[PATCH] uml: implement {get,set}_thread_area for i386

Implement sys_[gs]et_thread_area and the corresponding ptrace operations for
UML.  This is the main chunk, additional parts follow.  This implementation is
now well tested and has run reliably for some time, and we've understood all
the previously existing problems.

Their implementation saves the new GDT content and then forwards the call to
the host when appropriate, i.e.  immediately when the target process is
running or on context switch otherwise (i.e.  on fork and on ptrace() calls).

In SKAS mode, we must switch registers on each context switch (because SKAS
does not switches tls_array together with current->mm).

Also, added get_cpu() locking; this has been done for SKAS mode, since TT does
not need it (it does not use smp_processor_id()).

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Acked-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/arch/um/kernel/ptrace.c b/arch/um/kernel/ptrace.c
index 394582202ce6..60d2eda995c1 100644
--- a/arch/um/kernel/ptrace.c
+++ b/arch/um/kernel/ptrace.c
@@ -185,6 +185,16 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data)
                 ret = set_fpxregs(data, child);
                 break;
 #endif
+        case PTRACE_GET_THREAD_AREA:
+                ret = ptrace_get_thread_area(child, addr,
+                                             (struct user_desc __user *) data);
+                break;
+
+        case PTRACE_SET_THREAD_AREA:
+                ret = ptrace_set_thread_area(child, addr,
+                                             (struct user_desc __user *) data);
+                break;
+
         case PTRACE_FAULTINFO: {
                 /* Take the info from thread->arch->faultinfo,
                  * but transfer max. sizeof(struct ptrace_faultinfo).