tracing: Implement creating an instance based on a given memory region

Allow for creating a new instance by passing in an address and size to map
the ring buffer for the instance to.

This will allow features like a pstore memory mapped region to be used for
an tracing instance ring buffer that can be retrieved from one boot to the
next.

Link: https://lkml.kernel.org/r/20240612232025.692086240@goodmis.org
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: Daniel Bristot de Oliveira <bristot@redhat.com>
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: Youssef Esmat <youssefesmat@google.com>
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>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 578a49ff5c32ef91f024837e423f831942babeaa..ff2b504fbe0021df24de19f87087ea5a65e89286 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4921,6 +4921,11 @@ static int tracing_open(struct inode *inode, struct file *file)
 static bool
 trace_ok_for_array(struct tracer *t, struct trace_array *tr)
 {
+#ifdef CONFIG_TRACER_SNAPSHOT
+       /* arrays with mapped buffer range do not have snapshots */
+       if (tr->range_addr_start && t->use_max_tr)
+               return false;
+#endif
        return (tr->flags & TRACE_ARRAY_FL_GLOBAL) || t->allow_instances;
 }
 
@@ -8664,11 +8669,13 @@ tracing_init_tracefs_percpu(struct trace_array *tr, long cpu)
                                tr, cpu, &tracing_entries_fops);
 
 #ifdef CONFIG_TRACER_SNAPSHOT
-       trace_create_cpu_file("snapshot", TRACE_MODE_WRITE, d_cpu,
-                               tr, cpu, &snapshot_fops);
+       if (!tr->range_addr_start) {
+               trace_create_cpu_file("snapshot", TRACE_MODE_WRITE, d_cpu,
+                                     tr, cpu, &snapshot_fops);
 
-       trace_create_cpu_file("snapshot_raw", TRACE_MODE_READ, d_cpu,
-                               tr, cpu, &snapshot_raw_fops);
+               trace_create_cpu_file("snapshot_raw", TRACE_MODE_READ, d_cpu,
+                                     tr, cpu, &snapshot_raw_fops);
+       }
 #endif
 }
 
@@ -9205,7 +9212,18 @@ allocate_trace_buffer(struct trace_array *tr, struct array_buffer *buf, int size
 
        buf->tr = tr;
 
-       buf->buffer = ring_buffer_alloc(size, rb_flags);
+       if (tr->range_addr_start && tr->range_addr_size) {
+               buf->buffer = ring_buffer_alloc_range(size, rb_flags, 0,
+                                                     tr->range_addr_start,
+                                                     tr->range_addr_size);
+               /*
+                * This is basically the same as a mapped buffer,
+                * with the same restrictions.
+                */
+               tr->mapped++;
+       } else {
+               buf->buffer = ring_buffer_alloc(size, rb_flags);
+       }
        if (!buf->buffer)
                return -ENOMEM;
 
@@ -9242,6 +9260,10 @@ static int allocate_trace_buffers(struct trace_array *tr, int size)
                return ret;
 
 #ifdef CONFIG_TRACER_MAX_TRACE
+       /* Fix mapped buffer trace arrays do not have snapshot buffers */
+       if (tr->range_addr_start)
+               return 0;
+
        ret = allocate_trace_buffer(tr, &tr->max_buffer,
                                    allocate_snapshot ? size : 1);
        if (MEM_FAIL(ret, "Failed to allocate trace buffer\n")) {
@@ -9342,7 +9364,9 @@ static int trace_array_create_dir(struct trace_array *tr)
 }
 
 static struct trace_array *
-trace_array_create_systems(const char *name, const char *systems)
+trace_array_create_systems(const char *name, const char *systems,
+                          unsigned long range_addr_start,
+                          unsigned long range_addr_size)
 {
        struct trace_array *tr;
        int ret;
@@ -9368,6 +9392,10 @@ trace_array_create_systems(const char *name, const char *systems)
                        goto out_free_tr;
        }
 
+       /* Only for boot up memory mapped ring buffers */
+       tr->range_addr_start = range_addr_start;
+       tr->range_addr_size = range_addr_size;
+
        tr->trace_flags = global_trace.trace_flags & ~ZEROED_TRACE_FLAGS;
 
        cpumask_copy(tr->tracing_cpumask, cpu_all_mask);
@@ -9425,7 +9453,7 @@ trace_array_create_systems(const char *name, const char *systems)
 
 static struct trace_array *trace_array_create(const char *name)
 {
-       return trace_array_create_systems(name, NULL);
+       return trace_array_create_systems(name, NULL, 0, 0);
 }
 
 static int instance_mkdir(const char *name)
@@ -9479,7 +9507,7 @@ struct trace_array *trace_array_get_by_name(const char *name, const char *system
                        goto out_unlock;
        }
 
-       tr = trace_array_create_systems(name, systems);
+       tr = trace_array_create_systems(name, systems, 0, 0);
 
        if (IS_ERR(tr))
                tr = NULL;
@@ -9672,8 +9700,10 @@ init_tracer_tracefs(struct trace_array *tr, struct dentry *d_tracer)
                MEM_FAIL(1, "Could not allocate function filter files");
 
 #ifdef CONFIG_TRACER_SNAPSHOT
-       trace_create_file("snapshot", TRACE_MODE_WRITE, d_tracer,
-                         tr, &snapshot_fops);
+       if (!tr->range_addr_start) {
+               trace_create_file("snapshot", TRACE_MODE_WRITE, d_tracer,
+                                 tr, &snapshot_fops);
+       }
 #endif
 
        trace_create_file("error_log", TRACE_MODE_WRITE, d_tracer,

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 749a182dab480c8d62c0567612695f2dad3a6d5d..5dd48932509c76589caeece67e021dbb2be7342e 100644 (file)
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -336,7 +336,6 @@ struct trace_array {
        bool                    allocated_snapshot;
        spinlock_t              snapshot_trigger_lock;
        unsigned int            snapshot;
-       unsigned int            mapped;
        unsigned long           max_latency;
 #ifdef CONFIG_FSNOTIFY
        struct dentry           *d_max_latency;
@@ -344,6 +343,11 @@ struct trace_array {
        struct irq_work         fsnotify_irqwork;
 #endif
 #endif
+       /* The below is for memory mapped ring buffer */
+       unsigned int            mapped;
+       unsigned long           range_addr_start;
+       unsigned long           range_addr_size;
+
        struct trace_pid_list   __rcu *filtered_pids;
        struct trace_pid_list   __rcu *filtered_no_pids;
        /*