4 files changed, 29 insertions, 6 deletions

diff --git a/arch/i386/boot/compressed/relocs.c b/arch/i386/boot/compressed/relocs.c
index b0e21c3cee5c..2d77ee728f92 100644
--- a/arch/i386/boot/compressed/relocs.c
+++ b/arch/i386/boot/compressed/relocs.c
@@ -31,6 +31,7 @@ static const char* safe_abs_relocs[] = {
                 "__kernel_rt_sigreturn",
                 "__kernel_sigreturn",
                 "SYSENTER_RETURN",
+                "VDSO_NOTE_MASK",
                 "xen_irq_disable_direct_reloc",
                 "xen_save_fl_direct_reloc",
 };
diff --git a/arch/i386/kernel/vsyscall-note.S b/arch/i386/kernel/vsyscall-note.S
index 271f16a8ca01..07c0daf78237 100644
--- a/arch/i386/kernel/vsyscall-note.S
+++ b/arch/i386/kernel/vsyscall-note.S
@@ -14,7 +14,6 @@ ELFNOTE_START(Linux, 0, "a")
 ELFNOTE_END
 
 #ifdef CONFIG_XEN
-
 /*
  * Add a special note telling glibc's dynamic linker a fake hardware
  * flavor that it will use to choose the search path for libraries in the
@@ -28,15 +27,19 @@ ELFNOTE_END
  * It should contain:
  *      hwcap 1 nosegneg
  * to match the mapping of bit to name that we give here.
+ *
+ * At runtime, the fake hardware feature will be considered to be present
+ * if its bit is set in the mask word.  So, we start with the mask 0, and
+ * at boot time we set VDSO_NOTE_NONEGSEG_BIT if running under Xen.
  */
 
-/* Bit used for the pseudo-hwcap for non-negative segments.  We use
-   bit 1 to avoid bugs in some versions of glibc when bit 0 is
-   used; the choice is otherwise arbitrary. */
-#define VDSO_NOTE_NONEGSEG_BIT  1
+#include "../xen/vdso.h"        /* Defines VDSO_NOTE_NONEGSEG_BIT.  */
 
+        .globl VDSO_NOTE_MASK
 ELFNOTE_START(GNU, 2, "a")
-        .long 1, 1<<VDSO_NOTE_NONEGSEG_BIT              /* ncaps, mask */
+        .long 1                 /* ncaps */
+VDSO_NOTE_MASK:
+        .long 0                 /* mask */
         .byte VDSO_NOTE_NONEGSEG_BIT; .asciz "nosegneg" /* bit, name */
 ELFNOTE_END
 #endif
diff --git a/arch/i386/xen/setup.c b/arch/i386/xen/setup.c
index 2fe6eac510f0..f84e77226646 100644
--- a/arch/i386/xen/setup.c
+++ b/arch/i386/xen/setup.c
@@ -19,6 +19,7 @@
 #include <xen/features.h>
 
 #include "xen-ops.h"
+#include "vdso.h"
 
 /* These are code, but not functions.  Defined in entry.S */
 extern const char xen_hypervisor_callback[];
@@ -55,6 +56,18 @@ static void xen_idle(void)
         }
 }
 
+/*
+ * Set the bit indicating "nosegneg" library variants should be used.
+ */
+static void fiddle_vdso(void)
+{
+        extern u32 VDSO_NOTE_MASK; /* See ../kernel/vsyscall-note.S.  */
+        extern char vsyscall_int80_start;
+        u32 *mask = (u32 *) ((unsigned long) &VDSO_NOTE_MASK - VDSO_PRELINK +
+                             &vsyscall_int80_start);
+        *mask |= 1 << VDSO_NOTE_NONEGSEG_BIT;
+}
+
 void __init xen_arch_setup(void)
 {
         struct physdev_set_iopl set_iopl;
@@ -93,4 +106,6 @@ void __init xen_arch_setup(void)
 #endif
 
         paravirt_disable_iospace();
+
+        fiddle_vdso();
 }
diff --git a/arch/i386/xen/vdso.h b/arch/i386/xen/vdso.h
new file mode 100644
index 000000000000..861fedfe5230
--- /dev/null
+++ b/arch/i386/xen/vdso.h
@@ -0,0 +1,4 @@
+/* Bit used for the pseudo-hwcap for non-negative segments.  We use
+   bit 1 to avoid bugs in some versions of glibc when bit 0 is
+   used; the choice is otherwise arbitrary. */
+#define VDSO_NOTE_NONEGSEG_BIT  1