Re: [PATCHv5 3/4] tracing: Add register read/write tracing support

[Sai Prakash Ranjan]

On 12/6/2021 2:29 PM, Arnd Bergmann wrote:
> On Mon, Dec 6, 2021 at 9:28 AM Sai Prakash Ranjan
> <quic_saipraka@xxxxxxxxxxx> wrote:
> > diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
> > index 420ff4bc67fd..9f55bcc51de1 100644
> > --- a/kernel/trace/Kconfig
> > +++ b/kernel/trace/Kconfig
> > @@ -95,6 +95,13 @@ config RING_BUFFER_ALLOW_SWAP
> >           Allow the use of ring_buffer_swap_cpu.
> >           Adds a very slight overhead to tracing when enabled.
> >
> > +config TRACE_MMIO_ACCESS
> > +       bool "Register read/write tracing"
> > +       depends on TRACING
> > +       help
> > +         Create tracepoints for MMIO read/write operations. These trace events
> > +         can be used for logging all MMIO read/write operations.
> I think this needs a 'depends on ARCH_HAVE_TRACE_MMIO_ACCESS'
> or similar.

Sure, will add it.

> > +void log_read_mmio(u8 width, const volatile void __iomem *addr)
> > +{
> > +       trace_rwmmio_read(CALLER_ADDR0, CALLER_ADDR1, width, addr);
> > +}
> Here, it may be better to pass the caller address as an argument, I think
> CALLER_ADDR1 is not always reliable, though it's possible that it is
> in the configurations when this file gets enabled.

Do you mean that we use __builtin_return_address(0,1) directly here or 
that I pass
__func__ as the argument to log_read/write_mmio or is there some other 
way to
pass the caller address?

Thanks,
Sai