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LoongArch: Add cflag -fno-isolate-erroneous-paths-dereference

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Currently, when compiling with GCC, there is no "break 7" instruction
for zero division due to using the option -mno-check-zero-division, but
the compiler still generates "break 0" instruction for zero division.

Here is a simple example:

  $ cat test.c
  int div(int a)
  {
	  return a / 0;
  }
  $ gcc -O2 -S test.c -o test.s

GCC generates "break 0" on LoongArch and "ud2" on x86, objtool decodes
"ud2" as INSN_BUG for x86, so decode "break 0" as INSN_BUG can fix the
objtool warnings for LoongArch, but this is not the intention.

When decoding "break 0" as INSN_TRAP in the previous commit, the aim is
to handle "break 0" as a trap. The generated "break 0" for zero division
by GCC is not proper, it should generate a break instruction with proper
bug type, so add the GCC option -fno-isolate-erroneous-paths-dereference
to avoid generating the unexpected "break 0" instruction for now.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/r/202509200413.7uihAxJ5-lkp@intel.com/
Fixes: baad7830ee ("objtool/LoongArch: Mark types based on break immediate code")
Suggested-by: WANG Rui <wangrui@loongson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
This commit is contained in:
Tiezhu Yang
2025-10-02 22:38:57 +08:00
committed by Huacai Chen
parent 2b5f663820
commit abb2a55722
1 changed files with 1 additions and 1 deletions
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2
arch/loongarch/Makefile
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@@ -129,7 +129,7 @@ KBUILD_RUSTFLAGS_KERNEL += -Crelocation-model=pie
LDFLAGS_vmlinux += -static -pie --no-dynamic-linker -z notext $(call ld-option, --apply-dynamic-relocs)
endif
cflags-y += $(call cc-option, -mno-check-zero-division)
cflags-y += $(call cc-option, -mno-check-zero-division -fno-isolate-erroneous-paths-dereference)
ifndef CONFIG_KASAN
cflags-y += -fno-builtin-memcpy -fno-builtin-memmove -fno-builtin-memset