[PATCH v2] hw/misc: applesmc: use host osk as default on macs

[Pedro Tôrres]

When running on a Mac, QEMU is able to get the host OSK and use it as
the default value for the AppleSMC device. The OSK query operation
doesn't require administrator privileges and can be executed by any user
on the system. This patch is based on Phil Dennis-Jordan's description
of the process for reading OSK from SCM on macOS:
https://lists.nongnu.org/archive/html/qemu-devel/2021-10/msg02843.html

In the future, this could also be extended to work on Linux and Windows
when running on Macs. Just implement the applesmc_read_osk function for
those platforms.

The Apple SMC driver for Linux is currently being rewritten by Hector
Martin as part of the effort to bring Linux to Macs with Apple Silicon
(Asahi Linux). When the new driver gets merged to the Linux Kernel, it
will be a good time to extend this to work with it.

Signed-off-by: Pedro Tôrres <t0rr3sp3dr0@gmail.com>
---
hw/misc/applesmc.c | 75 ++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 73 insertions(+), 2 deletions(-)

diff --git a/hw/misc/applesmc.c b/hw/misc/applesmc.c
index 81cd6b6423..d7f6702cf0 100644
--- a/hw/misc/applesmc.c
+++ b/hw/misc/applesmc.c
@@ -5,6 +5,7 @@
 *
 *  Authors: Alexander Graf <agraf@suse.de>
 *           Susanne Graf <suse@csgraf.de>
+ *           Pedro Tôrres <t0rr3sp3dr0@gmail.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
@@ -28,8 +29,16 @@
 * This driver was mostly created by looking at the Linux AppleSMC driver
 * implementation and does not support IRQ.
 *
+ * Reading OSK from SCM on macOS was implemented based on Phil Dennis-Jordan's
+ * description of the process:
+ * https://lists.nongnu.org/archive/html/qemu-devel/2021-10/msg02843.html
+ * 
 */

+#if defined(__APPLE__) && defined(__MACH__)
+#include <IOKit/IOKitLib.h>
+#endif
+
#include "qemu/osdep.h"
#include "hw/isa/isa.h"
#include "hw/qdev-properties.h"
@@ -312,9 +321,62 @@ static const MemoryRegionOps applesmc_err_io_ops = {
    },
};

+static bool applesmc_read_osk(uint8_t *osk)
+{
+#if defined(__APPLE__) && defined(__MACH__)
+    struct AppleSMCParams {
+        uint32_t key;
+        uint8_t __pad0[16];
+        uint8_t result;
+        uint8_t __pad1[7];
+        uint32_t size;
+        uint8_t __pad2[10];
+        uint8_t data8;
+        uint8_t __pad3[5];
+        uint8_t output[32];
+    };
+
+    io_service_t svc;
+    io_connect_t conn;
+    kern_return_t ret;
+    size_t size = sizeof(struct AppleSMCParams);
+    struct AppleSMCParams params_in = { .size = 32, .data8 = 5 };
+    struct AppleSMCParams params_out = {};
+
+    svc = IOServiceGetMatchingService(0, IOServiceMatching("AppleSMC"));
+    if (svc == 0) {
+        return false;
+    }
+
+    ret = IOServiceOpen(svc, mach_task_self(), 0, &conn);
+    if (ret != 0) {
+        return false;
+    }
+
+    for (params_in.key = 'OSK0'; params_in.key <= 'OSK1'; ++params_in.key) {
+        ret = IOConnectCallStructMethod(conn, 2, &params_in, size, 
&params_out, &size);
+        if (ret != 0) {
+            return false;
+        }
+
+        if (params_out.result != 0) {
+            return false;
+        }
+        memcpy(osk, params_out.output, params_in.size);
+
+        osk += params_in.size;
+    }
+
+    return true;
+#else
+    return false;
+#endif
+}
+
static void applesmc_isa_realize(DeviceState *dev, Error **errp)
{
    AppleSMCState *s = APPLE_SMC(dev);
+    bool valid_osk = false;

    memory_region_init_io(&s->io_data, OBJECT(s), &applesmc_data_io_ops, s,
                          "applesmc-data", 1);
@@ -331,8 +393,17 @@ static void applesmc_isa_realize(DeviceState *dev, Error 
**errp)
    isa_register_ioport(&s->parent_obj, &s->io_err,
                        s->iobase + APPLESMC_ERR_PORT);

-    if (!s->osk || (strlen(s->osk) != 64)) {
-        warn_report("Using AppleSMC with invalid key");
+    if (s->osk) {
+        valid_osk = strlen(s->osk) == 64;
+    } else {
+        valid_osk = applesmc_read_osk((uint8_t *) default_osk);
+        if (valid_osk) {
+            warn_report("Using AppleSMC with host OSK");
+            s->osk = default_osk;
+        }
+    }
+    if (!valid_osk) {
+        warn_report("Using AppleSMC with invalid OSK");
        s->osk = default_osk;
    }

-- 
2.32.0 (Apple Git-132)