[DTrace-devel] [PATCH 01/12] proc: use a rawtp for the proc:::exit probe

[Eugene Loh]

Reviewed-by: Eugene Loh <eugene.loh at oracle.com>

Do we need an audit to find more rawtp opportunities in existing code?

Also...

On 1/5/24 00:24, Kris Van Hees via DTrace-devel wrote:
> diff --git a/libdtrace/dt_prov_proc.c b/libdtrace/dt_prov_proc.c
> @@ -204,10 +204,10 @@ static void enable(dtrace_hdl_t *dtp, dt_probe_t *prp)
>   	} else if (strcmp(prp->desc->prb, "exit") == 0 ||
>   		   strcmp(prp->desc->prb, "lwp-exit") == 0) {
>   		pd.id = DTRACE_IDNONE;
> -		pd.prv = "fbt";
> +		pd.prv = "rawtp";
>   		pd.mod = "";
> -		pd.fun = "taskstats_exit";
> -		pd.prb = "entry";
> +		pd.fun = "";
> +		pd.prb = "sched_process_exit";
>   
>   		uprp = dt_probe_lookup(dtp, &pd);
>   		assert(uprp != NULL);
> @@ -323,7 +323,7 @@ static int trampoline(dt_pcb_t *pcb, uint_t exitlbl)
>   		int		rc = 0;
>   		uint_t		lbl_out = dt_irlist_label(dlp);
>   
> -		emit(dlp,  BPF_LOAD(BPF_DW, BPF_REG_0, BPF_REG_7, DMST_ARG(1)));
> +		emit(dlp,  BPF_LOAD(BPF_DW, BPF_REG_0, BPF_REG_7, DMST_ARG(0)));

I'm confused on this one.  We're switching from
         taskstats_exit(tsk, group_dead);
to
         trace_sched_process_exit(tsk);
So it seems we want arg0 in either case.  So the patch is right, but it 
means (iiuc) that there was a bug in the code.  So if a bug is being 
fixed, doesn't that mean there should be a test change?

>   		emit(dlp,  BPF_BRANCH_IMM(BPF_JEQ, BPF_REG_0, 0, exitlbl));
>   
>   		if (!cfp)
> @@ -342,9 +342,9 @@ static int trampoline(dt_pcb_t *pcb, uint_t exitlbl)
>   		/*
>   		 * This implements:
>   		 *	%r1 = tsk->exit_code
> -		 *	if ((%r1 & 0x7f) == 0) args[0] = 1;
> -		 *	else if (%r1 & 0x80) args[0] = 3;
> -		 *	else args[0] = 2;
> +		 *	if ((%r1 & 0x7f) == 0) args[0] = 1;	// CLD_EXITED
> +		 *	else if (%r1 & 0x80) args[0] = 3;	// CLD_DUMPED
> +		 *	else args[0] = 2;			// CLD_KILLED
>   		 */
>   		emit(dlp,  BPF_MOV_REG(BPF_REG_1, BPF_REG_FP));
>   		emit(dlp,  BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, DT_STK_SPILL(0)));