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

Prasanna Kumar T S M
2025-01-30T09:45:06Z

On 28-01-2025 03:03, Weinan Liu wrote:
> 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) { \

Looks good to me.

Reviewed-by: Prasanna Kumar T S M <ptsm@linux.microsoft.com>.