Merge branch 'Add bpf_get_func_ip helper'

Jiri Olsa says:

====================
Add bpf_get_func_ip helper that returns IP address of the
caller function for trampoline and krobe programs.

There're 2 specific implementation of the bpf_get_func_ip
helper, one for trampoline progs and one for kprobe/kretprobe
progs.

The trampoline helper call is replaced/inlined by the verifier
with simple move instruction. The kprobe/kretprobe is actual
helper call that returns prepared caller address.

Also available at:
  https://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git
  bpf/get_func_ip

v4 changes:
  - dropped jit/x86 check for get_func_ip tracing check [Alexei]
  - added code to bpf_get_func_ip_tracing [Alexei]
    and tested that it works without inlining [Alexei]
  - changed has_get_func_ip to check_get_func_ip [Andrii]
  - replaced test assert loop with explicit asserts [Andrii]
  - adde bpf_program__attach_kprobe_opts function
    and use it for offset setup [Andrii]
  - used bpf_program__set_autoload(false) for test6 [Andrii]
  - added Masami's ack

v3 changes:
  - resend with Masami in cc and v3 in each patch subject

v2 changes:
  - use kprobe_running to get kprobe instead of cpu var [Masami]
  - added support to add kprobe on function+offset
    and test for that [Alan]
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

4 files changed, 179 insertions, 10 deletions

diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 3544ec5234f0..2db6925e04f4 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4841,6 +4841,12 @@ union bpf_attr {
  *		**-EINVAL** if *timer* was not initialized with bpf_timer_init() earlier.
  *		**-EDEADLK** if callback_fn tried to call bpf_timer_cancel() on its
  *		own timer which would have led to a deadlock otherwise.
+ *
+ * u64 bpf_get_func_ip(void *ctx)
+ * 	Description
+ * 		Get address of the traced function (for tracing and kprobe programs).
+ * 	Return
+ * 		Address of the traced function.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -5016,6 +5022,7 @@ union bpf_attr {
 	FN(timer_set_callback),		\
 	FN(timer_start),		\
 	FN(timer_cancel),		\
+	FN(get_func_ip),		\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 88b99401040c..abe6d4842bb0 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -10346,19 +10346,25 @@ static int perf_event_open_probe(bool uprobe, bool retprobe, const char *name,
 	return pfd;
 }
 
-struct bpf_link *bpf_program__attach_kprobe(struct bpf_program *prog,
-					    bool retprobe,
-					    const char *func_name)
+struct bpf_program_attach_kprobe_opts {
+	bool retprobe;
+	unsigned long offset;
+};
+
+static struct bpf_link*
+bpf_program__attach_kprobe_opts(struct bpf_program *prog,
+				const char *func_name,
+				struct bpf_program_attach_kprobe_opts *opts)
 {
 	char errmsg[STRERR_BUFSIZE];
 	struct bpf_link *link;
 	int pfd, err;
 
-	pfd = perf_event_open_probe(false /* uprobe */, retprobe, func_name,
-				    0 /* offset */, -1 /* pid */);
+	pfd = perf_event_open_probe(false /* uprobe */, opts->retprobe, func_name,
+				    opts->offset, -1 /* pid */);
 	if (pfd < 0) {
 		pr_warn("prog '%s': failed to create %s '%s' perf event: %s\n",
-			prog->name, retprobe ? "kretprobe" : "kprobe", func_name,
+			prog->name, opts->retprobe ? "kretprobe" : "kprobe", func_name,
 			libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
 		return libbpf_err_ptr(pfd);
 	}
@@ -10367,23 +10373,53 @@ struct bpf_link *bpf_program__attach_kprobe(struct bpf_program *prog,
 	if (err) {
 		close(pfd);
 		pr_warn("prog '%s': failed to attach to %s '%s': %s\n",
-			prog->name, retprobe ? "kretprobe" : "kprobe", func_name,
+			prog->name, opts->retprobe ? "kretprobe" : "kprobe", func_name,
 			libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
 		return libbpf_err_ptr(err);
 	}
 	return link;
 }
 
+struct bpf_link *bpf_program__attach_kprobe(struct bpf_program *prog,
+					    bool retprobe,
+					    const char *func_name)
+{
+	struct bpf_program_attach_kprobe_opts opts = {
+		.retprobe = retprobe,
+	};
+
+	return bpf_program__attach_kprobe_opts(prog, func_name, &opts);
+}
+
 static struct bpf_link *attach_kprobe(const struct bpf_sec_def *sec,
 				      struct bpf_program *prog)
 {
+	struct bpf_program_attach_kprobe_opts opts;
+	unsigned long offset = 0;
+	struct bpf_link *link;
 	const char *func_name;
-	bool retprobe;
+	char *func;
+	int n, err;
 
 	func_name = prog->sec_name + sec->len;
-	retprobe = strcmp(sec->sec, "kretprobe/") == 0;
+	opts.retprobe = strcmp(sec->sec, "kretprobe/") == 0;
+
+	n = sscanf(func_name, "%m[a-zA-Z0-9_.]+%lx", &func, &offset);
+	if (n < 1) {
+		err = -EINVAL;
+		pr_warn("kprobe name is invalid: %s\n", func_name);
+		return libbpf_err_ptr(err);
+	}
+	if (opts.retprobe && offset != 0) {
+		err = -EINVAL;
+		pr_warn("kretprobes do not support offset specification\n");
+		return libbpf_err_ptr(err);
+	}
 
-	return bpf_program__attach_kprobe(prog, retprobe, func_name);
+	opts.offset = offset;
+	link = bpf_program__attach_kprobe_opts(prog, func, &opts);
+	free(func);
+	return link;
 }
 
 struct bpf_link *bpf_program__attach_uprobe(struct bpf_program *prog,
diff --git a/tools/testing/selftests/bpf/prog_tests/get_func_ip_test.c b/tools/testing/selftests/bpf/prog_tests/get_func_ip_test.c
new file mode 100644
index 000000000000..088b3653610d
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/get_func_ip_test.c
@@ -0,0 +1,53 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include "get_func_ip_test.skel.h"
+
+void test_get_func_ip_test(void)
+{
+	struct get_func_ip_test *skel = NULL;
+	__u32 duration = 0, retval;
+	int err, prog_fd;
+
+	skel = get_func_ip_test__open();
+	if (!ASSERT_OK_PTR(skel, "get_func_ip_test__open"))
+		return;
+
+	/* test6 is x86_64 specifc because of the instruction
+	 * offset, disabling it for all other archs
+	 */
+#ifndef __x86_64__
+	bpf_program__set_autoload(skel->progs.test6, false);
+#endif
+
+	err = get_func_ip_test__load(skel);
+	if (!ASSERT_OK(err, "get_func_ip_test__load"))
+		goto cleanup;
+
+	err = get_func_ip_test__attach(skel);
+	if (!ASSERT_OK(err, "get_func_ip_test__attach"))
+		goto cleanup;
+
+	prog_fd = bpf_program__fd(skel->progs.test1);
+	err = bpf_prog_test_run(prog_fd, 1, NULL, 0,
+				NULL, NULL, &retval, &duration);
+	ASSERT_OK(err, "test_run");
+	ASSERT_EQ(retval, 0, "test_run");
+
+	prog_fd = bpf_program__fd(skel->progs.test5);
+	err = bpf_prog_test_run(prog_fd, 1, NULL, 0,
+				NULL, NULL, &retval, &duration);
+
+	ASSERT_OK(err, "test_run");
+
+	ASSERT_EQ(skel->bss->test1_result, 1, "test1_result");
+	ASSERT_EQ(skel->bss->test2_result, 1, "test2_result");
+	ASSERT_EQ(skel->bss->test3_result, 1, "test3_result");
+	ASSERT_EQ(skel->bss->test4_result, 1, "test4_result");
+	ASSERT_EQ(skel->bss->test5_result, 1, "test5_result");
+#ifdef __x86_64__
+	ASSERT_EQ(skel->bss->test6_result, 1, "test6_result");
+#endif
+
+cleanup:
+	get_func_ip_test__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/get_func_ip_test.c b/tools/testing/selftests/bpf/progs/get_func_ip_test.c
new file mode 100644
index 000000000000..acd587b6e859
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/get_func_ip_test.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+extern const void bpf_fentry_test1 __ksym;
+extern const void bpf_fentry_test2 __ksym;
+extern const void bpf_fentry_test3 __ksym;
+extern const void bpf_fentry_test4 __ksym;
+extern const void bpf_modify_return_test __ksym;
+extern const void bpf_fentry_test6 __ksym;
+
+__u64 test1_result = 0;
+SEC("fentry/bpf_fentry_test1")
+int BPF_PROG(test1, int a)
+{
+	__u64 addr = bpf_get_func_ip(ctx);
+
+	test1_result = (const void *) addr == &bpf_fentry_test1;
+	return 0;
+}
+
+__u64 test2_result = 0;
+SEC("fexit/bpf_fentry_test2")
+int BPF_PROG(test2, int a)
+{
+	__u64 addr = bpf_get_func_ip(ctx);
+
+	test2_result = (const void *) addr == &bpf_fentry_test2;
+	return 0;
+}
+
+__u64 test3_result = 0;
+SEC("kprobe/bpf_fentry_test3")
+int test3(struct pt_regs *ctx)
+{
+	__u64 addr = bpf_get_func_ip(ctx);
+
+	test3_result = (const void *) addr == &bpf_fentry_test3;
+	return 0;
+}
+
+__u64 test4_result = 0;
+SEC("kretprobe/bpf_fentry_test4")
+int BPF_KRETPROBE(test4)
+{
+	__u64 addr = bpf_get_func_ip(ctx);
+
+	test4_result = (const void *) addr == &bpf_fentry_test4;
+	return 0;
+}
+
+__u64 test5_result = 0;
+SEC("fmod_ret/bpf_modify_return_test")
+int BPF_PROG(test5, int a, int *b, int ret)
+{
+	__u64 addr = bpf_get_func_ip(ctx);
+
+	test5_result = (const void *) addr == &bpf_modify_return_test;
+	return ret;
+}
+
+__u64 test6_result = 0;
+SEC("kprobe/bpf_fentry_test6+0x5")
+int test6(struct pt_regs *ctx)
+{
+	__u64 addr = bpf_get_func_ip(ctx);
+
+	test6_result = (const void *) addr == &bpf_fentry_test6 + 5;
+	return 0;
+}