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

[Christophe Leroy (CS GROUP)]

Le 09/02/2026 à 14:25, Xie Yuanbin a écrit :
> 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;							\
> 	})
> ```

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