[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>

7 files changed, 110 insertions, 38 deletions

diff --git a/include/asm-um/desc.h b/include/asm-um/desc.h
index ac1d2a20d17..4ec34a51b62 100644
--- a/include/asm-um/desc.h
+++ b/include/asm-um/desc.h
@@ -1,6 +1,16 @@
 #ifndef __UM_DESC_H
 #define __UM_DESC_H
 
-#include "asm/arch/desc.h"
+/* Taken from asm-i386/desc.h, it's the only thing we need. The rest wouldn't
+ * compile, and has never been used. */
+#define LDT_empty(info) (\
+	(info)->base_addr	== 0	&& \
+	(info)->limit		== 0	&& \
+	(info)->contents	== 0	&& \
+	(info)->read_exec_only	== 1	&& \
+	(info)->seg_32bit	== 0	&& \
+	(info)->limit_in_pages	== 0	&& \
+	(info)->seg_not_present	== 1	&& \
+	(info)->useable		== 0	)
 
 #endif
diff --git a/include/asm-um/processor-i386.h b/include/asm-um/processor-i386.h
index 4108a579eb9..595f1c3e1e4 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"
 
diff --git a/include/asm-um/processor-x86_64.h b/include/asm-um/processor-x86_64.h
index e1e1255a1d3..10609af376c 100644
--- a/include/asm-um/processor-x86_64.h
+++ b/include/asm-um/processor-x86_64.h
@@ -28,6 +28,15 @@ extern inline void rep_nop(void)
                            .debugregs_seq	= 0, \
                            .faultinfo		= { 0, 0, 0 } }
 
+static inline void arch_flush_thread(struct arch_thread *thread)
+{
+}
+
+static inline void arch_copy_thread(struct arch_thread *from,
+                                    struct arch_thread *to)
+{
+}
+
 #include "asm/arch/user.h"
 
 #define current_text_addr() \
diff --git a/include/asm-um/ptrace-generic.h b/include/asm-um/ptrace-generic.h
index 8c57e384cb8..503484305e6 100644
--- a/include/asm-um/ptrace-generic.h
+++ b/include/asm-um/ptrace-generic.h
@@ -60,17 +60,9 @@ extern void show_regs(struct pt_regs *regs);
 extern void send_sigtrap(struct task_struct *tsk, union uml_pt_regs *regs,
 			 int error_code);
 
-#endif
+extern int arch_copy_tls(struct task_struct *new);
+extern void clear_flushed_tls(struct task_struct *task);
 
 #endif
 
-/*
- * Overrides for Emacs so that we follow Linus's tabbing style.
- * Emacs will notice this stuff at the end of the file and automatically
- * adjust the settings for this buffer only.  This must remain at the end
- * of the file.
- * ---------------------------------------------------------------------------
- * Local variables:
- * c-file-style: "linux"
- * End:
- */
+#endif
diff --git a/include/asm-um/ptrace-i386.h b/include/asm-um/ptrace-i386.h
index fe882b9d917..30656c962d7 100644
--- a/include/asm-um/ptrace-i386.h
+++ b/include/asm-um/ptrace-i386.h
@@ -8,8 +8,11 @@
 
 #define HOST_AUDIT_ARCH AUDIT_ARCH_I386
 
+#include "linux/compiler.h"
 #include "sysdep/ptrace.h"
 #include "asm/ptrace-generic.h"
+#include "asm/host_ldt.h"
+#include "choose-mode.h"
 
 #define PT_REGS_EAX(r) UPT_EAX(&(r)->regs)
 #define PT_REGS_EBX(r) UPT_EBX(&(r)->regs)
@@ -38,15 +41,31 @@
 
 #define user_mode(r) UPT_IS_USER(&(r)->regs)
 
-#endif
+extern int ptrace_get_thread_area(struct task_struct *child, int idx,
+                                  struct user_desc __user *user_desc);
 
-/*
- * Overrides for Emacs so that we follow Linus's tabbing style.
- * Emacs will notice this stuff at the end of the file and automatically
- * adjust the settings for this buffer only.  This must remain at the end
- * of the file.
- * ---------------------------------------------------------------------------
- * Local variables:
- * c-file-style: "linux"
- * End:
- */
+extern int ptrace_set_thread_area(struct task_struct *child, int idx,
+                                  struct user_desc __user *user_desc);
+
+extern int do_set_thread_area_skas(struct user_desc *info);
+extern int do_get_thread_area_skas(struct user_desc *info);
+
+extern int do_set_thread_area_tt(struct user_desc *info);
+extern int do_get_thread_area_tt(struct user_desc *info);
+
+extern int arch_switch_tls_skas(struct task_struct *from, struct task_struct *to);
+extern int arch_switch_tls_tt(struct task_struct *from, struct task_struct *to);
+
+static inline int do_get_thread_area(struct user_desc *info)
+{
+	return CHOOSE_MODE_PROC(do_get_thread_area_tt, do_get_thread_area_skas, info);
+}
+
+static inline int do_set_thread_area(struct user_desc *info)
+{
+	return CHOOSE_MODE_PROC(do_set_thread_area_tt, do_set_thread_area_skas, info);
+}
+
+struct task_struct;
+
+#endif
diff --git a/include/asm-um/ptrace-x86_64.h b/include/asm-um/ptrace-x86_64.h
index be51219a8ff..c894e68b1f9 100644
--- a/include/asm-um/ptrace-x86_64.h
+++ b/include/asm-um/ptrace-x86_64.h
@@ -8,6 +8,8 @@
 #define __UM_PTRACE_X86_64_H
 
 #include "linux/compiler.h"
+#include "asm/errno.h"
+#include "asm/host_ldt.h"
 
 #define signal_fault signal_fault_x86_64
 #define __FRAME_OFFSETS /* Needed to get the R* macros */
@@ -63,15 +65,26 @@ void signal_fault(struct pt_regs_subarch *regs, void *frame, char *where);
 
 #define profile_pc(regs) PT_REGS_IP(regs)
 
-#endif
+static inline int ptrace_get_thread_area(struct task_struct *child, int idx,
+                                         struct user_desc __user *user_desc)
+{
+        return -ENOSYS;
+}
 
-/*
- * Overrides for Emacs so that we follow Linus's tabbing style.
- * Emacs will notice this stuff at the end of the file and automatically
- * adjust the settings for this buffer only.  This must remain at the end
- * of the file.
- * ---------------------------------------------------------------------------
- * Local variables:
- * c-file-style: "linux"
- * End:
- */
+static inline int ptrace_set_thread_area(struct task_struct *child, int idx,
+                                         struct user_desc __user *user_desc)
+{
+        return -ENOSYS;
+}
+
+static inline void arch_switch_to_tt(struct task_struct *from,
+                                     struct task_struct *to)
+{
+}
+
+static inline void arch_switch_to_skas(struct task_struct *from,
+                                       struct task_struct *to)
+{
+}
+
+#endif
diff --git a/include/asm-um/segment.h b/include/asm-um/segment.h
index 55e40301f62..48775452e2c 100644
--- a/include/asm-um/segment.h
+++ b/include/asm-um/segment.h
@@ -1,4 +1,6 @@
 #ifndef __UM_SEGMENT_H
 #define __UM_SEGMENT_H
 
+#include "asm/arch/segment.h"
+
 #endif