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

Weinan Liu
2025-01-27T21:33:24Z

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