1 files changed, 81 insertions, 0 deletions
diff --git a/debug/programs/multicore.c b/debug/programs/multicore.c
new file mode 100644
index 0000000..d7dd845
--- /dev/null
+++ b/debug/programs/multicore.c
@@ -0,0 +1,81 @@
+#include <stdint.h>
+
+typedef struct {
+    int counter;
+} atomic_t;
+
+static inline int atomic_xchg(atomic_t *v, int n)
+{
+    register int c;
+
+    __asm__ __volatile__ (
+            "amoswap.w.aqrl %0, %2, %1"
+            : "=r" (c), "+A" (v->counter)
+            : "r" (n));
+    return c;
+}
+
+#define csr_read(csr)                                   \
+({                                                      \
+    register unsigned long __v;                         \
+    __asm__ __volatile__ ("csrr %0, " #csr              \
+                  : "=r" (__v));                        \
+    __v;                                                \
+})
+
+static inline void mb(void)
+{
+    __asm__ __volatile__ ("fence");
+}
+
+void get_lock(atomic_t *lock)
+{
+    while (atomic_xchg(lock, 1) == 1)
+        ;
+    mb();
+}
+
+void put_lock(atomic_t *lock)
+{
+    mb();
+    atomic_xchg(lock, 0);
+}
+
+static atomic_t buf_lock = { .counter = 0 };
+static char buf[32];
+static int buf_initialized;
+static unsigned hart_count[2];
+
+static const char case_bit = 'a' - 'A';
+volatile int initialized;
+
+int main()
+{
+    uint32_t hartid = csr_read(mhartid);
+    hart_count[hartid] = 0;
+
+    while (1) {
+        get_lock(&buf_lock);
+        hart_count[hartid]++;
+
+        if (!buf_initialized) {
+            for (unsigned i = 0; i < sizeof(buf); i++) {
+                buf[i] = 'A' + (i % 26);
+            }
+            buf_initialized = 1;
+        }
+
+        char first = buf[0];
+        int offset = (first & ~0x20) - 'A';
+        for (unsigned i = 0; i < sizeof(buf); i++) {
+            while (buf[i] != (first - offset + ((offset + i) % 26)))
+                ;
+
+            if (hartid & 1)
+                buf[i] = 'A' + ((i + hartid + hart_count[hartid]) % 26);
+            else
+                buf[i] = 'a' + ((i + hartid + hart_count[hartid]) % 26);
+        }
+        put_lock(&buf_lock);
+    }
+}