Ramdisk (#4)

* Some works towards ramdisk

* PMEM ramdisk working

* DTS cleanup

* Added some docs on ramdisk

* Change back to original memory size, added comment

* Cleanup

---------

Co-authored-by: Egil <egil.moller@freecode.no>

README.md

@@ -49,3 +49,18 @@ Please see https://github.com/franzflasch/linux_for_riscv_em
 ```sh
 ./build/riscv_em -f <linux_for_riscv_em-path>/output_mmu_rv32/opensbi/build/platform/generic/firmware/fw_payload.bin -d dts/riscv_em32_linux.dtb
 ```
+
+### RAM disk
+
+Make a filesystem image using the normal filesystem tools (e.g.
+mkfs.ext3, mksquashfs etc) with a maximum size of 200Mb. Then run
+
+```sh
+./build/riscv_em -f <linux_for_riscv_em-path>/output/linux/loader_64.bin -d dts/riscv_em.dtb -i mydiskimage.ext3
+```
+
+The filesystem will be available as `/dev/pmem0`, which can be either
+mounted from userspace, or specified as the root filesystem. Note that
+this does not use the initrd or initramdisk functionality, as that has
+severe size limitations (tries to unpack/copy the whole filesystem at
+boot).

dts/riscv_em.dts

@@ -29,11 +29,21 @@
         };
     };
 
+    /* Make sure these adresses and sizes match the actual
+    configuration in src/core/riscv_config.h */
     sram: memory@80000000 {
         device_type = "memory";
-        reg = <0x0 0x80000000 0x0 0x8000000>;
+        reg = <0x0 0x80000000 0x0  0x8000000>;
+        /* Example alternative configuration with much more RAM
+        reg = <0x0 0x80000000 0x0 0x40000000>;
+        */
     };
-
+
+    rom: memory@c0000000 {
+        compatible = "pmem-region";
+        reg = <0x0 0xc0000000 0x0 0xc800000>;
+    };
+
     soc {
         #address-cells = <2>;
         #size-cells = <2>;
@@ -74,4 +84,5 @@
             compatible = "simple-uart";
         };
     };
+
 };

src/core/riscv_config.h

@@ -11,6 +11,9 @@
 
 #define RAM_BASE_ADDR 0x80000000UL
 #define RAM_SIZE_BYTES 0x8000000UL /* 128MB such as the default for the qemu virt machine */
+/* Example alternative configuration with much more RAM
+#define RAM_SIZE_BYTES         0x40000000UL
+*/
 
 #define CLINT_BASE_ADDR 0x2000000UL
 #define CLINT_SIZE_BYTES 0x10000UL
@@ -30,4 +33,7 @@
                                   RV_EXTENSION_TO_MISA('S') | \
                                   RV_EXTENSION_TO_MISA('U') )
 
+#define FROM_BASE_ADDR 0xc0000000UL
+#define FROM_SIZE_BYTES 0xc800000UL
+
 #endif /* RISCV_CONFIG_H */

src/main.c

@@ -71,17 +71,19 @@ void start_uart_rx_thread(void *p)
 static void parse_options(int argc, 
                           char** argv, 
                           char **fw_file, 
-                          char **dtb_file, 
+                          char **dtb_file,
+                          char **initrd_file,
                           rv_uint_xlen *success_pc, 
                           uint64_t *num_cycles)
 {
     int c;
     char *arg_fw_file = NULL;
     char *arg_dtb_file = NULL;
+    char *arg_initrd_file = NULL;
     char *arg_success_pc = NULL;
     char *arg_num_cycles = NULL;
 
-    while ((c = getopt(argc, argv, "s:f:d:n:")) != -1)
+    while ((c = getopt(argc, argv, "s:f:d:i:n:")) != -1)
     {
         switch (c)
         {
@@ -113,6 +115,11 @@ static void parse_options(int argc,
                 // }
                 break;
             }
+            case 'i':
+            {
+                arg_initrd_file = optarg;
+                break;
+            }
             case 'n':
             {
                 arg_num_cycles = optarg;
@@ -144,26 +151,33 @@ static void parse_options(int argc,
         printf("No dtb specified! Linux will probably not work\n");
     }
 
+    if(arg_initrd_file == NULL)
+    {
+        printf("No initrd specified!\n");
+    }
+
     printf("FW file: %s\n", arg_fw_file);
     printf("Success PC: " PRINTF_FMT "\n", *success_pc);
     printf("Num Cycles: %ld\n", *num_cycles);
 
     *fw_file = arg_fw_file;
     *dtb_file = arg_dtb_file;
+    *initrd_file = arg_initrd_file;
 }
 
 
 int main(int argc, char *argv[])
 {
     char *fw_file = NULL;
     char *dtb_file = NULL;
+    char *initrd_file = NULL;
     rv_uint_xlen success_pc = 0;
     uint64_t num_cycles = 0;
 
-    parse_options(argc, argv, &fw_file, &dtb_file, &success_pc, &num_cycles);
+    parse_options(argc, argv, &fw_file, &dtb_file, &initrd_file, &success_pc, &num_cycles);
 
     rv_soc_td rv_soc;
-    rv_soc_init(&rv_soc, fw_file, dtb_file);
+    rv_soc_init(&rv_soc, fw_file, dtb_file, initrd_file);
 
     #ifndef RISCV_EM_DEBUG
         start_uart_rx_thread(&rv_soc);

src/soc/riscv_example_soc.c

@@ -44,6 +44,7 @@ static void rv_soc_init_mem_access_cbs(rv_soc_td *rv_soc)
         INIT_MEM_ACCESS_STRUCT(rv_soc, count++, uart_bus_access, &rv_soc->uart8250, UART8250_TX_REG_ADDR, UART_NS8250_NR_REGS);
     #endif
     INIT_MEM_ACCESS_STRUCT(rv_soc, count++, memory_bus_access, rv_soc->mrom, MROM_BASE_ADDR, MROM_SIZE_BYTES);
+    INIT_MEM_ACCESS_STRUCT(rv_soc, count++, memory_bus_access, rv_soc->from, FROM_BASE_ADDR, FROM_SIZE_BYTES);
 }
 
 static rv_ret rv_soc_bus_access(void *priv, privilege_level priv_level, bus_access_type access_type, rv_uint_xlen address, void *value, uint8_t len)
@@ -74,7 +75,7 @@ void rv_soc_dump_mem(rv_soc_td *rv_soc)
     }
 }
 
-void rv_soc_init(rv_soc_td *rv_soc, char *fw_file_name, char *dtb_file_name)
+void rv_soc_init(rv_soc_td *rv_soc, char *fw_file_name, char *dtb_file_name, char *initrd_file_name)
 {
     #define RESET_VEC_SIZE 10
     #define MiB 0x100000
@@ -86,11 +87,13 @@ void rv_soc_init(rv_soc_td *rv_soc, char *fw_file_name, char *dtb_file_name)
     uint64_t fdt_size = 0;
     uint64_t tmp = 0;
 
+    static uint8_t __attribute__((aligned (4))) soc_from[FROM_SIZE_BYTES] = { 0 };
     static uint8_t __attribute__((aligned (4))) soc_mrom[MROM_SIZE_BYTES] = { 0 };
     static uint8_t __attribute__((aligned (4))) soc_ram[RAM_SIZE_BYTES] = { 0 };
 
     /* Init everything to zero */
     memset(rv_soc, 0, sizeof(rv_soc_td));
+    rv_soc->from = soc_from;
     rv_soc->mrom = soc_mrom;
     rv_soc->ram = soc_ram;
 
@@ -113,6 +116,10 @@ void rv_soc_init(rv_soc_td *rv_soc, char *fw_file_name, char *dtb_file_name)
 
     write_mem_from_file(fw_file_name, soc_ram, sizeof(soc_ram));
 
+    if (initrd_file_name != NULL) {
+        write_mem_from_file(initrd_file_name, soc_from, FROM_SIZE_BYTES);
+    }
+
     /* this is the reset vector, taken from qemu v5.2 */
     uint32_t reset_vec[RESET_VEC_SIZE] = {
         0x00000297,                  /* 1:  auipc  t0, %pcrel_hi(fw_dyn) */

src/soc/riscv_example_soc.h

@@ -23,6 +23,7 @@ typedef struct rv_soc_struct
     rv_core_td rv_core0;
     uint8_t *mrom; /* Contains reset vector and device-tree? */
     uint8_t *ram;
+    uint8_t *from; /* Contains filesystem */
 
     clint_td clint;
     plic_td plic;
@@ -38,7 +39,7 @@ typedef struct rv_soc_struct
 } rv_soc_td;
 
 void rv_soc_dump_mem(rv_soc_td *rv_soc);
-void rv_soc_init(rv_soc_td *rv_soc, char *fw_file_name, char *dtb_file_name);
+void rv_soc_init(rv_soc_td *rv_soc, char *fw_file_name, char *dtb_file_name, char *initrd_file_name);
 void rv_soc_run(rv_soc_td *rv_soc, rv_uint_xlen success_pc, uint64_t num_cycles);
 
 #endif /* RISCV_EXAMPLE_SOC_H */