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

[Arnd Bergmann]

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.

> +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.

       Arnd