Re: [PATCH 4/5] powerpc/lib: Add LKDTM accessor for patching addr

[Christophe Leroy <christophe.leroy@csgroup.eu>]

Le 03/06/2020 à 07:19, Christopher M. Riedl a écrit :
> When live patching a STRICT_RWX kernel, a mapping is installed at a
> "patching address" with temporary write permissions. Provide a
> LKDTM-only accessor function for this address in preparation for a LKDTM
> test which attempts to "hijack" this mapping by writing to it from
> another CPU.
> 
> Signed-off-by: Christopher M. Riedl <cmr@informatik.wtf>
> ---
>   arch/powerpc/lib/code-patching.c | 7 +++++++
>   1 file changed, 7 insertions(+)
> 
> diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
> index df0765845204..c23453049116 100644
> --- a/arch/powerpc/lib/code-patching.c
> +++ b/arch/powerpc/lib/code-patching.c
> @@ -52,6 +52,13 @@ int raw_patch_instruction(struct ppc_inst *addr, struct ppc_inst instr)
>   static struct mm_struct *patching_mm __ro_after_init;
>   static unsigned long patching_addr __ro_after_init;
>   
> +#ifdef CONFIG_LKDTM
> +unsigned long read_cpu_patching_addr(unsigned int cpu)

If this fonction is not static, it means it is intended to be used from 
some other C file, so it should be declared in a .h too.

Christophe

> +{
> +	return patching_addr;
> +}
> +#endif
> +
>   void __init poking_init(void)
>   {
>   	spinlock_t *ptl; /* for protecting pte table */
>