[PATCH 1/3] powerpc/code-patching: work around code patching verification in patching tests

[Christophe Leroy]

Le 26/11/2021 à 04:22, Nicholas Piggin a écrit :
> Code patching tests patch the stack and (non-module) vmalloc space now,
> which falls afoul of the new address check.
> 
> The stack patching can easily be fixed, but the vmalloc patching is more
> difficult. For now, add an ugly workaround to skip the check while the
> test code is running.

This really looks hacky.

To skip the test, you can call do_patch_instruction() instead of calling 
patch_instruction().

> 
> Fixes: 8b8a8f0ab3f55 ("powerpc/code-patching: Improve verification of patchability")
> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
> ---
>   arch/powerpc/lib/code-patching.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
> index 5e2fe133639e..57e160963ab7 100644
> --- a/arch/powerpc/lib/code-patching.c
> +++ b/arch/powerpc/lib/code-patching.c
> @@ -187,10 +187,12 @@ static int do_patch_instruction(u32 *addr, struct ppc_inst instr)
>   
>   #endif /* CONFIG_STRICT_KERNEL_RWX */
>   
> +static bool skip_addr_verif = false;
> +
>   int patch_instruction(u32 *addr, struct ppc_inst instr)
>   {
>   	/* Make sure we aren't patching a freed init section */
> -	if (!kernel_text_address((unsigned long)addr))
> +	if (!skip_addr_verif && !kernel_text_address((unsigned long)addr))
>   		return 0;
>   
>   	return do_patch_instruction(addr, instr);
> @@ -738,11 +740,13 @@ static int __init test_code_patching(void)
>   {
>   	printk(KERN_DEBUG "Running code patching self-tests ...\n");
>   
> +	skip_addr_verif = true;
>   	test_branch_iform();
>   	test_branch_bform();
>   	test_create_function_call();
>   	test_translate_branch();
>   	test_prefixed_patching();
> +	skip_addr_verif = false;
>   
>   	return 0;
>   }
>