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authorMiroslav Benes <mbenes@suse.cz>2019-10-16 13:33:13 +0200
committerSteven Rostedt <rostedt@goodmis.org>2019-11-04 09:33:15 -0500
commit7162431dcf72032835d369c8d7b51311df407938 (patch)
tree194454e629a477bba5410fc5eab3303c5c089de4 /kernel
parenta99d8080aaf358d5d23581244e5da23b35e340b9 (diff)
downloadlinux-7162431dcf72032835d369c8d7b51311df407938.tar.bz2
ftrace: Introduce PERMANENT ftrace_ops flag
Livepatch uses ftrace for redirection to new patched functions. It means that if ftrace is disabled, all live patched functions are disabled as well. Toggling global 'ftrace_enabled' sysctl thus affect it directly. It is not a problem per se, because only administrator can set sysctl values, but it still may be surprising. Introduce PERMANENT ftrace_ops flag to amend this. If the FTRACE_OPS_FL_PERMANENT is set on any ftrace ops, the tracing cannot be disabled by disabling ftrace_enabled. Equally, a callback with the flag set cannot be registered if ftrace_enabled is disabled. Link: http://lkml.kernel.org/r/20191016113316.13415-2-mbenes@suse.cz Reviewed-by: Petr Mladek <pmladek@suse.com> Reviewed-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com> Signed-off-by: Miroslav Benes <mbenes@suse.cz> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/livepatch/patch.c3
-rw-r--r--kernel/trace/ftrace.c23
2 files changed, 23 insertions, 3 deletions
diff --git a/kernel/livepatch/patch.c b/kernel/livepatch/patch.c
index bd43537702bd..b552cf2d85f8 100644
--- a/kernel/livepatch/patch.c
+++ b/kernel/livepatch/patch.c
@@ -196,7 +196,8 @@ static int klp_patch_func(struct klp_func *func)
ops->fops.func = klp_ftrace_handler;
ops->fops.flags = FTRACE_OPS_FL_SAVE_REGS |
FTRACE_OPS_FL_DYNAMIC |
- FTRACE_OPS_FL_IPMODIFY;
+ FTRACE_OPS_FL_IPMODIFY |
+ FTRACE_OPS_FL_PERMANENT;
list_add(&ops->node, &klp_ops);
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index f296d89be757..89e9128652ef 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -326,6 +326,8 @@ int __register_ftrace_function(struct ftrace_ops *ops)
if (ops->flags & FTRACE_OPS_FL_SAVE_REGS_IF_SUPPORTED)
ops->flags |= FTRACE_OPS_FL_SAVE_REGS;
#endif
+ if (!ftrace_enabled && (ops->flags & FTRACE_OPS_FL_PERMANENT))
+ return -EBUSY;
if (!core_kernel_data((unsigned long)ops))
ops->flags |= FTRACE_OPS_FL_DYNAMIC;
@@ -6754,6 +6756,18 @@ int unregister_ftrace_function(struct ftrace_ops *ops)
}
EXPORT_SYMBOL_GPL(unregister_ftrace_function);
+static bool is_permanent_ops_registered(void)
+{
+ struct ftrace_ops *op;
+
+ do_for_each_ftrace_op(op, ftrace_ops_list) {
+ if (op->flags & FTRACE_OPS_FL_PERMANENT)
+ return true;
+ } while_for_each_ftrace_op(op);
+
+ return false;
+}
+
int
ftrace_enable_sysctl(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,
@@ -6771,8 +6785,6 @@ ftrace_enable_sysctl(struct ctl_table *table, int write,
if (ret || !write || (last_ftrace_enabled == !!ftrace_enabled))
goto out;
- last_ftrace_enabled = !!ftrace_enabled;
-
if (ftrace_enabled) {
/* we are starting ftrace again */
@@ -6783,12 +6795,19 @@ ftrace_enable_sysctl(struct ctl_table *table, int write,
ftrace_startup_sysctl();
} else {
+ if (is_permanent_ops_registered()) {
+ ftrace_enabled = true;
+ ret = -EBUSY;
+ goto out;
+ }
+
/* stopping ftrace calls (just send to ftrace_stub) */
ftrace_trace_function = ftrace_stub;
ftrace_shutdown_sysctl();
}
+ last_ftrace_enabled = !!ftrace_enabled;
out:
mutex_unlock(&ftrace_lock);
return ret;