From cf5cd89c3a93eb41213a0fe83be7ff79c3d9bb63 Mon Sep 17 00:00:00 2001
From: Mitchell Horne <mhorne@FreeBSD.org>
Date: Sun, 19 Jul 2020 23:34:52 +0000
Subject: [PATCH] riscv: look for bootargs in FDT

The FDT may contain a short /chosen/bootargs string which we should pass
to boot_parse_cmdline. Notably, this allows the use of qemu's -append
option to pass things like -s to boot to single user mode.

Submitted by:	Nathaniel Filardo <nwf20@cl.cam.ac.uk>
Reviewed by:	mhorne
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D25544
---
 sys/riscv/riscv/machdep.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/sys/riscv/riscv/machdep.c b/sys/riscv/riscv/machdep.c
index 2c6bd016ce6..6b42e9b4b8b 100644
--- a/sys/riscv/riscv/machdep.c
+++ b/sys/riscv/riscv/machdep.c
@@ -40,6 +40,7 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
 #include <sys/systm.h>
+#include <sys/boot.h>
 #include <sys/buf.h>
 #include <sys/bus.h>
 #include <sys/cons.h>
@@ -800,6 +801,19 @@ fake_preload_metadata(struct riscv_bootparams *rvbp)
 		    rvbp->kern_phys, rvbp->kern_phys + (lastaddr - KERNBASE));
 }
 
+#ifdef FDT
+static void
+parse_fdt_bootargs(void)
+{
+	char bootargs[512];
+
+	bootargs[sizeof(bootargs) - 1] = '\0';
+	if (fdt_get_chosen_bootargs(bootargs, sizeof(bootargs) - 1) == 0) {
+		boothowto |= boot_parse_cmdline(bootargs);
+	}
+}
+#endif
+
 static vm_offset_t
 parse_metadata(void)
 {
@@ -829,6 +843,8 @@ parse_metadata(void)
 #endif
 #ifdef FDT
 	try_load_dtb(kmdp);
+	if (kern_envp == NULL)
+		parse_fdt_bootargs();
 #endif
 	return (lastaddr);
 }