kboot: Expose m1n1 console log in phram MTD reserved memory node

This registers a log buffer IODEV similar to the frame buffer IODEV. It
is using a console IODEV to allow writing to the buffer until m1n1 jumps
to the next stage. This allows also to increase the buffer size without
increasing m1n1's size. The current CONSOLE_BUFFER_SIZE of 8k is not
large enough to hold the entire log of executing m1n1 under the
hypervisor on the M1 Ultra Mac Studio.

Signed-off-by: Janne Grunau <[email protected]>

src/iodev.c

@@ -18,17 +18,19 @@
 
 extern struct iodev iodev_uart;
 extern struct iodev iodev_fb;
+extern struct iodev iodev_log;
 extern struct iodev iodev_usb_vuart;
 
-struct iodev *iodevs[IODEV_MAX] = {
+struct iodev *iodevs[IODEV_NUM] = {
     [IODEV_UART] = &iodev_uart,
     [IODEV_FB] = &iodev_fb,
     [IODEV_USB_VUART] = &iodev_usb_vuart,
+    [IODEV_LOG] = &iodev_log,
 };
 
 char con_buf[CONSOLE_BUFFER_SIZE];
 size_t con_wp;
-size_t con_rp[IODEV_MAX];
+size_t con_rp[IODEV_NUM];
 
 void iodev_register_device(iodev_id_t id, struct iodev *dev)
 {
@@ -173,7 +175,7 @@ void iodev_console_write(const void *buf, size_t length)
     in_iodev++;
 
     dprintf("  iodev_console_write() wp=%d\n", con_wp);
-    for (iodev_id_t id = 0; id < IODEV_MAX; id++) {
+    for (iodev_id_t id = 0; id < IODEV_NUM; id++) {
         if (!iodevs[id])
             continue;
 
@@ -275,7 +277,7 @@ void iodev_console_kick(void)
 {
     iodev_console_write(NULL, 0);
 
-    for (iodev_id_t id = 0; id < IODEV_MAX; id++) {
+    for (iodev_id_t id = 0; id < IODEV_NUM; id++) {
         if (!iodevs[id])
             continue;
         if (!(iodevs[id]->usage & USAGE_CONSOLE))
@@ -287,7 +289,7 @@ void iodev_console_kick(void)
 
 void iodev_console_flush(void)
 {
-    for (iodev_id_t id = 0; id < IODEV_MAX; id++) {
+    for (iodev_id_t id = 0; id < IODEV_NUM; id++) {
         if (!iodevs[id])
             continue;
         if (!(iodevs[id]->usage & USAGE_CONSOLE))

src/iodev.h

@@ -14,6 +14,8 @@ typedef enum _iodev_id_t {
     IODEV_USB_VUART,
     IODEV_USB0,
     IODEV_MAX = IODEV_USB0 + USB_IODEV_COUNT,
+    IODEV_LOG = IODEV_MAX, // hidden log buffer iodev
+    IODEV_NUM,
 } iodev_id_t;
 
 typedef enum _iodev_usage_t {

src/kboot.c

@@ -11,6 +11,7 @@
 #include "display.h"
 #include "exception.h"
 #include "firmware.h"
+#include "iodev.h"
 #include "isp.h"
 #include "malloc.h"
 #include "mcc.h"
@@ -2265,6 +2266,54 @@ int kboot_set_chosen(const char *name, const char *value)
     return i;
 }
 
+#define LOGBUF_SIZE SZ_16K
+
+struct {
+    void *buffer;
+    size_t wp;
+} logbuf;
+
+static bool log_console_iodev_can_write(void *opaque)
+{
+    UNUSED(opaque);
+    return !!logbuf.buffer;
+}
+
+static ssize_t log_console_iodev_write(void *opaque, const void *buf, size_t len)
+{
+    UNUSED(opaque);
+
+    if (!logbuf.buffer)
+        return 0;
+
+    ssize_t wrote = 0;
+    size_t remain = LOGBUF_SIZE - logbuf.wp;
+    while (remain < len) {
+        memcpy(logbuf.buffer + logbuf.wp, buf, remain);
+        logbuf.wp = 0;
+        wrote += remain;
+        buf += remain;
+        len -= remain;
+        remain = LOGBUF_SIZE;
+    }
+    memcpy(logbuf.buffer + logbuf.wp, buf, len);
+    wrote += len;
+    logbuf.wp = (logbuf.wp + len) % LOGBUF_SIZE;
+
+    return wrote;
+}
+
+const struct iodev_ops iodev_log_ops = {
+    .can_write = log_console_iodev_can_write,
+    .write = log_console_iodev_write,
+};
+
+struct iodev iodev_log = {
+    .ops = &iodev_log_ops,
+    .usage = USAGE_CONSOLE,
+    .lock = SPINLOCK_INIT,
+};
+
 static int dt_setup_mtd_phram(void)
 {
     char node_name[64];
@@ -2279,6 +2328,20 @@ static int dt_setup_mtd_phram(void)
             bail("FDT: failed to setup ADT MTD phram label\n");
     }
 
+    // init memory backed iodev for console log
+    logbuf.buffer = (void *)top_of_memory_alloc(LOGBUF_SIZE);
+    if (!logbuf.buffer)
+        bail("FDT: failed to allocate m1n1 log buffer\n");
+
+    snprintf(node_name, sizeof(node_name), "flash@%lx", (u64)logbuf.buffer);
+    node = dt_get_or_add_reserved_mem(node_name, "phram", false, (u64)logbuf.buffer, SZ_16K);
+
+    if (node > 0) {
+        int ret = fdt_setprop_string(dt, node, "label", "m1n1_stage2.log");
+        if (ret)
+            bail("FDT: failed to setup m1n1 log MTD phram label\n");
+    }
+
     return 0;
 }
 
@@ -2307,6 +2370,7 @@ int kboot_prepare_dt(void *fdt)
     if (fdt_add_mem_rsv(dt, (u64)_base, ((u64)_end) - ((u64)_base)))
         bail("FDT: couldn't add reservation for m1n1\n");
 
+    /* setup console log buffer early to cpature as much log as possible */
     dt_setup_mtd_phram();
 
     if (dt_set_chosen())