tracing: Support to dump instance traces by ftrace_dump_on_oops

Currently ftrace only dumps the global trace buffer on an OOPs. For
debugging a production usecase, instance trace will be helpful to
check specific problems since global trace buffer may be used for
other purposes.

This patch extend the ftrace_dump_on_oops parameter to dump a specific
or multiple trace instances:

  - ftrace_dump_on_oops=0: as before -- don't dump
  - ftrace_dump_on_oops[=1]: as before -- dump the global trace buffer
  on all CPUs
  - ftrace_dump_on_oops=2 or =orig_cpu: as before -- dump the global
  trace buffer on CPU that triggered the oops
  - ftrace_dump_on_oops=<instance_name>: new behavior -- dump the
  tracing instance matching <instance_name>
  - ftrace_dump_on_oops[=2/orig_cpu],<instance1_name>[=2/orig_cpu],
  <instrance2_name>[=2/orig_cpu]: new behavior -- dump the global trace
  buffer and multiple instance buffer on all CPUs, or only dump on CPU
  that triggered the oops if =2 or =orig_cpu is given

Also, the sysctl node can handle the input accordingly.

Link: https://lore.kernel.org/linux-trace-kernel/20240223083126.1817731-1-quic_hyiwei@quicinc.com

Cc: Ross Zwisler <zwisler@google.com>
Cc: <mhiramat@kernel.org>
Cc: <mark.rutland@arm.com>
Cc: <mcgrof@kernel.org>
Cc: <keescook@chromium.org>
Cc: <j.granados@samsung.com>
Cc: <mathieu.desnoyers@efficios.com>
Cc: <corbet@lwn.net>
Signed-off-by: Huang Yiwei <quic_hyiwei@quicinc.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

1 files changed, 21 insertions, 5 deletions

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 479ff1737c2f..fa871d53641c 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1572,12 +1572,28 @@
 			The above will cause the "foo" tracing instance to trigger
 			a snapshot at the end of boot up.
 
-	ftrace_dump_on_oops[=orig_cpu]
+	ftrace_dump_on_oops[=2(orig_cpu) | =<instance>][,<instance> |
+			  ,<instance>=2(orig_cpu)]
 			[FTRACE] will dump the trace buffers on oops.
-			If no parameter is passed, ftrace will dump
-			buffers of all CPUs, but if you pass orig_cpu, it will
-			dump only the buffer of the CPU that triggered the
-			oops.
+			If no parameter is passed, ftrace will dump global
+			buffers of all CPUs, if you pass 2 or orig_cpu, it
+			will dump only the buffer of the CPU that triggered
+			the oops, or the specific instance will be dumped if
+			its name is passed. Multiple instance dump is also
+			supported, and instances are separated by commas. Each
+			instance supports only dump on CPU that triggered the
+			oops by passing 2 or orig_cpu to it.
+
+			ftrace_dump_on_oops=foo=orig_cpu
+
+			The above will dump only the buffer of "foo" instance
+			on CPU that triggered the oops.
+
+			ftrace_dump_on_oops,foo,bar=orig_cpu
+
+			The above will dump global buffer on all CPUs, the
+			buffer of "foo" instance on all CPUs and the buffer
+			of "bar" instance on CPU that triggered the oops.
 
 	ftrace_filter=[function-list]
 			[FTRACE] Limit the functions traced by the function