vdso: Fetch page frame number on init

We will need it in parasite code to detect run time vdso area.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

arch/arm/vdso.c

@@ -9,6 +9,7 @@
 #define LOG_PREFIX "vdso: "
 
 struct vdso_symtable vdso_sym_rt = VDSO_SYMTABLE_INIT;
+u64 vdso_pfn = VDSO_BAD_PFN;
 
 int vdso_init(void)
 {

arch/x86/vdso.c

@@ -15,6 +15,7 @@
 #include "crtools.h"
 #include "kerndat.h"
 #include "vdso.h"
+#include "util.h"
 #include "log.h"
 #include "mem.h"
 
@@ -24,6 +25,7 @@
 #define LOG_PREFIX "vdso: "
 
 struct vdso_symtable vdso_sym_rt = VDSO_SYMTABLE_INIT;
+u64 vdso_pfn = VDSO_BAD_PFN;
 
 static int vdso_fill_self_symtable(struct vdso_symtable *s)
 {
@@ -65,7 +67,31 @@ static int vdso_fill_self_symtable(struct vdso_symtable *s)
 
 int vdso_init(void)
 {
+	int ret = -1, fd;
+	off_t off;
+
 	if (vdso_fill_self_symtable(&vdso_sym_rt))
 		return -1;
-	return 0;
+
+	fd = open_proc(getpid(), "pagemap");
+	if (fd < 0)
+		return -1;
+
+	off = (vdso_sym_rt.vma_start / PAGE_SIZE) * sizeof(u64);
+	if (lseek(fd, off, SEEK_SET) != off) {
+		pr_perror("Failed to seek address %lx\n", vdso_sym_rt.vma_start);
+		goto out;
+	}
+
+	ret = read(fd, &vdso_pfn, sizeof(vdso_pfn));
+	if (ret < 0 || ret != sizeof(vdso_pfn)) {
+		pr_perror("Can't read pme for pid %d", getpid());
+		ret = -1;
+	} else {
+		vdso_pfn = PME_PFRAME(vdso_pfn);
+		ret = 0;
+	}
+out:
+	close(fd);
+	return ret;
 }

include/vdso.h

@@ -4,6 +4,7 @@
 #include <sys/mman.h>
 
 #include "asm/vdso.h"
+#include "asm/int.h"
 
 #define VDSO_PROT		(PROT_READ | PROT_EXEC)
 
@@ -26,6 +27,7 @@ enum {
 #define VDSO_SYMBOL_TIME_NAME		"__vdso_time"
 
 #define VDSO_BAD_ADDR		(-1ul)
+#define VDSO_BAD_PFN		(-1ull)
 
 struct vdso_symbol {
 	char		name[32];
@@ -67,6 +69,7 @@ static inline unsigned long vdso_vma_size(struct vdso_symtable *t)
 }
 
 extern struct vdso_symtable vdso_sym_rt;
+extern u64 vdso_pfn;
 extern int vdso_init(void);
 
 #endif /* __CR_VDSO_H__ */