[PATCH] i386: Relocate VDSO ELF headers to match mapped location with COMPAT_VDSO

Some versions of libc can't deal with a VDSO which doesn't have its
ELF headers matching its mapped address.  COMPAT_VDSO maps the VDSO at
a specific system-wide fixed address.  Previously this was all done at
build time, on the grounds that the fixed VDSO address is always at
the top of the address space.  However, a hypervisor may reserve some
of that address space, pushing the fixmap address down.

This patch does the adjustment dynamically at runtime, depending on
the runtime location of the VDSO fixmap.

[ Patch has been through several hands: Jan Beulich wrote the orignal
  version; Zach reworked it, and Jeremy converted it to relocate phdrs
  as well as sections. ]

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Zachary Amsden <zach@vmware.com>
Cc: "Jan Beulich" <JBeulich@novell.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Roland McGrath <roland@redhat.com>

1 files changed, 0 insertions, 4 deletions

diff --git a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S
index c61c6b67e856..e901952dff37 100644
--- a/arch/i386/kernel/entry.S
+++ b/arch/i386/kernel/entry.S
@@ -305,16 +305,12 @@ sysenter_past_esp:
         pushl $(__USER_CS)
         CFI_ADJUST_CFA_OFFSET 4
         /*CFI_REL_OFFSET cs, 0*/
-#ifndef CONFIG_COMPAT_VDSO
         /*
          * Push current_thread_info()->sysenter_return to the stack.
          * A tiny bit of offset fixup is necessary - 4*4 means the 4 words
          * pushed above; +8 corresponds to copy_thread's esp0 setting.
          */
         pushl (TI_sysenter_return-THREAD_SIZE+8+4*4)(%esp)
-#else
-        pushl $SYSENTER_RETURN
-#endif
         CFI_ADJUST_CFA_OFFSET 4
         CFI_REL_OFFSET eip, 0