[PATCH v3 2/8] arm64, unwind: build kernel with sframe V3 info

Dylan Hatch
2026-04-06T18:50:20Z

Build with -Wa,--gsframe-3 flags to generate a .sframe section. This
will be used for in-kernel reliable stacktrace in cases where the frame
pointer alone is insufficient.

Currently, the sframe format only supports arm64, x86_64 and s390x
architectures.

Signed-off-by: Weinan Liu <wnliu@google.com>
Signed-off-by: Dylan Hatch <dylanbhatch@google.com>
Reviewed-by: Prasanna Kumar T S M <ptsm@linux.microsoft.com>
---
MAINTAINERS | 1 +
Makefile | 8 ++++++++
arch/Kconfig | 7 +++++++
arch/arm64/Kconfig | 1 +
arch/arm64/Kconfig.debug | 13 +++++++++++++
arch/arm64/include/asm/unwind_sframe.h | 12 ++++++++++++
arch/arm64/kernel/vdso/Makefile | 2 +-
include/asm-generic/vmlinux.lds.h | 15 +++++++++++++++
8 files changed, 58 insertions(+), 1 deletion(-)
create mode 100644 arch/arm64/include/asm/unwind_sframe.h

diff --git a/MAINTAINERS b/MAINTAINERS
index cfc7dec88da4..a7d75f9cb5f4 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -27561,6 +27561,7 @@ STACK UNWINDING
M: Josh Poimboeuf <jpoimboe@kernel.org>
M: Steven Rostedt <rostedt@goodmis.org>
S: Maintained
+F: arch/*/include/asm/unwind_sframe.h
F: include/linux/sframe.h
F: include/linux/unwind*.h
F: kernel/unwind/
diff --git a/Makefile b/Makefile
index 2b15f0b4a0cb..e03d09ea6a23 100644
--- a/Makefile
+++ b/Makefile
@@ -1110,6 +1110,14 @@ endif
# Ensure compilers do not transform certain loops into calls to wcslen()
KBUILD_CFLAGS += -fno-builtin-wcslen

+# build with sframe table
+ifdef CONFIG_SFRAME_UNWINDER
+CC_FLAGS_SFRAME := -Wa,--gsframe-3
+KBUILD_CFLAGS += $(CC_FLAGS_SFRAME)
+KBUILD_AFLAGS += $(CC_FLAGS_SFRAME)
+export CC_FLAGS_SFRAME
+endif
+
# change __FILE__ to the relative path to the source directory
ifdef building_out_of_srctree
KBUILD_CPPFLAGS += -fmacro-prefix-map=$(srcroot)/=
diff --git a/arch/Kconfig b/arch/Kconfig
index 6695c222c728..c87e489fa978 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -520,6 +520,13 @@ config SFRAME_VALIDATION

If unsure, say N.

+config ARCH_SUPPORTS_SFRAME_UNWINDER
+ bool
+ help
+ An architecture can select this if it enables the sframe (Simple
+ Frame) unwinder for unwinding kernel stack traces. It uses unwind
+ table that is directly generatedby toolchain based on DWARF CFI information.
+
config HAVE_PERF_REGS
bool
help
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 38dba5f7e4d2..189bc199ad2e 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -112,6 +112,7 @@ config ARM64
select ARCH_SUPPORTS_SCHED_SMT
select ARCH_SUPPORTS_SCHED_CLUSTER
select ARCH_SUPPORTS_SCHED_MC
+ select ARCH_SUPPORTS_SFRAME_UNWINDER
select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
select ARCH_WANT_COMPAT_IPC_PARSE_VERSION if COMPAT
select ARCH_WANT_DEFAULT_BPF_JIT
diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
index 265c4461031f..df291d64812f 100644
--- a/arch/arm64/Kconfig.debug
+++ b/arch/arm64/Kconfig.debug
@@ -20,4 +20,17 @@ config ARM64_RELOC_TEST
depends on m
tristate "Relocation testing module"

+config SFRAME_UNWINDER
+ bool "Sframe unwinder"
+ depends on AS_SFRAME3
+ depends on 64BIT
+ depends on ARCH_SUPPORTS_SFRAME_UNWINDER
+ select SFRAME_LOOKUP
+ help
+ This option enables the sframe (Simple Frame) unwinder for unwinding
+ kernel stack traces. It uses unwind table that is directly generated
+ by toolchain based on DWARF CFI information. In, practice this can
+ provide more reliable stacktrace results than unwinding with frame
+ pointers alone.
+
source "drivers/hwtracing/coresight/Kconfig"
diff --git a/arch/arm64/include/asm/unwind_sframe.h b/arch/arm64/include/asm/unwind_sframe.h
new file mode 100644
index 000000000000..1682c079e387
--- /dev/null
+++ b/arch/arm64/include/asm/unwind_sframe.h
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_ARM64_UNWIND_SFRAME_H
+#define _ASM_ARM64_UNWIND_SFRAME_H
+
+#ifdef CONFIG_ARM64
+
+#define SFRAME_REG_SP 31
+#define SFRAME_REG_FP 29
+
+#endif
+
+#endif /* _ASM_ARM64_UNWIND_SFRAME_H */
diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
index 7dec05dd33b7..c60ef921956f 100644
--- a/arch/arm64/kernel/vdso/Makefile
+++ b/arch/arm64/kernel/vdso/Makefile
@@ -38,7 +38,7 @@ ccflags-y += -DDISABLE_BRANCH_PROFILING -DBUILD_VDSO
CC_FLAGS_REMOVE_VDSO := $(CC_FLAGS_FTRACE) -Os $(CC_FLAGS_SCS) \
$(RANDSTRUCT_CFLAGS) $(KSTACK_ERASE_CFLAGS) \
$(GCC_PLUGINS_CFLAGS) \
- $(CC_FLAGS_LTO) $(CC_FLAGS_CFI) \
+ $(CC_FLAGS_LTO) $(CC_FLAGS_CFI) $(CC_FLAGS_SFRAME) \
-Wmissing-prototypes -Wmissing-declarations

CC_FLAGS_ADD_VDSO := -O2 -mcmodel=tiny -fasynchronous-unwind-tables
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 1e1580febe4b..0a5c2f6cc4c0 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -491,6 +491,8 @@
*(.rodata1) \
} \
\
+ SFRAME \
+ \
/* PCI quirks */ \
.pci_fixup : AT(ADDR(.pci_fixup) - LOAD_OFFSET) { \
BOUNDED_SECTION_PRE_LABEL(.pci_fixup_early, _pci_fixups_early, __start, __end) \
@@ -911,6 +913,19 @@
#define TRACEDATA
#endif

+#ifdef CONFIG_SFRAME_UNWINDER
+#define SFRAME \
+ /* sframe */ \
+ .sframe : AT(ADDR(.sframe) - LOAD_OFFSET) { \
+ __start_sframe_header = .; \
+ KEEP(*(.sframe)) \
+ KEEP(*(.init.sframe)) \
+ __stop_sframe_header = .; \
+ }
+#else
+#define SFRAME
+#endif
+
#ifdef CONFIG_PRINTK_INDEX
#define PRINTK_INDEX \
.printk_index : AT(ADDR(.printk_index) - LOAD_OFFSET) { \
--
2.53.0.1213.gd9a14994de-goog