[PATCH v4 3/5] powerpc/64: Convert patch_instruction() to patch_u32()

[Hari Bathini]

On 15/05/24 8:14 am, Benjamin Gray wrote:
> This use of patch_instruction() is working on 32 bit data, and can fail
> if the data looks like a prefixed instruction and the extra write
> crosses a page boundary. Use patch_u32() to fix the write size.
> 
> Fixes: 8734b41b3efe ("powerpc/module_64: Fix livepatching for RO modules")
> Link: https://lore.kernel.org/all/20230203004649.1f59dbd4@yea/
> Signed-off-by: Benjamin Gray <bgray at linux.ibm.com>

Tested-by: Hari Bathini <hbathini at linux.ibm.com>

> 
> ---
> 
> v2: * Added the fixes tag, it seems appropriate even if the subject does
>        mention a more robust solution being required.
> 
> patch_u64() should be more efficient, but judging from the bug report
> it doesn't seem like the data is doubleword aligned.
> ---
>   arch/powerpc/kernel/module_64.c | 5 ++---
>   1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
> index 7112adc597a8..e9bab599d0c2 100644
> --- a/arch/powerpc/kernel/module_64.c
> +++ b/arch/powerpc/kernel/module_64.c
> @@ -651,12 +651,11 @@ static inline int create_stub(const Elf64_Shdr *sechdrs,
>   	// func_desc_t is 8 bytes if ABIv2, else 16 bytes
>   	desc = func_desc(addr);
>   	for (i = 0; i < sizeof(func_desc_t) / sizeof(u32); i++) {
> -		if (patch_instruction(((u32 *)&entry->funcdata) + i,
> -				      ppc_inst(((u32 *)(&desc))[i])))
> +		if (patch_u32(((u32 *)&entry->funcdata) + i, ((u32 *)&desc)[i]))
>   			return 0;
>   	}
>   
> -	if (patch_instruction(&entry->magic, ppc_inst(STUB_MAGIC)))
> +	if (patch_u32(&entry->magic, STUB_MAGIC))
>   		return 0;
>   
>   	return 1;