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: Ben Hutchings <ben@decadent.org.uk>
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 4a4896ba4db3e7ba7ac844a1ded4a76610ccd5a1..8fcd6a42b3a18f0e5f83bc022cbd6d22a6049bec 100644 (file)
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -782,7 +782,6 @@ SYM_CODE_START(__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
@@ -791,7 +790,6 @@ 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 61e65e3ebd538aa47821e3a3f1fb5f42ad01cd32..559c82b83475753fd2e0c5ce23e209e47ceab443 100644 (file)
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -249,7 +249,6 @@ 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
@@ -258,7 +257,6 @@ 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 07c5642ab6d767a3090147f6df0273deb6be423d..b44e6d1bd820ee4b15f8194a1eb8791eb4b5bbcd 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
 
 /*