ARM EABI: disable OABI support by default

OABI is rarely used in ARM EABI systems nowadays, so disable its support
by default.  Add --enable-arm-oabi option to enable ARM OABI support.

* configure.ac: New option --enable-arm-oabi.
* syscall.c (get_scno) [ARM]: Check ENABLE_ARM_OABI macro defined by
configure instead of undocumented STRACE_KNOWS_ONLY_EABI macro.
aarch64: Fix decoding of arm struct stat64

We need to handle this situation more like x86-64.  32-bit arm and i386
actually have a common struct stat64, except the arm one must not be
packed.  Additionally, on aarch64 the 32-bit personality is personality 0.

Signed-off-by: Elliott Hughes <enh@google.com>
x86-64: fix clone(2) argument order for x86 processes

Without this patch, strace claims that parent_tidptr == tls, which is
clearly wrong.  It is expected that parent_tidptr == child_tidptr.

* process.c [X86_64] (ARG_CTID, ARG_TLS): Take current
personality into account.

Signed-off-by: Elliott Hughes <enh@google.com>
Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
x32: fix clone(2) argument order for x86 processes

Apply the same fix that was made for x86_64.

* process.c [X32] (ARG_CTID, ARG_TLS): Take current
personality into account.
x86-64: decode clone LDT user_desc entries for x86 processes

* mem.c [X86_64]: Include asm/ldt.h.
[X86_64] (print_ldt_entry, sys_modify_ldt, sys_set_thread_area,
sys_get_thread_area): Define.
* process.c [X86_64]: Include asm/ldt.h.
(sys_clone) [X86_64]: Decode LDT entry if current_personality == 1.

Signed-off-by: Elliott Hughes <enh@google.com>
Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
x32: decode clone LDT user_desc entries for x86 processes

* mem.c [X32]: Include asm/ldt.h.
[X32] (print_ldt_entry, sys_modify_ldt, sys_set_thread_area,
sys_get_thread_area): Define.
* process.c [X32]: Include asm/ldt.h.
(sys_clone) [X32]: Decode LDT entry if current_personality == 1.
x86_64, x32: enable decoding of modify_ldt, get_thread_area, and set_thread_area

* linux/dummy.h [X86_64 || X32]: Do not redirect sys_modify_ldt,
sys_get_thread_area, and sys_set_thread_area to printargs.
mips: enable decoding of set_thread_area

* linux/dummy.h [MIPS]: Do not redirect sys_set_thread_area to printargs.
* mem.c [MIPS] (sys_set_thread_area): Define.
Make int3 example in comments more cut-n-pastable

I found that I use it quite often. Lets make it so that
after cut-n-pasting it into a file, there is no need
to edit the result (e.g. no need to remove C comment
chars from every line.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Refactor LDT decoding

* configure.ac (AC_CHECK_TYPES): Remove struct user_desc.
* ldt.c: New file.
* Makefile.am (strace_SOURCES): Add ldt.c.
* mem.c: Do not include <asm/ldt.h>.
(print_ldt_entry): Remove.
(sys_modify_ldt, sys_set_thread_area, sys_get_thread_area): Move...
* ldt.c: ... here.
* process.c: Do not include <asm/ldt.h>.
(sys_clone) [I386 || X86_64 || X32]: Use print_user_desc.