This is a note to let you know that I've just added the patch titled

retpoline: Introduce start/end markers of indirect thunk

to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: retpoline-introduce-start-end-markers-of-indirect-thunk.patch and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From 736e80a4213e9bbce40a7c050337047128b472ac Mon Sep 17 00:00:00 2001

From: Masami Hiramatsu mhiramat@kernel.org Date: Fri, 19 Jan 2018 01:14:21 +0900 Subject: retpoline: Introduce start/end markers of indirect thunk

From: Masami Hiramatsu mhiramat@kernel.org

commit 736e80a4213e9bbce40a7c050337047128b472ac upstream.

Introduce start/end markers of __x86_indirect_thunk_* functions. To make it easy, consolidate .text.__x86.indirect_thunk.* sections to one .text.__x86.indirect_thunk section and put it in the end of kernel text section and adds __indirect_thunk_start/end so that other subsystem (e.g. kprobes) can identify it.

Signed-off-by: Masami Hiramatsu mhiramat@kernel.org Signed-off-by: Thomas Gleixner tglx@linutronix.de Acked-by: David Woodhouse dwmw@amazon.co.uk Cc: Andi Kleen ak@linux.intel.com Cc: Peter Zijlstra peterz@infradead.org Cc: Ananth N Mavinakayanahalli ananth@linux.vnet.ibm.com Cc: Arjan van de Ven arjan@linux.intel.com Cc: Greg Kroah-Hartman gregkh@linux-foundation.org Link: https://lkml.kernel.org/r/151629206178.10241.6828804696410044771.stgit@devbo... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- arch/x86/include/asm/nospec-branch.h | 3 +++ arch/x86/kernel/vmlinux.lds.S | 7 +++++++ arch/x86/lib/retpoline.S | 2 +- 3 files changed, 11 insertions(+), 1 deletion(-)

--- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -171,6 +171,9 @@ enum spectre_v2_mitigation { SPECTRE_V2_IBRS, };

+extern char __indirect_thunk_start[]; +extern char __indirect_thunk_end[]; + /* * On VMEXIT we must ensure that no RSB predictions learned in the guest * can be followed in the host, by overwriting the RSB completely. Both --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -104,6 +104,13 @@ SECTIONS IRQENTRY_TEXT *(.fixup) *(.gnu.warning) + +#ifdef CONFIG_RETPOLINE + __indirect_thunk_start = .; + *(.text.__x86.indirect_thunk) + __indirect_thunk_end = .; +#endif + /* End of text section */ _etext = .; } :text = 0x9090 --- a/arch/x86/lib/retpoline.S +++ b/arch/x86/lib/retpoline.S @@ -9,7 +9,7 @@ #include <asm/nospec-branch.h>

.macro THUNK reg - .section .text.__x86.indirect_thunk.\reg + .section .text.__x86.indirect_thunk

ENTRY(__x86_indirect_thunk_\reg) CFI_STARTPROC

Patches currently in stable-queue which might be from mhiramat@kernel.org are

queue-4.4/kprobes-x86-disable-optimizing-on-the-function-jumps-to-indirect-thunk.patch queue-4.4/kprobes-x86-blacklist-indirect-thunk-functions-for-kprobes.patch queue-4.4/retpoline-introduce-start-end-markers-of-indirect-thunk.patch