[PATCH v11 11/18] 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 in v9:
  - Avoid wasting memory for bpf_kprobe_multi_pt_regs when
    CONFIG_HAVE_PT_REGS_TO_FTRACE_REGS_CAST=y
---
 kernel/trace/bpf_trace.c |   27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index f72b421abe9b..77fd63027286 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2602,7 +2602,7 @@ struct bpf_session_run_ctx {
        void *data;
 };
 
-#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;
@@ -2625,6 +2625,13 @@ struct user_syms {
        char *buf;
 };
 
+#ifndef CONFIG_HAVE_PT_REGS_TO_FTRACE_REGS_CAST
+static DEFINE_PER_CPU(struct pt_regs, bpf_kprobe_multi_pt_regs);
+#define bpf_kprobe_multi_pt_regs_ptr() this_cpu_ptr(&bpf_kprobe_multi_pt_regs)
+#else
+#define bpf_kprobe_multi_pt_regs_ptr() (NULL)
+#endif
+
 static int copy_user_syms(struct user_syms *us, unsigned long __user *usyms, 
u32 cnt)
 {
        unsigned long __user usymbol;
@@ -2819,7 +2826,7 @@ 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,
                           bool is_return, void *data)
 {
        struct bpf_kprobe_multi_run_ctx run_ctx = {
@@ -2831,6 +2838,7 @@ kprobe_multi_link_prog_run(struct bpf_kprobe_multi_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)) {
@@ -2841,6 +2849,7 @@ kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link 
*link,
 
        migrate_disable();
        rcu_read_lock();
+       regs = ftrace_partial_regs(fregs, bpf_kprobe_multi_pt_regs_ptr());
        old_run_ctx = bpf_set_run_ctx(&run_ctx.session_ctx.run_ctx);
        err = bpf_prog_run(link->link.prog, regs);
        bpf_reset_run_ctx(old_run_ctx);
@@ -2857,15 +2866,11 @@ kprobe_multi_link_handler(struct fprobe *fp, unsigned 
long fentry_ip,
                          unsigned long ret_ip, struct ftrace_regs *fregs,
                          void *data)
 {
-       struct pt_regs *regs = ftrace_get_regs(fregs);
        struct bpf_kprobe_multi_link *link;
        int err;
 
-       if (!regs)
-               return 0;
-
        link = container_of(fp, struct bpf_kprobe_multi_link, fp);
-       err = kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), regs, 
false, data);
+       err = kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), fregs, 
false, data);
        return is_kprobe_session(link->link.prog) ? err : 0;
 }
 
@@ -2875,13 +2880,9 @@ 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, true, 
data);
+       kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), fregs, true, 
data);
 }
 
 static int symbols_cmp_r(const void *a, const void *b, const void *priv)
@@ -3142,7 +3143,7 @@ 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;