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

On 12/6/2021 2:29 PM, Arnd Bergmann wrote:

On Mon, Dec 6, 2021 at 9:28 AM Sai Prakash Ranjan
[off-list ref] wrote:

quoted

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.

quoted

+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

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