2016-10-19 20:33 GMT+03:00 Mikulas Patocka [off-list ref]:

On Wed, 19 Oct 2016, Mikulas Patocka wrote:

quoted

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.

quoted

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".

Hi Mikulas,

could you give attached patch a shot?
In about 10 hours I'll be at work and will have debian-x32 install,
but for now, I can't test it.
Thanks again on catching that.

-- 
             Dmitry