[PATCH v3 3/6] powerpc/kexec: Disable ftrace before switching to the new kernel

[Michael Ellerman]

"Naveen N. Rao" <naveen.n.rao at linux.vnet.ibm.com> writes:
> If function_graph tracer is enabled during kexec, we see the below
> exception in the simulator:
> 	root@(none):/# kexec -e
> 	kvm: exiting hardware virtualization
> 	kexec_core: Starting new kernel
> 	[   19.262020070,5] OPAL: Switch to big-endian OS
> 	kexec: Starting switchover sequence.
> 	Interrupt to 0xC000000000004380 from 0xC000000000004380
> 	** Execution stopped: Continuous Interrupt, Instruction caused exception,  **
>
> Now that we have a more effective way to disable ftrace, let's use that
> before switching to a new kernel during kexec.
>
> Signed-off-by: Naveen N. Rao <naveen.n.rao at linux.vnet.ibm.com>
> ---
>  arch/powerpc/kernel/machine_kexec.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/arch/powerpc/kernel/machine_kexec.c b/arch/powerpc/kernel/machine_kexec.c
> index 2694d078741d..4a1b24a9dd61 100644
> --- a/arch/powerpc/kernel/machine_kexec.c
> +++ b/arch/powerpc/kernel/machine_kexec.c
> @@ -95,16 +95,14 @@ void arch_crash_save_vmcoreinfo(void)
>   */
>  void machine_kexec(struct kimage *image)
>  {
> -	int save_ftrace_enabled;
> -
> -	save_ftrace_enabled = __ftrace_enabled_save();
> +	get_paca()->ftrace_disabled = 1;

This doesn't compile on 32-bit:

  Failed: powerpc-next/corenet32_smp_defconfig/powerpc-5.3		(http://kisskb.ozlabs.ibm.com/kisskb/buildresult/13314085/log/)
    /kisskb/src/arch/powerpc/kernel/machine_kexec.c:105:12: error: invalid type argument of '->' (have 'int')
    /kisskb/src/arch/powerpc/kernel/machine_kexec.c:98:12: error: invalid type argument of '->' (have 'int')
    /kisskb/src/arch/powerpc/kernel/machine_kexec.c:98:2: error: implicit declaration of function 'get_paca' [-Werror=implicit-function-declaration]


A wrapper is probably best that does nothing on 32-bit.

cheers