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authorAndy Lutomirski <luto@MIT.EDU>2011-05-23 09:31:24 -0400
committerThomas Gleixner <tglx@linutronix.de>2011-05-24 14:51:28 +0200
commit8c49d9a74bac5ea3f18480307057241b808fcc0c (patch)
treea9d2d8160ca37e9292e605cf3cdd85b29646c4b7 /arch/x86/include/asm
parentd762f4383100c2a87b1a3f2d678cd3b5425655b4 (diff)
x86-64: Clean up vdso/kernel shared variables
Variables that are shared between the vdso and the kernel are currently a bit of a mess. They are each defined with their own magic, they are accessed differently in the kernel, the vsyscall page, and the vdso, and one of them (vsyscall_clock) doesn't even really exist. This changes them all to use a common mechanism. All of them are delcared in vvar.h with a fixed address (validated by the linker script). In the kernel (as before), they look like ordinary read-write variables. In the vsyscall page and the vdso, they are accessed through a new macro VVAR, which gives read-only access. The vdso is now loaded verbatim into memory without any fixups. As a side bonus, access from the vdso is faster because a level of indirection is removed. While we're at it, pack jiffies and vgetcpu_mode into the same cacheline. Signed-off-by: Andy Lutomirski <luto@mit.edu> Cc: Andi Kleen <andi@firstfloor.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: "David S. Miller" <davem@davemloft.net> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Borislav Petkov <bp@amd64.org> Link: http://lkml.kernel.org/r/%3C7357882fbb51fa30491636a7b6528747301b7ee9.1306156808.git.luto%40mit.edu%3E Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/x86/include/asm')
-rw-r--r--arch/x86/include/asm/vdso.h14
-rw-r--r--arch/x86/include/asm/vgtod.h2
-rw-r--r--arch/x86/include/asm/vsyscall.h12
-rw-r--r--arch/x86/include/asm/vvar.h52
4 files changed, 54 insertions, 26 deletions
diff --git a/arch/x86/include/asm/vdso.h b/arch/x86/include/asm/vdso.h
index 9064052b73d..bb0522850b7 100644
--- a/arch/x86/include/asm/vdso.h
+++ b/arch/x86/include/asm/vdso.h
@@ -1,20 +1,6 @@
#ifndef _ASM_X86_VDSO_H
#define _ASM_X86_VDSO_H
-#ifdef CONFIG_X86_64
-extern const char VDSO64_PRELINK[];
-
-/*
- * Given a pointer to the vDSO image, find the pointer to VDSO64_name
- * as that symbol is defined in the vDSO sources or linker script.
- */
-#define VDSO64_SYMBOL(base, name) \
-({ \
- extern const char VDSO64_##name[]; \
- (void *)(VDSO64_##name - VDSO64_PRELINK + (unsigned long)(base)); \
-})
-#endif
-
#if defined CONFIG_X86_32 || defined CONFIG_COMPAT
extern const char VDSO32_PRELINK[];
diff --git a/arch/x86/include/asm/vgtod.h b/arch/x86/include/asm/vgtod.h
index 3d61e204826..646b4c1ca69 100644
--- a/arch/x86/include/asm/vgtod.h
+++ b/arch/x86/include/asm/vgtod.h
@@ -23,8 +23,6 @@ struct vsyscall_gtod_data {
struct timespec wall_to_monotonic;
struct timespec wall_time_coarse;
};
-extern struct vsyscall_gtod_data __vsyscall_gtod_data
-__section_vsyscall_gtod_data;
extern struct vsyscall_gtod_data vsyscall_gtod_data;
#endif /* _ASM_X86_VGTOD_H */
diff --git a/arch/x86/include/asm/vsyscall.h b/arch/x86/include/asm/vsyscall.h
index d0983d255fb..d55597351f6 100644
--- a/arch/x86/include/asm/vsyscall.h
+++ b/arch/x86/include/asm/vsyscall.h
@@ -16,27 +16,19 @@ enum vsyscall_num {
#ifdef __KERNEL__
#include <linux/seqlock.h>
-#define __section_vgetcpu_mode __attribute__ ((unused, __section__ (".vgetcpu_mode"), aligned(16)))
-#define __section_jiffies __attribute__ ((unused, __section__ (".jiffies"), aligned(16)))
-
/* Definitions for CONFIG_GENERIC_TIME definitions */
-#define __section_vsyscall_gtod_data __attribute__ \
- ((unused, __section__ (".vsyscall_gtod_data"),aligned(16)))
-#define __section_vsyscall_clock __attribute__ \
- ((unused, __section__ (".vsyscall_clock"),aligned(16)))
#define __vsyscall_fn \
__attribute__ ((unused, __section__(".vsyscall_fn"))) notrace
#define VGETCPU_RDTSCP 1
#define VGETCPU_LSL 2
-extern int __vgetcpu_mode;
-extern volatile unsigned long __jiffies;
-
/* kernel space (writeable) */
extern int vgetcpu_mode;
extern struct timezone sys_tz;
+#include <asm/vvar.h>
+
extern void map_vsyscall(void);
#endif /* __KERNEL__ */
diff --git a/arch/x86/include/asm/vvar.h b/arch/x86/include/asm/vvar.h
new file mode 100644
index 00000000000..341b3559452
--- /dev/null
+++ b/arch/x86/include/asm/vvar.h
@@ -0,0 +1,52 @@
+/*
+ * vvar.h: Shared vDSO/kernel variable declarations
+ * Copyright (c) 2011 Andy Lutomirski
+ * Subject to the GNU General Public License, version 2
+ *
+ * A handful of variables are accessible (read-only) from userspace
+ * code in the vsyscall page and the vdso. They are declared here.
+ * Some other file must define them with DEFINE_VVAR.
+ *
+ * In normal kernel code, they are used like any other variable.
+ * In user code, they are accessed through the VVAR macro.
+ *
+ * Each of these variables lives in the vsyscall page, and each
+ * one needs a unique offset within the little piece of the page
+ * reserved for vvars. Specify that offset in DECLARE_VVAR.
+ * (There are 896 bytes available. If you mess up, the linker will
+ * catch it.)
+ */
+
+/* Offset of vars within vsyscall page */
+#define VSYSCALL_VARS_OFFSET (3072 + 128)
+
+#if defined(__VVAR_KERNEL_LDS)
+
+/* The kernel linker script defines its own magic to put vvars in the
+ * right place.
+ */
+#define DECLARE_VVAR(offset, type, name) \
+ EMIT_VVAR(name, VSYSCALL_VARS_OFFSET + offset)
+
+#else
+
+#define DECLARE_VVAR(offset, type, name) \
+ static type const * const vvaraddr_ ## name = \
+ (void *)(VSYSCALL_START + VSYSCALL_VARS_OFFSET + (offset));
+
+#define DEFINE_VVAR(type, name) \
+ type __vvar_ ## name \
+ __attribute__((section(".vsyscall_var_" #name), aligned(16)))
+
+#define VVAR(name) (*vvaraddr_ ## name)
+
+#endif
+
+/* DECLARE_VVAR(offset, type, name) */
+
+DECLARE_VVAR(0, volatile unsigned long, jiffies)
+DECLARE_VVAR(8, int, vgetcpu_mode)
+DECLARE_VVAR(128, struct vsyscall_gtod_data, vsyscall_gtod_data)
+
+#undef DECLARE_VVAR
+#undef VSYSCALL_VARS_OFFSET