Most LoongArch processors are vulnerable to Spectre-V1 Proof-of-Concept
(PoC). And the generic mechanism, __user pointer sanitization, can be
used as a mitigation. This means to use array_index_nospec() to prevent
out of boundry access in syscall and other critical paths.

Implement the arch-specific cpu_show_spectre_v1() to show CPU Spectre-V1
vulnerabilites correctly.

Cc: stable@vger.kernel.org
Link: https://cc-sw.com/chinese-loongarch-architecture-evaluation-part-3-of-3/
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
---
 arch/loongarch/kernel/cpu-probe.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/loongarch/kernel/cpu-probe.c b/arch/loongarch/kernel/cpu-probe.c
index 8654a1eff834..c8947c798195 100644
--- a/arch/loongarch/kernel/cpu-probe.c
+++ b/arch/loongarch/kernel/cpu-probe.c
@@ -402,3 +402,9 @@ void cpu_probe(void)
 
 	cpu_report();
 }
+
+ssize_t cpu_show_spectre_v1(struct device *dev,
+			    struct device_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "Mitigation: __user pointer sanitization\n");
+}
-- 
2.52.0

Hi Huacai,

kernel test robot noticed the following build warnings:

[auto build test WARNING on linus/master]
[also build test WARNING on v7.0-rc7 next-20260410]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Huacai-Chen/LoongArch-Show-CPU-vulnerabilites-correctly/20260411-011556
base:   linus/master
patch link:    https://lore.kernel.org/r/20260409122348.2438400-1-chenhuacai%40loongson.cn
patch subject: [PATCH] LoongArch: Show CPU vulnerabilites correctly
config: loongarch-randconfig-001-20260411 (https://download.01.org/0day-ci/archive/20260411/202604110810.YFUm5KE1-lkp@intel.com/config)
compiler: loongarch64-linux-gcc (GCC) 14.3.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260411/202604110810.YFUm5KE1-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202604110810.YFUm5KE1-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> arch/loongarch/kernel/cpu-probe.c:407:36: warning: 'struct device_attribute' declared inside parameter list will not be visible outside of this definition or declaration
     407 |                             struct device_attribute *attr, char *buf)
         |                                    ^~~~~~~~~~~~~~~~
>> arch/loongarch/kernel/cpu-probe.c:406:9: warning: no previous prototype for 'cpu_show_spectre_v1' [-Wmissing-prototypes]
     406 | ssize_t cpu_show_spectre_v1(struct device *dev,
         |         ^~~~~~~~~~~~~~~~~~~


vim +407 arch/loongarch/kernel/cpu-probe.c

   405	
 > 406	ssize_t cpu_show_spectre_v1(struct device *dev,
 > 407				    struct device_attribute *attr, char *buf)

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Hi Huacai,

kernel test robot noticed the following build warnings:

[auto build test WARNING on linus/master]
[also build test WARNING on v7.0-rc7 next-20260410]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Huacai-Chen/LoongArch-Show-CPU-vulnerabilites-correctly/20260411-011556
base:   linus/master
patch link:    https://lore.kernel.org/r/20260409122348.2438400-1-chenhuacai%40loongson.cn
patch subject: [PATCH] LoongArch: Show CPU vulnerabilites correctly
config: loongarch-allnoconfig (https://download.01.org/0day-ci/archive/20260411/202604110604.ckBnAnTg-lkp@intel.com/config)
compiler: clang version 23.0.0git (https://github.com/llvm/llvm-project ae825cb8cea7f3ac8e5e4096f22713845cf5e501)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260411/202604110604.ckBnAnTg-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202604110604.ckBnAnTg-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> arch/loongarch/kernel/cpu-probe.c:407:15: warning: declaration of 'struct device_attribute' will not be visible outside of this function [-Wvisibility]
     407 |                             struct device_attribute *attr, char *buf)
         |                                    ^
>> arch/loongarch/kernel/cpu-probe.c:406:9: warning: no previous prototype for function 'cpu_show_spectre_v1' [-Wmissing-prototypes]
     406 | ssize_t cpu_show_spectre_v1(struct device *dev,
         |         ^
   arch/loongarch/kernel/cpu-probe.c:406:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
     406 | ssize_t cpu_show_spectre_v1(struct device *dev,
         | ^
         | static 
   2 warnings generated.


vim +407 arch/loongarch/kernel/cpu-probe.c

   405	
 > 406	ssize_t cpu_show_spectre_v1(struct device *dev,
 > 407				    struct device_attribute *attr, char *buf)

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki