kselftest: arm64: fake_sigreturn_bad_magic

Add a simple fake_sigreturn testcase which builds a ucontext_t with a bad
magic header and place it onto the stack. Expects a SIGSEGV on test PASS.

Introduce a common utility assembly trampoline function to invoke a
sigreturn while placing the provided sigframe at wanted alignment and
also an helper to make space when needed inside the sigframe reserved
area.

Reviewed-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 52 insertions, 0 deletions

diff --git a/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_magic.c b/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_magic.c
new file mode 100644
index 000000000000..8dc600a7d4fd
--- /dev/null
+++ b/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_magic.c
@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 ARM Limited
+ *
+ * Place a fake sigframe on the stack including a BAD Unknown magic
+ * record: on sigreturn Kernel must spot this attempt and the test
+ * case is expected to be terminated via SEGV.
+ */
+
+#include <signal.h>
+#include <ucontext.h>
+
+#include "test_signals_utils.h"
+#include "testcases.h"
+
+struct fake_sigframe sf;
+
+static int fake_sigreturn_bad_magic_run(struct tdescr *td,
+					siginfo_t *si, ucontext_t *uc)
+{
+	struct _aarch64_ctx *shead = GET_SF_RESV_HEAD(sf), *head;
+
+	/* just to fill the ucontext_t with something real */
+	if (!get_current_context(td, &sf.uc))
+		return 1;
+
+	/* need at least 2*HDR_SZ space: KSFT_BAD_MAGIC + terminator. */
+	head = get_starting_head(shead, HDR_SZ * 2, GET_SF_RESV_SIZE(sf), NULL);
+	if (!head)
+		return 0;
+
+	/*
+	 * use a well known NON existent bad magic...something
+	 * we should pretty sure won't be ever defined in Kernel
+	 */
+	head->magic = KSFT_BAD_MAGIC;
+	head->size = HDR_SZ;
+	write_terminator_record(GET_RESV_NEXT_HEAD(head));
+
+	ASSERT_BAD_CONTEXT(&sf.uc);
+	fake_sigreturn(&sf, sizeof(sf), 0);
+
+	return 1;
+}
+
+struct tdescr tde = {
+		.name = "FAKE_SIGRETURN_BAD_MAGIC",
+		.descr = "Trigger a sigreturn with a sigframe with a bad magic",
+		.sig_ok = SIGSEGV,
+		.timeout = 3,
+		.run = fake_sigreturn_bad_magic_run,
+};