[PATCH v20 09/19] bpf: Enable kprobe_multi feature if CONFIG_FPROBE is enabled

Masami Hiramatsu (Google)
2024-12-06T00:10:56Z

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 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 88aad3e3742c..852400170c5c 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2550,7 +2550,7 @@ 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;
@@ -2573,6 +2573,13 @@ struct user_syms {
char *buf;
};

+#ifndef CONFIG_HAVE_FTRACE_REGS_HAVING_PT_REGS
+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;
@@ -2767,7 +2774,7 @@ 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 = {
@@ -2779,6 +2786,7 @@ 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)) {
@@ -2789,6 +2797,7 @@ 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);
@@ -2805,15 +2814,11 @@ 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;
}

@@ -2823,13 +2828,9 @@ 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)
@@ -3090,7 +3091,7 @@ 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;