@@ -211,4 +211,6 @@ int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node);
#define trace_rb_cpu_prepare NULL
#endif
+int ring_buffer_kho_write(void *fdt, struct trace_buffer *buffer);
+
#endif /* _LINUX_RING_BUFFER_H */
@@ -20,6 +20,7 @@
#include <linux/percpu.h>
#include <linux/mutex.h>
#include <linux/delay.h>
+#include <linux/kexec.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/hash.h>
@@ -5859,6 +5860,81 @@ int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
return 0;
}
+#ifdef CONFIG_FTRACE_KHO
+static int rb_kho_write_cpu(void *fdt, struct trace_buffer *buffer, int cpu)
+{
+ int i = 0;
+ int err = 0;
+ struct list_head *tmp;
+ const char compatible[] = "ftrace,cpu-v1";
+ char name[] = "cpuffffffff";
+ int nr_pages;
+ struct ring_buffer_per_cpu *cpu_buffer;
+ bool first_loop = true;
+ struct kho_mem *mem;
+ uint64_t mem_len;
+
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ return 0;
+
+ cpu_buffer = buffer->buffers[cpu];
+
+ nr_pages = cpu_buffer->nr_pages;
+ mem_len = sizeof(*mem) * nr_pages * 2;
+ mem = vmalloc(mem_len);
+
+ snprintf(name, sizeof(name), "cpu%x", cpu);
+
+ err |= fdt_begin_node(fdt, name);
+ err |= fdt_property(fdt, "compatible", compatible, sizeof(compatible));
+ err |= fdt_property(fdt, "cpu", &cpu, sizeof(cpu));
+
+ for (tmp = rb_list_head(cpu_buffer->pages);
+ tmp != rb_list_head(cpu_buffer->pages) || first_loop;
+ tmp = rb_list_head(tmp->next), first_loop = false) {
+ struct buffer_page *bpage = (struct buffer_page *)tmp;
+
+ /* Ring is larger than it should be? */
+ if (i >= (nr_pages * 2)) {
+ pr_err("ftrace ring has more pages than nr_pages (%d / %d)", i, nr_pages);
+ err = -EINVAL;
+ break;
+ }
+
+ /* First describe the bpage */
+ mem[i++] = (struct kho_mem) {
+ .addr = __pa(bpage),
+ .len = sizeof(*bpage)
+ };
+
+ /* Then the data page */
+ mem[i++] = (struct kho_mem) {
+ .addr = __pa(bpage->page),
+ .len = PAGE_SIZE
+ };
+ }
+
+ err |= fdt_property(fdt, "mem", mem, mem_len);
+ err |= fdt_end_node(fdt);
+
+ vfree(mem);
+ return err;
+}
+
+int ring_buffer_kho_write(void *fdt, struct trace_buffer *buffer)
+{
+ int err, i;
+
+ for (i = 0; i < buffer->cpus; i++) {
+ err = rb_kho_write_cpu(fdt, buffer, i);
+ if (err)
+ return err;
+ }
+
+ return 0;
+}
+#endif
+
#ifdef CONFIG_RING_BUFFER_STARTUP_TEST
/*
* This is a basic integrity check of the ring buffer.
@@ -10577,6 +10577,21 @@ void __init early_trace_init(void)
init_events();
}
+static int trace_kho_write_trace_array(void *fdt, struct trace_array *tr)
+{
+ const char *name = tr->name ? tr->name : "global-trace";
+ const char compatible[] = "ftrace,array-v1";
+ int err = 0;
+
+ err |= fdt_begin_node(fdt, name);
+ err |= fdt_property(fdt, "compatible", compatible, sizeof(compatible));
+ err |= fdt_property(fdt, "trace-flags", &tr->trace_flags, sizeof(tr->trace_flags));
+ err |= ring_buffer_kho_write(fdt, tr->array_buffer.buffer);
+ err |= fdt_end_node(fdt);
+
+ return err;
+}
+
static int trace_kho_notifier(struct notifier_block *self,
unsigned long cmd,
void *v)
@@ -10603,6 +10618,7 @@ static int trace_kho_notifier(struct notifier_block *self,
err |= fdt_begin_node(fdt, "ftrace");
err |= fdt_property(fdt, "compatible", compatible, sizeof(compatible));
+ err |= trace_kho_write_trace_array(fdt, &global_trace);
err |= fdt_end_node(fdt);
if (!err) {
When we do a kexec handover, we want to preserve previous ftrace data into the new kernel. At the point when we write out the handover data, ftrace may still be running and recording new events and we want to capture all of those too. To allow the new kernel to revive all trace data up to reboot, we store all locations of trace buffers as well as their linked list metadata. We can then later reuse the linked list to reconstruct the head pointer. This patch implements the write-out logic for trace buffers. Signed-off-by: Alexander Graf <graf@amazon.com> --- v1 -> v2: - Leave the node generation code that needs to know the name in trace.c so that ring buffers can stay anonymous v2 -> v3: - s/"global_trace"/"global-trace"/ - s/"trace_flags"/"trace-flags"/ --- include/linux/ring_buffer.h | 2 + kernel/trace/ring_buffer.c | 76 +++++++++++++++++++++++++++++++++++++ kernel/trace/trace.c | 16 ++++++++ 3 files changed, 94 insertions(+)