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Diffstat (limited to 'arch/x86/include/asm/segment.h')
-rw-r--r--arch/x86/include/asm/segment.h49
1 files changed, 39 insertions, 10 deletions
diff --git a/arch/x86/include/asm/segment.h b/arch/x86/include/asm/segment.h
index 7d5a1929d76b..1549caa098f0 100644
--- a/arch/x86/include/asm/segment.h
+++ b/arch/x86/include/asm/segment.h
@@ -2,6 +2,7 @@
#define _ASM_X86_SEGMENT_H
#include <linux/const.h>
+#include <asm/alternative.h>
/*
* Constructor for a conventional segment GDT (or LDT) entry.
@@ -207,13 +208,6 @@
#define __USER_CS (GDT_ENTRY_DEFAULT_USER_CS*8 + 3)
#define __PER_CPU_SEG (GDT_ENTRY_PER_CPU*8 + 3)
-/* TLS indexes for 64-bit - hardcoded in arch_prctl(): */
-#define FS_TLS 0
-#define GS_TLS 1
-
-#define GS_TLS_SEL ((GDT_ENTRY_TLS_MIN+GS_TLS)*8 + 3)
-#define FS_TLS_SEL ((GDT_ENTRY_TLS_MIN+FS_TLS)*8 + 3)
-
#endif
#ifndef CONFIG_PARAVIRT
@@ -249,10 +243,13 @@ extern const char early_idt_handler_array[NUM_EXCEPTION_VECTORS][EARLY_IDT_HANDL
#endif
/*
- * Load a segment. Fall back on loading the zero
- * segment if something goes wrong..
+ * Load a segment. Fall back on loading the zero segment if something goes
+ * wrong. This variant assumes that loading zero fully clears the segment.
+ * This is always the case on Intel CPUs and, even on 64-bit AMD CPUs, any
+ * failure to fully clear the cached descriptor is only observable for
+ * FS and GS.
*/
-#define loadsegment(seg, value) \
+#define __loadsegment_simple(seg, value) \
do { \
unsigned short __val = (value); \
\
@@ -269,6 +266,38 @@ do { \
: "+r" (__val) : : "memory"); \
} while (0)
+#define __loadsegment_ss(value) __loadsegment_simple(ss, (value))
+#define __loadsegment_ds(value) __loadsegment_simple(ds, (value))
+#define __loadsegment_es(value) __loadsegment_simple(es, (value))
+
+#ifdef CONFIG_X86_32
+
+/*
+ * On 32-bit systems, the hidden parts of FS and GS are unobservable if
+ * the selector is NULL, so there's no funny business here.
+ */
+#define __loadsegment_fs(value) __loadsegment_simple(fs, (value))
+#define __loadsegment_gs(value) __loadsegment_simple(gs, (value))
+
+#else
+
+static inline void __loadsegment_fs(unsigned short value)
+{
+ asm volatile(" \n"
+ "1: movw %0, %%fs \n"
+ "2: \n"
+
+ _ASM_EXTABLE_HANDLE(1b, 2b, ex_handler_clear_fs)
+
+ : : "rm" (value) : "memory");
+}
+
+/* __loadsegment_gs is intentionally undefined. Use load_gs_index instead. */
+
+#endif
+
+#define loadsegment(seg, value) __loadsegment_ ## seg (value)
+
/*
* Save a segment register away:
*/