x86/speculation: Fix RSB filling with CONFIG_RETPOLINE=n

If a kernel is built with CONFIG_RETPOLINE=n, but the user still wants
to mitigate Spectre v2 using IBRS or eIBRS, the RSB filling will be
silently disabled.

There's nothing retpoline-specific about RSB buffer filling.  Remove the
CONFIG_RETPOLINE guards around it.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 887420844066454f696f60dd78aa69a520580699..e309e7156038935ab92cd025616c5c765e3a5214 100644 (file)
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -698,7 +698,6 @@ SYM_CODE_START(__switch_to_asm)
        movl    %ebx, PER_CPU_VAR(__stack_chk_guard)
 #endif
 
-#ifdef CONFIG_RETPOLINE
        /*
         * When switching from a shallower to a deeper call stack
         * the RSB may either underflow or use entries populated
@@ -707,7 +706,6 @@ SYM_CODE_START(__switch_to_asm)
         * speculative execution to prevent attack.
         */
        FILL_RETURN_BUFFER %ebx, RSB_CLEAR_LOOPS, X86_FEATURE_RSB_CTXSW
-#endif
 
        /* Restore flags or the incoming task to restore AC state. */
        popfl

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 65e3b8b7cbe5e9f0cb37c94716836270d3d5f4cf..a4ba162e52c34351c9c7e34aa2d77f1f3ecdb384 100644 (file)
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -255,7 +255,6 @@ SYM_FUNC_START(__switch_to_asm)
        movq    %rbx, PER_CPU_VAR(fixed_percpu_data) + stack_canary_offset
 #endif
 
-#ifdef CONFIG_RETPOLINE
        /*
         * When switching from a shallower to a deeper call stack
         * the RSB may either underflow or use entries populated
@@ -264,7 +263,6 @@ SYM_FUNC_START(__switch_to_asm)
         * speculative execution to prevent attack.
         */
        FILL_RETURN_BUFFER %r12, RSB_CLEAR_LOOPS, X86_FEATURE_RSB_CTXSW
-#endif
 
        /* restore callee-saved registers */
        popq    %r15

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index bba42bd78edfb0b98ab2f875a5c1fdd32d8fa772..08b03c12e6c25314b6b619c5e697bfbb03b0f8d3 100644 (file)
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -122,11 +122,9 @@
   * monstrosity above, manually.
   */
 .macro FILL_RETURN_BUFFER reg:req nr:req ftr:req
-#ifdef CONFIG_RETPOLINE
        ALTERNATIVE "jmp .Lskip_rsb_\@", "", \ftr
        __FILL_RETURN_BUFFER(\reg,\nr,%_ASM_SP)
 .Lskip_rsb_\@:
-#endif
 .endm
 
 /*