x86/speculation: Fix RSB filling with CONFIG_RETPOLINE=n

commit 8e17604f4274d62c69fb5419d49bd59d03fffcc0 upstream.

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>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index bde3e0f85425fc98b50236df01adf838da41c9e0..2d837fb54c31b004b02e2cdb9f929430a4c51244 100644 (file)
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -750,7 +750,6 @@ ENTRY(__switch_to_asm)
        movl    %ebx, PER_CPU_VAR(stack_canary)+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
@@ -759,7 +758,6 @@ ENTRY(__switch_to_asm)
         * speculative execution to prevent attack.
         */
        FILL_RETURN_BUFFER %ebx, RSB_CLEAR_LOOPS, X86_FEATURE_RSB_CTXSW
-#endif
 
        /* restore callee-saved registers */
        popfl

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 4a45808a27c2e0a1b345c1474fc3e439456a3b12..c82136030d58fe1d98b7ba12a1a4523fdd4af577 100644 (file)
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -305,7 +305,6 @@ ENTRY(__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
@@ -314,7 +313,6 @@ ENTRY(__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 460360cfab5abda0fea3a0a5b509c907895ca658..b7201f24796c83db7e5fa3222cde7adfd621f285 100644 (file)
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -155,11 +155,9 @@
   * 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
 
 #else /* __ASSEMBLY__ */