[DTrace-devel] [PATCH 2/2] rawfbt: prvname is not properly set
Kris Van Hees
kris.van.hees at oracle.com
Thu Jan 15 22:18:11 UTC 2026
On Tue, Jan 13, 2026 at 04:42:05PM -0500, eugene.loh at oracle.com wrote:
> From: Eugene Loh <eugene.loh at oracle.com>
>
> The char array prvname[] is set for each provider. It is used in the
> file that implements the provider. It might also be passed to
> dt_sdt_populate() via a function argument.
>
> However, dt_provider_tp.h also defines the macro GROUP_DATA in terms of
> prvname. In turn, GROUP_DATA is used not only in dt_prov_dtrace.c but
> then again in dt_prov_fbt.c to define FBT_GROUP_DATA.
>
> In commit 0b7c5a632 ("fbt, rawfbt: consolidate code to avoid duplication"),
> the fbt and rawfbt providers are combined into a single file. Thus, two
> uses of prvname collide. The in-file collisions get resolved, but the
> cascade of macro definitions does not: FBT_GROUP_DATA ends up using
> "fbt" for both fbt and rawfbt providers. As a result, it is possible
> for rawfbt probes not to be seen.
>
> Notice that GROUP_DATA is always paired with prp->desc->prb. Therefore,
> simply replace:
> -#define GROUP_DATA getpid(), prvname
> +#define PROBE_DATA getpid(), prp->desc->prv, prp->desc->prb
> This makes the code more compact and relieves the macro definitions from
> needing prvname. It also makes the FBT_GROUP_DATA macro unnecessary.
>
> The format (FMT) macro is similarly renamed and redefined to include the
> probe info.
>
> Add a test to check that a rawfbt probe can be found behind an fbt probe
> when the probe description has a wildcard provider.
>
> Orabug: 38842114
> Signed-off-by: Eugene Loh <eugene.loh at oracle.com>
> ---
> libdtrace/dt_prov_dtrace.c | 14 ++++++-------
> libdtrace/dt_prov_fbt.c | 13 ++++++------
> libdtrace/dt_prov_rawtp.c | 4 ++--
> libdtrace/dt_prov_sdt.c | 4 ++--
> libdtrace/dt_provider_tp.h | 12 +++++------
> .../providers/rawfbt/tst.wildcard-provider.d | 20 +++++++++++++++++++
> .../providers/rawfbt/tst.wildcard-provider.r | 2 ++
> 7 files changed, 45 insertions(+), 24 deletions(-)
> create mode 100644 test/unittest/providers/rawfbt/tst.wildcard-provider.d
> create mode 100644 test/unittest/providers/rawfbt/tst.wildcard-provider.r
>
> diff --git a/libdtrace/dt_prov_dtrace.c b/libdtrace/dt_prov_dtrace.c
> index 34b5d8e24..102afd84e 100644
> --- a/libdtrace/dt_prov_dtrace.c
> +++ b/libdtrace/dt_prov_dtrace.c
> @@ -243,8 +243,8 @@ static int attach(dtrace_hdl_t *dtp, const dt_probe_t *prp, int bpf_fd)
> /* add a uprobe */
> fd = open(UPROBE_EVENTS, O_WRONLY | O_APPEND);
> if (fd != -1) {
> - rc = dprintf(fd, "p:" GROUP_FMT "/%s %s\n",
> - GROUP_DATA, prp->desc->prb, spec);
> + rc = dprintf(fd, "p:" PROBE_FMT " %s\n",
> + PROBE_DATA, spec);
> close(fd);
> }
> free(spec);
> @@ -252,14 +252,14 @@ static int attach(dtrace_hdl_t *dtp, const dt_probe_t *prp, int bpf_fd)
> return -ENOENT;
>
> /* open format file */
> - len = snprintf(NULL, 0, "%s" GROUP_FMT "/%s/format",
> - EVENTSFS, GROUP_DATA, prp->desc->prb) + 1;
> + len = snprintf(NULL, 0, "%s" PROBE_FMT "/format",
> + EVENTSFS, PROBE_DATA) + 1;
> fn = dt_alloc(dtp, len);
> if (fn == NULL)
> return -ENOENT;
>
> - snprintf(fn, len, "%s" GROUP_FMT "/%s/format",
> - EVENTSFS, GROUP_DATA, prp->desc->prb);
> + snprintf(fn, len, "%s" PROBE_FMT "/format",
> + EVENTSFS, PROBE_DATA);
How about also changing this to use asprintf() rather than doing the douoble
snprintf (one to get the langth, the alloc, and then actually populate).
> f = fopen(fn, "r");
> dt_free(dtp, fn);
> if (f == NULL)
> @@ -300,7 +300,7 @@ static void detach(dtrace_hdl_t *dtp, const dt_probe_t *prp)
> if (fd == -1)
> return;
>
> - dprintf(fd, "-:" GROUP_FMT "/%s\n", GROUP_DATA, prp->desc->prb);
> + dprintf(fd, "-:" PROBE_FMT "\n", PROBE_DATA);
> close(fd);
> }
>
> diff --git a/libdtrace/dt_prov_fbt.c b/libdtrace/dt_prov_fbt.c
> index 3feac56ea..8dbf9740a 100644
> --- a/libdtrace/dt_prov_fbt.c
> +++ b/libdtrace/dt_prov_fbt.c
> @@ -53,8 +53,7 @@ static const char prvname[] = "fbt";
>
> #define KPROBE_EVENTS TRACEFS "kprobe_events"
>
> -#define FBT_GROUP_FMT GROUP_FMT "_%s"
> -#define FBT_GROUP_DATA GROUP_DATA, prp->desc->prb
> +#define FBT_PROBE_FMT "dt_%d_%s_%s"
>
> static const dtrace_pattr_t pattr = {
> { DTRACE_STABILITY_EVOLVING, DTRACE_STABILITY_EVOLVING, DTRACE_CLASS_COMMON },
> @@ -508,16 +507,16 @@ static int kprobe_attach(dtrace_hdl_t *dtp, const dt_probe_t *prp, int bpf_fd)
> if (fd == -1)
> goto out;
>
> - rc = dprintf(fd, "%c:" FBT_GROUP_FMT "/%s %s\n",
> + rc = dprintf(fd, "%c:" FBT_PROBE_FMT "/%s %s\n",
> prp->desc->prb[0] == 'e' ? 'p' : 'r',
> - FBT_GROUP_DATA, tpn, fun);
> + PROBE_DATA, tpn, fun);
> close(fd);
> if (rc == -1)
> goto out;
>
> /* create format file name */
> - if (asprintf(&fn, "%s" FBT_GROUP_FMT "/%s/format", EVENTSFS,
> - FBT_GROUP_DATA, tpn) == -1)
> + if (asprintf(&fn, "%s" FBT_PROBE_FMT "/%s/format", EVENTSFS,
> + PROBE_DATA, tpn) == -1)
> goto out;
>
> /* open format file */
> @@ -583,7 +582,7 @@ static void kprobe_detach(dtrace_hdl_t *dtp, const dt_probe_t *prp)
> }
> }
>
> - dprintf(fd, "-:" FBT_GROUP_FMT "/%s\n", FBT_GROUP_DATA, tpn);
> + dprintf(fd, "-:" FBT_PROBE_FMT "/%s\n", PROBE_DATA, tpn);
> close(fd);
>
> if (tpn != prp->desc->fun)
> diff --git a/libdtrace/dt_prov_rawtp.c b/libdtrace/dt_prov_rawtp.c
> index 709f7040f..e3269f4b3 100644
> --- a/libdtrace/dt_prov_rawtp.c
> +++ b/libdtrace/dt_prov_rawtp.c
> @@ -56,7 +56,7 @@ static const dtrace_pattr_t pattr = {
> /*
> * The PROBE_LIST file lists all tracepoints in a <group>:<name> format.
> * We need to ignore these groups:
> - * - GROUP_FMT (created by DTrace processes)
> + * - PROBE_SFMT
> * - kprobes and uprobes
> * - syscalls (handled by a different provider)
> * - pid and usdt probes (ditto)
> @@ -89,7 +89,7 @@ static int populate(dtrace_hdl_t *dtp)
>
> *p++ = '\0';
>
> - if (sscanf(buf, GROUP_SFMT, &dummy, &str) == 2) {
> + if (sscanf(buf, PROBE_SFMT, &dummy, &str) == 2) {
> free(str);
> continue;
> }
> diff --git a/libdtrace/dt_prov_sdt.c b/libdtrace/dt_prov_sdt.c
> index 74555f5be..ee2cc3c27 100644
> --- a/libdtrace/dt_prov_sdt.c
> +++ b/libdtrace/dt_prov_sdt.c
> @@ -54,7 +54,7 @@ static const dtrace_pattr_t pattr = {
> /*
> * The PROBE_LIST file lists all tracepoints in a <group>:<name> format.
> * We need to ignore these groups:
> - * - GROUP_FMT (created by DTrace processes)
> + * - PROBE_SFMT
> * - kprobes and uprobes
> * - syscalls (handled by a different provider)
> * - pid and usdt probes (ditto)
> @@ -87,7 +87,7 @@ static int populate(dtrace_hdl_t *dtp)
>
> *p++ = '\0';
>
> - if (sscanf(buf, GROUP_SFMT, &dummy, &str) == 2) {
> + if (sscanf(buf, PROBE_SFMT, &dummy, &str) == 2) {
> free(str);
> continue;
> }
> diff --git a/libdtrace/dt_provider_tp.h b/libdtrace/dt_provider_tp.h
> index f131b1e02..406609d1b 100644
> --- a/libdtrace/dt_provider_tp.h
> +++ b/libdtrace/dt_provider_tp.h
> @@ -18,13 +18,13 @@ extern "C" {
> * Tracepoint group naming format for DTrace providers. Providers may append
> * to this format string as needed.
> *
> - * GROUP_DATA provides the necessary data items to populate the format string
> - * (PID of the dtrace process and the provider name). GROUP_SFMT is like
> - * GROUP_FMT, but for sscanf().
> + * PROBE_DATA provides the necessary data items to populate the format string.
> + * PROBE_FMT formats that data.
> + * PROBE_SFMT is a format string for recognizing PROBE_FMT data in sscanf().
> */
> -#define GROUP_FMT "dt_%d_%s"
> -#define GROUP_SFMT "dt_%d_%ms"
> -#define GROUP_DATA getpid(), prvname
> +#define PROBE_DATA getpid(), prp->desc->prv, prp->desc->prb
> +#define PROBE_FMT "dt_%d_%s/%s"
> +#define PROBE_SFMT "dt_%d_%ms"
>
> typedef struct tp_probe tp_probe_t;
>
> diff --git a/test/unittest/providers/rawfbt/tst.wildcard-provider.d b/test/unittest/providers/rawfbt/tst.wildcard-provider.d
> new file mode 100644
> index 000000000..ad9f4c779
> --- /dev/null
> +++ b/test/unittest/providers/rawfbt/tst.wildcard-provider.d
> @@ -0,0 +1,20 @@
> +/*
> + * Oracle Linux DTrace.
> + * Copyright (c) 2026, 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.
> + */
> +
> +/*
> + * ASSERTION: rawfbt probes can be found even when a wildcard provider
> + * description also allows fbt probes.
> + */
> +
> +#pragma D option quiet
> +
> +BEGIN,
> +*fbt:vmlinux:do_sys_open*:entry
> +{
> + printf("success\n");
> + exit(0);
> +}
I am confused how this test accomplishes verification of the assertion. If
a regular FBT probe satisfies the probe description, wouldn't this pass also?
Wouldn't a -l based test be better here, where you can test that the output
does indeed report both the fbt probe and the rawfbt probe that match?
> diff --git a/test/unittest/providers/rawfbt/tst.wildcard-provider.r b/test/unittest/providers/rawfbt/tst.wildcard-provider.r
> new file mode 100644
> index 000000000..b34a52d2f
> --- /dev/null
> +++ b/test/unittest/providers/rawfbt/tst.wildcard-provider.r
> @@ -0,0 +1,2 @@
> +success
> +
> --
> 2.47.3
>
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