[src/trunk]: src/sys/arch/evbarm/fdt When the root= boot arg is missing, atte...

[jmcneill <jmcneill%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/260927b9e558
branches:  trunk
changeset: 835226:260927b9e558
user:      jmcneill <jmcneill%NetBSD.org@localhost>
date:      Mon Aug 27 09:54:16 2018 +0000

description:
When the root= boot arg is missing, attempt to autodetect the root device
by comparing a hash of a disk device's MBR with the hash passed in from
the bootloader.

diffstat:

 sys/arch/evbarm/fdt/fdt_machdep.c |  89 ++++++++++++++++++++++++++++++++++++++-
 1 files changed, 87 insertions(+), 2 deletions(-)

diffs (138 lines):

diff -r fb0762e20780 -r 260927b9e558 sys/arch/evbarm/fdt/fdt_machdep.c
--- a/sys/arch/evbarm/fdt/fdt_machdep.c Mon Aug 27 09:52:16 2018 +0000
+++ b/sys/arch/evbarm/fdt/fdt_machdep.c Mon Aug 27 09:54:16 2018 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: fdt_machdep.c,v 1.33 2018/08/23 22:34:03 jmcneill Exp $ */
+/* $NetBSD: fdt_machdep.c,v 1.34 2018/08/27 09:54:16 jmcneill Exp $ */
 
 /*-
  * Copyright (c) 2015-2017 Jared McNeill <jmcneill%invisible.ca@localhost>
@@ -27,7 +27,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: fdt_machdep.c,v 1.33 2018/08/23 22:34:03 jmcneill Exp $");
+__KERNEL_RCSID(0, "$NetBSD: fdt_machdep.c,v 1.34 2018/08/27 09:54:16 jmcneill Exp $");
 
 #include "opt_machdep.h"
 #include "opt_bootconfig.h"
@@ -54,6 +54,12 @@
 #include <sys/reboot.h>
 #include <sys/termios.h>
 #include <sys/extent.h>
+#include <sys/bootblock.h>
+#include <sys/disklabel.h>
+#include <sys/vnode.h>
+#include <sys/kauth.h>
+#include <sys/fcntl.h>
+#include <sys/md5.h>
 
 #include <dev/cons.h>
 #include <uvm/uvm_extern.h>
@@ -110,6 +116,7 @@
 
 static void fdt_update_stdout_path(void);
 static void fdt_device_register(device_t, void *);
+static void fdt_cpu_rootconf(void);
 static void fdt_reset(void);
 static void fdt_powerdown(void);
 
@@ -416,6 +423,7 @@
        cpu_reset_address = fdt_reset;
        cpu_powerdown_address = fdt_powerdown;
        evbarm_device_register = fdt_device_register;
+       evbarm_cpu_rootconf = fdt_cpu_rootconf;
 
        /* Talk to the user */
        VPRINTF("\nNetBSD/evbarm (fdt) booting ...\n");
@@ -544,6 +552,63 @@
 }
 
 static void
+fdt_detect_root_device(device_t dev)
+{
+       struct mbr_sector mbr;
+       uint8_t buf[DEV_BSIZE];
+       uint8_t hash[16];
+       const uint8_t *rhash;
+       char rootarg[32];
+       struct vnode *vp;
+       MD5_CTX md5ctx;
+       int error, len;
+       size_t resid;
+       u_int part;
+
+       const int chosen = OF_finddevice("/chosen");
+       if (chosen < 0)
+               return;
+
+       if (of_hasprop(chosen, "netbsd,mbr") &&
+           of_hasprop(chosen, "netbsd,partition")) {
+
+               /*
+                * The bootloader has passed in a partition index and MD5 hash
+                * of the MBR sector. Read the MBR of this device, calculate the
+                * hash, and compare it with the value passed in.
+                */
+               rhash = fdtbus_get_prop(chosen, "netbsd,mbr", &len);
+               if (rhash == NULL || len != 16)
+                       return;
+               of_getprop_uint32(chosen, "netbsd,partition", &part);
+               if (part >= MAXPARTITIONS)
+                       return;
+
+               vp = opendisk(dev);
+               if (!vp)
+                       return;
+               error = vn_rdwr(UIO_READ, vp, buf, sizeof(buf), 0, UIO_SYSSPACE,
+                   0, NOCRED, &resid, NULL);
+               VOP_CLOSE(vp, FREAD, NOCRED);
+               vput(vp);
+
+               if (error != 0)
+                       return;
+
+               memcpy(&mbr, buf, sizeof(mbr));
+               MD5Init(&md5ctx);
+               MD5Update(&md5ctx, (void *)&mbr, sizeof(mbr));
+               MD5Final(hash, &md5ctx);
+
+               if (memcmp(rhash, hash, 16) != 0)
+                       return;
+
+               snprintf(rootarg, sizeof(rootarg), " root=%s%c", device_xname(dev), part + 'a');
+               strcat(boot_args, rootarg);
+       }
+}
+
+static void
 fdt_device_register(device_t self, void *aux)
 {
        const struct arm_platform *plat = arm_fdt_platform();
@@ -556,6 +621,26 @@
 }
 
 static void
+fdt_cpu_rootconf(void)
+{
+       device_t dev;
+       deviter_t di;
+       char *ptr;
+
+       for (dev = deviter_first(&di, 0); dev; dev = deviter_next(&di)) {
+               if (device_class(dev) != DV_DISK)
+                       continue;
+
+               if (get_bootconf_option(boot_args, "root", BOOTOPT_TYPE_STRING, &ptr) != 0)
+                       break;
+
+               if (device_is_a(dev, "ld") || device_is_a(dev, "sd") || device_is_a(dev, "ld"))
+                       fdt_detect_root_device(dev);
+       }
+       deviter_release(&di);
+}
+
+static void
 fdt_reset(void)
 {
        const struct arm_platform *plat = arm_fdt_platform();