commit c291a380d610060240c76fc3cadfce6450abfdc8
Author: Wolfgang Mauerer <wolfgang.mauerer@domain.hid>
Date:   Fri Dec 11 10:59:00 2009 +0100

    Add support for sharing kernel/userland data between Xenomai and Linux
    
    A new structure (struct xnshared) is introduced. It allows us to share
    generic data between user and kernel of Linux and Xenomai; a bitmap
    of feature flags located at the beginning of the structure identifies
    which data are shared. The structure is allocated in the global semaphore
    heap, and xnsysinfo.xnshared_offset identifies the offset of the
    structure within the heap.
    
    Currently, no shared features are yet supported - the patch only
    introduces the necessary ABI changes. When the need arises
    to share data between said entities, the structure must
    be accordingly extended, and a new feature bit must be added
    to the flags.
    
    Signed-off-by: Wolfgang Mauerer <wolfgang.mauerer@domain.hid>
    Signed-off-by: Jan Kiszka <jan.kiszka@domain.hid>

diff --git a/include/asm-generic/syscall.h b/include/asm-generic/syscall.h
index 483b99f..8f1ddc6 100644
--- a/include/asm-generic/syscall.h
+++ b/include/asm-generic/syscall.h
@@ -53,6 +53,7 @@
 typedef struct xnsysinfo {
 	unsigned long long cpufreq;	/* CPU frequency */
 	unsigned long tickval;		/* Tick duration (ns) */
+	unsigned long xnvdso_off;  	/* Offset of xnvdso in the sem heap */
 } xnsysinfo_t;
 
 #define SIGSHADOW  SIGWINCH
diff --git a/include/nucleus/xnvdso.h b/include/nucleus/xnvdso.h
new file mode 100644
index 0000000..cc2ec20
--- /dev/null
+++ b/include/nucleus/xnvdso.h
@@ -0,0 +1,36 @@
+#ifndef XNVDSO_H
+#define XNVDSO_H
+
+/*
+ * Data shared between Xenomai kernel/userland and the Linux kernel/userland
+ * on the global semaphore heap. The features element indicates which data are
+ * shared. Notice that struct xnvdso may only grow, but never shrink.
+ */
+struct xnvdso {
+	unsigned long long features;
+
+	/* Embed domain specific structures that describe the
+	 * shared data here */
+};
+
+/*
+ * For each shared feature, add a flag below. For now, the set is still
+ * empty.
+ */
+/*
+#define XNVDSO_FEAT_A	0x0000000000000001
+#define XNVDSO_FEAT_B	0x0000000000000002
+#define XNVDSO_FEAT_C	0x0000000000000004
+#define XNVDSO_FEATURES	(XNVDSO_FEAT_A | XNVDSO_FEAT_B | XVDSO_FEAT_C)
+*/
+
+#define XNVDSO_FEATURES 0x0000000000000000
+
+extern struct xnvdso *xnvdso;
+
+static inline int xnvdso_test_feature(unsigned long long feature)
+{
+	return testbits(xnvdso->features, feature);
+}
+
+#endif
diff --git a/ksrc/nucleus/module.c b/ksrc/nucleus/module.c
index 5404182..40ee9a6 100644
--- a/ksrc/nucleus/module.c
+++ b/ksrc/nucleus/module.c
@@ -34,6 +34,7 @@
 #include <nucleus/pipe.h>
 #endif /* CONFIG_XENO_OPT_PIPE */
 #include <nucleus/select.h>
+#include <nucleus/xnvdso.h>
 #include <asm/xenomai/bits/init.h>
 
 MODULE_DESCRIPTION("Xenomai nucleus");
@@ -51,6 +52,9 @@ u_long xnmod_sysheap_size;
 
 int xeno_nucleus_status = -EINVAL;
 
+struct xnvdso *xnvdso;
+EXPORT_SYMBOL_GPL(xnvdso);
+
 struct xnsys_ppd __xnsys_global_ppd;
 EXPORT_SYMBOL_GPL(__xnsys_global_ppd);
 
@@ -82,6 +86,21 @@ void xnmod_alloc_glinks(xnqueue_t *freehq)
 }
 EXPORT_SYMBOL_GPL(xnmod_alloc_glinks);
 
+/*
+ * We re-use the global semaphore heap to provide a multi-purpose shared
+ * memory area between Xenomai and Linux - for both kernel and userland
+ */
+void __init xnheap_init_shared(void)
+{
+	xnvdso = (struct xnvdso *)xnheap_alloc(&__xnsys_global_ppd.sem_heap,
+						  sizeof(*xnvdso));
+
+	if (!xnvdso)
+		xnpod_fatal("Xenomai: cannot allocate memory for xnvdso!\n");
+
+	xnvdso->features = XNVDSO_FEATURES;
+}
+
 int __init __xeno_sys_init(void)
 {
 	int ret;
@@ -106,6 +125,8 @@ int __init __xeno_sys_init(void)
 		goto cleanup_arch;
 
 	xnheap_set_label(&__xnsys_global_ppd.sem_heap, "global sem heap");
+
+	xnheap_init_shared();
 #endif
 	
 #ifdef __KERNEL__
diff --git a/ksrc/nucleus/shadow.c b/ksrc/nucleus/shadow.c
index 0c94a60..d8bced3 100644
--- a/ksrc/nucleus/shadow.c
+++ b/ksrc/nucleus/shadow.c
@@ -50,6 +50,7 @@
 #include <nucleus/trace.h>
 #include <nucleus/stat.h>
 #include <nucleus/sys_ppd.h>
+#include <nucleus/xnvdso.h>
 #include <asm/xenomai/features.h>
 #include <asm/xenomai/syscall.h>
 #include <asm/xenomai/bits/shadow.h>
@@ -1746,6 +1747,9 @@ static int xnshadow_sys_info(struct pt_regs *regs)
 
 	info.cpufreq = xnarch_get_cpu_freq();
 
+	info.xnvdso_off =
+	  xnheap_mapped_offset(&xnsys_ppd_get(1)->sem_heap, xnvdso);
+
 	return __xn_safe_copy_to_user((void __user *)infarg, &info, sizeof(info));
 }