"ftrace: Rework event_create_dir()" triggers boot error messages

[Steven Rostedt]

On Wed, 18 Dec 2019 22:58:23 -0500
Qian Cai <cai at lca.pw> wrote:

> The linux-next commit "ftrace: Rework event_create_dir()” [1] triggers boot warnings
> for Clang-build (Clang version 8.0.1) kernels (reproduced on both arm64 and powerpc).
> Reverted it (with trivial conflict fixes) on the top of today’s linux-next fixed the issue.
> 
> configs:
> https://raw.githubusercontent.com/cailca/linux-mm/master/arm64.config
> https://raw.githubusercontent.com/cailca/linux-mm/master/powerpc.config
> 
> [1] https://lore.kernel.org/lkml/20191111132458.342979914@infradead.org/
> 
> [  115.799327][    T1] Registered efivars operations
> [  115.849770][    T1] clocksource: Switched to clocksource arch_sys_counter
> [  115.901145][    T1] Could not initialize trace point events/sys_enter_rt_sigreturn
> [  115.908854][    T1] Could not create directory for event sys_enter_rt_sigreturn
> [  115.998949][    T1] Could not initialize trace point events/sys_enter_restart_syscall
> [  116.006802][    T1] Could not create directory for event sys_enter_restart_syscall
> [  116.062702][    T1] Could not initialize trace point events/sys_enter_getpid
> [  116.069828][    T1] Could not create directory for event sys_enter_getpid
> [  116.078058][    T1] Could not initialize trace point events/sys_enter_gettid
> [  116.085181][    T1] Could not create directory for event sys_enter_gettid
> [  116.093405][    T1] Could not initialize trace point events/sys_enter_getppid
> [  116.100612][    T1] Could not create directory for event sys_enter_getppid
> [  116.108989][    T1] Could not initialize trace point events/sys_enter_getuid
> [  116.116058][    T1] Could not create directory for event sys_enter_getuid
> [  116.124250][    T1] Could not initialize trace point events/sys_enter_geteuid
> [  116.131457][    T1] Could not create directory for event sys_enter_geteuid
> [  116.139840][    T1] Could not initialize trace point events/sys_enter_getgid
> [  116.146908][    T1] Could not create directory for event sys_enter_getgid
> [  116.155163][    T1] Could not initialize trace point events/sys_enter_getegid
> [  116.162370][    T1] Could not create directory for event sys_enter_getegid
> [  116.178015][    T1] Could not initialize trace point events/sys_enter_setsid
> [  116.185138][    T1] Could not create directory for event sys_enter_setsid
> [  116.269307][    T1] Could not initialize trace point events/sys_enter_sched_yield
> [  116.276811][    T1] Could not create directory for event sys_enter_sched_yield
> [  116.527652][    T1] Could not initialize trace point events/sys_enter_munlockall
> [  116.535126][    T1] Could not create directory for event sys_enter_munlockall
> [  116.622096][    T1] Could not initialize trace point events/sys_enter_vhangup
> [  116.629307][    T1] Could not create directory for event sys_enter_vhangup
> [  116.783867][    T1] Could not initialize trace point events/sys_enter_sync
> [  116.790819][    T1] Could not create directory for event sys_enter_sync
> [  117.723402][    T1] pnp: PnP ACPI init

I noticed that all of the above have zero parameters. Does the
following patch fix it?

(note, I prefer "ret" and "i" on different lines anyway)

-- Steve

diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index 53935259f701..abb70c71fe60 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -269,7 +269,8 @@ static int __init syscall_enter_define_fields(struct trace_event_call *call)
 	struct syscall_trace_enter trace;
 	struct syscall_metadata *meta = call->data;
 	int offset = offsetof(typeof(trace), args);
-	int ret, i;
+	int ret = 0;
+	int i;
 
 	for (i = 0; i < meta->nb_args; i++) {
 		ret = trace_define_field(call, meta->types[i],