mac99
> warning: no loadable sections found in added symbol-file system-supplied
> DSO at 0x7ffff7ffa000
> [Thread debugging using libthread_db enabled]
> Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
> [New Thread 0x7fffe9eee700 (LWP 29713)]
> [New Thread 0x7fffe6bf5700 (LWP 29714)]
> [New Thread 0x7fffe63f4700 (LWP 29715)]
> Trying to write invalid spr 0 (0x000) at 00f113c0
> Trying to read invalid spr 0 (0x000) at 00f113c8
> Trying to write privileged spr 955 (0x3bb) at 00f164b8
> Trying to write invalid spr 959 (0x3bf) at 00f16520
> Trying to read invalid spr 959 (0x3bf) at 00f16528
> Trying to write privileged spr 955 (0x3bb) at 00f164b8
> Trying to write invalid spr 959 (0x3bf) at 00f16520
> Trying to read invalid spr 959 (0x3bf) at 00f16528
>
> Program received signal SIGSEGV, Segmentation fault.
> [Switching to Thread 0x7fffe63f4700 (LWP 29715)]
> 0x00007ffff7e20010 in ?? ()
> (gdb) bt
> #0  0x00007ffff7e20010 in ?? ()
> #1  0x0000000000000002 in ?? ()
> #2  0x0000000068090040 in ?? ()
> #3  0x0000000000000002 in ?? ()
> #4  0x6b67829c063b8d00 in ?? ()
> #5  0x6b67829c063b8d00 in ?? ()
> #6  0x000000000043986d in tcg_temp_new_internal_i32
> (address@hidden) at
> /home/build/src/qemu/git/qemu/tcg/tcg.c:632
> #7  0x00000000004434a5 in tcg_temp_new_i32 () at
> /home/build/src/qemu/git/qemu/tcg/tcg.h:807
> #8  tcg_gen_andc_i32 (ret=0xa, arg1=0x7fffe63f3848, arg2=0x3f) at
> /home/build/src/qemu/git/qemu/tcg/tcg-op.c:411
> #9  0x00000000005099ad in gen_op_arith_compute_ov (address@hidden,
> address@hidden, arg2=0xd8, address@hidden, address@hidden,
> ctx=<error reading variable: Unhandled dwarf expression opcode 0xfa>)
>     at /home/build/src/qemu/git/qemu/target/ppc/translate.c:821
> #10 0x00000000005631b1 in gen_op_arith_add (compute_rc0=true,
> compute_ov=true, compute_ca=true, add_ca=false, arg2=0xa, arg1=0x6a,
> ret=0x3a, ctx=0x7fffe63f3800) at
> /home/build/src/qemu/git/qemu/target/ppc/translate.c:895
> #11 gen_addco (ctx=0x7fffe63f3800) at
> /home/build/src/qemu/git/qemu/target/ppc/translate.c:931
> #12 0x00000000005796ba in gen_intermediate_code
> (address@hidden, address@hidden) at
> /home/build/src/qemu/git/qemu/target/ppc/translate.c:7287
> #13 0x000000000043381a in tb_gen_code (address@hidden,
> address@hidden, address@hidden, flags=16432,
> address@hidden) at /home/build/src/qemu/git/qemu/translate-all.c:1281
> #14 0x0000000000435a32 in tb_find (tb_exit=0, last_tb=0x0,
> cpu=0x7ffff7e20010) at /home/build/src/qemu/git/qemu/cpu-exec.c:370
> #15 cpu_exec (address@hidden) at
> /home/build/src/qemu/git/qemu/cpu-exec.c:685
> #16 0x000000000047457e in tcg_cpu_exec (cpu=0x7ffff7e20010) at
> /home/build/src/qemu/git/qemu/cpus.c:1251
> #17 0x00000000004748b4 in qemu_tcg_rr_cpu_thread_fn (arg=<optimized
> out>) at /home/build/src/qemu/git/qemu/cpus.c:1347
> #18 0x00007ffff2a50b50 in start_thread (arg=<optimized out>) at
> pthread_create.c:304
> #19 0x00007ffff279afbd in clone () at
> ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
> #20 0x0000000000000000 in ?? ()
> (gdb)
>
> git bisect points to the following commit:
>
> commit dc0ad84449a4e2f28d2cc055998cb10c1a4d89a9
> Author: Nikunj A Dadhania <address@hidden>
> Date:   Mon Feb 27 10:27:57 2017 +0530
>
>     target/ppc: update overflow flags for add/sub
>
>     * SO and OV reflects overflow of the 64-bit result in 64-bit mode
>       and overflow of the low-order 32-bit result in 32-bit mode
>
>     * OV32 reflects overflow of the low-order 32-bit independent of
>       the mode
>
>     Signed-off-by: Nikunj A Dadhania <address@hidden>
>     Signed-off-by: David Gibson <address@hidden>
>
> Interestingly enough if I recompile with CFLAGS="-O0 -g" to try and get
> a full backtrace then the segfault goes away which suggests this could
> be tickling a compiler bug somewhere - although even in this
> configuration, I am seeing video artifacts during OS 9 boot which
> suggests something still isn't quite right.

Yes, I reviewed the code, looks correct. Should be some optimization
related.

>
> This is on a Debian wheezy x86_64 system with gcc 4.7.2.

Will have a detailed look today.

Regards
Nikunj