Merge branch 'x86-fgraph-bpf-fix-orc-stack-unwind-from-kprobe_multi'

Jiri Olsa says:

====================
x86/fgraph,bpf: Fix ORC stack unwind from kprobe_multi

hi,
Mahe reported missing function from stack trace on top of kprobe multi
program. It turned out the latest fix [1] needs some more fixing.

v2 changes:
- keep the unwind same as for kprobes, attached function
  is part of entry probe stacktrace, not kretprobe [Steven]
- several change in trigger bench [Andrii]
- added selftests for standard kprobes and fentry/fexit probes [Andrii]

Note I'll try to add similar stacktrace adjustment for fentry/fexit
in separate patchset to not complicate this change.

thanks,
jirka

[1] https://lore.kernel.org/bpf/20251104215405.168643-1-jolsa@kernel.org/
---
====================

Link: https://patch.msgid.link/20260126211837.472802-1-jolsa@kernel.org
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

arch/x86/include/asm/ftrace.h

@@ -57,7 +57,7 @@ arch_ftrace_get_regs(struct ftrace_regs *fregs)
 }
 
 #define arch_ftrace_partial_regs(regs) do {	\
-	regs->flags &= ~X86_EFLAGS_FIXED;	\
+	regs->flags |= X86_EFLAGS_FIXED;	\
 	regs->cs = __KERNEL_CS;			\
 } while (0)
 

arch/x86/kernel/ftrace_64.S

@@ -364,6 +364,9 @@ SYM_CODE_START(return_to_handler)
 	UNWIND_HINT_UNDEFINED
 	ANNOTATE_NOENDBR
 
+	/* Store original rsp for pt_regs.sp value. */
+	movq %rsp, %rdi
+
 	/* Restore return_to_handler value that got eaten by previous ret instruction. */
 	subq $8, %rsp
 	UNWIND_HINT_FUNC
@@ -374,7 +377,7 @@ SYM_CODE_START(return_to_handler)
 	movq %rax, RAX(%rsp)
 	movq %rdx, RDX(%rsp)
 	movq %rbp, RBP(%rsp)
-	movq %rsp, RSP(%rsp)
+	movq %rdi, RSP(%rsp)
 	movq %rsp, %rdi
 
 	call ftrace_return_to_handler

tools/testing/selftests/bpf/bench.c

@@ -265,6 +265,7 @@ static const struct argp_option opts[] = {
 	{ "verbose", 'v', NULL, 0, "Verbose debug output"},
 	{ "affinity", 'a', NULL, 0, "Set consumer/producer thread affinity"},
 	{ "quiet", 'q', NULL, 0, "Be more quiet"},
+	{ "stacktrace", 's', NULL, 0, "Get stack trace"},
 	{ "prod-affinity", ARG_PROD_AFFINITY_SET, "CPUSET", 0,
 	  "Set of CPUs for producer threads; implies --affinity"},
 	{ "cons-affinity", ARG_CONS_AFFINITY_SET, "CPUSET", 0,
@@ -350,6 +351,9 @@ static error_t parse_arg(int key, char *arg, struct argp_state *state)
 	case 'q':
 		env.quiet = true;
 		break;
+	case 's':
+		env.stacktrace = true;
+		break;
 	case ARG_PROD_AFFINITY_SET:
 		env.affinity = true;
 		if (parse_num_list(arg, &env.prod_cpus.cpus,

tools/testing/selftests/bpf/bench.h

@@ -26,6 +26,7 @@ struct env {
 	bool list;
 	bool affinity;
 	bool quiet;
+	bool stacktrace;
 	int consumer_cnt;
 	int producer_cnt;
 	int nr_cpus;

tools/testing/selftests/bpf/benchs/bench_trigger.c

@@ -146,6 +146,7 @@ static void setup_ctx(void)
 	bpf_program__set_autoload(ctx.skel->progs.trigger_driver, true);
 
 	ctx.skel->rodata->batch_iters = args.batch_iters;
+	ctx.skel->rodata->stacktrace = env.stacktrace;
 }
 
 static void load_ctx(void)

tools/testing/selftests/bpf/prog_tests/stacktrace_ips.c

@@ -74,11 +74,20 @@ static void test_stacktrace_ips_kprobe_multi(bool retprobe)
 
 	load_kallsyms();
 
-	check_stacktrace_ips(bpf_map__fd(skel->maps.stackmap), skel->bss->stack_key, 4,
-			     ksym_get_addr("bpf_testmod_stacktrace_test_3"),
-			     ksym_get_addr("bpf_testmod_stacktrace_test_2"),
-			     ksym_get_addr("bpf_testmod_stacktrace_test_1"),
-			     ksym_get_addr("bpf_testmod_test_read"));
+	if (retprobe) {
+		check_stacktrace_ips(bpf_map__fd(skel->maps.stackmap), skel->bss->stack_key, 4,
+				     ksym_get_addr("bpf_testmod_stacktrace_test_3"),
+				     ksym_get_addr("bpf_testmod_stacktrace_test_2"),
+				     ksym_get_addr("bpf_testmod_stacktrace_test_1"),
+				     ksym_get_addr("bpf_testmod_test_read"));
+	} else {
+		check_stacktrace_ips(bpf_map__fd(skel->maps.stackmap), skel->bss->stack_key, 5,
+				     ksym_get_addr("bpf_testmod_stacktrace_test"),
+				     ksym_get_addr("bpf_testmod_stacktrace_test_3"),
+				     ksym_get_addr("bpf_testmod_stacktrace_test_2"),
+				     ksym_get_addr("bpf_testmod_stacktrace_test_1"),
+				     ksym_get_addr("bpf_testmod_test_read"));
+	}
 
 cleanup:
 	stacktrace_ips__destroy(skel);
@@ -128,6 +137,99 @@ static void test_stacktrace_ips_raw_tp(void)
 	stacktrace_ips__destroy(skel);
 }
 
+static void test_stacktrace_ips_kprobe(bool retprobe)
+{
+	LIBBPF_OPTS(bpf_kprobe_opts, opts,
+		.retprobe = retprobe
+	);
+	LIBBPF_OPTS(bpf_test_run_opts, topts);
+	struct stacktrace_ips *skel;
+
+	skel = stacktrace_ips__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "stacktrace_ips__open_and_load"))
+		return;
+
+	if (!skel->kconfig->CONFIG_UNWINDER_ORC) {
+		test__skip();
+		goto cleanup;
+	}
+
+	skel->links.kprobe_test = bpf_program__attach_kprobe_opts(
+						skel->progs.kprobe_test,
+						"bpf_testmod_stacktrace_test", &opts);
+	if (!ASSERT_OK_PTR(skel->links.kprobe_test, "bpf_program__attach_kprobe_opts"))
+		goto cleanup;
+
+	trigger_module_test_read(1);
+
+	load_kallsyms();
+
+	if (retprobe) {
+		check_stacktrace_ips(bpf_map__fd(skel->maps.stackmap), skel->bss->stack_key, 4,
+				     ksym_get_addr("bpf_testmod_stacktrace_test_3"),
+				     ksym_get_addr("bpf_testmod_stacktrace_test_2"),
+				     ksym_get_addr("bpf_testmod_stacktrace_test_1"),
+				     ksym_get_addr("bpf_testmod_test_read"));
+	} else {
+		check_stacktrace_ips(bpf_map__fd(skel->maps.stackmap), skel->bss->stack_key, 5,
+				     ksym_get_addr("bpf_testmod_stacktrace_test"),
+				     ksym_get_addr("bpf_testmod_stacktrace_test_3"),
+				     ksym_get_addr("bpf_testmod_stacktrace_test_2"),
+				     ksym_get_addr("bpf_testmod_stacktrace_test_1"),
+				     ksym_get_addr("bpf_testmod_test_read"));
+	}
+
+cleanup:
+	stacktrace_ips__destroy(skel);
+}
+
+static void test_stacktrace_ips_trampoline(bool retprobe)
+{
+	LIBBPF_OPTS(bpf_test_run_opts, topts);
+	struct stacktrace_ips *skel;
+
+	skel = stacktrace_ips__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "stacktrace_ips__open_and_load"))
+		return;
+
+	if (!skel->kconfig->CONFIG_UNWINDER_ORC) {
+		test__skip();
+		goto cleanup;
+	}
+
+	if (retprobe) {
+		skel->links.fexit_test = bpf_program__attach_trace(skel->progs.fexit_test);
+		if (!ASSERT_OK_PTR(skel->links.fexit_test, "bpf_program__attach_trace"))
+			goto cleanup;
+	} else {
+		skel->links.fentry_test = bpf_program__attach_trace(skel->progs.fentry_test);
+		if (!ASSERT_OK_PTR(skel->links.fentry_test, "bpf_program__attach_trace"))
+			goto cleanup;
+	}
+
+	trigger_module_test_read(1);
+
+	load_kallsyms();
+
+	if (retprobe) {
+		check_stacktrace_ips(bpf_map__fd(skel->maps.stackmap), skel->bss->stack_key, 4,
+				     ksym_get_addr("bpf_testmod_stacktrace_test_3"),
+				     ksym_get_addr("bpf_testmod_stacktrace_test_2"),
+				     ksym_get_addr("bpf_testmod_stacktrace_test_1"),
+				     ksym_get_addr("bpf_testmod_test_read"));
+	} else {
+		check_stacktrace_ips(bpf_map__fd(skel->maps.stackmap), skel->bss->stack_key, 5,
+				     ksym_get_addr("bpf_testmod_stacktrace_test"),
+				     ksym_get_addr("bpf_testmod_stacktrace_test_3"),
+				     ksym_get_addr("bpf_testmod_stacktrace_test_2"),
+				     ksym_get_addr("bpf_testmod_stacktrace_test_1"),
+				     ksym_get_addr("bpf_testmod_test_read"));
+	}
+
+cleanup:
+	stacktrace_ips__destroy(skel);
+}
+
 static void __test_stacktrace_ips(void)
 {
 	if (test__start_subtest("kprobe_multi"))
@@ -136,6 +238,14 @@ static void __test_stacktrace_ips(void)
 		test_stacktrace_ips_kprobe_multi(true);
 	if (test__start_subtest("raw_tp"))
 		test_stacktrace_ips_raw_tp();
+	if (test__start_subtest("kprobe"))
+		test_stacktrace_ips_kprobe(false);
+	if (test__start_subtest("kretprobe"))
+		test_stacktrace_ips_kprobe(true);
+	if (test__start_subtest("fentry"))
+		test_stacktrace_ips_trampoline(false);
+	if (test__start_subtest("fexit"))
+		test_stacktrace_ips_trampoline(true);
 }
 #else
 static void __test_stacktrace_ips(void)

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

@@ -31,6 +31,13 @@ int unused(void)
 
 __u32 stack_key;
 
+SEC("kprobe")
+int kprobe_test(struct pt_regs *ctx)
+{
+	stack_key = bpf_get_stackid(ctx, &stackmap, 0);
+	return 0;
+}
+
 SEC("kprobe.multi")
 int kprobe_multi_test(struct pt_regs *ctx)
 {
@@ -46,4 +53,24 @@ int rawtp_test(void *ctx)
 	return 0;
 }
 
+SEC("fentry/bpf_testmod_stacktrace_test")
+int fentry_test(struct pt_regs *ctx)
+{
+	/*
+	 * Skip 2 bpf_program/trampoline stack entries:
+	 * - bpf_prog_bd1f7a949f55fb03_fentry_test
+	 * - bpf_trampoline_182536277701
+	 */
+	stack_key = bpf_get_stackid(ctx, &stackmap, 2);
+	return 0;
+}
+
+SEC("fexit/bpf_testmod_stacktrace_test")
+int fexit_test(struct pt_regs *ctx)
+{
+	/* Skip 2 bpf_program/trampoline stack entries, check fentry_test. */
+	stack_key = bpf_get_stackid(ctx, &stackmap, 2);
+	return 0;
+}
+
 char _license[] SEC("license") = "GPL";

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

@@ -25,6 +25,34 @@ static __always_inline void inc_counter(void)
 	__sync_add_and_fetch(&hits[cpu & CPU_MASK].value, 1);
 }
 
+volatile const int stacktrace;
+
+typedef __u64 stack_trace_t[128];
+
+struct {
+	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
+	 __uint(max_entries, 1);
+	__type(key, __u32);
+	__type(value, stack_trace_t);
+} stack_heap SEC(".maps");
+
+static __always_inline void do_stacktrace(void *ctx)
+{
+	if (!stacktrace)
+		return;
+
+	__u64 *ptr = bpf_map_lookup_elem(&stack_heap, &(__u32){0});
+
+	if (ptr)
+		bpf_get_stack(ctx, ptr, sizeof(stack_trace_t), 0);
+}
+
+static __always_inline void handle(void *ctx)
+{
+	inc_counter();
+	do_stacktrace(ctx);
+}
+
 SEC("?uprobe")
 int bench_trigger_uprobe(void *ctx)
 {
@@ -81,21 +109,21 @@ int trigger_driver_kfunc(void *ctx)
 SEC("?kprobe/bpf_get_numa_node_id")
 int bench_trigger_kprobe(void *ctx)
 {
-	inc_counter();
+	handle(ctx);
 	return 0;
 }
 
 SEC("?kretprobe/bpf_get_numa_node_id")
 int bench_trigger_kretprobe(void *ctx)
 {
-	inc_counter();
+	handle(ctx);
 	return 0;
 }
 
 SEC("?kprobe.multi/bpf_get_numa_node_id")
 int bench_trigger_kprobe_multi(void *ctx)
 {
-	inc_counter();
+	handle(ctx);
 	return 0;
 }
 
@@ -108,7 +136,7 @@ int bench_kprobe_multi_empty(void *ctx)
 SEC("?kretprobe.multi/bpf_get_numa_node_id")
 int bench_trigger_kretprobe_multi(void *ctx)
 {
-	inc_counter();
+	handle(ctx);
 	return 0;
 }
 
@@ -121,34 +149,34 @@ int bench_kretprobe_multi_empty(void *ctx)
 SEC("?fentry/bpf_get_numa_node_id")
 int bench_trigger_fentry(void *ctx)
 {
-	inc_counter();
+	handle(ctx);
 	return 0;
 }
 
 SEC("?fexit/bpf_get_numa_node_id")
 int bench_trigger_fexit(void *ctx)
 {
-	inc_counter();
+	handle(ctx);
 	return 0;
 }
 
 SEC("?fmod_ret/bpf_modify_return_test_tp")
 int bench_trigger_fmodret(void *ctx)
 {
-	inc_counter();
+	handle(ctx);
 	return -22;
 }
 
 SEC("?tp/bpf_test_run/bpf_trigger_tp")
 int bench_trigger_tp(void *ctx)
 {
-	inc_counter();
+	handle(ctx);
 	return 0;
 }
 
 SEC("?raw_tp/bpf_trigger_tp")
 int bench_trigger_rawtp(void *ctx)
 {
-	inc_counter();
+	handle(ctx);
 	return 0;
 }