linux-mips
[Top] [All Lists]

[PATCH] Improve ramdisk support

To: linux-mips@linux-mips.org
Subject: [PATCH] Improve ramdisk support
From: Thiemo Seufer <ica2_ts@csv.ica.uni-stuttgart.de>
Date: Sun, 21 Nov 2004 04:06:14 +0100
Cc: ralf@linux-mips.org
Original-recipient: rfc822;linux-mips@linux-mips.org
Sender: linux-mips-bounce@linux-mips.org
User-agent: Mutt/1.5.6i
Hello All,

there are currently two methods to use an initial ramdisk in the
kernel, either by compiling it in via CONFIG_EMBEDDED_RAMDISK or by
tacking the ramdisk on the kernel image via addinitrd. A third method
currently under development is a compiled in cpio archive handled via
initramfs.

There is, however, no way to add an initial ramdisk after the kernel
was built. The appended patch introduces "rd_start" and "rd_size"
command line parameters which allow a bootloader to preload the
ramdisk and make its location known to the kernel by feeding
appropriate rd_start/rd_size values.

Debian used an earlier version of this patch for several years now.


Thiemo


Index: arch/mips/kernel/setup.c
===================================================================
RCS file: /home/cvs/linux/arch/mips/kernel/setup.c,v
retrieving revision 1.171
diff -u -p -r1.171 setup.c
--- arch/mips/kernel/setup.c    28 Jun 2004 21:04:12 -0000      1.171
+++ arch/mips/kernel/setup.c    20 Nov 2004 16:46:39 -0000
@@ -194,6 +194,68 @@ static inline void parse_cmdline_early(v
        }
 }
 
+static inline int parse_rd_cmdline(unsigned long* rd_start, unsigned long* 
rd_end)
+{
+       /*
+        * "rd_start=0xNNNNNNNN" defines the memory address of an initrd
+        * "rd_size=0xNN" it's size
+        */
+       unsigned long start = 0;
+       unsigned long size = 0;
+       unsigned long end;
+       char cmd_line[CL_SIZE];
+       char *start_str;
+       char *size_str;
+       char *tmp;
+
+       strcpy(cmd_line, command_line);
+       *command_line = 0;
+       tmp = cmd_line;
+       /* Ignore "rd_start=" strings in other parameters. */
+       start_str = strstr(cmd_line, "rd_start=");
+       if (start_str && start_str != cmd_line && *(start_str - 1) != ' ')
+               start_str = strstr(start_str, " rd_start=");
+       while (start_str) {
+               if (start_str != cmd_line)
+                       strncat(command_line, tmp, start_str - tmp);
+               start = memparse(start_str + 9, &start_str);
+               tmp = start_str + 1;
+               start_str = strstr(start_str, " rd_start=");
+       }
+       if (*tmp)
+               strcat(command_line, tmp);
+
+       strcpy(cmd_line, command_line);
+       *command_line = 0;
+       tmp = cmd_line;
+       /* Ignore "rd_size" strings in other parameters. */
+       size_str = strstr(cmd_line, "rd_size=");
+       if (size_str && size_str != cmd_line && *(size_str - 1) != ' ')
+               size_str = strstr(size_str, " rd_size=");
+       while (size_str) {
+               if (size_str != cmd_line)
+                       strncat(command_line, tmp, size_str - tmp);
+               size = memparse(size_str + 8, &size_str);
+               tmp = size_str + 1;
+               size_str = strstr(size_str, " rd_size=");
+       }
+       if (*tmp)
+               strcat(command_line, tmp);
+
+#ifdef CONFIG_MIPS64
+       /* HACK: Guess if the sign extension was forgotten */
+       if (start > 0x0000000080000000 && start < 0x00000000ffffffff)
+               start |= 0xffffffff00000000;
+#endif
+
+       end = start + size;
+       if (start && end) {
+               *rd_start = start;
+               *rd_end = end;
+               return 1;
+       }
+       return 0;
+}
 
 #define PFN_UP(x)      (((x) + PAGE_SIZE - 1) >> PAGE_SHIFT)
 #define PFN_DOWN(x)    ((x) >> PAGE_SHIFT)
@@ -205,30 +267,45 @@ static inline void parse_cmdline_early(v
 static inline void bootmem_init(void)
 {
        unsigned long start_pfn;
+       unsigned long reserved_end = (unsigned long)&_end;
 #ifndef CONFIG_SGI_IP27
-       unsigned long bootmap_size, max_low_pfn, first_usable_pfn;
+       unsigned long first_usable_pfn;
+       unsigned long bootmap_size;
        int i;
 #endif
 #ifdef CONFIG_BLK_DEV_INITRD
-       unsigned long tmp;
-       unsigned long *initrd_header;
+       int initrd_reserve_bootmem = 0;
 
-       tmp = (((unsigned long)&_end + PAGE_SIZE-1) & PAGE_MASK) - 8;
-       if (tmp < (unsigned long)&_end)
-               tmp += PAGE_SIZE;
-       initrd_header = (unsigned long *)tmp;
-       if (initrd_header[0] == 0x494E5244) {
-               initrd_start = (unsigned long)&initrd_header[2];
-               initrd_end = initrd_start + initrd_header[1];
+       /* Board specific code should have set up initrd_start and initrd_end */
+       ROOT_DEV = Root_RAM0;
+       if (&__rd_start != &__rd_end) {
+               initrd_start = (unsigned long)&__rd_start;
+               initrd_end = (unsigned long)&__rd_end;
+       } else if (parse_rd_cmdline(&initrd_start, &initrd_end)) {
+               reserved_end = max(reserved_end, initrd_end);
+               initrd_reserve_bootmem = 1;
+       } else {
+               unsigned long tmp;
+               unsigned long *initrd_header;
+
+               tmp = ((reserved_end + PAGE_SIZE-1) & PAGE_MASK) - 8;
+               if (tmp < reserved_end)
+                       tmp += PAGE_SIZE;
+               initrd_header = (unsigned long *)tmp;
+               if (initrd_header[0] == 0x494E5244) {
+                       initrd_start = (unsigned long)&initrd_header[2];
+                       initrd_end = initrd_start + initrd_header[1];
+                       reserved_end = max(reserved_end, initrd_end);
+                       initrd_reserve_bootmem = 1;
+               }
        }
-       start_pfn = PFN_UP(CPHYSADDR((&_end)+(initrd_end - initrd_start) + 
PAGE_SIZE));
-#else
+#endif /* CONFIG_BLK_DEV_INITRD */
+
        /*
         * Partially used pages are not usable - thus
         * we are rounding upwards.
         */
-       start_pfn = PFN_UP(CPHYSADDR(&_end));
-#endif /* CONFIG_BLK_DEV_INITRD */
+       start_pfn = PFN_UP(CPHYSADDR(reserved_end));
 
 #ifndef CONFIG_SGI_IP27
        /* Find the highest page frame number we have available.  */
@@ -341,21 +418,14 @@ static inline void bootmem_init(void)
 
        /* Reserve the bootmap memory.  */
        reserve_bootmem(PFN_PHYS(first_usable_pfn), bootmap_size);
-#endif
+#endif /* CONFIG_SGI_IP27 */
 
 #ifdef CONFIG_BLK_DEV_INITRD
-       /* Board specific code should have set up initrd_start and initrd_end */
-       ROOT_DEV = Root_RAM0;
-       if (&__rd_start != &__rd_end) {
-               initrd_start = (unsigned long)&__rd_start;
-               initrd_end = (unsigned long)&__rd_end;
-       }
        initrd_below_start_ok = 1;
        if (initrd_start) {
                unsigned long initrd_size = ((unsigned char *)initrd_end) - 
((unsigned char *)initrd_start);
                printk("Initial ramdisk at: 0x%p (%lu bytes)\n",
-                      (void *)initrd_start,
-                      initrd_size);
+                      (void *)initrd_start, initrd_size);
 
                if (CPHYSADDR(initrd_end) > PFN_PHYS(max_low_pfn)) {
                        printk("initrd extends beyond end of memory "
@@ -363,7 +433,11 @@ static inline void bootmem_init(void)
                               sizeof(long) * 2, CPHYSADDR(initrd_end),
                               sizeof(long) * 2, PFN_PHYS(max_low_pfn));
                        initrd_start = initrd_end = 0;
+                       initrd_reserve_bootmem = 0;
                }
+
+               if (initrd_reserve_bootmem)
+                       reserve_bootmem(CPHYSADDR(initrd_start), initrd_size);
        }
 #endif /* CONFIG_BLK_DEV_INITRD  */
 }

<Prev in Thread] Current Thread [Next in Thread>