"Naveen N. Rao" <naveen.n....@linux.vnet.ibm.com> writes: > We can't take a trap in most parts of real mode code. Instead of adding > the 'notrace' annotation to all C functions that can be invoked from > real mode, detect that we are in real mode on ftrace entry and return > back. > > Signed-off-by: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com> > --- > This RFC only handles -mprofile-kernel to demonstrate the approach being > considered. We will need to handle other ftrace entry if we decide to > continue down this path.
Paul and I were talking about having a paca flag for this, ie. paca->safe_to_ftrace (or whatever). I'm not sure if you've talked to him and decided this is a better approach. I guess I'm 50/50 on which is better, they both have pluses and minuses. cheers > diff --git a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S > b/arch/powerpc/kernel/trace/ftrace_64_mprofile.S > index 3f3e81852422..ecc0e8e38ead 100644 > --- a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S > +++ b/arch/powerpc/kernel/trace/ftrace_64_mprofile.S > @@ -56,6 +56,21 @@ _GLOBAL(ftrace_caller) > > /* Load special regs for save below */ > mfmsr r8 > + > + /* Only proceed if we are not in real mode and can take interrupts */ > + andi. r9, r8, MSR_IR|MSR_DR|MSR_RI > + cmpdi r9, MSR_IR|MSR_DR|MSR_RI > + beq 1f > + mflr r8 > + mtctr r8 > + REST_GPR(9, r1) > + REST_GPR(8, r1) > + addi r1, r1, SWITCH_FRAME_SIZE > + ld r0, LRSAVE(r1) > + mtlr r0 > + bctr > + > +1: > mfctr r9 > mfxer r10 > mfcr r11 > -- > 2.16.1