Index: head/sys/amd64/amd64/machdep.c
===================================================================
--- head/sys/amd64/amd64/machdep.c
+++ head/sys/amd64/amd64/machdep.c
@@ -1853,6 +1853,15 @@
 	if (late_console)
 		cninit();
 
+	/*
+	 * Dump the boot metadata. We have to wait for cninit() since console
+	 * output is required. If it's grossly incorrect the kernel will never
+	 * make it this far.
+	 */
+	if ((boothowto & RB_VERBOSE) &&
+	    getenv_is_true("debug.dump_modinfo_at_boot"))
+		preload_dump();
+
 #ifdef DEV_ISA
 #ifdef DEV_ATPIC
 	elcr_probe();
Index: head/sys/arm/arm/machdep.c
===================================================================
--- head/sys/arm/arm/machdep.c
+++ head/sys/arm/arm/machdep.c
@@ -1027,6 +1027,15 @@
 	debugf(" dtbp = 0x%08x\n", (uint32_t)dtbp);
 	arm_print_kenv();
 
+	/*
+	 * Dump the boot metadata. We have to wait for cninit() since console
+	 * output is required. If it's grossly incorrect the kernel will never
+	 * make it this far.
+	 */
+	if ((boothowto & RB_VERBOSE) &&
+	    getenv_is_true("debug.dump_modinfo_at_boot"))
+		preload_dump();
+
 	env = kern_getenv("kernelname");
 	if (env != NULL) {
 		strlcpy(kernelname, env, sizeof(kernelname));
Index: head/sys/arm64/arm64/machdep.c
===================================================================
--- head/sys/arm64/arm64/machdep.c
+++ head/sys/arm64/arm64/machdep.c
@@ -1242,6 +1242,15 @@
 		panic("Invalid bus configuration: %s",
 		    kern_getenv("kern.cfg.order"));
 
+	/*
+	 * Dump the boot metadata. We have to wait for cninit() since console
+	 * output is required. If it's grossly incorrect the kernel will never
+	 * make it this far.
+	 */
+	if ((boothowto & RB_VERBOSE) &&
+	    getenv_is_true("debug.dump_modinfo_at_boot"))
+		preload_dump();
+
 	init_proc0(abp->kern_stack);
 	msgbufinit(msgbufp, msgbufsize);
 	mutex_init();
Index: head/sys/kern/subr_module.c
===================================================================
--- head/sys/kern/subr_module.c
+++ head/sys/kern/subr_module.c
@@ -3,6 +3,8 @@
  *
  * Copyright (c) 1998 Michael Smith
  * All rights reserved.
+ * Copyright (c) 2020 NetApp Inc.
+ * Copyright (c) 2020 Klara Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -32,7 +34,11 @@
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/linker.h>
+#include <sys/sbuf.h>
+#include <sys/sysctl.h>
 
+#include <machine/metadata.h>
+
 #include <vm/vm.h>
 #include <vm/vm_extern.h>
 
@@ -304,3 +310,249 @@
 	}
     }
 }
+
+/*
+ * Parse the modinfo type and append to the provided sbuf.
+ */
+static void
+preload_modinfo_type(struct sbuf *sbp, int type)
+{
+
+	if ((type & MODINFO_METADATA) == 0) {
+		switch (type) {
+		case MODINFO_END:
+			sbuf_cat(sbp, "MODINFO_END");
+			break;
+		case MODINFO_NAME:
+			sbuf_cat(sbp, "MODINFO_NAME");
+			break;
+		case MODINFO_TYPE:
+			sbuf_cat(sbp, "MODINFO_TYPE");
+			break;
+		case MODINFO_ADDR:
+			sbuf_cat(sbp, "MODINFO_ADDR");
+			break;
+		case MODINFO_SIZE:
+			sbuf_cat(sbp, "MODINFO_SIZE");
+			break;
+		case MODINFO_EMPTY:
+			sbuf_cat(sbp, "MODINFO_EMPTY");
+			break;
+		case MODINFO_ARGS:
+			sbuf_cat(sbp, "MODINFO_ARGS");
+			break;
+		default:
+			sbuf_cat(sbp, "unrecognized modinfo attribute");
+		}
+
+		return;
+	}
+
+	sbuf_cat(sbp, "MODINFO_METADATA | ");
+	switch (type & ~MODINFO_METADATA) {
+	case MODINFOMD_ELFHDR:
+		sbuf_cat(sbp, "MODINFOMD_ELFHDR");
+		break;
+	case MODINFOMD_SSYM:
+		sbuf_cat(sbp, "MODINFOMD_SSYM");
+		break;
+	case MODINFOMD_ESYM:
+		sbuf_cat(sbp, "MODINFOMD_ESYM");
+		break;
+	case MODINFOMD_DYNAMIC:
+		sbuf_cat(sbp, "MODINFOMD_DYNAMIC");
+		break;
+	case MODINFOMD_ENVP:
+		sbuf_cat(sbp, "MODINFOMD_ENVP");
+		break;
+	case MODINFOMD_HOWTO:
+		sbuf_cat(sbp, "MODINFOMD_HOWTO");
+		break;
+	case MODINFOMD_KERNEND:
+		sbuf_cat(sbp, "MODINFOMD_KERNEND");
+		break;
+	case MODINFOMD_SHDR:
+		sbuf_cat(sbp, "MODINFOMD_SHDR");
+		break;
+	case MODINFOMD_CTORS_ADDR:
+		sbuf_cat(sbp, "MODINFOMD_CTORS_ADDR");
+		break;
+	case MODINFOMD_CTORS_SIZE:
+		sbuf_cat(sbp, "MODINFOMD_CTORS_SIZE");
+		break;
+	case MODINFOMD_FW_HANDLE:
+		sbuf_cat(sbp, "MODINFOMD_FW_HANDLE");
+		break;
+	case MODINFOMD_KEYBUF:
+		sbuf_cat(sbp, "MODINFOMD_KEYBUF");
+		break;
+#ifdef MODINFOMD_SMAP
+	case MODINFOMD_SMAP:
+		sbuf_cat(sbp, "MODINFOMD_SMAP");
+		break;
+#endif
+#ifdef MODINFOMD_SMAP_XATTR
+	case MODINFOMD_SMAP_XATTR:
+		sbuf_cat(sbp, "MODINFOMD_SMAP_XATTR");
+		break;
+#endif
+#ifdef MODINFOMD_DTBP
+	case MODINFOMD_DTBP:
+		sbuf_cat(sbp, "MODINFOMD_DTBP");
+		break;
+#endif
+#ifdef MODINFOMD_EFI_MAP
+	case MODINFOMD_EFI_MAP:
+		sbuf_cat(sbp, "MODINFOMD_EFI_MAP");
+		break;
+#endif
+#ifdef MODINFOMD_EFI_FB
+	case MODINFOMD_EFI_FB:
+		sbuf_cat(sbp, "MODINFOMD_EFI_FB");
+		break;
+#endif
+#ifdef MODINFOMD_MODULEP
+	case MODINFOMD_MODULEP:
+		sbuf_cat(sbp, "MODINFOMD_MODULEP");
+		break;
+#endif
+	default:
+		sbuf_cat(sbp, "unrecognized metadata type");
+	}
+}
+
+/*
+ * Print the modinfo value, depending on type.
+ */
+static void
+preload_modinfo_value(struct sbuf *sbp, uint32_t *bptr, int type, int len)
+{
+#ifdef __LP64__
+#define sbuf_print_vmoffset(sb, o)	sbuf_printf(sb, "0x%016lx", o);
+#else
+#define sbuf_print_vmoffset(sb, o)	sbuf_printf(sb, "0x%08x", o);
+#endif
+
+	switch (type) {
+	case MODINFO_NAME:
+	case MODINFO_TYPE:
+	case MODINFO_ARGS:
+		sbuf_printf(sbp, "%s", (char *)bptr);
+		break;
+	case MODINFO_SIZE:
+	case MODINFO_METADATA | MODINFOMD_CTORS_SIZE:
+		sbuf_printf(sbp, "%lu", *(u_long *)bptr);
+		break;
+	case MODINFO_ADDR:
+	case MODINFO_METADATA | MODINFOMD_SSYM:
+	case MODINFO_METADATA | MODINFOMD_ESYM:
+	case MODINFO_METADATA | MODINFOMD_DYNAMIC:
+	case MODINFO_METADATA | MODINFOMD_KERNEND:
+	case MODINFO_METADATA | MODINFOMD_ENVP:
+	case MODINFO_METADATA | MODINFOMD_CTORS_ADDR:
+#ifdef MODINFOMD_SMAP
+	case MODINFO_METADATA | MODINFOMD_SMAP:
+#endif
+#ifdef MODINFOMD_SMAP_XATTR
+	case MODINFO_METADATA | MODINFOMD_SMAP_XATTR:
+#endif
+#ifdef MODINFOMD_DTBP
+	case MODINFO_METADATA | MODINFOMD_DTBP:
+#endif
+#ifdef MODINFOMD_EFI_FB
+	case MODINFO_METADATA | MODINFOMD_EFI_FB:
+#endif
+		sbuf_print_vmoffset(sbp, *(vm_offset_t *)bptr);
+		break;
+	case MODINFO_METADATA | MODINFOMD_HOWTO:
+		sbuf_printf(sbp, "0x%08x", *bptr);
+		break;
+	case MODINFO_METADATA | MODINFOMD_SHDR:
+	case MODINFO_METADATA | MODINFOMD_ELFHDR:
+	case MODINFO_METADATA | MODINFOMD_FW_HANDLE:
+	case MODINFO_METADATA | MODINFOMD_KEYBUF:
+#ifdef MODINFOMD_EFI_MAP
+	case MODINFO_METADATA | MODINFOMD_EFI_MAP:
+#endif
+		/* Don't print data buffers. */
+		sbuf_cat(sbp, "buffer contents omitted");
+		break;
+	default:
+		break;
+	}
+#undef sbuf_print_vmoffset
+}
+
+static void
+preload_dump_internal(struct sbuf *sbp)
+{
+	uint32_t *bptr, type, len;
+
+	KASSERT(preload_metadata != NULL,
+	    ("%s called without setting up preload_metadata", __func__));
+
+	/*
+	 * Iterate through the TLV-encoded sections.
+	 */
+	bptr = (uint32_t *)preload_metadata;
+	sbuf_putc(sbp, '\n');
+	while (bptr[0] != MODINFO_END || bptr[0] != MODINFO_END) {
+		sbuf_printf(sbp, " %p:\n", bptr);
+		type = *bptr++;
+		len = *bptr++;
+
+		sbuf_printf(sbp, "\ttype:\t(%#04x) ", type);
+		preload_modinfo_type(sbp, type);
+		sbuf_putc(sbp, '\n');
+		sbuf_printf(sbp, "\tlen:\t%u\n", len);
+		sbuf_cat(sbp, "\tvalue:\t");
+		preload_modinfo_value(sbp, bptr, type, len);
+		sbuf_putc(sbp, '\n');
+
+		bptr += roundup(len, sizeof(u_long)) / sizeof(uint32_t);
+	}
+}
+
+/*
+ * Print the preloaded data to the console. Called from the machine-dependent
+ * initialization routines, e.g. hammer_time().
+ */
+void
+preload_dump(void)
+{
+	char buf[512];
+	struct sbuf sb;
+
+	/*
+	 * This function is expected to be called before malloc is available,
+	 * so use a static buffer and struct sbuf.
+	 */
+	sbuf_new(&sb, buf, sizeof(buf), SBUF_FIXEDLEN);
+	sbuf_set_drain(&sb, sbuf_printf_drain, NULL);
+	preload_dump_internal(&sb);
+
+	sbuf_finish(&sb);
+	sbuf_delete(&sb);
+}
+
+static int
+sysctl_preload_dump(SYSCTL_HANDLER_ARGS)
+{
+	struct sbuf sb;
+	int error;
+
+	if (preload_metadata == NULL)
+		return (EINVAL);
+
+	sbuf_new_for_sysctl(&sb, NULL, 512, req);
+	preload_dump_internal(&sb);
+
+	error = sbuf_finish(&sb);
+	sbuf_delete(&sb);
+
+	return (error);
+}
+SYSCTL_PROC(_debug, OID_AUTO, dump_modinfo,
+    CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE,
+    NULL, 0, sysctl_preload_dump, "A",
+    "pretty-print the bootloader metadata");
Index: head/sys/riscv/riscv/machdep.c
===================================================================
--- head/sys/riscv/riscv/machdep.c
+++ head/sys/riscv/riscv/machdep.c
@@ -949,6 +949,15 @@
 
 	cninit();
 
+	/*
+	 * Dump the boot metadata. We have to wait for cninit() since console
+	 * output is required. If it's grossly incorrect the kernel will never
+	 * make it this far.
+	 */
+	if ((boothowto & RB_VERBOSE) &&
+	    getenv_is_true("debug.dump_modinfo_at_boot"))
+		preload_dump();
+
 	init_proc0(rvbp->kern_stack);
 
 	msgbufinit(msgbufp, msgbufsize);
Index: head/sys/sys/linker.h
===================================================================
--- head/sys/sys/linker.h
+++ head/sys/sys/linker.h
@@ -257,6 +257,7 @@
 extern caddr_t		preload_search_info(caddr_t _mod, int _inf);
 extern void		preload_delete_name(const char *_name);
 extern void		preload_bootstrap_relocate(vm_offset_t _offset);
+extern void		preload_dump(void);
 
 #ifdef KLD_DEBUG