diff mbox series

[v9,29/36] bpf: Enable kprobe_multi feature if CONFIG_FPROBE is enabled

Message ID 171318568081.254850.16193015880509111721.stgit@devnote2 (mailing list archive)
State Superseded
Headers show
Series tracing: fprobe: function_graph: Multi-function graph and fprobe on fgraph | expand

Commit Message

Masami Hiramatsu (Google) April 15, 2024, 12:54 p.m. UTC 
From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Enable kprobe_multi feature if CONFIG_FPROBE is enabled. The pt_regs is
converted from ftrace_regs by ftrace_partial_regs(), thus some registers
may always returns 0. But it should be enough for function entry (access
arguments) and exit (access return value).

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Florent Revest <revest@chromium.org>
---
 Changes from previous series: NOTHING, Update against the new series.
---
 kernel/trace/bpf_trace.c |   22 +++++++++-------------
 1 file changed, 9 insertions(+), 13 deletions(-)

Comments

Andrii Nakryiko April 25, 2024, 8:09 p.m. UTC | #1 
On Mon, Apr 15, 2024 at 6:22 AM Masami Hiramatsu (Google)
<mhiramat@kernel.org> wrote:
>
> From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
>
> Enable kprobe_multi feature if CONFIG_FPROBE is enabled. The pt_regs is
> converted from ftrace_regs by ftrace_partial_regs(), thus some registers
> may always returns 0. But it should be enough for function entry (access
> arguments) and exit (access return value).
>
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> Acked-by: Florent Revest <revest@chromium.org>
> ---
>  Changes from previous series: NOTHING, Update against the new series.
> ---
>  kernel/trace/bpf_trace.c |   22 +++++++++-------------
>  1 file changed, 9 insertions(+), 13 deletions(-)
>
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index e51a6ef87167..57b1174030c9 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -2577,7 +2577,7 @@ static int __init bpf_event_init(void)
>  fs_initcall(bpf_event_init);
>  #endif /* CONFIG_MODULES */
>
> -#if defined(CONFIG_FPROBE) && defined(CONFIG_DYNAMIC_FTRACE_WITH_REGS)
> +#ifdef CONFIG_FPROBE
>  struct bpf_kprobe_multi_link {
>         struct bpf_link link;
>         struct fprobe fp;
> @@ -2600,6 +2600,8 @@ struct user_syms {
>         char *buf;
>  };
>
> +static DEFINE_PER_CPU(struct pt_regs, bpf_kprobe_multi_pt_regs);

this is a waste if CONFIG_HAVE_PT_REGS_TO_FTRACE_REGS_CAST=y, right?
Can we guard it?


> +
>  static int copy_user_syms(struct user_syms *us, unsigned long __user *usyms, u32 cnt)
>  {
>         unsigned long __user usymbol;
> @@ -2792,13 +2794,14 @@ static u64 bpf_kprobe_multi_entry_ip(struct bpf_run_ctx *ctx)
>
>  static int
>  kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link,
> -                          unsigned long entry_ip, struct pt_regs *regs)
> +                          unsigned long entry_ip, struct ftrace_regs *fregs)
>  {
>         struct bpf_kprobe_multi_run_ctx run_ctx = {
>                 .link = link,
>                 .entry_ip = entry_ip,
>         };
>         struct bpf_run_ctx *old_run_ctx;
> +       struct pt_regs *regs;
>         int err;
>
>         if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1)) {
> @@ -2809,6 +2812,7 @@ kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link,
>
>         migrate_disable();
>         rcu_read_lock();
> +       regs = ftrace_partial_regs(fregs, this_cpu_ptr(&bpf_kprobe_multi_pt_regs));

and then pass NULL if defined(CONFIG_HAVE_PT_REGS_TO_FTRACE_REGS_CAST)?


>         old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx);
>         err = bpf_prog_run(link->link.prog, regs);
>         bpf_reset_run_ctx(old_run_ctx);
> @@ -2826,13 +2830,9 @@ kprobe_multi_link_handler(struct fprobe *fp, unsigned long fentry_ip,
>                           void *data)
>  {
>         struct bpf_kprobe_multi_link *link;
> -       struct pt_regs *regs = ftrace_get_regs(fregs);
> -
> -       if (!regs)
> -               return 0;
>
>         link = container_of(fp, struct bpf_kprobe_multi_link, fp);
> -       kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), regs);
> +       kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), fregs);
>         return 0;
>  }
>
> @@ -2842,13 +2842,9 @@ kprobe_multi_link_exit_handler(struct fprobe *fp, unsigned long fentry_ip,
>                                void *data)
>  {
>         struct bpf_kprobe_multi_link *link;
> -       struct pt_regs *regs = ftrace_get_regs(fregs);
> -
> -       if (!regs)
> -               return;
>
>         link = container_of(fp, struct bpf_kprobe_multi_link, fp);
> -       kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), regs);
> +       kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), fregs);
>  }
>
>  static int symbols_cmp_r(const void *a, const void *b, const void *priv)
> @@ -3107,7 +3103,7 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr
>         kvfree(cookies);
>         return err;
>  }
> -#else /* !CONFIG_FPROBE || !CONFIG_DYNAMIC_FTRACE_WITH_REGS */
> +#else /* !CONFIG_FPROBE */
>  int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
>  {
>         return -EOPNOTSUPP;
>
>
Masami Hiramatsu (Google) April 29, 2024, 2:57 p.m. UTC | #2 
On Thu, 25 Apr 2024 13:09:32 -0700
Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:

> On Mon, Apr 15, 2024 at 6:22 AM Masami Hiramatsu (Google)
> <mhiramat@kernel.org> wrote:
> >
> > From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> >
> > Enable kprobe_multi feature if CONFIG_FPROBE is enabled. The pt_regs is
> > converted from ftrace_regs by ftrace_partial_regs(), thus some registers
> > may always returns 0. But it should be enough for function entry (access
> > arguments) and exit (access return value).
> >
> > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> > Acked-by: Florent Revest <revest@chromium.org>
> > ---
> >  Changes from previous series: NOTHING, Update against the new series.
> > ---
> >  kernel/trace/bpf_trace.c |   22 +++++++++-------------
> >  1 file changed, 9 insertions(+), 13 deletions(-)
> >
> > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> > index e51a6ef87167..57b1174030c9 100644
> > --- a/kernel/trace/bpf_trace.c
> > +++ b/kernel/trace/bpf_trace.c
> > @@ -2577,7 +2577,7 @@ static int __init bpf_event_init(void)
> >  fs_initcall(bpf_event_init);
> >  #endif /* CONFIG_MODULES */
> >
> > -#if defined(CONFIG_FPROBE) && defined(CONFIG_DYNAMIC_FTRACE_WITH_REGS)
> > +#ifdef CONFIG_FPROBE
> >  struct bpf_kprobe_multi_link {
> >         struct bpf_link link;
> >         struct fprobe fp;
> > @@ -2600,6 +2600,8 @@ struct user_syms {
> >         char *buf;
> >  };
> >
> > +static DEFINE_PER_CPU(struct pt_regs, bpf_kprobe_multi_pt_regs);
> 
> this is a waste if CONFIG_HAVE_PT_REGS_TO_FTRACE_REGS_CAST=y, right?
> Can we guard it?

Good catch! Yes, we can guard it.

> 
> 
> > +
> >  static int copy_user_syms(struct user_syms *us, unsigned long __user *usyms, u32 cnt)
> >  {
> >         unsigned long __user usymbol;
> > @@ -2792,13 +2794,14 @@ static u64 bpf_kprobe_multi_entry_ip(struct bpf_run_ctx *ctx)
> >
> >  static int
> >  kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link,
> > -                          unsigned long entry_ip, struct pt_regs *regs)
> > +                          unsigned long entry_ip, struct ftrace_regs *fregs)
> >  {
> >         struct bpf_kprobe_multi_run_ctx run_ctx = {
> >                 .link = link,
> >                 .entry_ip = entry_ip,
> >         };
> >         struct bpf_run_ctx *old_run_ctx;
> > +       struct pt_regs *regs;
> >         int err;
> >
> >         if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1)) {
> > @@ -2809,6 +2812,7 @@ kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link,
> >
> >         migrate_disable();
> >         rcu_read_lock();
> > +       regs = ftrace_partial_regs(fregs, this_cpu_ptr(&bpf_kprobe_multi_pt_regs));
> 
> and then pass NULL if defined(CONFIG_HAVE_PT_REGS_TO_FTRACE_REGS_CAST)?

Indeed.

Thank you!

> 
> 
> >         old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx);
> >         err = bpf_prog_run(link->link.prog, regs);
> >         bpf_reset_run_ctx(old_run_ctx);
> > @@ -2826,13 +2830,9 @@ kprobe_multi_link_handler(struct fprobe *fp, unsigned long fentry_ip,
> >                           void *data)
> >  {
> >         struct bpf_kprobe_multi_link *link;
> > -       struct pt_regs *regs = ftrace_get_regs(fregs);
> > -
> > -       if (!regs)
> > -               return 0;
> >
> >         link = container_of(fp, struct bpf_kprobe_multi_link, fp);
> > -       kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), regs);
> > +       kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), fregs);
> >         return 0;
> >  }
> >
> > @@ -2842,13 +2842,9 @@ kprobe_multi_link_exit_handler(struct fprobe *fp, unsigned long fentry_ip,
> >                                void *data)
> >  {
> >         struct bpf_kprobe_multi_link *link;
> > -       struct pt_regs *regs = ftrace_get_regs(fregs);
> > -
> > -       if (!regs)
> > -               return;
> >
> >         link = container_of(fp, struct bpf_kprobe_multi_link, fp);
> > -       kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), regs);
> > +       kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), fregs);
> >  }
> >
> >  static int symbols_cmp_r(const void *a, const void *b, const void *priv)
> > @@ -3107,7 +3103,7 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr
> >         kvfree(cookies);
> >         return err;
> >  }
> > -#else /* !CONFIG_FPROBE || !CONFIG_DYNAMIC_FTRACE_WITH_REGS */
> > +#else /* !CONFIG_FPROBE */
> >  int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
> >  {
> >         return -EOPNOTSUPP;
> >
> >
diff mbox series

Patch

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index e51a6ef87167..57b1174030c9 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2577,7 +2577,7 @@  static int __init bpf_event_init(void)
 fs_initcall(bpf_event_init);
 #endif /* CONFIG_MODULES */
 
-#if defined(CONFIG_FPROBE) && defined(CONFIG_DYNAMIC_FTRACE_WITH_REGS)
+#ifdef CONFIG_FPROBE
 struct bpf_kprobe_multi_link {
 	struct bpf_link link;
 	struct fprobe fp;
@@ -2600,6 +2600,8 @@  struct user_syms {
 	char *buf;
 };
 
+static DEFINE_PER_CPU(struct pt_regs, bpf_kprobe_multi_pt_regs);
+
 static int copy_user_syms(struct user_syms *us, unsigned long __user *usyms, u32 cnt)
 {
 	unsigned long __user usymbol;
@@ -2792,13 +2794,14 @@  static u64 bpf_kprobe_multi_entry_ip(struct bpf_run_ctx *ctx)
 
 static int
 kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link,
-			   unsigned long entry_ip, struct pt_regs *regs)
+			   unsigned long entry_ip, struct ftrace_regs *fregs)
 {
 	struct bpf_kprobe_multi_run_ctx run_ctx = {
 		.link = link,
 		.entry_ip = entry_ip,
 	};
 	struct bpf_run_ctx *old_run_ctx;
+	struct pt_regs *regs;
 	int err;
 
 	if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1)) {
@@ -2809,6 +2812,7 @@  kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link,
 
 	migrate_disable();
 	rcu_read_lock();
+	regs = ftrace_partial_regs(fregs, this_cpu_ptr(&bpf_kprobe_multi_pt_regs));
 	old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx);
 	err = bpf_prog_run(link->link.prog, regs);
 	bpf_reset_run_ctx(old_run_ctx);
@@ -2826,13 +2830,9 @@  kprobe_multi_link_handler(struct fprobe *fp, unsigned long fentry_ip,
 			  void *data)
 {
 	struct bpf_kprobe_multi_link *link;
-	struct pt_regs *regs = ftrace_get_regs(fregs);
-
-	if (!regs)
-		return 0;
 
 	link = container_of(fp, struct bpf_kprobe_multi_link, fp);
-	kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), regs);
+	kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), fregs);
 	return 0;
 }
 
@@ -2842,13 +2842,9 @@  kprobe_multi_link_exit_handler(struct fprobe *fp, unsigned long fentry_ip,
 			       void *data)
 {
 	struct bpf_kprobe_multi_link *link;
-	struct pt_regs *regs = ftrace_get_regs(fregs);
-
-	if (!regs)
-		return;
 
 	link = container_of(fp, struct bpf_kprobe_multi_link, fp);
-	kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), regs);
+	kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), fregs);
 }
 
 static int symbols_cmp_r(const void *a, const void *b, const void *priv)
@@ -3107,7 +3103,7 @@  int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr
 	kvfree(cookies);
 	return err;
 }
-#else /* !CONFIG_FPROBE || !CONFIG_DYNAMIC_FTRACE_WITH_REGS */
+#else /* !CONFIG_FPROBE */
 int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
 {
 	return -EOPNOTSUPP;