[PATCH] Improve ramdisk support

[PATCH] Improve ramdisk support

[Thiemo Seufer]

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  */
 }

Re: [PATCH] Improve ramdisk support

[Thiemo Seufer]

Thiemo Seufer wrote:
> 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.

CONFIG_EMBEDDED_RAMDISK is gone now. The updated patch below removes
some leftovers.


Thiemo


Index: arch/mips/au1000/common/setup.c
===================================================================
RCS file: /home/cvs/linux/arch/mips/au1000/common/setup.c,v
retrieving revision 1.20
diff -u -p -r1.20 setup.c
--- arch/mips/au1000/common/setup.c	11 Oct 2004 20:01:14 -0000	1.20
+++ arch/mips/au1000/common/setup.c	21 Nov 2004 16:14:03 -0000
@@ -42,11 +42,6 @@
 #include <asm/mach-au1x00/au1000.h>
 #include <asm/time.h>
 
-#ifdef CONFIG_BLK_DEV_INITRD
-extern unsigned long initrd_start, initrd_end;
-extern void * __rd_start, * __rd_end;
-#endif
-
 extern char * __init prom_getcmdline(void);
 extern void __init board_setup(void);
 extern void au1000_restart(char *);
@@ -153,12 +148,6 @@ static int __init au1x00_setup(void)
 	iomem_resource.start = IOMEM_RESOURCE_START;
 	iomem_resource.end = IOMEM_RESOURCE_END;
 
-#ifdef CONFIG_BLK_DEV_INITRD
-	ROOT_DEV = MKDEV(RAMDISK_MAJOR, 0);
-	initrd_start = (unsigned long)&__rd_start;
-	initrd_end = (unsigned long)&__rd_end;
-#endif
-
 	while (au_readl(SYS_COUNTER_CNTRL) & SYS_CNTRL_E0S);
 	au_writel(SYS_CNTRL_E0 | SYS_CNTRL_EN0, SYS_COUNTER_CNTRL);
 	au_sync();
Index: arch/mips/dec/setup.c
===================================================================
RCS file: /home/cvs/linux/arch/mips/dec/setup.c,v
retrieving revision 1.41
diff -u -p -r1.41 setup.c
--- arch/mips/dec/setup.c	20 Aug 2004 09:19:01 -0000	1.41
+++ arch/mips/dec/setup.c	21 Nov 2004 16:14:03 -0000
@@ -48,11 +48,6 @@ extern irqreturn_t dec_intr_halt(int irq
 
 extern asmlinkage void decstation_handle_int(void);
 
-#ifdef CONFIG_BLK_DEV_INITRD
-extern unsigned long initrd_start, initrd_end;
-extern void * __rd_start, * __rd_end;
-#endif
-
 spinlock_t ioasic_ssr_lock;
 
 volatile u32 *ioasic_base;
@@ -136,11 +131,6 @@ extern void dec_timer_setup(struct irqac
 
 static void __init decstation_setup(void)
 {
-#ifdef CONFIG_BLK_DEV_INITRD
-	ROOT_DEV = MKDEV(RAMDISK_MAJOR, 0);
-	initrd_start = (unsigned long)&__rd_start;
-	initrd_end = (unsigned long)&__rd_end;
-#endif
 	board_be_init = dec_be_init;
 	board_time_init = dec_time_init;
 	board_timer_setup = dec_timer_setup;
Index: arch/mips/dec/boot/decstation.c
===================================================================
RCS file: /home/cvs/linux/arch/mips/dec/boot/decstation.c,v
retrieving revision 1.2
diff -u -p -r1.2 decstation.c
--- arch/mips/dec/boot/decstation.c	4 Jun 2003 18:14:26 -0000	1.2
+++ arch/mips/dec/boot/decstation.c	21 Nov 2004 16:14:03 -0000
@@ -26,7 +26,6 @@
 #define INITRD_SIZE (*(unsigned long *) (PARAM+0x21c))
 
 extern int _ftext, _end;		/* begin and end of kernel image */
-extern void *__rd_start, *__rd_end;	/* begin and end of ramdisk image */
 extern void kernel_entry(int, char **, unsigned long, int *);
 
 void * memcpy(void * dest, const void *src, unsigned int count)
@@ -81,11 +80,5 @@ void dec_entry(int argc, char **argv,
 		rex_clear_cache();
 	}
 
-#ifdef CONFIG_BLK_DEV_INITRD
-	LOADER_TYPE = 1;
-	INITRD_START = (long)&__rd_start;
-	INITRD_SIZE = (long)&__rd_end - (long)&__rd_start;
-#endif
-
 	kernel_entry(argc, argv, magic, prom_vec);
 }
Index: arch/mips/jmr3927/rbhma3100/setup.c
===================================================================
RCS file: /home/cvs/linux/arch/mips/jmr3927/rbhma3100/setup.c,v
retrieving revision 1.14
diff -u -p -r1.14 setup.c
--- arch/mips/jmr3927/rbhma3100/setup.c	20 Aug 2004 11:29:06 -0000	1.14
+++ arch/mips/jmr3927/rbhma3100/setup.c	21 Nov 2004 16:14:03 -0000
@@ -184,10 +184,6 @@ unsigned long jmr3927_do_gettimeoffset(v
 }
 
 
-#if defined(CONFIG_BLK_DEV_INITRD)
-extern unsigned long __rd_start, __rd_end, initrd_start, initrd_end;
-#endif
-
 //#undef DO_WRITE_THROUGH
 #define DO_WRITE_THROUGH
 #define DO_ENABLE_CACHE
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	21 Nov 2004 16:14:03 -0000
@@ -56,8 +56,6 @@ unsigned int PCI_DMA_BUS_IS_PHYS;
 
 EXPORT_SYMBOL(PCI_DMA_BUS_IS_PHYS);
 
-extern void * __rd_start, * __rd_end;
-
 /*
  * Setup information
  *
@@ -194,6 +192,68 @@ 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 +265,42 @@ 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 (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 +413,14 @@ 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 +428,11 @@ 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  */
 }
Index: arch/mips/sibyte/cfe/setup.c
===================================================================
RCS file: /home/cvs/linux/arch/mips/sibyte/cfe/setup.c,v
retrieving revision 1.19
diff -u -p -r1.19 setup.c
--- arch/mips/sibyte/cfe/setup.c	21 Nov 2004 13:50:35 -0000	1.19
+++ arch/mips/sibyte/cfe/setup.c	21 Nov 2004 16:14:04 -0000
@@ -56,7 +56,6 @@ int cfe_cons_handle;
 
 #ifdef CONFIG_BLK_DEV_INITRD
 extern unsigned long initrd_start, initrd_end;
-extern void * __rd_start, * __rd_end;
 #endif
 
 #ifdef CONFIG_KGDB
Index: arch/mips/sibyte/swarm/setup.c
===================================================================
RCS file: /home/cvs/linux/arch/mips/sibyte/swarm/setup.c,v
retrieving revision 1.32
diff -u -p -r1.32 setup.c
--- arch/mips/sibyte/swarm/setup.c	14 Sep 2004 21:23:33 -0000	1.32
+++ arch/mips/sibyte/swarm/setup.c	21 Nov 2004 16:14:04 -0000
@@ -52,10 +52,6 @@ extern int m41t81_probe(void);
 extern int m41t81_set_time(unsigned long);
 extern unsigned long m41t81_get_time(void);
 
-#ifdef CONFIG_BLK_DEV_INITRD
-extern void * __rd_start, * __rd_end;
-#endif
-
 const char *get_system_type(void)
 {
 	return "SiByte " SIBYTE_BOARD_NAME;

Re: [PATCH] Improve ramdisk support

[Ralf Baechle]

On Sun, Nov 21, 2004 at 05:20:54PM +0100, Thiemo Seufer wrote:

> CONFIG_EMBEDDED_RAMDISK is gone now. The updated patch below removes
> some leftovers.

Thanks for updating your patch so quickly.

  Ralf