[3.11.y.z extended stable] Patch "arm64: vdso: prevent ld from aligning PT_LOAD segments to 64k" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    arm64: vdso: prevent ld from aligning PT_LOAD segments to 64k

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 2d71fd5edef2dd11c0effc4f245cf63f3229ee21 Mon Sep 17 00:00:00 2001
From: Will Deacon <will.deacon at arm.com>
Date: Tue, 4 Feb 2014 14:41:26 +0000
Subject: arm64: vdso: prevent ld from aligning PT_LOAD segments to 64k

commit 40507403485fcb56b83d6ddfc954e9b08305054c upstream.

Whilst the text segment for our VDSO is marked as PT_LOAD in the ELF
headers, it is mapped by the kernel and not actually subject to
demand-paging. ld doesn't realise this, and emits a p_align field of 64k
(the maximum supported page size), which conflicts with the load address
picked by the kernel on 4k systems, which will be 4k aligned. This
causes GDB to fail with "Failed to read a valid object file image from
memory" when attempting to load the VDSO.

This patch passes the -n option to ld, which prevents it from aligning
PT_LOAD segments to the maximum page size.

Reported-by: Kyle McMartin <kyle at redhat.com>
Acked-by: Kyle McMartin <kyle at redhat.com>
Signed-off-by: Will Deacon <will.deacon at arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas at arm.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 arch/arm64/kernel/vdso/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
index d8064af..6d20b7d 100644
--- a/arch/arm64/kernel/vdso/Makefile
+++ b/arch/arm64/kernel/vdso/Makefile
@@ -48,7 +48,7 @@ $(obj-vdso): %.o: %.S

 # Actual build commands
 quiet_cmd_vdsold = VDSOL $@
-      cmd_vdsold = $(CC) $(c_flags) -Wl,-T $^ -o $@
+      cmd_vdsold = $(CC) $(c_flags) -Wl,-n -Wl,-T $^ -o $@
 quiet_cmd_vdsoas = VDSOA $@
       cmd_vdsoas = $(CC) $(a_flags) -c -o $@ $<

--
1.8.3.2