如何调试在启动过程中冻结的Linux内核？

Question

我有一个带有二进制Linux 2.6.18内核的旧设备，该内核通常会引导到其rootfs。 但是，如果我尝试从源代码编译此内核，则生成的内核二进制文件将在引导过程中冻结。 我没有用于构建当前正在正常引导的先前内核二进制文件的.config文件。

引导程序冻结，不提供错误输出。 这是启动日志：

Linux version 2.6.18-6.2 (myuser@host) (gcc version 4.2.0 20070124 (prerelease) - BRCM 10ts-20080721) #10 SMP Sun Apr 28 18:25:24 BRT 2013
Fetching vars from bootloader... OK (E,d,B,C)
Detected 512 MB on MEMC0 (strap 0x23430310)
Board strapped at 512 MB, default is 256 MB
Options: sata=1 enet=1 emac_1=1 no_mdio=0 docsis=0 ebi_war=0 pci=1 smp=1
CPU revision is: 0002a044
FPU revision is: 00130001
Primary instruction cache 32kB, physically tagged, 2-way, linesize 64 bytes.
Primary data cache 64kB, 4-way, linesize 64 bytes.
<6>Synthesized TLB refill handler (23 instructions).
<6>Synthesized TLB load handler fastpath (37 instructions).
<6>Synthesized TLB store handler fastpath (37 instructions).
<6>Synthesized TLB modify handler fastpath (36 instructions).
Determined physical RAM map:
 memory: 10000000 @ 00000000 (usable)
 memory: 10000000 @ 20000000 (usable)
Using 32MB for memory, overwrite by passing mem=xx
User-defined physical RAM map:
node [00000000, 02000000: RAM]
node [02000000, 0e000000: RSVD]
node [20000000, 10000000: RAM]
<5>Reserving 224 MB upper memory starting at 02000000
<7>On node 0 totalpages: 65536
<7>  DMA zone: 65536 pages, LIFO batch:15
<7>On node 1 totalpages: 65536
<7>  Normal zone: 65536 pages, LIFO batch:15
Built 2 zonelists.  Total pages: 131072
<5>Kernel command line: root=/dev/mtdblock3 rw rootfstype=jffs2 console=ttyS0,115200
PID hash table entries: 4096 (order: 12, 16384 bytes)
mips_counter_frequency = 202000000 from Calibration, = 202500000 from header(CPU_MHz/2)
Dentry cache hash table entries: 65536 (order: 6, 262144 bytes)
Inode-cache hash table entries: 32768 (order: 5, 131072 bytes)
Memory: 286336k/524288k available (2924k kernel code, 237760k reserved, 544k data, 164k init, 0k highmem)
Mount-cache hash table entries: 512
Checking for 'wait' instruction...  available.
plat_prepare_cpus: ENABLING 2nd Thread...
TP0: prom_boot_secondary: Kick off 2nd CPU...
CPU revision is: 0002a044
FPU revision is: 00130001
Primary instruction cache 32kB, physically tagged, 2-way, linesize 64 bytes.
Primary data cache 64kB, 4-way, linesize 64 bytes.
Synthesized TLB refill handler (23 instructions).
Brought up 2 CPUs
migration_cost=1000
NET: Registered protocol family 16
registering PCI controller with io_map_base unset
registering PCI controller with io_map_base unset
SCSI subsystem initialized
usbcore: registered new driver usbfs
usbcore: registered new driver hub
NET: Registered protocol family 2
IP route cache hash table entries: 16384 (order: 4, 65536 bytes)
TCP established hash table entries: 65536 (order: 7, 524288 bytes)
TCP bind hash table entries: 32768 (order: 6, 262144 bytes)
TCP: Hash tables configured (established 65536 bind 32768)
TCP reno registered
brcm-pm: disabling power to USB block
brcm-pm: disabling power to ENET block
brcm-pm: disabling power to SATA block
squashfs: version 3.2-r2 (2007/01/15) Phillip Lougher
JFFS2 version 2.2. (NAND) (SUMMARY)  (C) 2001-2006 Red Hat, Inc.
io scheduler noop registered
io scheduler anticipatory registered (default)
io scheduler deadline registered
io scheduler cfq registered
Serial: 8250/16550 driver $Revision: 1.1.1.1 $ 3 ports, IRQ sharing disabled
serial8250: ttyS0 at MMIO 0x0 (irq = 22) is a 16550A
serial8250: ttyS1 at MMIO 0x0 (irq = 66) is a 16550A
serial8250: ttyS2 at MMIO 0x0 (irq = 67) is a 16550A
loop: loaded (max 8 devices)
brcm-pm: enabling power to ENET block

我该如何调试呢？ 也欢迎对冻结的可能解决方案有任何见解。

Answer 1

解决此问题的一种方法是启用CONFIG_EARLY_PRINTK并在您怀疑冻结的内核代码中添加一些printk()语句（很可能某些驱动程序配置参数错误）。

另外，您可以通过查看/boot/config-*或/proc/config.gz来获取旧内核配置（仅当旧内核启用了选项CONFIG_IKCONFIG_PROC该/boot/config-*才存在）。

Answer 2

有一些调试器选项，例如kdb和kgdb，但我总是发现它们有些不稳定。 可能更多，如果您甚至无法启动计算机。 我同意CONFIG_EARLY_PRINTK的建议，并建议您确保引导时获得内核输出（而不是“安静”），但看来您已经拥有了。

上面的“ GPIO”建议可以起作用-但非常依赖系统且麻烦。 就是说，我认为您想要一个比“开始添加很多printk的”更好的答案。 您可以从有问题的以太网驱动程序（BRC-PM？）开始，或尝试删除该驱动程序以查看是否相关。

需要进行一些调查-很抱歉，但是没有“魔术子弹”！ ：-O

Answer 3

将initcall_debug添加到CONFIG_CMDLINE （内核命令行）。

CONFIG_CMDLINE="root=/dev/ram0 rw mem=512M@0x0 initrd=0x800000,16M console=ttyS0,38400n8 rootfstype=ext2 init=/bin/busybox init -s initcall_debug"