移植linux内核到s3c6410(根文件系统加载失败问题解决：Kernel panic - not syncing: VFS: Unable to mount root fs)
List of all partitions:
No filesystem could mount root, tried: ext2
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(1,0)
Backtrace:
[<c003167c>] (dump_backtrace+0x0/0x114) from [<c02c0a64>] (dump_stack+0x18/0x1c)
r6:00008000 r5:c03c8ca4 r4:c03c8ca4
[<c02c0a4c>] (dump_stack+0x0/0x1c) from [<c02c0acc>] (panic+0x64/0x180)
[<c02c0a68>] (panic+0x0/0x180) from [<c0009134>] (mount_block_root+0x260/0x2b0)
r3:00000000 r2:00000020 r1:cf82df60 r0:c035b458
[<c0008ed4>] (mount_block_root+0x0/0x2b0) from [<c00091d8>] (mount_root+0x54/0x6c)
[<c0009184>] (mount_root+0x0/0x6c) from [<c0009360>] (prepare_namespace+0x170/0x1c4)
r5:c00267ed r4:c03c8480
[<c00091f0>] (prepare_namespace+0x0/0x1c4) from [<c0008610>] (kernel_init+0x110/0x150)
r5:c0025dac r4:c03c8420
[<c0008500>] (kernel_init+0x0/0x150) from [<c0049e90>] (do_exit+0x0/0x6d4)
r5:c0008500 r4:00000000
定位步骤：
1、是否内核参数里的initrd的地址和大小不对？
u-boot的处理：setup_initrd_tag，initrd_start/initrd_end是根据bootm参数的第二个地址然后解析头（image_header_t）而得来的，所以这个参数不应该有问题才对。
#ifdef CONFIG_INITRD_TAG
if (initrd_start && initrd_end)
setup_initrd_tag (bd, initrd_start, initrd_end);
#endif
内核的处理：
ATAG_INITRD
static int __init parse_tag_initrd(const struct tag *tag)
{
printk(KERN_WARNING "ATAG_INITRD is deprecated; "
"please update your bootloader.\n");
phys_initrd_start = __virt_to_phys(tag->u.initrd.start);
phys_initrd_size = tag->u.initrd.size;
return 0;
}
__tagtable(ATAG_INITRD, parse_tag_initrd);
bootargs: initrd = start,size
static int __init early_initrd(char *p)
{
unsigned long start, size;
char *endp;
start = memparse(p, &endp);
if (*endp == ',') {
size = memparse(endp + 1, NULL);
phys_initrd_start = start;
phys_initrd_size = size;
}
return 0;
}
early_param("initrd", early_initrd);
优先级也是bootargs>ATAG_INITRD,但是我没有在bootargs里定义initrd参数，所以默认从文件里去读应该不会有什么问题的。
而且加了打印也确认这个start和size是OK的。
2、研究initrd启动流程
由于我使用的是cpio格式的initrd，所以内核处理流程为：
populate_rootfs-->unpack_to_rootfs解压到根文件系统。
reset_init-->kernel_init-->init_post执行用户初始化文件（ramdisk_execute_comman>execute_command>/sbin/init>/etc/init>/bin/init>/bin/sh），按上面顺序查找执行。
如果在根文件系统里找不到ramdisk_execute_command ，证明是老格式的initrd，不需要进入 prepare_namespace，直接进入init_post。
if (!ramdisk_execute_command)
ramdisk_execute_command = "/init";
if (sys_access((const char __user *) ramdisk_execute_command, 0) != 0) {
ramdisk_execute_command = NULL;
prepare_namespace();
}
init_post();
ramdisk_execute_comman，execute_command怎么来的呢？
由下面的代码，可以确认ramdisk_execute_comman是bootargs里的rdinit=来得到。而execute_command 由init=来得到。
static int __init init_setup(char *str)
{
unsigned int i;
execute_command = str;
for (i = 1; i < MAX_INIT_ARGS; i++)
argv_init[i] = NULL;
return 1;
}
__setup("init=", init_setup);
static int __init rdinit_setup(char *str)
{
unsigned int i;
ramdisk_execute_command = str;
/* See "auto" comment in init_setup */
for (i = 1; i < MAX_INIT_ARGS; i++)
argv_init[i] = NULL;
return 1;
}
__setup("rdinit=", rdinit_setup);
从打印看执行到了prepare_namespace，这说明是ramdisk_execute_comman找不到造成的。
检查bootargs参数：
root=/dev/ram rootfstype=ext2 init=/linuxrc console=ttySAC0,115200 mem=256M@0x50000000
确实传递不对，init=/linuxrc 是对应execute_command，rdinit=才是ramdisk_execute_comman。
修改后问题依旧，再看代码
sys_access((const char __user *) ramdisk_execute_command, 0) != 0
难道是ramdisk里没有linuxrc文件？确认ramdisk的rootfs目录下的文件，确实拷贝出错了，脚本有问题：
cp -a $BUSYBOXSOURCE/_install/ .
把文件目录拷贝到了根目录，而不是文件里的内容。
3、修改后出现了另外的问题：
Freeing init memory: 148K
ramdisk_execute_command=/linuxrc
linuxrc used greatest stack depth: 6072 bytes left
Kernel panic - not syncing: Attempted to kill init!
Backtrace:
[<c003169c>] (dump_backtrace+0x0/0x114) from [<c02c0a84>] (dump_stack+0x18/0x1c)
r6:c03ae324 r5:c03c8ca4 r4:c03c8ca4
[<c02c0a6c>] (dump_stack+0x0/0x1c) from [<c02c0aec>] (panic+0x64/0x180)
[<c02c0a88>] (panic+0x0/0x180) from [<c0049f2c>] (do_exit+0x7c/0x6d4)
r3:cf82ba80 r2:cf82bc94 r1:cf82bc60 r0:c0360377
[<c0049eb0>] (do_exit+0x0/0x6d4) from [<c004a608>] (do_group_exit+0x84/0xb8)
[<c004a584>] (do_group_exit+0x0/0xb8) from [<c0058c04>] (get_signal_to_deliver+0x348/0x384)
r4:0830009f
[<c00588bc>] (get_signal_to_deliver+0x0/0x384) from [<c0030338>] (do_signal+0x70/0x600)
[<c00302c8>] (do_signal+0x0/0x600) from [<c00308e8>] (do_notify_resume+0x20/0x64)
[<c00308c8>] (do_notify_resume+0x0/0x64) from [<c002daf8>] (work_pending+0x24/0x28)
r4:beea9bf0
OK
搜索了网上的资料后，使用arm-linux-gcc 4.0.0以上的编译器编译内核时需要加上这个配置：
Kernel Features --->
[*] Use the ARM EABI to compile the kernel
[*] Allow old ABI binaries to run with this kernel (EXPERIMENTA)
重新编译内核后，加载到单板上执行，初始化成功，bash shell #出来啦，高兴啊！！！
MINI6410 # bootm 0x50800000 0x51800000
## Booting image at 50800000 ...
Image Name: Linux-2.6.38
Image Type: ARM Linux Kernel Image (uncompressed)
Data Size: 1925280 Bytes = 1.8 MB
Load Address: 50008000
Entry Point: 50008000
Verifying Checksum ... OK
OK
## Loading Ramdisk Image at 51800000 ...
Image Name: ramdisk1.0
Image Type: ARM Linux RAMDisk Image (gzip compressed)
Data Size: 1040671 Bytes = 1016.3 kB
Load Address: 00000000
Entry Point: 00000000
Verifying Checksum ... OK
Starting kernel ...
Uncompressing Linux... done, booting the kernel.
start_kernel ok
__log_buf=503b9724
setup arch
u.mem.start=50000000
u.mem.size=10000000
1
r_banks=00000001
start=50000000
u.mem.size=10000000
root=/dev/ram0 rdinit=/linuxrc console=ttySAC0,115200 mem=256M@0x50000000
2
r_banks=00000001
start=50000000
u.mem.size=10000000
3
r_banks=00000001
start=50000000
u.mem.size=10000000
1:
root=/dev/ram0 rdinit=/linuxrc console=ttySAC0,115200 mem=256M@0x50000000
IRQ init
Linux version 2.6.38 ([email protected]) (gcc version 4.4.3 (ctng-1.6.1) ) #35 Sat Jul 30 18:27:28 CST 2011
CPU: ARMv6-compatible processor [410fb766] revision 6 (ARMv7), cr=00c5387f
CPU: VIPT nonaliasing data cache, VIPT nonaliasing instruction cache
Machine: MINI6410
Memory policy: ECC disabled, Data cache writeback
CPU S3C6410 (id 0x36410101)
S3C24XX Clocks, Copyright 2004 Simtec Electronics
camera: no parent clock specified
S3C64XX: PLL settings, A=532000000, M=532000000, E=24000000
S3C64XX: HCLK2=266000000, HCLK=133000000, PCLK=66500000
mout_apll: source is fout_apll (1), rate is 532000000
mout_epll: source is epll (1), rate is 24000000
mout_mpll: source is mpll (1), rate is 532000000
mmc_bus: source is mout_epll (0), rate is 24000000
mmc_bus: source is mout_epll (0), rate is 24000000
mmc_bus: source is mout_epll (0), rate is 24000000
usb-bus-host: source is clk_48m (0), rate is 48000000
uclk1: source is dout_mpll (1), rate is 66500000
spi-bus: source is mout_epll (0), rate is 24000000
spi-bus: source is mout_epll (0), rate is 24000000
audio-bus: source is mout_epll (0), rate is 24000000
audio-bus: source is mout_epll (0), rate is 24000000
audio-bus: source is mout_epll (0), rate is 24000000
irda-bus: source is mout_epll (0), rate is 24000000
camera: no parent clock specified
Built 1 zonelists in Zone order, mobility grouping on. Total pages: 65024
Kernel command line: root=/dev/ram0 rdinit=/linuxrc console=ttySAC0,115200 mem=256M@0x50000000
PID hash table entries: 1024 (order: 0, 4096 bytes)
Dentry cache hash table entries: 32768 (order: 5, 131072 bytes)
Inode-cache hash table entries: 16384 (order: 4, 65536 bytes)
Memory: 256MB = 256MB total
Memory: 254576k/254576k available, 7568k reserved, 0K highmem
Virtual kernel memory layout:
vector : 0xffff0000 - 0xffff1000 ( 4 kB)
fixmap : 0xfff00000 - 0xfffe0000 ( 896 kB)
DMA : 0xff600000 - 0xffe00000 ( 8 MB)
vmalloc : 0xd0800000 - 0xf6000000 ( 600 MB)
lowmem : 0xc0000000 - 0xd0000000 ( 256 MB)
pkmap : 0xbfe00000 - 0xc0000000 ( 2 MB)
modules : 0xbf000000 - 0xbfe00000 ( 14 MB)
.init : 0xc0008000 - 0xc002b000 ( 140 kB)
.text : 0xc002b000 - 0xc03902e8 (3477 kB)
.data : 0xc0392000 - 0xc03b8560 ( 154 kB)
NR_IRQS:246
VIC @f6000000: id 0x00041192, vendor 0x41
VIC @f6010000: id 0x00041192, vendor 0x41
Console: colour dummy device 80x30
console [ttySAC0] enabled
Calibrating delay loop... 530.84 BogoMIPS (lpj=2654208)
pid_max: default: 32768 minimum: 301
Security Framework initialized
SELinux: Initializing.
Mount-cache hash table entries: 512
CPU: Testing write buffer coherency: ok
hw perfevents: enabled with v6 PMU driver, 3 counters available
NET: Registered protocol family 16
MINI6410: Option string mini6410=0
MINI6410: selected LCD display is 480x272
hw-breakpoint: found 6 breakpoint and 1 watchpoint registers.
hw-breakpoint: maximum watchpoint size is 4 bytes.
S3C6410: Initialising architecture
bio: create slab <bio-0> at 0
usbcore: registered new interface driver usbfs
usbcore: registered new interface driver hub
usbcore: registered new device driver usb
NetLabel: Initializing
NetLabel: domain hash size = 128
NetLabel: protocols = UNLABELED CIPSOv4
NetLabel: unlabeled traffic allowed by default
NET: Registered protocol family 2
IP route cache hash table entries: 2048 (order: 1, 8192 bytes)
TCP established hash table entries: 8192 (order: 4, 65536 bytes)
TCP bind hash table entries: 8192 (order: 3, 32768 bytes)
TCP: Hash tables configured (established 8192 bind 8192)
TCP reno registered
UDP hash table entries: 256 (order: 0, 4096 bytes)
UDP-Lite hash table entries: 256 (order: 0, 4096 bytes)
NET: Registered protocol family 1
initrd_start=0xc1800040,err =ox0
Trying to unpack rootfs image as initramfs...
Freeing initrd memory: 1016K
audit: initializing netlink socket (disabled)
type=2000 audit(0.650:1): initialized
VFS: Disk quotas dquot_6.5.2
Dquot-cache hash table entries: 1024 (order 0, 4096 bytes)
msgmni has been set to 499
cryptomgr_test used greatest stack depth: 7212 bytes left
Block layer SCSI generic (bsg) driver version 0.4 loaded (major 254)
io scheduler noop registered
io scheduler deadline registered
io scheduler cfq registered (default)
Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled
s3c6400-uart.0: ttySAC0 at MMIO 0x7f005000 (irq = 16) is a S3C6400/10
s3c6400-uart.1: ttySAC1 at MMIO 0x7f005400 (irq = 20) is a S3C6400/10
s3c6400-uart.2: ttySAC2 at MMIO 0x7f005800 (irq = 24) is a S3C6400/10
s3c6400-uart.3: ttySAC3 at MMIO 0x7f005c00 (irq = 28) is a S3C6400/10
brd: module loaded
Uniform Multi-Platform E-IDE driver
ide-gd driver 1.18
mousedev: PS/2 mouse device common for all mice
usbcore: registered new interface driver usbhid
usbhid: USB HID core driver
TCP bic registered
Initializing XFRM netlink socket
NET: Registered protocol family 17
Registering the dns_resolver key type
registered taskstats version 1
Initalizing network drop monitor service
Freeing init memory: 140K
ramdisk_execute_command=/linuxrc
mount used greatest stack depth: 6344 bytes left
rcS used greatest stack depth: 6240 bytes left
Processing /etc/profile... Done
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