Patch "x86/retpoline: Simplify vmexit_fill_RSB()" has been added to the 4.15-stable tree

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

x86/retpoline: Simplify vmexit_fill_RSB()

to the 4.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
x86retpoline_Simplify_vmexit_fill_RSB().patch
and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Subject: x86/retpoline: Simplify vmexit_fill_RSB()
From: Borislav Petkov [email protected]
Date: Sat Jan 27 16:24:33 2018 +0000

From: Borislav Petkov [email protected]

commit 1dde7415e99933bb7293d6b2843752cbdb43ec11

Simplify it to call an asm-function instead of pasting 41 insn bytes at every call site. Also, add alignment to the macro as suggested here:

https://support.google.com/faqs/answer/7625886

[dwmw2: Clean up comments, let it clobber %ebx and just tell the compiler]

---
 arch/x86/entry/entry_32.S             |    3 -
 arch/x86/entry/entry_64.S             |    3 -
 arch/x86/include/asm/asm-prototypes.h |    3 +
 arch/x86/include/asm/nospec-branch.h  |   70 +++-------------------------------
 arch/x86/lib/Makefile                 |    1 
 arch/x86/lib/retpoline.S              |   56 +++++++++++++++++++++++++++
 6 files changed, 71 insertions(+), 65 deletions(-)

@@ -252,7 +252,8 @@ ENTRY(__switch_to_asm)
 	 * exist, overwrite the RSB with entries which capture
 	 * speculative execution to prevent attack.
 	 */
-	FILL_RETURN_BUFFER %ebx, RSB_CLEAR_LOOPS, X86_FEATURE_RSB_CTXSW
+	/* Clobbers %ebx */
+	FILL_RETURN_BUFFER RSB_CLEAR_LOOPS, X86_FEATURE_RSB_CTXSW
 #endif
 
 	/* restore callee-saved registers */

@@ -499,7 +499,8 @@ ENTRY(__switch_to_asm)
 	 * exist, overwrite the RSB with entries which capture
 	 * speculative execution to prevent attack.
 	 */
-	FILL_RETURN_BUFFER %r12, RSB_CLEAR_LOOPS, X86_FEATURE_RSB_CTXSW
+	/* Clobbers %rbx */
+	FILL_RETURN_BUFFER RSB_CLEAR_LOOPS, X86_FEATURE_RSB_CTXSW
 #endif
 
 	/* restore callee-saved registers */

@@ -38,4 +38,7 @@ INDIRECT_THUNK(dx)
 INDIRECT_THUNK(si)
 INDIRECT_THUNK(di)
 INDIRECT_THUNK(bp)
+asmlinkage void __fill_rsb(void);
+asmlinkage void __clear_rsb(void);
+
 #endif /* CONFIG_RETPOLINE */

@@ -27,6 +27,7 @@ lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) +=
 lib-$(CONFIG_INSTRUCTION_DECODER) += insn.o inat.o insn-eval.o
 lib-$(CONFIG_RANDOMIZE_BASE) += kaslr.o
 lib-$(CONFIG_RETPOLINE) += retpoline.o
+OBJECT_FILES_NON_STANDARD_retpoline.o :=y
 
 obj-y += msr.o msr-reg.o msr-reg-export.o hweight.o
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.15/x86pti_Do_not_enable_PTI_on_CPUs_which_are_not_vulnerable_to_Meltdown.patch queue-4.15/x86cpufeatures_Add_Intel_feature_bits_for_Speculation_Control.patch queue-4.15/x86alternative_Print_unadorned_pointers.patch queue-4.15/x86cpufeatures_Add_CPUID_7_EDX_CPUID_leaf.patch queue-4.15/x86bugs_Drop_one_mitigation_from_dmesg.patch queue-4.15/x86speculation_Simplify_indirect_branch_prediction_barrier().patch queue-4.15/x86nospec_Fix_header_guards_names.patch queue-4.15/x86retpoline_Simplify_vmexit_fill_RSB().patch queue-4.15/x86cpufeatures_Clean_up_Spectre_v2_related_CPUID_flags.patch