[DTrace-devel] [PATCH 05/13] Make a provider-specific attach()
Kris Van Hees
kris.van.hees at oracle.com
Mon Jul 6 09:07:03 PDT 2020
This should be redone to come in the patch series *after* the introduction
of the provider-specific probe data. That way you do not introduce a function
that requires the dt_probe_t to be non-const.
As discussed before, functions in provider implementations should be taking
const dt_probe_t as argument, becuase they should not modify the dt_probe_t
data.
With the introduction of provider specific data, probe_fini can also be made
to take const dt_probe_t which is a good thing.
On Wed, Jul 01, 2020 at 10:41:10PM -0400, eugene.loh at oracle.com wrote:
> From: Eugene Loh <eugene.loh at oracle.com>
>
> We used dt_bpf_attach() to attach BPF programs to probes. This
> was suitable for the tracepoint-like providers to date, which used
> established event IDs to enable probes to get their file descriptors
> and then attach the BPF program fd; however, the approach is
> inadequate for some other providers.
>
> Remove dt_bpf_attach(), instead calling a provider-specific attach()
> function.
>
> Note that many providers actually are tracepoint-like. So, they can
> share a common attach() function. That function, tp_event_attach(),
> is supplied by the sdt provider in the same way as that provider
> supplies the common tp_event_info() function.
>
> Signed-off-by: Eugene Loh <eugene.loh at oracle.com>
> ---
> libdtrace/dt_bpf.c | 37 +++----------------------------------
> libdtrace/dt_prov_dtrace.c | 1 +
> libdtrace/dt_prov_fbt.c | 1 +
> libdtrace/dt_prov_sdt.c | 29 +++++++++++++++++++++++++++++
> libdtrace/dt_prov_syscall.c | 1 +
> libdtrace/dt_provider.h | 3 +++
> 6 files changed, 38 insertions(+), 34 deletions(-)
>
> diff --git a/libdtrace/dt_bpf.c b/libdtrace/dt_bpf.c
> index d5282b94..573c8357 100644
> --- a/libdtrace/dt_bpf.c
> +++ b/libdtrace/dt_bpf.c
> @@ -317,39 +317,6 @@ dt_bpf_load_prog(dtrace_hdl_t *dtp, const dt_probe_t *prp,
> return rc;
> }
>
> -/*
> - * Attach a BPF program to a probe.
> - */
> -int
> -dt_bpf_attach(dtrace_hdl_t *dtp, dt_probe_t *prp, int bpf_fd)
> -{
> - /*
> - * If we have not yet created a perf event for this probe, do that now
> - * and cache the file descriptor so we only need to do this once.
> - */
> - if (prp->event_fd == -1) {
> - int fd;
> - struct perf_event_attr attr = { 0, };
> -
> - attr.type = PERF_TYPE_TRACEPOINT;
> - attr.sample_type = PERF_SAMPLE_RAW;
> - attr.sample_period = 1;
> - attr.wakeup_events = 1;
> - attr.config = prp->event_id;
> -
> - fd = perf_event_open(&attr, -1, 0, -1, 0);
> - if (fd < 0)
> - return dt_set_errno(dtp, errno);
> -
> - prp->event_fd = fd;
> - }
> -
> - if (ioctl(prp->event_fd, PERF_EVENT_IOC_SET_BPF, bpf_fd) < 0)
> - return dt_set_errno(dtp, errno);
> -
> - return 0;
> -}
> -
> int
> dt_bpf_stmt(dtrace_hdl_t *dtp, dtrace_prog_t *pgp, dtrace_stmtdesc_t *sdp,
> void *data)
> @@ -369,7 +336,9 @@ dt_bpf_stmt(dtrace_hdl_t *dtp, dtrace_prog_t *pgp, dtrace_stmtdesc_t *sdp,
> if (fd < 0)
> return fd;
>
> - rc = dt_bpf_attach(dtp, prp, fd);
> + if (!prp->prov->impl->attach)
> + return -1;
> + rc = prp->prov->impl->attach(dtp, prp, fd);
> if (rc < 0)
> return rc;
>
> diff --git a/libdtrace/dt_prov_dtrace.c b/libdtrace/dt_prov_dtrace.c
> index fe9759de..34c99388 100644
> --- a/libdtrace/dt_prov_dtrace.c
> +++ b/libdtrace/dt_prov_dtrace.c
> @@ -317,5 +317,6 @@ dt_provimpl_t dt_dtrace = {
> .populate = &populate,
> .trampoline = &trampoline,
> .probe_info = &probe_info,
> + .attach = &tp_event_attach,
> .probe_fini = &probe_fini,
> };
> diff --git a/libdtrace/dt_prov_fbt.c b/libdtrace/dt_prov_fbt.c
> index 1aa3ca3c..cb80082e 100644
> --- a/libdtrace/dt_prov_fbt.c
> +++ b/libdtrace/dt_prov_fbt.c
> @@ -358,5 +358,6 @@ dt_provimpl_t dt_fbt = {
> .populate = &populate,
> .trampoline = &trampoline,
> .probe_info = &probe_info,
> + .attach = &tp_event_attach,
> .probe_fini = &probe_fini,
> };
> diff --git a/libdtrace/dt_prov_sdt.c b/libdtrace/dt_prov_sdt.c
> index 6d99653a..1a445c65 100644
> --- a/libdtrace/dt_prov_sdt.c
> +++ b/libdtrace/dt_prov_sdt.c
> @@ -19,13 +19,16 @@
> #include <stdlib.h>
> #include <string.h>
> #include <unistd.h>
> +#include <sys/ioctl.h>
> #include <linux/bpf.h>
> +#include <linux/perf_event.h>
> #include <sys/stat.h>
> #include <sys/types.h>
>
> #include <bpf_asm.h>
>
> #include "dt_impl.h"
> +#include "dt_bpf.h"
> #include "dt_bpf_builtins.h"
> #include "dt_provider.h"
> #include "dt_probe.h"
> @@ -223,6 +226,31 @@ done:
> return 0;
> }
>
> +int tp_event_attach(dtrace_hdl_t *dtp, dt_probe_t *prp, int bpf_fd)
> +{
> + if (prp->event_fd == -1) {
> + int fd;
> + struct perf_event_attr attr = { 0, };
> +
> + attr.type = PERF_TYPE_TRACEPOINT;
> + attr.sample_type = PERF_SAMPLE_RAW;
> + attr.sample_period = 1;
> + attr.wakeup_events = 1;
> + attr.config = prp->event_id;
> +
> + fd = perf_event_open(&attr, -1, 0, -1, 0);
> + if (fd < 0)
> + return dt_set_errno(dtp, errno);
> +
> + prp->event_fd = fd;
> + }
> +
> + if (ioctl(prp->event_fd, PERF_EVENT_IOC_SET_BPF, bpf_fd) < 0)
> + return dt_set_errno(dtp, errno);
> +
> + return 0;
> +}
> +
> /*
> * The PROBE_LIST file lists all tracepoints in a <group>:<name> format.
> * We need to ignore these groups:
> @@ -409,5 +437,6 @@ dt_provimpl_t dt_sdt = {
> .prog_type = BPF_PROG_TYPE_TRACEPOINT,
> .populate = &populate,
> .trampoline = &trampoline,
> + .attach = &tp_event_attach,
> .probe_info = &probe_info,
> };
> diff --git a/libdtrace/dt_prov_syscall.c b/libdtrace/dt_prov_syscall.c
> index 0b0ca954..cb54ce5a 100644
> --- a/libdtrace/dt_prov_syscall.c
> +++ b/libdtrace/dt_prov_syscall.c
> @@ -271,4 +271,5 @@ dt_provimpl_t dt_syscall = {
> .populate = &populate,
> .trampoline = &trampoline,
> .probe_info = &probe_info,
> + .attach = &tp_event_attach,
> };
> diff --git a/libdtrace/dt_provider.h b/libdtrace/dt_provider.h
> index 50f663f1..acd01983 100644
> --- a/libdtrace/dt_provider.h
> +++ b/libdtrace/dt_provider.h
> @@ -65,12 +65,15 @@ typedef struct dt_provimpl {
> int (*provide)(dtrace_hdl_t *dtp, /* provide probes */
> const dtrace_probedesc_t *pdp);
> void (*trampoline)(dt_pcb_t *pcb); /* generate BPF trampoline */
> + int (*attach)(dtrace_hdl_t *dtp, /* attach BPF program to probe */
> + struct dt_probe *prp, int bpf_fd);
> int (*probe_fini)(dtrace_hdl_t *dtp, /* probe cleanup */
> struct dt_probe *prb);
> } dt_provimpl_t;
>
> extern int tp_event_info(dtrace_hdl_t *dtp, FILE *f, int skip, int *idp,
> int *argcp, dt_argdesc_t **argvp);
> +extern int tp_event_attach(dtrace_hdl_t *dtp, struct dt_probe *prp, int bpf_fd);
>
> extern dt_provimpl_t dt_dtrace;
> extern dt_provimpl_t dt_fbt;
> --
> 2.18.2
>
>
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