x86 vDSO: vdso32 build

This builds the 32-bit vDSO images in the arch/x86/vdso subdirectory.
Nothing uses the images yet, but this paves the way for consolidating
the vDSO build logic all in one place.  The new images use a linker
script sharing the layout parts from vdso-layout.lds.S with the 64-bit
vDSO.  A new vdso32-syms.lds is generated in the style of vdso-syms.lds.

Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 37 insertions, 0 deletions

diff --git a/arch/x86/vdso/vdso32/vdso32.lds.S b/arch/x86/vdso/vdso32/vdso32.lds.S
new file mode 100644
index 000000000000..976124bb5f92
--- /dev/null
+++ b/arch/x86/vdso/vdso32/vdso32.lds.S
@@ -0,0 +1,37 @@
+/*
+ * Linker script for 32-bit vDSO.
+ * We #include the file to define the layout details.
+ * Here we only choose the prelinked virtual address.
+ *
+ * This file defines the version script giving the user-exported symbols in
+ * the DSO.  We can define local symbols here called VDSO* to make their
+ * values visible using the asm-x86/vdso.h macros from the kernel proper.
+ */
+
+#define VDSO_PRELINK 0
+#include "../vdso-layout.lds.S"
+
+/* The ELF entry point can be used to set the AT_SYSINFO value.  */
+ENTRY(__kernel_vsyscall);
+
+/*
+ * This controls what userland symbols we export from the vDSO.
+ */
+VERSION
+{
+        LINUX_2.5 {
+        global:
+                __kernel_vsyscall;
+                __kernel_sigreturn;
+                __kernel_rt_sigreturn;
+        local: *;
+        };
+}
+
+/*
+ * Symbols we define here called VDSO* get their values into vdso32-syms.h.
+ */
+VDSO32_PRELINK          = VDSO_PRELINK;
+VDSO32_vsyscall         = __kernel_vsyscall;
+VDSO32_sigreturn        = __kernel_sigreturn;
+VDSO32_rt_sigreturn     = __kernel_rt_sigreturn;