bpf: Return value in kprobe get_func_ip only for entry address

Changing return value of kprobe's version of bpf_get_func_ip
to return zero if the attach address is not on the function's
entry point.

For kprobes attached in the middle of the function we can't easily
get to the function address especially now with the CONFIG_X86_KERNEL_IBT
support.

If user cares about current IP for kprobes attached within the
function body, they can get it with PT_REGS_IP(ctx).

Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Martynas Pumputis <m@lambda.lt>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20220926153340.1621984-6-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index ead35f39f185aa1117816498e87a72b9f798d998..d6bd10759eaf9e88cde316bdf47d3192058ea2e6 100644 (file)
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4951,6 +4951,7 @@ union bpf_attr {
  *             Get address of the traced function (for tracing and kprobe programs).
  *     Return
  *             Address of the traced function.
+ *             0 for kprobes placed within the function (not at the entry).
  *
  * u64 bpf_get_attach_cookie(void *ctx)
  *     Description

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index ebd1b348beb366b6b746b671981f8c9b5e8c083d..688552df95cacaf24817852e7eef3b23dd4f2e78 100644 (file)
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1048,7 +1048,10 @@ BPF_CALL_1(bpf_get_func_ip_kprobe, struct pt_regs *, regs)
 {
        struct kprobe *kp = kprobe_running();
 
-       return kp ? (uintptr_t)kp->addr : 0;
+       if (!kp || !(kp->flags & KPROBE_FLAG_ON_FUNC_ENTRY))
+               return 0;
+
+       return get_entry_ip((uintptr_t)kp->addr);
 }
 
 static const struct bpf_func_proto bpf_get_func_ip_proto_kprobe = {

diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index ead35f39f185aa1117816498e87a72b9f798d998..d6bd10759eaf9e88cde316bdf47d3192058ea2e6 100644 (file)
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4951,6 +4951,7 @@ union bpf_attr {
  *             Get address of the traced function (for tracing and kprobe programs).
  *     Return
  *             Address of the traced function.
+ *             0 for kprobes placed within the function (not at the entry).
  *
  * u64 bpf_get_attach_cookie(void *ctx)
  *     Description

diff --git a/tools/testing/selftests/bpf/progs/get_func_ip_test.c b/tools/testing/selftests/bpf/progs/get_func_ip_test.c
index a587aeca5ae0848b759a2cfc95a22a0a564e87e5..6db70757bc8b145217277a4d71dafa19848257c7 100644 (file)
--- a/tools/testing/selftests/bpf/progs/get_func_ip_test.c
+++ b/tools/testing/selftests/bpf/progs/get_func_ip_test.c
@@ -69,7 +69,7 @@ int test6(struct pt_regs *ctx)
 {
        __u64 addr = bpf_get_func_ip(ctx);
 
-       test6_result = (const void *) addr == &bpf_fentry_test6 + 5;
+       test6_result = (const void *) addr == 0;
        return 0;
 }
 
@@ -79,6 +79,6 @@ int test7(struct pt_regs *ctx)
 {
        __u64 addr = bpf_get_func_ip(ctx);
 
-       test7_result = (const void *) addr == &bpf_fentry_test7 + 5;
+       test7_result = (const void *) addr == 0;
        return 0;
 }