Re: [PATCH] powerpc/lib: fix book3s/32 boot failure due to code patching

[Christophe Leroy]

Oops, forgot to tell it's for 4.9. Resending with proper subject.

Le 15/05/2019 Ã 08:39, Christophe Leroy a ÃcritÂ:
> [Backport of upstream commit b45ba4a51cde29b2939365ef0c07ad34c8321789]
>
> On powerpc32, patch_instruction() is called by apply_feature_fixups()
> which is called from early_init()
>
> There is the following note in front of early_init():
>   * Note that the kernel may be running at an address which is different
>   * from the address that it was linked at, so we must use RELOC/PTRRELOC
>   * to access static data (including strings).  -- paulus
>
> Therefore init_mem_is_free must be accessed with PTRRELOC()
>
> Fixes: 1c38a84d4586 ("powerpc: Avoid code patching freed init sections")
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=203597
> Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
>
> ---
> Can't apply the upstream commit as such due to several other unrelated stuff
> like for instance STRICT_KERNEL_RWX which are missing.
> So instead, using same approach as for commit 252eb55816a6f69ef9464cad303cdb3326cdc61d
> ---
>   arch/powerpc/lib/code-patching.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
> index 14535ad4cdd1..c312955977ce 100644
> --- a/arch/powerpc/lib/code-patching.c
> +++ b/arch/powerpc/lib/code-patching.c
> @@ -23,7 +23,7 @@ int patch_instruction(unsigned int *addr, unsigned int instr)
>   	int err;
>   
>   	/* Make sure we aren't patching a freed init section */
> -	if (init_mem_is_free && init_section_contains(addr, 4)) {
> +	if (*PTRRELOC(&init_mem_is_free) && init_section_contains(addr, 4)) {
>   		pr_debug("Skipping init section patching addr: 0x%px\n", addr);
>   		return 0;
>   	}