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tracing: Add "traceoff" flag to boot time tracing instances

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Add a "flags" delimiter (^) to the "trace_instance" kernel command line
parameter, and add the "traceoff" flag. The format is:

   trace_instance=<name>[^<flag1>[^<flag2>]][@<memory>][,<events>]

The code allows for more than one flag to be added, but currently only
"traceoff" is done so.

The motivation for this change came from debugging with the persistent
ring buffer and having trace_printk() writing to it. The trace_printk
calls are always enabled, and the boot after the crash was having the
unwanted trace_printks from the current boot inject into the ring buffer
with the trace_printks of the crash kernel, making the output very
confusing.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Vincent Donnefort <vdonnefort@google.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vineeth Pillai <vineeth@bitbyteword.org>
Cc: Beau Belgrave <beaub@linux.microsoft.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Ross Zwisler <zwisler@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Alexander Aring <aahringo@redhat.com>
Cc: "Luis Claudio R. Goncalves" <lgoncalv@redhat.com>
Cc: Tomas Glozar <tglozar@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Jonathan Corbet" <corbet@lwn.net>
Link: https://lore.kernel.org/20240823014019.053229958@goodmis.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt
2024-08-22 21:39:03 -04:00
committed by Steven Rostedt (Google)
parent eb2dcde9f9
commit b6fc31b687
2 changed files with 47 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files
kernel/trace/trace.c
+30 -1
View File
@@ -10468,10 +10468,36 @@ __init static void enable_instances(void)
phys_addr_t start = 0;
phys_addr_t size = 0;
unsigned long addr = 0;
bool traceoff = false;
char *flag_delim;
char *addr_delim;
tok = strsep(&curr_str, ",");
name = strsep(&tok, "@");
flag_delim = strchr(tok, '^');
addr_delim = strchr(tok, '@');
if (addr_delim)
*addr_delim++ = '\0';
if (flag_delim)
*flag_delim++ = '\0';
name = tok;
if (flag_delim) {
char *flag;
while ((flag = strsep(&flag_delim, "^"))) {
if (strcmp(flag, "traceoff") == 0)
traceoff = true;
else
pr_info("Tracing: Invalid instance flag '%s' for %s\n",
flag, name);
}
}
tok = addr_delim;
if (tok && isdigit(*tok)) {
start = memparse(tok, &tok);
if (!start) {
@@ -10519,6 +10545,9 @@ __init static void enable_instances(void)
continue;
}
if (traceoff)
tracer_tracing_off(tr);
/* Only allow non mapped buffers to be deleted */
if (!start)
trace_array_put(tr);