[PATCH 1/3] powerpc: Properly return error code from do_patch_instruction()

[Christophe Leroy]

Le 23/04/2020 à 17:09, Naveen N. Rao a écrit :
> With STRICT_KERNEL_RWX, we are currently ignoring return value from
> __patch_instruction() in do_patch_instruction(), resulting in the error
> not being propagated back. Fix the same.

Good patch.

Be aware that there is ongoing work which tend to wanting to replace 
error reporting by BUG_ON() . See 
https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=166003

> 
> Fixes: 37bc3e5fd764f ("powerpc/lib/code-patching: Use alternate map for patch_instruction()")
> Signed-off-by: Naveen N. Rao <naveen.n.rao at linux.vnet.ibm.com>
> ---
>   arch/powerpc/lib/code-patching.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
> index 3345f039a876..5c713a6c0bd8 100644
> --- a/arch/powerpc/lib/code-patching.c
> +++ b/arch/powerpc/lib/code-patching.c
> @@ -138,7 +138,7 @@ static inline int unmap_patch_area(unsigned long addr)
>   
>   static int do_patch_instruction(unsigned int *addr, unsigned int instr)
>   {
> -	int err;
> +	int err, rc = 0;
>   	unsigned int *patch_addr = NULL;
>   	unsigned long flags;
>   	unsigned long text_poke_addr;
> @@ -163,7 +163,7 @@ static int do_patch_instruction(unsigned int *addr, unsigned int instr)
>   	patch_addr = (unsigned int *)(text_poke_addr) +
>   			((kaddr & ~PAGE_MASK) / sizeof(unsigned int));
>   
> -	__patch_instruction(addr, instr, patch_addr);
> +	rc = __patch_instruction(addr, instr, patch_addr);
>   
>   	err = unmap_patch_area(text_poke_addr);
>   	if (err)
> @@ -172,7 +172,7 @@ static int do_patch_instruction(unsigned int *addr, unsigned int instr)
>   out:
>   	local_irq_restore(flags);
>   
> -	return err;
> +	return rc ? rc : err;

That's not really consistent. __patch_instruction() and 
unmap_patch_area() return a valid minus errno, while in case of 
map_patch_area() failure, err has value -1

>   }
>   #else /* !CONFIG_STRICT_KERNEL_RWX */
>   
> 

Christophe