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Thu, 30 Apr 2026 15:29:29 +0800 (CST) Received: from DESKTOP-A37P9LK.huawei.com (10.67.109.17) by kwepemj100009.china.huawei.com (7.202.194.3) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.36; Thu, 30 Apr 2026 15:29:29 +0800 From: Xie Yuanbin To: , , , , , , CC: , , , , , Subject: Re: [PATCH 2/2] powerpc/text-patching: Fix possible stringop-overread compilation error Date: Thu, 30 Apr 2026 15:28:38 +0800 Message-ID: <20260430072913.62348-1-xieyuanbin1@huawei.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <5cfae419-427a-471b-8bbe-645f56442e2c@kernel.org> References: <5cfae419-427a-471b-8bbe-645f56442e2c@kernel.org> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-Originating-IP: [10.67.109.17] X-ClientProxiedBy: kwepems200002.china.huawei.com (7.221.188.68) To kwepemj100009.china.huawei.com (7.202.194.3) Hi, Christophe Leroy! On Mon, 9 Feb 2026 14:41:51 +0100, Christophe Leroy (CS GROUP) wrote: > On 09/02/2026 14:25, Xie Yuanbin wrote: >> When CONFIG_PPC64_ELF_ABI_V1=y, it seems that the try of lookupinp >> the original non-dot symbol is missing. >> >> What about this (Only the compilation test is performed): >> ```c >> static inline unsigned long __ppc_kallsyms_lookup_name(const char *name) >> { >> unsigned long addr = kallsyms_lookup_name(name); >> >> if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && addr) >> addr = ppc_function_entry((void *)addr); >> >> return addr; >> } >> >> #define ppc_kallsyms_lookup_name(x) ({ \ >> unsigned long addr = 0; \ >> if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V1)) \ >> addr = __ppc_kallsyms_lookup_name("." x); \ >> if (!addr) \ >> addr = __ppc_kallsyms_lookup_name(x); \ >> addr; \ >> }) >> ``` > > Good point. > > To avoid duplicating the string I'd suggest: > > static inline unsigned long __ppc_kallsyms_lookup_name(const char *name) > { > unsigned long addr = kallsyms_lookup_name(name); > > if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V1) && !addr) > addr = kallsyms_lookup_name(name + 1); > if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && addr) > addr = ppc_function_entry((void *)addr); > > return addr; > } > > #ifdef CONFIG_PPC64_ELF_ABI_V1 > #define ppc_kallsyms_lookup_name(x) __ppc_kallsyms_lookup_name("." x); > #else > #define ppc_kallsyms_lookup_name(x) __ppc_kallsyms_lookup_name(x) > #endif I would like to submit the modification as a new patch, and include you as Co-developer. Do you agree? Full of the patch: ```patch >From fbf07e5c1a97da7c8572435537f2b92213ede39d Mon Sep 17 00:00:00 2001 From: Xie Yuanbin Date: Thu, 30 Apr 2026 14:15:26 +0800 Subject: [PATCH V2] powerpc/text-patching: simplify the implementation of ppc_kallsyms_lookup_name() ppc_kallsyms_lookup_name() is called only twice in the kernel code, and the parameters are all constant strings. strnlen(name, KSYM_NAME_LEN) is called inside ppc_kallsyms_lookup_name(), when the compiler detects that KSYM_NAME_LEN is larger then the constant strings, the following error will be triggered: ```log CC arch/powerpc/kernel/optprobes.o In file included from ./arch/powerpc/include/asm/kprobes.h:24, from ./include/linux/kprobes.h:31, from arch/powerpc/kernel/optprobes.c:8: In function ‘ppc_kallsyms_lookup_name’, inlined from ‘arch_prepare_optimized_kprobe’ at arch/powerpc/kernel/optprobes.c:209:21: ./arch/powerpc/include/asm/text-patching.h:232:13: error: ‘strnlen’ specified bound 512 exceeds source size 19 [-Werror=stringop-overread] 232 | if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ In function ‘ppc_kallsyms_lookup_name’, inlined from ‘arch_prepare_optimized_kprobe’ at arch/powerpc/kernel/optprobes.c:210:22: ./arch/powerpc/include/asm/text-patching.h:232:13: error: ‘strnlen’ specified bound 512 exceeds source size 13 [-Werror=stringop-overread] 232 | if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ cc1: all warnings being treated as errors ``` The error can be reproduced in the following ways: Use lastest linux-next source, change ppc_kallsyms_lookup_name() to __always_inline, use default ppc64_defconfig, set CONFIG_EXPERT=y, CONFIG_PPC64_BIG_ENDIAN_ELF_ABI_V2=n, CONFIG_CC_OPTIMIZE_FOR_SIZE=y, and use gcc-14 or a later version for compilation. Since ppc_kallsyms_lookup_name() is called only twice in the kernel, and the parameters are all constant strins, simplify the implementation of ppc_kallsyms_lookup_name() and avoid calling strnlen(). Cc: Andy Shevchenko Cc: Kees Cook Co-developed-by: Christophe Leroy (CS GROUP) Signed-off-by: Christophe Leroy (CS GROUP) Signed-off-by: Xie Yuanbin --- v1->v2: https://lore.kernel.org/20260205100517.292858-2-xieyuanbin1@huawei.com - Not use strlen() arch/powerpc/include/asm/text-patching.h | 42 ++++++++---------------- 1 file changed, 17 insertions(+), 33 deletions(-) diff --git a/arch/powerpc/include/asm/text-patching.h b/arch/powerpc/include/asm/text-patching.h index e7f14720f630..2d3f698cb4f1 100644 --- a/arch/powerpc/include/asm/text-patching.h +++ b/arch/powerpc/include/asm/text-patching.h @@ -221,39 +221,23 @@ static inline unsigned long ppc_global_function_entry(void *func) * - For ABIv1, we lookup the dot variant. * - For ABIv2, we return the local entry point. */ -static inline unsigned long ppc_kallsyms_lookup_name(const char *name) -{ - unsigned long addr; -#ifdef CONFIG_PPC64_ELF_ABI_V1 - /* check for dot variant */ - char dot_name[1 + KSYM_NAME_LEN]; - bool dot_appended = false; - - if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN) - return 0; - - if (name[0] != '.') { - dot_name[0] = '.'; - dot_name[1] = '\0'; - strlcat(dot_name, name, sizeof(dot_name)); - dot_appended = true; - } else { - dot_name[0] = '\0'; - strlcat(dot_name, name, sizeof(dot_name)); - } - addr = kallsyms_lookup_name(dot_name); - if (!addr && dot_appended) - /* Let's try the original non-dot symbol lookup */ - addr = kallsyms_lookup_name(name); -#elif defined(CONFIG_PPC64_ELF_ABI_V2) - addr = kallsyms_lookup_name(name); - if (addr) - addr = ppc_function_entry((void *)addr); -#else - addr = kallsyms_lookup_name(name); -#endif - return addr; -} +static inline unsigned long __ppc_kallsyms_lookup_name(const char *name) +{ + unsigned long addr = kallsyms_lookup_name(name); + + if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V1) && !addr) + addr = kallsyms_lookup_name(name + 1); + if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && addr) + addr = ppc_function_entry((void *)addr); + + return addr; +} + +#ifdef CONFIG_PPC64_ELF_ABI_V1 +#define ppc_kallsyms_lookup_name(x) __ppc_kallsyms_lookup_name("." x) +#else +#define ppc_kallsyms_lookup_name(x) __ppc_kallsyms_lookup_name(x) +#endif /* * Some instruction encodings commonly used in dynamic ftracing -- 2.53.0 ```