[PATCH 5/7] x86/speculation: Annotate intra-function calls

[Alexandre Chartre <alexandre.chartre@oracle.com>]

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, 16 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 5c24a7b35166..a2885f801e13 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -77,13 +77,27 @@
 	.popsection
 .endm
 
+/*
+ * 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.
+ */
+.macro INTRA_FUNCTION_CALL dst:req
+	.Lannotate_\@:
+	.pushsection .discard.intra_function_call
+	_ASM_PTR .Lannotate_\@
+	.popsection
+	call \dst
+.endm
+
 /*
  * These are the bare retpoline primitives for indirect jmp and call.
  * Do not use these directly; they only exist to make the ALTERNATIVE
  * invocation below less ugly.
  */
 .macro RETPOLINE_JMP reg:req
-	call	.Ldo_rop_\@
+	INTRA_FUNCTION_CALL .Ldo_rop_\@
 .Lspec_trap_\@:
 	pause
 	lfence
@@ -102,7 +116,7 @@
 .Ldo_retpoline_jmp_\@:
 	RETPOLINE_JMP \reg
 .Ldo_call_\@:
-	call	.Ldo_retpoline_jmp_\@
+	INTRA_FUNCTION_CALL .Ldo_retpoline_jmp_\@
 .endm
 
 /*
-- 
2.18.2