[PATCH 10/15] tracing: Introduce kho serialization
From: Alexander Graf <graf@amazon.com>
Date: 2023-12-13 00:07:18
Also in:
kexec, linux-arm-kernel, linux-devicetree, linux-doc, linux-mm, lkml
Subsystem:
the rest, tracing · Maintainers:
Linus Torvalds, Steven Rostedt, Masami Hiramatsu
We want to be able to transfer ftrace state from one kernel to the next. To start off with, let's establish all the boiler plate to get a write hook when KHO wants to serialize and fill out basic data. Follow-up patches will fill in serialization of ring buffers and events. Signed-off-by: Alexander Graf <graf@amazon.com> --- kernel/trace/trace.c | 52 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 52 insertions(+)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 7700ca1be2a5..3e7f61cf773e 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c@@ -32,6 +32,7 @@ #include <linux/percpu.h> #include <linux/splice.h> #include <linux/kdebug.h> +#include <linux/kexec.h> #include <linux/string.h> #include <linux/mount.h> #include <linux/rwsem.h>
@@ -866,6 +867,10 @@ static struct tracer *trace_types __read_mostly; */ DEFINE_MUTEX(trace_types_lock); +#ifdef CONFIG_FTRACE_KHO +static bool trace_in_kho; +#endif + /* * serialize the access of the ring buffer *
@@ -10591,12 +10596,59 @@ void __init early_trace_init(void) init_events(); } +#ifdef CONFIG_FTRACE_KHO +static int trace_kho_notifier(struct notifier_block *self, + unsigned long cmd, + void *v) +{ + const char compatible[] = "ftrace-v1"; + void *fdt = v; + int err = 0; + + switch (cmd) { + case KEXEC_KHO_ABORT: + if (trace_in_kho) + mutex_unlock(&trace_types_lock); + trace_in_kho = false; + return NOTIFY_DONE; + case KEXEC_KHO_DUMP: + /* Handled below */ + break; + default: + return NOTIFY_BAD; + } + + if (unlikely(tracing_disabled)) + return NOTIFY_DONE; + + err |= fdt_begin_node(fdt, "ftrace"); + err |= fdt_property(fdt, "compatible", compatible, sizeof(compatible)); + err |= fdt_end_node(fdt); + + if (!err) { + /* Hold all future allocations */ + mutex_lock(&trace_types_lock); + trace_in_kho = true; + } + + return err ? NOTIFY_BAD : NOTIFY_DONE; +} + +static struct notifier_block trace_kho_nb = { + .notifier_call = trace_kho_notifier, +}; +#endif + void __init trace_init(void) { trace_event_init(); if (boot_instance_index) enable_instances(); + +#ifdef CONFIG_FTRACE_KHO + register_kho_notifier(&trace_kho_nb); +#endif } __init static void clear_boot_tracer(void)
--
2.40.1
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