![]() Indeed, many times you will discover that the kernel has encountered an error that led to a call to panic(). ![]() If you know where to find them, you can often pinpoint the exact problem that is causing the boot to hang. Very often, when your board hangs on boot, quite a few messages are stuck in the printk buffer. ![]() One of its shortcomings is that you can't see any printk messages until later in the boot sequence when the console device has been initialized. printk itself is a very robust implementation. When we discussed printk debugging in Section 14.3.6, we pointed out some of the limitations of this method. Serial port setup, called by yosemite.c platform-initialization fileīinds platform-specific progress routine to generic ppc machine-dependent infrastructure All these filenames are unique, so they can be found without full pathname references. Consult the following files in the Linux source tree for details of how this debugging system is implemented: The AMCC Yosemite platform is an excellent example of this infrastructure. * Map in all of RAM starting at KERNELBASE */ Here is an example of its usage found in. Of course, you can add your own early debug messages in other places in the kernel. Using this feature, you can often tell where your board is getting stuck during the boot process. Id mach(): done <= Start of messages enabled by Image Type: PowerPC Linux Kernel Image (gzip compressed) Listing 14-22 provides an example of this feature in use on a PowerPC target using the U-Boot bootloader. At the present time, this feature is limited to the PowerPC architecture, but nothing prevents you from duplicating the functionality in other architectures. This Linux kernel-configuration option adds support for debug messages very early in the boot process. The first tool you might have available is CONFIG_SERIAL_TEXT_DEBUG. ![]() With some knowledge and a JTAG debugger, there are ways to determine what went awry. Thus starts the long and sometimes frustrating learning curve of embedded Linux! Many things that can go wrong could lead to this common failure. I am trying to boot Linux on my board, and I get stuck after this message prints to my console: One of the most frequently asked questions on the various mailing lists that serve embedded Linux goes something like this: ![]()
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