Subject: Re: linux-next: changed messages in qemu boot

From: Michael Ellerman <[email-masked]>
Date: Tue, 24 May 2022 12:22:45 +1000

"Naveen N. Rao" <[email-masked]> writes:
> Stephen Rothwell wrote:
>> Hi all,
>> 
>> Today's linux-next bboot of the powerpc pseries_le_defconfig build
>> produced these different kernel messages (diff from yesterday's tree):
>> 
>> - ftrace: allocating 33658 entries in 13 pages
>> - ftrace: allocated 13 pages with 3 groups
>> + ftrace-powerpc: Address of ftrace_regs_caller out of range of kernel_toc.
>
> Thanks for the report. I think that is due to:
> https://patchwork.ozlabs.org/project/linuxppc-dev/patch/bb6626e8[email-masked]/

Yep, I bisected it there.

I should really read my email before bisecting :)

> The below diff fixes it for me:
>
> diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
> index 46c002a8388804..7418da705d43ac 100644
> --- a/arch/powerpc/kernel/trace/ftrace.c
> +++ b/arch/powerpc/kernel/trace/ftrace.c
> @@ -746,7 +746,7 @@ int __init ftrace_dyn_arch_init(void)
>  
>         reladdr = addr - kernel_toc_addr();
>  
> -       if (reladdr >= SZ_2G || reladdr < -SZ_2G) {
> +       if (reladdr >= SZ_2G || reladdr < -_UL(SZ_2G)) {
>                 pr_err("Address of %ps out of range of kernel_toc.\n",
>                                 (void *)addr);
>                 return -1;

I did:

	if (reladdr >= SZ_2G || reladdr < -(long)SZ_2G) {

Which more closely matches what the old code did, and I think is more
obvious? ie. we don't want to negate the unsigned value, we want a
signed value, and then the negative of that.

cheers