[PATCH 1/8] unwind: build kernel with sframe info

[Weinan Liu <wnliu@google.com>]

Use the -Wa,--gsframe flags to build the code, so GAS will generate
a new .sframe section for the stack trace information.
Currently, the sframe format only supports arm64 and x86_64
architectures. Add this configuration on arm64 to enable sframe
unwinder in the future.

Signed-off-by: Weinan Liu <wnliu@google.com>
---
 Makefile                          |  6 ++++++
 arch/Kconfig                      |  8 ++++++++
 arch/arm64/Kconfig.debug          | 10 ++++++++++
 include/asm-generic/vmlinux.lds.h | 12 ++++++++++++
 4 files changed, 36 insertions(+)

diff --git a/Makefile b/Makefile
index b9464c88ac72..35200c39b98d 100644
--- a/Makefile
+++ b/Makefile
@@ -1064,6 +1064,12 @@ ifdef CONFIG_CC_IS_GCC
 KBUILD_CFLAGS   += -fconserve-stack
 endif
 
+# build with sframe table
+ifdef CONFIG_SFRAME_UNWIND_TABLE
+KBUILD_CFLAGS	+= -Wa,--gsframe
+KBUILD_AFLAGS	+= -Wa,--gsframe
+endif
+
 # change __FILE__ to the relative path to the source directory
 ifdef building_out_of_srctree
 KBUILD_CPPFLAGS += $(call cc-option,-fmacro-prefix-map=$(srcroot)/=)
diff --git a/arch/Kconfig b/arch/Kconfig
index 6682b2a53e34..ae70f7dbe326 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1736,4 +1736,12 @@ config ARCH_WANTS_PRE_LINK_VMLINUX
 	  An architecture can select this if it provides arch/<arch>/tools/Makefile
 	  with .arch.vmlinux.o target to be linked into vmlinux.
 
+config AS_HAS_SFRAME_SUPPORT
+	# Detect availability of the AS option -Wa,--gsframe for generating
+	# sframe unwind table.
+	def_bool $(cc-option,-Wa$(comma)--gsframe)
+
+config SFRAME_UNWIND_TABLE
+	bool
+
 endmenu
diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
index 265c4461031f..ed619fcb18b3 100644
--- a/arch/arm64/Kconfig.debug
+++ b/arch/arm64/Kconfig.debug
@@ -20,4 +20,14 @@ config ARM64_RELOC_TEST
 	depends on m
 	tristate "Relocation testing module"
 
+config SFRAME_UNWINDER
+	bool "Sframe unwinder"
+	depends on AS_HAS_SFRAME_SUPPORT
+	depends on 64BIT
+	select SFRAME_UNWIND_TABLE
+	help
+	  This option enables the sframe (Simple Frame) unwinder for unwinding
+	  kernel stack traces. It uses unwind table that is direclty generated
+	  by toolchain based on DWARF CFI information
+
 source "drivers/hwtracing/coresight/Kconfig"
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 54504013c749..6a437bd084c7 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -469,6 +469,8 @@ defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG)
 		*(.rodata1)						\
 	}								\
 									\
+	SFRAME								\
+									\
 	/* PCI quirks */						\
 	.pci_fixup        : AT(ADDR(.pci_fixup) - LOAD_OFFSET) {	\
 		BOUNDED_SECTION_PRE_LABEL(.pci_fixup_early,  _pci_fixups_early,  __start, __end) \
@@ -886,6 +888,16 @@ defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG)
 #define TRACEDATA
 #endif
 
+#ifdef CONFIG_SFRAME_UNWIND_TABLE
+#define SFRAME							\
+	/* sframe */						\
+	.sframe        : AT(ADDR(.sframe) - LOAD_OFFSET) {	\
+		BOUNDED_SECTION_BY(.sframe, _sframe_header)	\
+	}
+#else
+#define SFRAME
+#endif
+
 #ifdef CONFIG_PRINTK_INDEX
 #define PRINTK_INDEX							\
 	.printk_index : AT(ADDR(.printk_index) - LOAD_OFFSET) {		\
-- 
2.48.1.262.g85cc9f2d1e-goog