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

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Message-ID: <f2dcdcf95240149bfd21e118209bf3b94efad857.1730150953.git.jpoimboe@kernel.org>
Date: Mon, 28 Oct 2024 14:47:29 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: x86@...nel.org
Cc: Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	linux-kernel@...r.kernel.org,
	Indu Bhagat <indu.bhagat@...cle.com>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	linux-perf-users@...r.kernel.org,
	Mark Brown <broonie@...nel.org>,
	linux-toolchains@...r.kernel.org,
	Jordan Rome <jordalgo@...a.com>,
	Sam James <sam@...too.org>,
	linux-trace-kernel@...r.kerne.org,
	Andrii Nakryiko <andrii.nakryiko@...il.com>,
	Jens Remus <jremus@...ux.ibm.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Florian Weimer <fweimer@...hat.com>,
	Andy Lutomirski <luto@...nel.org>
Subject: [PATCH v3 02/19] x86/asm: Avoid emitting DWARF CFI for non-VDSO

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@...nel.org>
---
 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