[PATCH V3 9/9] x86/speculation: Annotate intra-function calls

Alexandre Chartre
2020-04-14T10:41:19Z

Some speculative execution mitigations (like retpoline) use intra-
function calls. Provide a macro to annotate such intra-function calls
so they can be properly handled by objtool, and use this macro to
annotate intra-function calls.

Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
---
arch/x86/include/asm/nospec-branch.h | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 20594ea99c21..89ae2f9cc873 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -3,6 +3,7 @@
#ifndef _ASM_X86_NOSPEC_BRANCH_H_
#define _ASM_X86_NOSPEC_BRANCH_H_

+#include <linux/frame.h>
#include <linux/static_key.h>

#include <asm/alternative.h>
@@ -20,6 +21,15 @@
#define ANNOTATE_NOSPEC_ALTERNATIVE \
ANNOTATE_IGNORE_ALTERNATIVE

+/*
+ * Intra-function call instruction. This should be used as a substitute
+ * for the call instruction when doing an intra-function call. It is
+ * similar to the call instruction but it tells objtool that this is
+ * an intra-function call.
+ */
+#define INTRA_FUNCTION_CALL \
+ ANNOTATE_INTRA_FUNCTION_CALL call
+
/*
* Fill the CPU return stack buffer.
*
@@ -47,13 +57,13 @@
#define __FILL_RETURN_BUFFER_BEGIN(reg, nr, sp) \
mov $(nr/2), reg; \
771: \
- call 772f; \
+ INTRA_FUNCTION_CALL 772f; \
773: /* speculation trap */ \
pause; \
lfence; \
jmp 773b; \
772: \
- call 774f; \
+ INTRA_FUNCTION_CALL 774f; \
775: /* speculation trap */ \
pause; \
lfence; \
@@ -90,7 +100,7 @@
* invocation below less ugly.
*/
.macro RETPOLINE_JMP reg:req
- call .Ldo_rop_\@
+ INTRA_FUNCTION_CALL .Ldo_rop_\@
.Lspec_trap_\@:
pause
lfence
@@ -110,7 +120,7 @@
.Ldo_retpoline_jmp_\@:
RETPOLINE_JMP \reg
.Ldo_call_\@:
- call .Ldo_retpoline_jmp_\@
+ INTRA_FUNCTION_CALL .Ldo_retpoline_jmp_\@
.endm

/*
--
2.18.2