Commit b2620fac authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Borislav Petkov
Browse files

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: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
parent d7caac99

arch/x86/entry/entry_32.S

+0 −2
Original line number Diff line number Diff line
@@ -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

arch/x86/entry/entry_64.S

+0 −2
Original line number Diff line number Diff line
@@ -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

arch/x86/include/asm/nospec-branch.h

+0 −2
Original line number Diff line number Diff line
@@ -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



/*