From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	Tiezhu Yang <yangtiezhu@loongson.cn>,
	Huacai Chen <chenhuacai@loongson.cn>
Subject: [PATCH 6.12 312/460] LoongArch: Give more information if kmem access failed
Date: Mon, 23 Mar 2026 14:45:08 +0100
Message-ID: <20260323134534.168977637@linuxfoundation.org>
In-Reply-To: <20260323134526.647552166@linuxfoundation.org>
References: <20260323134526.647552166@linuxfoundation.org>
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6.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Tiezhu Yang <yangtiezhu@loongson.cn>

commit a47f0754bdd01f971c9715acdbdd3a07515c8f83 upstream.

If memory access such as copy_{from, to}_kernel_nofault() failed, its
users do not know what happened, so it is very useful to print the
exception code for such cases. Furthermore, it is better to print the
caller function to know where is the entry.

Here are the low level call chains:

  copy_from_kernel_nofault()
    copy_from_kernel_nofault_loop()
      __get_kernel_nofault()

  copy_to_kernel_nofault()
    copy_to_kernel_nofault_loop()
      __put_kernel_nofault()

Cc: stable@vger.kernel.org
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/loongarch/include/asm/uaccess.h |   14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

--- a/arch/loongarch/include/asm/uaccess.h
+++ b/arch/loongarch/include/asm/uaccess.h
@@ -196,8 +196,13 @@ do {									\
 									\
 	__get_kernel_common(*((type *)(dst)), sizeof(type),		\
 			    (__force type *)(src));			\
-	if (unlikely(__gu_err))						\
+	if (unlikely(__gu_err))	{					\
+		pr_info("%s: memory access failed, ecode 0x%x\n",	\
+			__func__, read_csr_excode());			\
+		pr_info("%s: the caller is %pS\n",			\
+			__func__, __builtin_return_address(0));		\
 		goto err_label;						\
+	}								\
 } while (0)
 
 #define __put_kernel_nofault(dst, src, type, err_label)			\
@@ -207,8 +212,13 @@ do {									\
 									\
 	__pu_val = *(__force type *)(src);				\
 	__put_kernel_common(((type *)(dst)), sizeof(type));		\
-	if (unlikely(__pu_err))						\
+	if (unlikely(__pu_err))	{					\
+		pr_info("%s: memory access failed, ecode 0x%x\n",	\
+			__func__, read_csr_excode());			\
+		pr_info("%s: the caller is %pS\n",			\
+			__func__, __builtin_return_address(0));		\
 		goto err_label;						\
+	}								\
 } while (0)
 
 extern unsigned long __copy_user(void *to, const void *from, __kernel_size_t n);