Re: [Qemu-devel] [PATCH] Add MIPS ELF loader

[Thiemo Seufer <ths@networkno.de>]

On Tue, Mar 28, 2006 at 08:57:15AM +0200, Dirk Behme wrote:
> Hi,
> 
> ELF loader feature for MIPS in patch
> 
> http://lists.gnu.org/archive/html/qemu-devel/2006-03/msg00033.html
> 
> was rejected because it breaks loading of raw kernel images:
> 
> http://lists.gnu.org/archive/html/qemu-devel/2006-03/msg00082.html
> 
> What about the patch in attachment? It first tries to load
> image as an ELF file. If this fails it falls back to raw
> image load. Additionally, it takes feature of patch above to
> go on even if no BIOS is found.

A slightly more polished version with less noisy messages is appended.
It also adjusts the ramdisk load address to physical addressing,
similiar to the binary kernel load.


Thiemo


Index: qemu-work/hw/mips_r4k.c
===================================================================
--- qemu-work.orig/hw/mips_r4k.c	2006-03-28 12:27:55.000000000 +0100
+++ qemu-work/hw/mips_r4k.c	2006-03-28 13:49:10.000000000 +0100
@@ -1,6 +1,8 @@
 #define KERNEL_LOAD_ADDR 0x80010000
 #define INITRD_LOAD_ADDR 0x80800000
 
+#define PHYSADDR(addr) ((addr) & 0x1fffffff)
+
 extern FILE *logfile;
 
 static PITState *pit;
@@ -101,6 +105,108 @@
     cpu_mips_update_count(env, 1, 0);
 }
 
+#include "disas.h"
+
+#define ELF_CLASS   ELFCLASS32
+#ifdef TARGET_WORDS_BIGENDIAN
+# define ELF_DATA    ELFDATA2MSB
+#else
+# define ELF_DATA    ELFDATA2LSB
+#endif
+#define ELF_ARCH    EM_MIPS
+
+#include "elf.h"
+
+#ifndef BSWAP_NEEDED
+#define bswap_ehdr32(e) do { } while (0)
+#define bswap_phdr32(e) do { } while (0)
+#define bswap_shdr32(e) do { } while (0)
+#define bswap_sym32(e) do { } while (0)
+#endif
+
+#define SZ		32
+#define elf_word        uint32_t
+#define bswapSZs	bswap32s
+#include "elf_ops.h"
+
+static int load_mips_kernel_elf(const char *filename, elf_word *entry)
+{
+    struct elf32_hdr ehdr;
+    int retval, fd, i;
+    Elf32_Half machine;
+
+    fd = open(filename, O_RDONLY | O_BINARY);
+    if (fd < 0)
+	goto error;
+
+    retval = read(fd, &ehdr, sizeof(ehdr));
+    if (retval < 0)
+	goto error;
+
+    if (ehdr.e_ident[0] != 0x7f || ehdr.e_ident[1] != 'E'
+	|| ehdr.e_ident[2] != 'L' || ehdr.e_ident[3] != 'F')
+	goto error;
+    machine = tswap16(ehdr.e_machine);
+    if (machine == EM_MIPS) {
+	struct elf32_phdr phdr;
+
+	bswap_ehdr32(&ehdr);
+
+	*entry = ehdr.e_entry;
+	retval = lseek(fd, ehdr.e_phoff, SEEK_SET);
+	if (retval < 0)
+	    goto error;
+
+	for (i = 0; i < ehdr.e_phnum; i++) {
+	    retval = read(fd, &phdr, sizeof(phdr));
+	    if (retval < 0)
+		goto error;
+	    bswap_phdr32(&phdr);
+	    if (phdr.p_type == PT_LOAD) {
+		uint8_t *addr;
+		size_t sz = phdr.p_filesz;
+
+		if (phdr.p_vaddr < 0x80000000
+		    || phdr.p_memsz > 0x20000000
+		    || (phdr.p_vaddr < 0xa0000000
+			&& (phdr.p_vaddr + phdr.p_memsz) >= 0xa0000000)
+		    || (phdr.p_vaddr < 0xc0000000
+			&& (phdr.p_vaddr + phdr.p_memsz) >= 0xc0000000))
+		    goto error;
+		addr = (uint8_t *)(phys_ram_base + PHYSADDR(phdr.p_vaddr));
+		retval = lseek(fd, phdr.p_offset, SEEK_SET);
+		if (retval < 0)
+		    goto error;
+		while (sz) {
+		    retval = read(fd, addr, sz);
+		    switch (retval) {
+		    case -1:
+			goto error;
+		    case 0: /* EOF */
+			if (sz)
+			    goto error;
+			break;
+		    default:
+			if (sz < retval)
+			    goto error;
+			sz -= retval;
+			retval = 0;
+			break;
+		    }
+		}
+	    }
+	}
+	load_symbols32(&ehdr, fd);
+    }
+
+    close(fd);
+    return retval;
+ error:
+    close(fd);
+    return -1;
+}
+
+
 static void io_writeb (void *opaque, target_phys_addr_t addr, uint32_t value)
 {
 #if 0
@@ -183,72 +319,70 @@
                     const char *initrd_filename)
 {
     char buf[1024];
-    target_ulong kernel_base, kernel_size, initrd_base, initrd_size;
+    elf_word entry = 0;
     unsigned long bios_offset;
     int io_memory;
-    int linux_boot;
     int ret;
     CPUState *env;
-
-    printf("%s: start\n", __func__);
-    linux_boot = (kernel_filename != NULL);
+    int i;
 
     env = cpu_init();
     register_savevm("cpu", 0, 3, cpu_save, cpu_load, env);
 
     /* allocate RAM */
     cpu_register_physical_memory(0, ram_size, IO_MEM_RAM);
+
+    /* Try to load a BIOS image. If this fails, we continue regardless,
+       but initialize the hardware ourselves. When a kernel gets
+       preloaded we also initialize the hardware, since the BIOS wasn't
+       run. */
     bios_offset = ram_size + vga_ram_size;
     snprintf(buf, sizeof(buf), "%s/%s", bios_dir, BIOS_FILENAME);
     printf("%s: load BIOS '%s' size %d\n", __func__, buf, BIOS_SIZE);
     ret = load_image(buf, phys_ram_base + bios_offset);
-    if (ret != BIOS_SIZE) {
-        fprintf(stderr, "qemu: could not load MIPS bios '%s'\n", buf);
-        exit(1);
+    if (ret == BIOS_SIZE) {
+	cpu_register_physical_memory((uint32_t)(0x1fc00000),
+				     BIOS_SIZE, bios_offset | IO_MEM_ROM);
+	env->PC = 0xBFC00000;
+	if (!kernel_filename)
+	    return;
+    } else {
+	/* not fatal */
+        fprintf(stderr, "qemu: Warning, could not load MIPS bios '%s'\n",
+		buf);
     }
-    cpu_register_physical_memory((uint32_t)(0x1fc00000),
-                                 BIOS_SIZE, bios_offset | IO_MEM_ROM);
-#if 0
-    memcpy(phys_ram_base + 0x10000, phys_ram_base + bios_offset, BIOS_SIZE);
-    env->PC = 0x80010004;
-#else
-    env->PC = 0xBFC00004;
-#endif
-    if (linux_boot) {
-        kernel_base = KERNEL_LOAD_ADDR;
-        /* now we can load the kernel */
-        kernel_size = load_image(kernel_filename,
-                                phys_ram_base + (kernel_base - 0x80000000));
-        if (kernel_size == (target_ulong) -1) {
-            fprintf(stderr, "qemu: could not load kernel '%s'\n", 
-                    kernel_filename);
-            exit(1);
-        }
+
+    if (kernel_filename) {
+	if (!load_mips_kernel_elf(kernel_filename, &entry))
+	    env->PC = entry;
+	else {
+	    /* try to load as binary image */
+            if (load_image(kernel_filename,
+			   phys_ram_base + PHYSADDR(KERNEL_LOAD_ADDR))
+		== (target_ulong) -1) {
+		fprintf(stderr, "qemu: could not load kernel '%s'\n",
+			kernel_filename);
+                exit(1);
+            }
+	    env->PC = KERNEL_LOAD_ADDR;
+	}
+
         /* load initrd */
         if (initrd_filename) {
-            initrd_base = INITRD_LOAD_ADDR;
-            initrd_size = load_image(initrd_filename,
-                                     phys_ram_base + initrd_base);
-            if (initrd_size == (target_ulong) -1) {
+            if (load_image(initrd_filename,
+			   phys_ram_base + PHYSADDR(INITRD_LOAD_ADDR))
+		== (target_ulong) -1) {
                 fprintf(stderr, "qemu: could not load initial ram disk '%s'\n", 
                         initrd_filename);
                 exit(1);
             }
-        } else {
-            initrd_base = 0;
-            initrd_size = 0;
         }
-        env->PC = KERNEL_LOAD_ADDR;
+
 	/* Store command line.  */
         strcpy (phys_ram_base + (16 << 20) - 256, kernel_cmdline);
         /* FIXME: little endian support */
         *(int *)(phys_ram_base + (16 << 20) - 260) = tswap32 (0x12345678);
         *(int *)(phys_ram_base + (16 << 20) - 264) = tswap32 (ram_size);
-    } else {
-        kernel_base = 0;
-        kernel_size = 0;
-        initrd_base = 0;
-        initrd_size = 0;
     }
 
     /* Init internal devices */