Wrong signal handling in qemu-aarch64.

[Maxim Ostapenko]

Running GCC 5.0 testsuite under qemu-aarch64, I noticed that tests connected with stack unwinding fail with:

qemu: uncaught target signal 11 (Segmentation fault) - core dumped

or run into infinite loop.

Here is one example:

$ /home/max/build/gcc-aarch64/gcc/xgcc -B/home/max/build/gcc-aarch64/gcc/ /home/max/src/toolchain/gcc/gcc/testsuite/gcc.dg/cleanup-11.c -fexceptions -fnon-call-exceptions -O2 -lm -o ./cleanup-11.exe

$ qemu-aarch64 -L /home/max/install/aarch64/aarch64-linux/sys-root/ -R 0 -/cleanup-11.exe
qemu: uncaught target signal 11 (Segmentation fault) - core dumped.

Actually, this caused by ABI incompatibility between Linux Kernel (trunk) and qemu-aarch64. In fact, size of siginfo structure in Linux and target_siginfo structure in qemu-aarch64 differ:

sizeof (struct target_siginfo) = 136 // QEMU
sizeof (struct siginfo) = 128 // Linux Kernel

This caused by wrong TARGET_SI_PAD_SIZE defined in linux-user/syscall_defs.h:

#define TARGET_SI_PAD_SIZE ((TARGET_SI_MAX_SIZE/sizeof(int)) - 3)

In Kernel respective value is:

#define SI_PAD_SIZE ((SI_MAX_SIZE - __ARCH_SI_PREAMBLE_SIZE) / sizeof(int))
.............................................
#define __ARCH_SI_PREAMBLE_SIZE (4 * sizeof(int)) // for Aarch64

Trivial fix, changing TARGET_SI_PAD_SIZE to right value, is attached.