[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, 31 insertions, 4 deletions

diff --git a/include/asm-um/processor-i386.h b/include/asm-um/processor-i386.h
index 4108a579eb92..595f1c3e1e40 100644
--- a/include/asm-um/processor-i386.h
+++ b/include/asm-um/processor-i386.h
@@ -1,4 +1,4 @@
-/* 
+/*
  * Copyright (C) 2002 Jeff Dike (jdike@karaya.com)
  * Licensed under the GPL
  */
@@ -6,21 +6,48 @@
 #ifndef __UM_PROCESSOR_I386_H
 #define __UM_PROCESSOR_I386_H
 
+#include "linux/string.h"
+#include "asm/host_ldt.h"
+#include "asm/segment.h"
+
 extern int host_has_xmm;
 extern int host_has_cmov;
 
 /* include faultinfo structure */
 #include "sysdep/faultinfo.h"
 
+struct uml_tls_struct {
+        struct user_desc tls;
+        unsigned flushed:1;
+        unsigned present:1;
+};
+
 struct arch_thread {
+        struct uml_tls_struct tls_array[GDT_ENTRY_TLS_ENTRIES];
         unsigned long debugregs[8];
         int debugregs_seq;
         struct faultinfo faultinfo;
 };
 
-#define INIT_ARCH_THREAD { .debugregs           = { [ 0 ... 7 ] = 0 }, \
-                           .debugregs_seq       = 0, \
-                           .faultinfo           = { 0, 0, 0 } }
+#define INIT_ARCH_THREAD { \
+        .tls_array              = { [ 0 ... GDT_ENTRY_TLS_ENTRIES - 1 ] = \
+                                    { .present = 0, .flushed = 0 } }, \
+        .debugregs              = { [ 0 ... 7 ] = 0 }, \
+        .debugregs_seq          = 0, \
+        .faultinfo              = { 0, 0, 0 } \
+}
+
+static inline void arch_flush_thread(struct arch_thread *thread)
+{
+        /* Clear any TLS still hanging */
+        memset(&thread->tls_array, 0, sizeof(thread->tls_array));
+}
+
+static inline void arch_copy_thread(struct arch_thread *from,
+                                    struct arch_thread *to)
+{
+        memcpy(&to->tls_array, &from->tls_array, sizeof(from->tls_array));
+}
 
 #include "asm/arch/user.h"