6.17-stable review patch. If anyone has any objections, please let me know.
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From: Tiezhu Yang yangtiezhu@loongson.cn
[ Upstream commit abb2a5572264b425e6dd9c213b735a82ab0ca68a ]
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: baad7830ee9a ("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 Signed-off-by: Sasha Levin sashal@kernel.org --- arch/loongarch/Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile index ae419e32f22e2..f2a585b4a9375 100644 --- a/arch/loongarch/Makefile +++ b/arch/loongarch/Makefile @@ -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