diff mbox series

[4.19,20/34] x86/speculation: Fix RSB filling with CONFIG_RETPOLINE=n

Message ID 20221117091952.1940850-21-suleiman@google.com (mailing list archive)
State New, archived
Headers show
Series Intel RETBleed mitigations for 4.19. | expand

Commit Message

Suleiman Souhlal Nov. 17, 2022, 9:19 a.m. UTC 
From: Josh Poimboeuf <jpoimboe@kernel.org>

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>
Signed-off-by: Suleiman Souhlal <suleiman@google.com>
---
 arch/x86/entry/entry_32.S            | 2 --
 arch/x86/entry/entry_64.S            | 2 --
 arch/x86/include/asm/nospec-branch.h | 2 --
 3 files changed, 6 deletions(-)
diff mbox series

Patch

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 37d9016d4768..78b308f2f2ea 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -643,7 +643,6 @@  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
@@ -652,7 +651,6 @@  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 55b61b34c462..3f418aedef8d 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -367,7 +367,6 @@  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
@@ -376,7 +375,6 @@  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 0f4cddf621b4..ca6e421a3467 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -159,11 +159,9 @@ 
   * 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__ */