Allow to modify bootargs for system emulation

.gitmodules

@@ -31,3 +31,7 @@
 	path = tests/quake
 	url = https://github.com/sysprog21/quake-embedded
 	shallow = true
+[submodule "src/dtc"]
+	path = src/dtc
+	url = https://git.kernel.org/pub/scm/utils/dtc/dtc.git
+	shallow = true

Makefile

@@ -269,6 +269,7 @@ $(OBJS): $(GDBSTUB_LIB)
 endif
 
 $(OUT)/%.o: src/%.c $(deps_emcc)
+	$(Q)mkdir -p $(shell dirname $@)
 	$(VECHO) "  CC\t$@\n"
 	$(Q)$(CC) -o $@ $(CFLAGS) $(CFLAGS_emcc) -c -MMD -MF $@.d $<
 

mk/system.mk

@@ -1,6 +1,9 @@
 # Peripherals for system emulation
 ifeq ($(call has, SYSTEM), 1)
 
+CFLAGS += -Isrc/dtc/libfdt
+LIBFDT_HACK := $(shell git submodule update --init src/dtc)
+
 DEV_SRC := src/devices
 
 DTC ?= dtc
@@ -25,6 +28,7 @@ DEV_OBJS := $(patsubst $(DEV_SRC)/%.c, $(DEV_OUT)/%.o, $(wildcard $(DEV_SRC)/*.c
 deps := $(DEV_OBJS:%.o=%.o.d)
 
 OBJS_EXT += system.o
+OBJS_EXT += dtc/libfdt/fdt.o dtc/libfdt/fdt_ro.o dtc/libfdt/fdt_rw.o
 
 # system target execution by using default dependencies
 LINUX_IMAGE_DIR := linux-image

src/main.c

@@ -42,7 +42,7 @@ static char *opt_prog_name;
 /* target argc and argv */
 static int prog_argc;
 static char **prog_args;
-static const char *optstr = "tgqmhpd:a:k:i:";
+static const char *optstr = "tgqmhpd:a:k:i:b:";
 
 /* enable misaligned memory access */
 static bool opt_misaligned = false;
@@ -55,6 +55,7 @@ static char *prof_out_file;
 /* Linux kernel data */
 static char *opt_kernel_img;
 static char *opt_rootfs_img;
+static char *opt_bootargs;
 #endif
 
 static void print_usage(const char *filename)
@@ -72,6 +73,7 @@ static void print_usage(const char *filename)
 #if RV32_HAS(SYSTEM) && !RV32_HAS(ELF_LOADER)
             "  -k <image> : use <image> as kernel image\n"
             "  -i <image> : use <image> as rootfs\n"
+            "  -b <bootargs> : use customized <bootargs> for the kernel\n"
 #endif
             "  -d [filename]: dump registers as JSON to the "
             "given file or `-` (STDOUT)\n"
@@ -112,6 +114,10 @@ static bool parse_args(int argc, char **args)
             opt_rootfs_img = optarg;
             emu_argc++;
             break;
+        case 'b':
+            opt_bootargs = optarg;
+            emu_argc++;
+            break;
 #endif
         case 'q':
             opt_quiet_outputs = true;
@@ -257,6 +263,7 @@ int main(int argc, char **args)
 #if RV32_HAS(SYSTEM) && !RV32_HAS(ELF_LOADER)
     attr.data.system.kernel = opt_kernel_img;
     attr.data.system.initrd = opt_rootfs_img;
+    attr.data.system.bootargs = opt_bootargs;
 #else
     attr.data.user.elf_program = opt_prog_name;
 #endif

src/riscv.c

@@ -14,6 +14,7 @@
 
 #if RV32_HAS(SYSTEM) && !RV32_HAS(ELF_LOADER)
 #include <termios.h>
+#include "dtc/libfdt/libfdt.h"
 #endif
 
 #if !defined(_WIN32) && !defined(_WIN64)
@@ -259,11 +260,61 @@ static void map_file(char **ram_loc, const char *name)
     exit(EXIT_FAILURE);
 }
 
-static void load_dtb(char **ram_loc)
+#define ALIGN_FDT(x) (((x) + (FDT_TAGSIZE) - 1) & ~((FDT_TAGSIZE) - 1))
+static char *realloc_property(char *fdt,
+                              int nodeoffset,
+                              const char *name,
+                              int newlen)
+{
+    int delta = 0;
+    int oldlen = 0;
+
+    if (!fdt_get_property(fdt, nodeoffset, name, &oldlen))
+        /* strings + property header */
+        delta = sizeof(struct fdt_property) + strlen(name) + 1;
+
+    if (newlen > oldlen)
+        /* actual value in off_struct */
+        delta += ALIGN_FDT(newlen) - ALIGN_FDT(oldlen);
+
+    int new_sz = fdt_totalsize(fdt) + delta;
+    /* Assume the pre-allocated RAM is enough here, so we
+     * don't realloc any memory for fdt */
+    fdt_open_into(fdt, fdt, new_sz);
+    return fdt;
+}
+
+static void load_dtb(char **ram_loc, char *bootargs)
 {
 #include "minimal_dtb.h"
-    memcpy(*ram_loc, minimal, sizeof(minimal));
-    *ram_loc += sizeof(minimal);
+    char *blob = *ram_loc;
+    char *buf;
+    size_t len;
+    int node, err;
+    int totalsize;
+
+    memcpy(blob, minimal, sizeof(minimal));
+
+    if (bootargs) {
+        node = fdt_path_offset(blob, "/chosen");
+        assert(node > 0);
+
+        len = strlen(bootargs) + 1;
+        buf = malloc(len);
+        assert(buf);
+        memcpy(buf, bootargs, len - 1);
+        buf[len] = 0;
+        err = fdt_setprop(blob, node, "bootargs", buf, len + 1);
+        if (err == -FDT_ERR_NOSPACE) {
+            blob = realloc_property(blob, node, "bootargs", len);
+            err = fdt_setprop(blob, node, "bootargs", buf, len);
+        }
+        free(buf);
+        assert(!err);
+    }
+
+    totalsize = fdt_totalsize(blob);
+    *ram_loc += totalsize;
     return;
 }
 
@@ -418,7 +469,7 @@ riscv_t *rv_create(riscv_user_t rv_attr)
 
     uint32_t dtb_addr = attr->mem->mem_size - (1 * 1024 * 1024);
     ram_loc = ((char *) attr->mem->mem_base) + dtb_addr;
-    load_dtb(&ram_loc);
+    load_dtb(&ram_loc, attr->data.system.bootargs);
     /*
      * Load optional initrd image at last 8 MiB before the dtb region to
      * prevent kernel from overwritting it

src/riscv.h

@@ -551,6 +551,7 @@ typedef struct {
 typedef struct {
     char *kernel;
     char *initrd;
+    char *bootargs;
 } vm_system_t;
 #endif /* RV32_HAS(SYSTEM) */