target/arm: Enable SCTLR_EL1.BT0 for aarch64-linux-user

This controls whether the PACI{A,B}SP instructions trap with BTYPE=3
(indirect branch from register other than x16/x17).  The linux kernel
sets this in bti_enable().

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/998
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20220427042312.294300-1-richard.henderson@linaro.org
[PMM: remove stray change to makefile comment]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 42 insertions, 0 deletions

diff --git a/tests/tcg/aarch64/bti-3.c b/tests/tcg/aarch64/bti-3.c
new file mode 100644
index 0000000000..a852856d9a
--- /dev/null
+++ b/tests/tcg/aarch64/bti-3.c
@@ -0,0 +1,42 @@
+/*
+ * BTI vs PACIASP
+ */
+
+#include "bti-crt.inc.c"
+
+static void skip2_sigill(int sig, siginfo_t *info, ucontext_t *uc)
+{
+    uc->uc_mcontext.pc += 8;
+    uc->uc_mcontext.pstate = 1;
+}
+
+#define BTYPE_1() \
+    asm("mov %0,#1; adr x16, 1f; br x16; 1: hint #25; mov %0,#0" \
+        : "=r"(skipped) : : "x16", "x30")
+
+#define BTYPE_2() \
+    asm("mov %0,#1; adr x16, 1f; blr x16; 1: hint #25; mov %0,#0" \
+        : "=r"(skipped) : : "x16", "x30")
+
+#define BTYPE_3() \
+    asm("mov %0,#1; adr x15, 1f; br x15; 1: hint #25; mov %0,#0" \
+        : "=r"(skipped) : : "x15", "x30")
+
+#define TEST(WHICH, EXPECT) \
+    do { WHICH(); fail += skipped ^ EXPECT; } while (0)
+
+int main()
+{
+    int fail = 0;
+    int skipped;
+
+    /* Signal-like with SA_SIGINFO.  */
+    signal_info(SIGILL, skip2_sigill);
+
+    /* With SCTLR_EL1.BT0 set, PACIASP is not compatible with type=3. */
+    TEST(BTYPE_1, 0);
+    TEST(BTYPE_2, 0);
+    TEST(BTYPE_3, 1);
+
+    return fail;
+}