It was decided years ago that .cfi_* annotations aren't maintainable in
the kernel.  They were replaced by objtool unwind hints.  For the kernel
proper, ensure the CFI_* macros don't do anything.

On the other hand the VDSO library *does* use them, so user space can
unwind through it.

Make sure these macros only work for VDSO.  They aren't actually being
used outside of VDSO anyway, so there's no functional change.

Signed-off-by: Josh Poimboeuf <jpoim...@kernel.org>
---
 arch/x86/include/asm/dwarf2.h | 51 ++++++++++++++++++++++++-----------
 1 file changed, 35 insertions(+), 16 deletions(-)

diff --git a/arch/x86/include/asm/dwarf2.h b/arch/x86/include/asm/dwarf2.h
index 430fca13bb56..b195b3c8677e 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
@@ -21,21 +30,31 @@
 #define CFI_UNDEFINED          .cfi_undefined
 #define CFI_ESCAPE             .cfi_escape
 
-#ifndef 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
-        * unwinding at runtime.  So only the offline DWARF information is
-        * 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
+#else /* !BUILD_VDSO */
+
+/*
+ * On x86, these macros aren't used outside VDSO.  As well they shouldn't be:
+ * they're fragile and very difficult to maintain.
+ */
+
+.macro nocfi args:vararg
+.endm
+
+#define CFI_STARTPROC          nocfi
+#define CFI_ENDPROC            nocfi
+#define CFI_DEF_CFA            nocfi
+#define CFI_DEF_CFA_REGISTER   nocfi
+#define CFI_DEF_CFA_OFFSET     nocfi
+#define CFI_ADJUST_CFA_OFFSET  nocfi
+#define CFI_OFFSET             nocfi
+#define CFI_REL_OFFSET         nocfi
+#define CFI_REGISTER           nocfi
+#define CFI_RESTORE            nocfi
+#define CFI_REMEMBER_STATE     nocfi
+#define CFI_RESTORE_STATE      nocfi
+#define CFI_UNDEFINED          nocfi
+#define CFI_ESCAPE             nocfi
+
+#endif /* !BUILD_VDSO */
 
 #endif /* _ASM_X86_DWARF2_H */
-- 
2.48.1


Reply via email to