如何debugging在启动时冻结的Linux内核？

我有一个具有二进制Linux 2.6.18内核的传统设备，可以正常引导到其rootfs。但是，如果我试图从源代码编译这个内核，那么在引导过程中产生的内核二进制文件将会冻结。我没有.config文件用于构build通常正在引导的以前的内核二进制文件。

启动冻结，没有提供错误输出。这里是启动日志：

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

我怎么去debugging呢？任何对冻结可能的解决scheme的见解也是受欢迎的。

解决这个问题的一个方法是启用CONFIG_EARLY_PRINTK并在怀疑是冻结的内核代码中添加一些printk()语句（很可能某些驱动程序的配置参数是错误的）。

另外，你也许可以通过查看/boot/config-*或者/proc/config.gz来获得旧的内核配置（只有在旧的内核启用了CONFIG_IKCONFIG_PROC选项的情况下才存在）。

有一些调试器选项，如kdb和kgdb，但我总是发现他们片状和气质。也许更多，如果你甚至不能让你的机器启动。我同意CONFIG_EARLY_PRINTK的建议，并建议你确保在启动时获得内核输出（而不是“安静”），但似乎你已经有了。

上面的“GPIO”建议可以工作 – 但是非常依赖系统和麻烦。这就是说，我认为你比“开始添加很多printk的”更好。你可以从有问题的以太网驱动程序（BRC-PM？）开始，或者尝试删除它，看看是否相关。

这将需要一些调查 – 对不起，但没有“魔术子弹”！：-O

添加initcall_debug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"