[RFC] Don't create sframes during build

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

Hi,

gcc in Debian, starting with 15.2.0-2, 14.3.0-6 enables sframe
generation. Unless options like -ffreestanding are passed. Since this
isn't done, there are a few warnings during compile
| crypto/chacha.o: warning: objtool: .sframe+0x30: data relocation to !ENDBR: chacha_stream_xor+0x0
| crypto/chacha.o: warning: objtool: .sframe+0x94: data relocation to !ENDBR: crypto_xchacha_crypt+0x0

followed by warnings at the end

|   AR      vmlinux.a
|   LD      vmlinux.o
| vmlinux.o: warning: objtool: .sframe+0x15c: data relocation to !ENDBR: repair_env_string+0x0
| vmlinux.o: warning: objtool: .sframe+0x1c0: data relocation to !ENDBR: run_init_process+0x0
| vmlinux.o: warning: objtool: .sframe+0x1d4: data relocation to !ENDBR: try_to_run_init_process+0x0
| vmlinux.o: warning: objtool: .sframe+0x1e8: data relocation to !ENDBR: rcu_read_unlock+0x0
…
| vmlinux.o: warning: objtool: .sframe+0x12765c: data relocation to !ENDBR: get_eff_addr_reg+0x0
| vmlinux.o: warning: objtool: .sframe+0x1276ac: data relocation to !ENDBR: get_seg_base_limit+0x0
|   OBJCOPY modules.builtin.modinfo

followed by a boom
|   LD      .tmp_vmlinux1
| ld: error: unplaced orphan section `.sframe' from `vmlinux.o'

We could drop the sframe during the final link but this does not get rid
of the objtool warnings so we would have to ignore them. But we don't
need it. So what about the following:

diff --git a/Makefile b/Makefile
--- a/Makefile
+++ b/Makefile
@@ -886,6 +886,8 @@ ifdef CONFIG_CC_IS_GCC
 KBUILD_CFLAGS	+= $(call cc-option,--param=allow-store-data-races=0)
 KBUILD_CFLAGS	+= $(call cc-option,-fno-allow-store-data-races)
 endif
+# No sframe generation for kernel if enabled by default
+KBUILD_CFLAGS	+= $(call cc-option,-Xassembler --gsframe=no)
 
 ifdef CONFIG_READABLE_ASM
 # Disable optimizations that make assembler listings hard to read.
-- 
2.51.0