Commit 0e253f7e authored by Jiri Olsa's avatar Jiri Olsa Committed by Alexei Starovoitov
Browse files

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: default avatarAndrii Nakryiko <andrii@kernel.org>
Acked-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Acked-by: default avatarMartynas Pumputis <m@lambda.lt>
Signed-off-by: default avatarJiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20220926153340.1621984-6-jolsa@kernel.org


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent c09eb2e5

include/uapi/linux/bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -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

kernel/trace/bpf_trace.c

+4 −1
Original line number Diff line number Diff line
@@ -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 = {

tools/include/uapi/linux/bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -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

tools/testing/selftests/bpf/progs/get_func_ip_test.c

+2 −2
Original line number Diff line number Diff line
@@ -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;

}