On 01/15/2018, 01:35 PM, Greg Kroah-Hartman wrote:
4.9-stable review patch. If anyone has any objections, please let me know.
May I ask if somebody has started the 4.4 port yet?
From: David Woodhouse dwmw@amazon.co.uk
commit 76b043848fd22dbf7f8bf3a1452f8c70d557b860 upstream.
Enable the use of -mindirect-branch=thunk-extern in newer GCC, and provide the corresponding thunks. Provide assembler macros for invoking the thunks in the same way that GCC does, from native and inline assembler.
This adds X86_FEATURE_RETPOLINE and sets it by default on all CPUs. In some circumstances, IBRS microcode features may be used instead, and the retpoline can be disabled.
On AMD CPUs if lfence is serialising, the retpoline can be dramatically simplified to a simple "lfence; jmp *\reg". A future patch, after it has been verified that lfence really is serialising in all circumstances, can enable this by setting the X86_FEATURE_RETPOLINE_AMD feature bit in addition to X86_FEATURE_RETPOLINE.
Do not align the retpoline in the altinstr section, because there is no guarantee that it stays aligned when it's copied over the oldinstr during alternative patching.
[ Andi Kleen: Rename the macros, add CONFIG_RETPOLINE option, export thunks] [ tglx: Put actual function CALL/JMP in front of the macros, convert to symbolic labels ] [ dwmw2: Convert back to numeric labels, merge objtool fixes ]
Signed-off-by: David Woodhouse dwmw@amazon.co.uk Signed-off-by: Thomas Gleixner tglx@linutronix.de Acked-by: Arjan van de Ven arjan@linux.intel.com Acked-by: Ingo Molnar mingo@kernel.org Cc: gnomes@lxorguk.ukuu.org.uk Cc: Rik van Riel riel@redhat.com Cc: Andi Kleen ak@linux.intel.com Cc: Josh Poimboeuf jpoimboe@redhat.com Cc: thomas.lendacky@amd.com Cc: Peter Zijlstra peterz@infradead.org Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Jiri Kosina jikos@kernel.org Cc: Andy Lutomirski luto@amacapital.net Cc: Dave Hansen dave.hansen@intel.com Cc: Kees Cook keescook@google.com Cc: Tim Chen tim.c.chen@linux.intel.com Cc: Greg Kroah-Hartman gregkh@linux-foundation.org Cc: Paul Turner pjt@google.com Link: https://lkml.kernel.org/r/1515707194-20531-4-git-send-email-dwmw@amazon.co.u... Signed-off-by: David Woodhouse dwmw@amazon.co.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
thanks,