x86/speculation: Fix RSB filling with CONFIG_RETPOLINE=n

commit b2620facef4889fefcbf2e87284f34dcd4189bce 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 c19974a493784e1cc40f75452a96179f1010625a..dbcea4281c309728d44f987679ead982081d23cd 100644 (file)
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -245,7 +245,6 @@ 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
@@ -254,7 +253,6 @@ 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 fee102f5a7d508fa51b1f5e95c9bb0fb6822c553..637a23d404e9521491141c48b97695e8523364f4 100644 (file)
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -357,7 +357,6 @@ ENTRY(__switch_to_asm)
        movq    %rbx, PER_CPU_VAR(irq_stack_union)+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
@@ -366,7 +365,6 @@ 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 */
        popfq

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 0d474525caecd6262e91b8f8be6322ad789439a6..da81adabac94f755116de9268b9d3d38f4f04615 100644 (file)
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -145,11 +145,9 @@
   * 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__ */