[RFC PATCH 31/32] bpf: Enable kprobe_multi feature if CONFIG_FPROBE is enabled

[Masami Hiramatsu (Google)]

From: Masami Hiramatsu (Google) <mhira...@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) <mhira...@kernel.org>
Acked-by: Florent Revest <rev...@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 a4b5e34b0419..96d6e9993f75 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2501,7 +2501,7 @@ 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;
@@ -2524,6 +2524,8 @@ 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;
@@ -2700,13 +2702,14 @@ 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)) {
@@ -2716,6 +2719,7 @@ 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);
@@ -2733,13 +2737,9 @@ 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;
 }
 
@@ -2749,13 +2749,9 @@ 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)
@@ -3012,7 +3008,7 @@ 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;