diff mbox series

[4.14,20/34] x86/speculation: Fix RSB filling with CONFIG_RETPOLINE=n

Message ID 20221027205512.17684-4-surajjs@amazon.com (mailing list archive)
State New, archived
Headers show
Series Retbleed & PBRSB Mitigations | expand

Commit Message

Jitindar Singh, Suraj Oct. 27, 2022, 8:55 p.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>
---
 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 c19974a49378..dbcea4281c30 100644
--- 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 fee102f5a7d5..637a23d404e9 100644
--- 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 0d474525caec..da81adabac94 100644
--- 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__ */