linux-kernel - Re: [PATCH 2/2] powerpc/text-patching: Fix possible stringop-overread compilation error

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Message-ID: <20260209132510.84205-1-xieyuanbin1@huawei.com>
Date: Mon, 9 Feb 2026 21:25:01 +0800
From: Xie Yuanbin <xieyuanbin1@...wei.com>
To: <chleroy@...nel.org>, <andriy.shevchenko@...el.com>,
	<maddy@...ux.ibm.com>, <mpe@...erman.id.au>, <npiggin@...il.com>,
	<kees@...nel.org>, <andy@...nel.org>
CC: <linuxppc-dev@...ts.ozlabs.org>, <linux-kernel@...r.kernel.org>,
	<linux-hardening@...r.kernel.org>, <lilinjie8@...wei.com>,
	<liaohua4@...wei.com>, <xieyuanbin1@...wei.com>
Subject: Re: [PATCH 2/2] powerpc/text-patching: Fix possible stringop-overread compilation error

On Fri, 6 Feb 2026 20:53:55 +0100, Christophe Leroy (CS GROUP) wrote:
> Le 06/02/2026 à 19:26, Kees Cook a écrit :
>>
>> Isn't it possible to do this and not need __compiletime_strlen at all?
>>
>> 	n_len = strnlen(name, min(__member_size(name), KSYM_NAME_LEN));
>
> ppc_kallsyms_lookup_name() only has two callers and they call it with a
> built-in string. I think we can do something a lot simpler, something
> like (untested):
>
> 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;
> }
>
> #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
>
> Christophe

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;							\
	})
```