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

[Michael Ellerman]

Michael Ellerman <mpe at ellerman.id.au> writes:

> "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.

Actually it should probably do __ftrace_enabled_save() etc. on 32-bit,
like the existing code does.

cheers