[DTrace-devel] [PATCH 07/61] Fix syscall:::return args

[Kris Van Hees]

On Fri, Jul 08, 2022 at 10:44:51AM -0400, eugene.loh--- via DTrace-devel wrote:
> From: Eugene Loh <eugene.loh at oracle.com>
> 
> Signed-off-by: Eugene Loh <eugene.loh at oracle.com>

Reviewed-by: Kris Van Hees <kris.van.hees at oracle.com>

... and I will push to dev (since I have it on my pre-push branch already).

> ---
>  libdtrace/dt_prov_syscall.c             |  8 ++++--
>  test/unittest/syscall/tst.return_args.d | 37 +++++++++++++++++++++++++
>  test/unittest/syscall/tst.return_args.r |  6 ++++
>  3 files changed, 49 insertions(+), 2 deletions(-)
>  create mode 100644 test/unittest/syscall/tst.return_args.d
>  create mode 100644 test/unittest/syscall/tst.return_args.r
> 
> diff --git a/libdtrace/dt_prov_syscall.c b/libdtrace/dt_prov_syscall.c
> index 2c6644d4..c078ce36 100644
> --- a/libdtrace/dt_prov_syscall.c
> +++ b/libdtrace/dt_prov_syscall.c
> @@ -159,6 +159,7 @@ static void trampoline(dt_pcb_t *pcb)
>  	dt_cg_tramp_clear_regs(pcb);
>  
>  	/*
> +	 * Copy in the probe args.
>  	 *	for (i = 0; i < argc; i++)
>  	 *		dctx->mst->argv[i] =
>  	 *			((struct syscall_data *)dctx->ctx)->arg[i];
> @@ -171,7 +172,8 @@ static void trampoline(dt_pcb_t *pcb)
>  	}
>  
>  	/*
> -	 *	for i = argc; i < ARRAY_SIZE(((dt_mstate_t *)0)->argv); i++)
> +	 * Zero the remaining probe args.
> +	 *	for ( ; i < ARRAY_SIZE(((dt_mstate_t *)0)->argv); i++)
>  	 *		dctx->mst->argv[i] = 0;
>  	 *				// stdw [%r7 + DMST_ARG(i)], 0
>  	 */
> @@ -181,12 +183,14 @@ static void trampoline(dt_pcb_t *pcb)
>  	/*
>  	 * For return probes, store the errno.  That is, examine arg0.
>  	 * If it is >=0 or <=-2048, ignore it.  Otherwise, store -arg0
> -	 * in dctx->mst->syscall_errno.
> +	 * in dctx->mst->syscall_errno.  In any case, copy arg0 to arg1
> +	 * as required for syscall:::return probe arguments.
>  	 */
>  	if (strcmp(pcb->pcb_probe->desc->prb, "return") == 0) {
>  		uint_t lbl_errno_done = dt_irlist_label(dlp);
>  
>  		emit(dlp,  BPF_LOAD(BPF_DW, BPF_REG_0, BPF_REG_7, DMST_ARG(0)));
> +		emit(dlp,  BPF_STORE(BPF_DW, BPF_REG_7, DMST_ARG(1), BPF_REG_0));
>  		emit(dlp,  BPF_BRANCH_IMM(BPF_JSGE, BPF_REG_0, 0, lbl_errno_done));
>  		emit(dlp,  BPF_BRANCH_IMM(BPF_JSLE, BPF_REG_0, -2048, lbl_errno_done));
>  		emit(dlp,  BPF_NEG_REG(BPF_REG_0));
> diff --git a/test/unittest/syscall/tst.return_args.d b/test/unittest/syscall/tst.return_args.d
> new file mode 100644
> index 00000000..459afec5
> --- /dev/null
> +++ b/test/unittest/syscall/tst.return_args.d
> @@ -0,0 +1,37 @@
> +/*
> + * Oracle Linux DTrace.
> + * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
> + * Licensed under the Universal Permissive License v 1.0 as shown at
> + * http://oss.oracle.com/licenses/upl.
> + */
> +
> +/* @@trigger: bogus-ioctl */
> +/* @@trigger-timing: before */
> +/* @@runtest-opts: $_pid */
> +
> +#pragma D option destructive
> +#pragma D option quiet
> +
> +BEGIN
> +{
> +	n = 0;
> +}
> +
> +syscall::ioctl:entry
> +/pid == $1/
> +{
> +	raise(SIGUSR1);
> +}
> +
> +syscall::open*:return
> +/pid == $1/
> +{
> +	n++;
> +	printf("%d %d\n", arg0, arg1);
> +}
> +
> +syscall::open*:return
> +/pid == $1 && n >= 5/
> +{
> +	exit(0);
> +}
> diff --git a/test/unittest/syscall/tst.return_args.r b/test/unittest/syscall/tst.return_args.r
> new file mode 100644
> index 00000000..93d7c505
> --- /dev/null
> +++ b/test/unittest/syscall/tst.return_args.r
> @@ -0,0 +1,6 @@
> +0 0
> +1 1
> +2 2
> +3 3
> +4 4
> +
> -- 
> 2.18.4
> 
> 
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