From a0cd0b1d0bc78b8ffe3292fbb4f14e4a15e16b7b Mon Sep 17 00:00:00 2001
From: Peter Maydell <peter.maydell@linaro.org>
Date: Fri, 16 Dec 2022 13:52:28 +0000
Subject: test15: Add execution tests from small MPU regions

Add some tests of execution from small MPU regions.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 test15.c | 90 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 84 insertions(+), 6 deletions(-)

diff --git a/test15.c b/test15.c
index 7f3b37e..7ecc846 100644
--- a/test15.c
+++ b/test15.c
@@ -69,6 +69,38 @@ void checkfault(unsigned v)
     }
 }
 
+typedef int testfn(int);
+
+static int tryexec(volatile char *p)
+{
+    uint32_t tval = 0;
+    testfn *f = (testfn *)((uintptr_t)p | 1);
+    testDiag("Tryexec %" PRIx32, (uint32_t)p);
+    /* The assumption is that the code at the dest address is
+     *   adds r0, #1; bx lr
+     * so we can call it, and it will increment our value for us.
+     * For non-executable code the exception handler will
+     * by-hand do the function return back to lr.
+     */
+    tval = f(tval);
+    testDiag("Returned with %" PRIx32, tval);
+    if (expect_fault == EXPECT_NO_FAULT && tval != 1) {
+        testFail("expected code to return 1 but got %" PRId32 "\n", tval);
+        return 0;
+    }
+    return 1;
+}
+
+static void write_exec_test_insns(volatile char *p)
+{
+    /* Write the "adds r0, #1; bx lr" sequence we'll use
+     * in tryexec().
+     */
+    volatile uint16_t *px = (uint16_t*)p;
+    px[0] = 0x3001; /* adds r0, 1 */
+    px[1] = 0x4770; /* bx lr */
+}
+
 void hard(uint32_t *sp)
 {
     testDiag("In HardFault handler");
@@ -91,12 +123,28 @@ void hard_entry(void)
 
 void mem(uint32_t *sp)
 {
-    uint32_t addr;
+    uint32_t cfsr = in32(SCB(0xd28));
+    uint32_t addr = in32(SCB(0xd34));
+
+    out32(SCB(0xd28), 0xff); /* W1C the MMFSR bits */
 
     sp = get_src_stack(sp);
-    inst_skip(sp);
-    addr = in32((void*)0xe000ed34);
-    testDiag("In MemFault, Addr 0x%" PRIx32 ", from 0x%" PRIx32, addr, sp[6]);
+
+    testDiag("In MemFault, CFSR 0x%" PRIx32 ", from 0x%" PRIX32, cfsr, sp[6]);
+    if (cfsr & 0x80) {
+        testDiag("...MMARVALID set, MMFAR is 0x%" PRIx32, addr);
+    }
+
+    if (cfsr & 0x1) {
+        /* IACCVIOL -- set PC to LR. Note that the LR will have the
+         * bit-0-means-Thumb convention but an exception frame PC slot
+         * has the "raw" PC.
+         */
+        sp[6] = sp[5] & ~1;
+    } else {
+        /* DACCVIOL -- just skip offending insn */
+        inst_skip(sp);
+    }
 
     switch(expect_fault) {
     case EXPECT_MEMFAULT:
@@ -174,7 +222,7 @@ void main(void)
     mpu_type = in32(SCB(0xD90));
     has_mpu = ((mpu_type >> 8) & 0xff) != 0;
 
-    testInit(4);
+    testInit(8);
 
     if (!has_mpu) {
         testDiag("No MPU present: nothing to test here");
@@ -201,10 +249,14 @@ void main(void)
     set_mpu(4, (uint32_t)testpage, 512,
             MPU_XN|MPU_NORMAL|MPU_NANA);
     set_mpu(5, (uint32_t)testpage + 512, 256,
-            MPU_XN|MPU_NORMAL|MPU_RWRW);
+            MPU_NORMAL|MPU_RWRW);
     set_mpu(6, (uint32_t)testpage + 768, 256,
             MPU_XN|MPU_NORMAL|MPU_NANA);
 
+    write_exec_test_insns(testpage + 256);
+    write_exec_test_insns(testpage + 600);
+    write_exec_test_insns(testpage + 768);
+
     testDiag("Enable MPU");
     enable_mpu(1,1,0);
 
@@ -228,5 +280,31 @@ void main(void)
     try(testpage + 600);
     checkfault(EXPECT_NO_FAULT);
 
+    /* Try to execute from various parts of the small page */
+    expect_fault = EXPECT_NO_FAULT;
+    testDiag("Execute from the accessible small page (should not fault)");
+    // TODO we get a HardFault here...
+    if (tryexec(testpage + 600)) {
+        checkfault(EXPECT_NO_FAULT);
+    }
+
+    expect_fault = EXPECT_MEMFAULT;
+    testDiag("Execute from the preceding small page (should fault)");
+    if (tryexec(testpage + 256)) {
+        checkfault(EXPECT_TAKEN_MEMFAULT);
+    }
+
+    expect_fault = EXPECT_MEMFAULT;
+    testDiag("Execute from the following small page (should fault)");
+    if (tryexec(testpage + 768)) {
+        checkfault(EXPECT_TAKEN_MEMFAULT);
+    }
+
+    expect_fault = EXPECT_NO_FAULT;
+    testDiag("Execute from the accessible small page again (should not fault)");
+    if (tryexec(testpage + 600)) {
+        checkfault(EXPECT_NO_FAULT);
+    }
+
     testDiag("Done.");
 }
-- 
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