x32: Add ptrace for x32

X32 ptrace is a hybrid of 64bit ptrace and compat ptrace with 32bit
address and longs.  It use 64bit ptrace to access the full 64bit
registers.  PTRACE_PEEKUSR and PTRACE_POKEUSR are only allowed to access
segment and debug registers.  PTRACE_PEEKUSR returns the lower 32bits
and PTRACE_POKEUSR zero-extends 32bit value to 64bit.   It works since
the upper 32bits of segment and debug registers of x32 process are always
zero.  GDB only uses PTRACE_PEEKUSR and PTRACE_POKEUSR to access
segment and debug registers.

[ hpa: changed TIF_X32 test to use !is_ia32_task() instead, and moved
  the system call number to the now-unused 521 slot. ]

Signed-off-by: "H.J. Lu" <hjl.tools@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Roland McGrath <roland@hack.frob.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Link: http://lkml.kernel.org/r/1329696488-16970-1-git-send-email-hpa@zytor.com

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/x86/syscalls/syscall_64.tbl b/arch/x86/syscalls/syscall_64.tbl
index 0d778b800884..dd29a9ea27c5 100644
--- a/arch/x86/syscalls/syscall_64.tbl
+++ b/arch/x86/syscalls/syscall_64.tbl
@@ -107,7 +107,7 @@
 98      common  getrusage               sys_getrusage
 99      common  sysinfo                 sys_sysinfo
 100     common  times                   sys_times
-101     common  ptrace                  sys_ptrace
+101     64      ptrace                  sys_ptrace
 102     common  getuid                  sys_getuid
 103     common  syslog                  sys_syslog
 104     common  getgid                  sys_getgid
@@ -331,7 +331,7 @@
 518     x32     sendmsg                 compat_sys_sendmsg
 519     x32     recvmsg                 compat_sys_recvmsg
 520     x32     execve                  stub_x32_execve
-# 521 available
+521     x32     ptrace                  compat_sys_ptrace
 522     x32     rt_sigpending           sys32_rt_sigpending
 523     x32     rt_sigtimedwait         compat_sys_rt_sigtimedwait
 524     x32     rt_sigqueueinfo         sys32_rt_sigqueueinfo