On Wed, 19 Oct 2016, Mikulas Patocka wrote:
> Hi
>
> In the kernel 4.9-rc1, the x32 support is seriously broken, a x32 process
> is killed with SIGKILL after returning from any signal handler.
I should have said they are killed with SIGSEGV, not SIGKILL.
> I use Debian sid x64-64 distribution with x32 architecture added from
> debian-ports.
>
> I bisected the bug and found out that it is caused by the patch
> 6846351052e685c2d1428e80ead2d7ca3d7ed913 ("x86/signal: Add
> SA_{X32,IA32}_ABI sa_flags").
>
> example (strace of a process after receiving the SIGWINCH signal):
>
> epoll_wait(10, 0xef6890, 32, -1) = -1 EINTR (Interrupted system call)
> --- SIGWINCH {si_signo=SIGWINCH, si_code=SI_USER, si_pid=1772, si_uid=0} ---
> poll([{fd=4, events=POLLOUT}], 1, 0) = 1 ([{fd=4, revents=POLLOUT}])
> write(4, "\0", 1) = 1
> rt_sigreturn({mask=[INT QUIT ILL TRAP BUS KILL SEGV USR2 PIPE ALRM STKFLT TSTP TTOU URG XCPU XFSZ VTALRM IO PWR SYS RTMIN]}) = 0
> --- SIGSEGV {si_signo=SIGSEGV, si_code=SI_KERNEL, si_addr=NULL} ---
> +++ killed by SIGSEGV +++
> Neoprávnìný pøístup do pamìti (SIGSEGV)
>
> Mikulas
BTW. when I take core dump of the killed x32 process, it shows:
ELF Header:
Magic: 7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00
Class: ELF32
Data: 2's complement, little endian
Version: 1 (current)
OS/ABI: UNIX - System V
ABI Version: 0
Type: CORE (Core file)
Machine: Intel 80386
^^^^^^^^^^^^^^^^^^^
So, the kernel somehow thinks that it is i386 process, not x32 process. A
core dump of a real x32 process shows "Class: ELF32, Machine: Advanced
Micro Devices X86-64".
Mikulas