[PATCH v3 02/19] x86/asm: Avoid emitting DWARF CFI for non-VDSO

From: Josh Poimboeuf
Date: Mon Oct 28 2024 - 17:48:42 EST


VDSO is the only part of the "kernel" using DWARF CFI directives. For
the kernel proper, ensure the CFI_* macros don't do anything.

These macros aren't yet being used outside of VDSO, so there's no
functional change.

Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
arch/x86/include/asm/dwarf2.h | 37 +++++++++++++++++++++++++++--------
1 file changed, 29 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/dwarf2.h b/arch/x86/include/asm/dwarf2.h
index 430fca13bb56..b1aa3fcd5bca 100644
--- a/arch/x86/include/asm/dwarf2.h
+++ b/arch/x86/include/asm/dwarf2.h
@@ -6,6 +6,15 @@
#warning "asm/dwarf2.h should be only included in pure assembly files"
#endif

+#ifdef BUILD_VDSO
+
+ /*
+ * For the vDSO, emit both runtime unwind information and debug
+ * symbols for the .dbg file.
+ */
+
+ .cfi_sections .eh_frame, .debug_frame
+
#define CFI_STARTPROC .cfi_startproc
#define CFI_ENDPROC .cfi_endproc
#define CFI_DEF_CFA .cfi_def_cfa
@@ -21,7 +30,8 @@
#define CFI_UNDEFINED .cfi_undefined
#define CFI_ESCAPE .cfi_escape

-#ifndef BUILD_VDSO
+#else /* !BUILD_VDSO */
+
/*
* Emit CFI data in .debug_frame sections, not .eh_frame sections.
* The latter we currently just discard since we don't do DWARF
@@ -29,13 +39,24 @@
* useful to anyone. Note we should not use this directive if we
* ever decide to enable DWARF unwinding at runtime.
*/
+
.cfi_sections .debug_frame
-#else
- /*
- * For the vDSO, emit both runtime unwind information and debug
- * symbols for the .dbg file.
- */
- .cfi_sections .eh_frame, .debug_frame
-#endif
+
+#define CFI_STARTPROC
+#define CFI_ENDPROC
+#define CFI_DEF_CFA
+#define CFI_DEF_CFA_REGISTER
+#define CFI_DEF_CFA_OFFSET
+#define CFI_ADJUST_CFA_OFFSET
+#define CFI_OFFSET
+#define CFI_REL_OFFSET
+#define CFI_REGISTER
+#define CFI_RESTORE
+#define CFI_REMEMBER_STATE
+#define CFI_RESTORE_STATE
+#define CFI_UNDEFINED
+#define CFI_ESCAPE
+
+#endif /* !BUILD_VDSO */

#endif /* _ASM_X86_DWARF2_H */
--
2.47.0