[PATCH] uml: maintain own LDT entries

Patch imlements full LDT handling in SKAS:
 * UML holds it's own LDT table, used to deliver data on
   modify_ldt(READ)
 * UML disables the default_ldt, inherited from the host (SKAS3)
   or resets LDT entries, set by host's clib and inherited in
   SKAS0
 * A new global variable skas_needs_stub is inserted, that
   can be used to decide, whether stub-pages must be supported
   or not.
 * Uses the syscall-stub to replace missing PTRACE_LDT (therefore,
   write_ldt_entry needs to be modified)

Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 138 insertions, 0 deletions

diff --git a/include/asm-um/ldt-i386.h b/include/asm-um/ldt-i386.h
new file mode 100644
index 000000000000..b42662929b6c
--- /dev/null
+++ b/include/asm-um/ldt-i386.h
@@ -0,0 +1,69 @@
+/*
+ * Copyright (C) 2004 Fujitsu Siemens Computers GmbH
+ * Licensed under the GPL
+ *
+ * Author: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
+ */
+
+#ifndef __ASM_LDT_I386_H
+#define __ASM_LDT_I386_H
+
+#include "asm/semaphore.h"
+#include "asm/arch/ldt.h"
+
+struct mmu_context_skas;
+extern void ldt_host_info(void);
+extern long init_new_ldt(struct mmu_context_skas * to_mm,
+                         struct mmu_context_skas * from_mm);
+extern void free_ldt(struct mmu_context_skas * mm);
+
+#define LDT_PAGES_MAX \
+        ((LDT_ENTRIES * LDT_ENTRY_SIZE)/PAGE_SIZE)
+#define LDT_ENTRIES_PER_PAGE \
+        (PAGE_SIZE/LDT_ENTRY_SIZE)
+#define LDT_DIRECT_ENTRIES \
+        ((LDT_PAGES_MAX*sizeof(void *))/LDT_ENTRY_SIZE)
+
+struct ldt_entry {
+        __u32 a;
+        __u32 b;
+};
+
+typedef struct uml_ldt {
+        int entry_count;
+        struct semaphore semaphore;
+        union {
+                struct ldt_entry * pages[LDT_PAGES_MAX];
+                struct ldt_entry entries[LDT_DIRECT_ENTRIES];
+        };
+} uml_ldt_t;
+
+/*
+ * macros stolen from include/asm-i386/desc.h
+ */
+#define LDT_entry_a(info) \
+        ((((info)->base_addr & 0x0000ffff) << 16) | ((info)->limit & 0x0ffff))
+
+#define LDT_entry_b(info) \
+        (((info)->base_addr & 0xff000000) | \
+        (((info)->base_addr & 0x00ff0000) >> 16) | \
+        ((info)->limit & 0xf0000) | \
+        (((info)->read_exec_only ^ 1) << 9) | \
+        ((info)->contents << 10) | \
+        (((info)->seg_not_present ^ 1) << 15) | \
+        ((info)->seg_32bit << 22) | \
+        ((info)->limit_in_pages << 23) | \
+        ((info)->useable << 20) | \
+        0x7000)
+
+#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/ldt.h b/include/asm-um/ldt.h
index e908439d338a..4466ff6de0fd 100644
--- a/include/asm-um/ldt.h
+++ b/include/asm-um/ldt.h
@@ -1,3 +1,72 @@
+/*
+ * Copyright (C) 2004 Fujitsu Siemens Computers GmbH
+ * Licensed under the GPL
+ *
+ * Author: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
+ */
+
+#ifndef __ASM_LDT_I386_H
+#define __ASM_LDT_I386_H
+
+#include "asm/semaphore.h"
+#include "asm/arch/ldt.h"
+
+struct mmu_context_skas;
+extern void ldt_host_info(void);
+extern long init_new_ldt(struct mmu_context_skas * to_mm,
+                         struct mmu_context_skas * from_mm);
+extern void free_ldt(struct mmu_context_skas * mm);
+
+#define LDT_PAGES_MAX \
+        ((LDT_ENTRIES * LDT_ENTRY_SIZE)/PAGE_SIZE)
+#define LDT_ENTRIES_PER_PAGE \
+        (PAGE_SIZE/LDT_ENTRY_SIZE)
+#define LDT_DIRECT_ENTRIES \
+        ((LDT_PAGES_MAX*sizeof(void *))/LDT_ENTRY_SIZE)
+
+struct ldt_entry {
+        __u32 a;
+        __u32 b;
+};
+
+typedef struct uml_ldt {
+        int entry_count;
+        struct semaphore semaphore;
+        union {
+                struct ldt_entry * pages[LDT_PAGES_MAX];
+                struct ldt_entry entries[LDT_DIRECT_ENTRIES];
+        };
+} uml_ldt_t;
+
+/*
+ * macros stolen from include/asm-i386/desc.h
+ */
+#define LDT_entry_a(info) \
+        ((((info)->base_addr & 0x0000ffff) << 16) | ((info)->limit & 0x0ffff))
+
+#define LDT_entry_b(info) \
+        (((info)->base_addr & 0xff000000) | \
+        (((info)->base_addr & 0x00ff0000) >> 16) | \
+        ((info)->limit & 0xf0000) | \
+        (((info)->read_exec_only ^ 1) << 9) | \
+        ((info)->contents << 10) | \
+        (((info)->seg_not_present ^ 1) << 15) | \
+        ((info)->seg_32bit << 22) | \
+        ((info)->limit_in_pages << 23) | \
+        ((info)->useable << 20) | \
+        0x7000)
+
+#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
 #ifndef __UM_LDT_H
 #define __UM_LDT_H