linux-stable/arch/loongarch
Tiezhu Yang 8f58c571bf LoongArch: Define symbol 'fault' as a local label in fpu.S
The initial aim is to silence the following objtool warnings:

  arch/loongarch/kernel/fpu.o: warning: objtool: _save_fp_context() falls through to next function fault()
  arch/loongarch/kernel/fpu.o: warning: objtool: _restore_fp_context() falls through to next function fault()
  arch/loongarch/kernel/fpu.o: warning: objtool: _save_lsx_context() falls through to next function fault()
  arch/loongarch/kernel/fpu.o: warning: objtool: _restore_lsx_context() falls through to next function fault()
  arch/loongarch/kernel/fpu.o: warning: objtool: _save_lasx_context() falls through to next function fault()
  arch/loongarch/kernel/fpu.o: warning: objtool: _restore_lasx_context() falls through to next function fault()

Currently, SYM_FUNC_START()/SYM_FUNC_END() defines the symbol 'fault' as
SYM_T_FUNC which is STT_FUNC, the objtool warnings are generated through
the following code:

tools/objtool/include/objtool/check.h:

static inline struct symbol *insn_func(struct instruction *insn)
{
	struct symbol *sym = insn->sym;

	if (sym && sym->type != STT_FUNC)
		sym = NULL;

	return sym;
}

tools/objtool/check.c:

static int validate_branch(struct objtool_file *file, struct symbol *func,
			   struct instruction *insn, struct insn_state state)
{
	...
		if (func && insn_func(insn) && func != insn_func(insn)->pfunc) {
	...
			WARN("%s() falls through to next function %s()",
			     func->name, insn_func(insn)->name);
			return 1;
		}
	...
}

We can see that the fixup can be a local label in the following code:

arch/loongarch/include/asm/asm-extable.h:
	.pushsection	__ex_table, "a";		\
	.balign		4;				\
	.long		((insn) - .);			\
	.long		((fixup) - .);			\
	.short		(type);				\
	.short		(data);				\
	.popsection;

	.macro		_asm_extable, insn, fixup
	__ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_FIXUP, 0)
	.endm

Like arch/loongarch/lib/*.S, just define the symbol 'fault' as a local
label in fpu.S.

Before:

$ readelf -s arch/loongarch/kernel/fpu.o | awk -F: /fault/'{print $2}'
 000000000000053c     8 FUNC    GLOBAL DEFAULT    1 fault

After:

$ readelf -s arch/loongarch/kernel/fpu.o | awk -F: /fault/'{print $2}'
 000000000000053c     0 NOTYPE  LOCAL  DEFAULT    1 .L_fpu_fault

Co-developed-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
2023-09-06 22:53:10 +08:00
..
boot loongarch: efi: enable generic EFI compressed boot 2022-09-20 09:50:31 +02:00
configs arch/*/configs/*defconfig: Replace AUTOFS4_FS by AUTOFS_FS 2023-07-29 14:08:22 -07:00
crypto LoongArch: crypto: Add crc32 and crc32c hw acceleration 2023-05-01 17:19:43 +08:00
include LoongArch: Use static defined zero page rather than allocated 2023-09-06 22:53:10 +08:00
kernel LoongArch: Define symbol 'fault' as a local label in fpu.S 2023-09-06 22:53:10 +08:00
lib LoongArch: Adjust {copy, clear}_user exception handler behavior 2023-09-06 22:53:10 +08:00
mm LoongArch: Use static defined zero page rather than allocated 2023-09-06 22:53:10 +08:00
net LoongArch: BPF: Fix check condition to call lu32id in move_imm() 2023-07-28 10:30:42 +08:00
pci LoongArch: Add FDT booting support from efi system table 2022-12-14 08:41:53 +08:00
power LoongArch: Export some arch-specific pm interfaces 2023-06-29 20:58:44 +08:00
vdso LoongArch: Add support to clone a time namespace 2023-06-29 20:58:43 +08:00
Kbuild LoongArch: Add BPF JIT support 2022-10-12 16:36:20 +08:00
Kconfig LoongArch: Remove redundant "source drivers/firmware/Kconfig" 2023-08-25 23:40:26 +08:00
Kconfig.debug LoongArch: Add prologue unwinder support 2022-08-12 13:10:11 +08:00
Makefile LoongArch: Replace -ffreestanding with finer-grained -fno-builtin's 2023-08-25 23:40:26 +08:00