From b34b144a8c7d6193566905518e2d2973d17fe4e7 Mon Sep 17 00:00:00 2001
From: Toby Jaffey <toby@ringtailsoftware.co.uk>
Date: Tue, 9 Dec 2025 00:15:25 +0000
Subject: [PATCH] Update example

---
 README.md | 44 ++++++++++++++++++++++++++++++++++----------
 1 file changed, 34 insertions(+), 10 deletions(-)

diff --git a/README.md b/README.md
index c888ad1..92c40bd 100644
--- a/README.md
+++ b/README.md
@@ -152,20 +152,39 @@ Here is a full example of a working VM host from [apps/host-mini](apps/host-mini
 // Precompiled binary program to print integers
 // This code expects to print via syscall 0x13C (UVM32_SYSCALL_PRINTD in common/uvm32_common_custom.h)
 uint8_t rom[] = {
-  0x23, 0x26, 0x11, 0x00, 0xef, 0x00, 0x00, 0x01, 0x73, 0x50, 0x80, 0x13,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x93, 0x07, 0x00, 0x00,
-  0x13, 0x07, 0xa0, 0x00, 0x73, 0x90, 0xc7, 0x13, 0x93, 0x87, 0x17, 0x00,
-  0xe3, 0x9c, 0xe7, 0xfe, 0x67, 0x80, 0x00, 0x00
+  0x23, 0x26, 0x11, 0x00, 0xef, 0x00, 0xc0, 0x00, 0xb7, 0x08, 0x00, 0x01,
+  0x73, 0x00, 0x00, 0x00, 0x37, 0xf5, 0xff, 0xff, 0xb7, 0x15, 0x00, 0x00,
+  0x37, 0xe6, 0xff, 0xff, 0x13, 0x07, 0xf0, 0x01, 0xb7, 0x47, 0x00, 0x00,
+  0xb7, 0x06, 0x00, 0x01, 0x13, 0x08, 0xd5, 0xcc, 0x93, 0x82, 0x35, 0x33,
+  0x13, 0x03, 0x76, 0xe6, 0x93, 0x83, 0x35, 0xb3, 0x13, 0x86, 0x16, 0x00,
+  0x63, 0xc8, 0x02, 0x09, 0x13, 0x0e, 0x03, 0x00, 0x63, 0xca, 0x63, 0x06,
+  0x93, 0x0e, 0x00, 0x00, 0x93, 0x05, 0x00, 0x00, 0x13, 0x0f, 0x00, 0x00,
+  0x93, 0x0f, 0x00, 0x00, 0x93, 0x06, 0x00, 0x02, 0x13, 0x85, 0x06, 0xfe,
+  0x63, 0x62, 0xa7, 0x04, 0x33, 0x85, 0xd5, 0x01, 0x63, 0xee, 0xa7, 0x02,
+  0x13, 0x05, 0x00, 0x00, 0x93, 0x08, 0x06, 0x00, 0x33, 0x8f, 0xef, 0x03,
+  0xb3, 0x8f, 0xd5, 0x41, 0x73, 0x00, 0x00, 0x00, 0x13, 0x5f, 0xbf, 0x40,
+  0xb3, 0x8f, 0xcf, 0x01, 0x33, 0x0f, 0x0f, 0x01, 0xb3, 0x85, 0xff, 0x03,
+  0x93, 0xd5, 0xc5, 0x00, 0x33, 0x05, 0xef, 0x03, 0x93, 0x5e, 0xc5, 0x00,
+  0x93, 0x86, 0x16, 0x00, 0x6f, 0xf0, 0xdf, 0xfb, 0x13, 0x85, 0x06, 0x00,
+  0x93, 0x08, 0x00, 0x00, 0x73, 0x00, 0x00, 0x00, 0x13, 0x0e, 0x1e, 0x09,
+  0xe3, 0xda, 0xc3, 0xf9, 0x13, 0x05, 0xa0, 0x00, 0x93, 0x08, 0x00, 0x00,
+  0x73, 0x00, 0x00, 0x00, 0x13, 0x08, 0x98, 0x19, 0xe3, 0xdc, 0x02, 0xf7,
+  0x37, 0x05, 0x00, 0x80, 0x13, 0x05, 0x05, 0x0e, 0x93, 0x08, 0x30, 0x00,
+  0x73, 0x00, 0x00, 0x00, 0x67, 0x80, 0x00, 0x00, 0x48, 0x65, 0x6c, 0x6c,
+  0x6f, 0x20, 0x77, 0x6f, 0x72, 0x6c, 0x64, 0x00
 };
 
 // Create an identifier for our host handler
+// syscalls exposed to vm environement
 typedef enum {
-    F_PRINTD,
+    F_PUTC,
+    F_PRINTLN,
 } f_code_t;
 
-// Map VM syscall UVM32_SYSCALL_PRINTD (0x13C) to F_PRINTD, tell VM to expect write of a U32
+// Map exposed syscalls to syscalls
 const uvm32_mapping_t env[] = {
-    { .syscall = UVM32_SYSCALL_PRINTD, .typ = UVM32_SYSCALL_TYP_U32_WR, .code = F_PRINTD },
+    { .syscall = UVM32_SYSCALL_PRINTLN, .typ = UVM32_SYSCALL_TYP_BUF_TERMINATED_WR, .code = F_PRINTLN },
+    { .syscall = UVM32_SYSCALL_PUTC, .typ = UVM32_SYSCALL_TYP_U32_WR, .code = F_PUTC },
 };
 
 int main(int argc, char *argv[]) {
@@ -185,12 +204,17 @@ int main(int argc, char *argv[]) {
             break;
             case UVM32_EVT_SYSCALL:    // vm has paused to handle UVM32_SYSCALL
                 switch((f_code_t)evt.data.syscall.code) {
-                    case F_PRINTD:
-                        // Type of F_PRINTD is UVM32_SYSCALL_TYP_U32_WR, so expect value in evt.data.syscall.val.u32
-                        printf("%d\n", evt.data.syscall.val.u32);
+                    case F_PUTC:
+                        printf("%c", evt.data.syscall.val.u32);
+                    break;
+                    case F_PRINTLN:
+                        printf("%.*s\n", evt.data.syscall.val.buf.len, evt.data.syscall.val.buf.ptr);
                     break;
                 }
             break;
+            case UVM32_EVT_ERR:
+                printf("UVM32_EVT_ERR '%s' (%d)\n", evt.data.err.errstr, (int)evt.data.err.errcode);
+            break;
             default:
             break;
         }