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

2 files changed, 101 insertions, 2 deletions

diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 50267386b766..93e7877a19c4 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -1130,6 +1130,100 @@ static int genregs32_set(struct task_struct *target,
         return ret;
 }
 
+#ifdef CONFIG_X86_X32_ABI
+static long x32_arch_ptrace(struct task_struct *child,
+                            compat_long_t request, compat_ulong_t caddr,
+                            compat_ulong_t cdata)
+{
+        unsigned long addr = caddr;
+        unsigned long data = cdata;
+        void __user *datap = compat_ptr(data);
+        int ret;
+
+        switch (request) {
+        /* Read 32bits at location addr in the USER area.  Only allow
+           to return the lower 32bits of segment and debug registers.  */
+        case PTRACE_PEEKUSR: {
+                u32 tmp;
+
+                ret = -EIO;
+                if ((addr & (sizeof(data) - 1)) || addr >= sizeof(struct user) ||
+                    addr < offsetof(struct user_regs_struct, cs))
+                        break;
+
+                tmp = 0;  /* Default return condition */
+                if (addr < sizeof(struct user_regs_struct))
+                        tmp = getreg(child, addr);
+                else if (addr >= offsetof(struct user, u_debugreg[0]) &&
+                         addr <= offsetof(struct user, u_debugreg[7])) {
+                        addr -= offsetof(struct user, u_debugreg[0]);
+                        tmp = ptrace_get_debugreg(child, addr / sizeof(data));
+                }
+                ret = put_user(tmp, (__u32 __user *)datap);
+                break;
+        }
+
+        /* Write the word at location addr in the USER area.  Only allow
+           to update segment and debug registers with the upper 32bits
+           zero-extended. */
+        case PTRACE_POKEUSR:
+                ret = -EIO;
+                if ((addr & (sizeof(data) - 1)) || addr >= sizeof(struct user) ||
+                    addr < offsetof(struct user_regs_struct, cs))
+                        break;
+
+                if (addr < sizeof(struct user_regs_struct))
+                        ret = putreg(child, addr, data);
+                else if (addr >= offsetof(struct user, u_debugreg[0]) &&
+                         addr <= offsetof(struct user, u_debugreg[7])) {
+                        addr -= offsetof(struct user, u_debugreg[0]);
+                        ret = ptrace_set_debugreg(child,
+                                                  addr / sizeof(data), data);
+                }
+                break;
+
+        case PTRACE_GETREGS:    /* Get all gp regs from the child. */
+                return copy_regset_to_user(child,
+                                           task_user_regset_view(current),
+                                           REGSET_GENERAL,
+                                           0, sizeof(struct user_regs_struct),
+                                           datap);
+
+        case PTRACE_SETREGS:    /* Set all gp regs in the child. */
+                return copy_regset_from_user(child,
+                                             task_user_regset_view(current),
+                                             REGSET_GENERAL,
+                                             0, sizeof(struct user_regs_struct),
+                                             datap);
+
+        case PTRACE_GETFPREGS:  /* Get the child FPU state. */
+                return copy_regset_to_user(child,
+                                           task_user_regset_view(current),
+                                           REGSET_FP,
+                                           0, sizeof(struct user_i387_struct),
+                                           datap);
+
+        case PTRACE_SETFPREGS:  /* Set the child FPU state. */
+                return copy_regset_from_user(child,
+                                             task_user_regset_view(current),
+                                             REGSET_FP,
+                                             0, sizeof(struct user_i387_struct),
+                                             datap);
+
+                /* normal 64bit interface to access TLS data.
+                   Works just like arch_prctl, except that the arguments
+                   are reversed. */
+        case PTRACE_ARCH_PRCTL:
+                return do_arch_prctl(child, data, addr);
+
+        default:
+                return compat_ptrace_request(child, request, addr, data);
+        }
+
+        return ret;
+}
+#endif
+
 long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
                         compat_ulong_t caddr, compat_ulong_t cdata)
 {
@@ -1139,6 +1233,11 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
         int ret;
         __u32 val;
 
+#ifdef CONFIG_X86_X32_ABI
+        if (!is_ia32_task())
+                return x32_arch_ptrace(child, request, caddr, cdata);
+#endif
+
         switch (request) {
         case PTRACE_PEEKUSR:
                 ret = getreg32(child, addr, &val);
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