linux-kernel - [PATCH] selftests/bpf: Fix uprobe syscall shadow stack test

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Message-ID: <20250821141557.13233-1-jolsa@kernel.org>
Date: Thu, 21 Aug 2025 16:15:57 +0200
From: Jiri Olsa <jolsa@...nel.org>
To: Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrii Nakryiko <andrii@...nel.org>
Cc: bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org,
	x86@...nel.org,
	Song Liu <songliubraving@...com>,
	Yonghong Song <yhs@...com>,
	John Fastabend <john.fastabend@...il.com>,
	Hao Luo <haoluo@...gle.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Alan Maguire <alan.maguire@...cle.com>,
	David Laight <David.Laight@...LAB.COM>,
	Thomas Weißschuh <thomas@...ch.de>,
	Ingo Molnar <mingo@...nel.org>
Subject: [PATCH] selftests/bpf: Fix uprobe syscall shadow stack test

Now that we have uprobe syscall working properly with shadow stack,
we can remove testing limitations for shadow stack tests and make
sure uprobe gets properly optimized.

Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
sending fix for changes posted in here [1]

[1] https://lore.kernel.org/bpf/20250821122822.671515652@infradead.org/T/#m571d8b1975e1f4ade55aa972940d8568647ac113

 .../selftests/bpf/prog_tests/uprobe_syscall.c | 24 +++++--------------
 1 file changed, 6 insertions(+), 18 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c b/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
index c1f945cacebc..5da0b49eeaca 100644
--- a/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
+++ b/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
@@ -403,8 +403,6 @@ static void *find_nop5(void *fn)
 
 typedef void (__attribute__((nocf_check)) *trigger_t)(void);
 
-static bool shstk_is_enabled;
-
 static void *check_attach(struct uprobe_syscall_executed *skel, trigger_t trigger,
 			  void *addr, int executed)
 {
@@ -413,7 +411,6 @@ static void *check_attach(struct uprobe_syscall_executed *skel, trigger_t trigge
 		__s32 raddr;
 	} __packed *call;
 	void *tramp = NULL;
-	__u8 *bp;
 
 	/* Uprobe gets optimized after first trigger, so let's press twice. */
 	trigger();
@@ -422,17 +419,11 @@ static void *check_attach(struct uprobe_syscall_executed *skel, trigger_t trigge
 	/* Make sure bpf program got executed.. */
 	ASSERT_EQ(skel->bss->executed, executed, "executed");
 
-	if (shstk_is_enabled) {
-		/* .. and check optimization is disabled under shadow stack. */
-		bp = (__u8 *) addr;
-		ASSERT_EQ(*bp, 0xcc, "int3");
-	} else {
-		/* .. and check the trampoline is as expected. */
-		call = (struct __arch_relative_insn *) addr;
-		tramp = (void *) (call + 1) + call->raddr;
-		ASSERT_EQ(call->op, 0xe8, "call");
-		ASSERT_OK(find_uprobes_trampoline(tramp), "uprobes_trampoline");
-	}
+	/* .. and check the trampoline is as expected. */
+	call = (struct __arch_relative_insn *) addr;
+	tramp = (void *) (call + 1) + call->raddr;
+	ASSERT_EQ(call->op, 0xe8, "call");
+	ASSERT_OK(find_uprobes_trampoline(tramp), "uprobes_trampoline");
 
 	return tramp;
 }
@@ -440,7 +431,7 @@ static void *check_attach(struct uprobe_syscall_executed *skel, trigger_t trigge
 static void check_detach(void *addr, void *tramp)
 {
 	/* [uprobes_trampoline] stays after detach */
-	ASSERT_OK(!shstk_is_enabled && find_uprobes_trampoline(tramp), "uprobes_trampoline");
+	ASSERT_OK(find_uprobes_trampoline(tramp), "uprobes_trampoline");
 	ASSERT_OK(memcmp(addr, nop5, 5), "nop5");
 }
 
@@ -642,7 +633,6 @@ static void test_uretprobe_shadow_stack(void)
 	}
 
 	/* Run all the tests with shadow stack in place. */
-	shstk_is_enabled = true;
 
 	test_uprobe_regs_equal(false);
 	test_uprobe_regs_equal(true);
@@ -655,8 +645,6 @@ static void test_uretprobe_shadow_stack(void)
 
 	test_regs_change();
 
-	shstk_is_enabled = false;
-
 	ARCH_PRCTL(ARCH_SHSTK_DISABLE, ARCH_SHSTK_SHSTK);
 }
 
-- 
2.50.1