Mostrando mensaje 9     < Anterior | Siguiente > Responder a este mensaje Asunto: [glisc] Problemas con el System.map del RedHat Linux??? Fecha: Miercoles, 11 de Abril, 2001  17:35:45 (-0400) Autor: Alfonso Fernandez <afernandez @......net> ayuda!!! What is the System.map file? Every time you compile a kernel, a file is created which maps the kernel address locations of important variables and functions to symbolic names. Think of this file as the way the kernel links symbolic names to addresses in the same way you would link a .o file to an executable with gcc. Every time you compile the kernel, the address of the variables and functions changes, so this look-up file needs to be rewritten. This file is called System.map, and appears at the top of the kernel directory source tree, usually /usr/src/linux. We call this information the `kernel symbol table'. What is System.map used for in kernel space? When a protection fault occurs, the klogd daemon translates important addresses (meaningless to us) in the kernel to thier symbolic equivalents (meaningful to us). This translated kernel message is then forwarded through whatever reporting mechanism klogd is using. The fact that the addresses get translated makes it easier for us to decipher what went wrong during the fault. A kernel developer can determine exactly what the kernel was doing when the error condition occurred. To this end, upon daemon initialization during bootup, klogd will look for a system map in 3 places, in the following order: /boot/System.map /System.map /usr/src/linux/System.map A few drivers will need System.map to resolve symbols (since they're linked against the kernel headers instead of, say, glibc). They will not work correctly without the System.map created for the particular kernel you're currently running. Note, there are actually two types of address resolution are performed by klogd. The first is static translation, which uses the System.map file. The second is dynamic translation which is used with some loadable modules and is not relevant here. What else uses the System.map Don't think that System.map is only useful for kernel oopses. Although the kernel itself doesn't really use System.map, other programs such as lsof and dosemu rely on an up to date kernel symbol table. What happens if I don't have a healthy System.map? Suppose you have 4 kernels. You need 4 separate System.map files, one for each kernel! Now if you see an error upon boot: System.map does not match actual kernel This error might appear together with a few other messages that say: module XXXX could not be loaded because some versions do not match. How do I remedy the above situation? The solution is to copy the file /usr/src/linux/System.map to /boot/System.map. Here's what I do. Suppose I have multiple kernels like: vmlinuz-2.2.14 vmlinuz-2.2.13 vmlinux-2.2.13.sound all located in /boot. Then I also have the following kernel symbol tables, also located in /boot: System.map-vmlinuz-2.2.14 System.map-vmlinuz-2.2.13 System.map-vmlinux-2.2.13.sound And make a symlink of the one I use most (System.map-vmlinuz-2.2.14) to /boot/Symbol.map. % ls -l /boot/ total 2170 -rw-r--r-- 1 root root 221778 Nov 3 1999 System.map-2.2.13 -rw-r--r-- 1 root root 232313 Jan 20 1999 System.map-2.2.13.sound -rw-r--r-- 1 root root 232426 Jan 29 1999 System.map-2.2.14 -rw-r--r-- 1 root root 12 Jan 29 1999 System.map -> System.map-2.2.14 -rw-r--r-- 1 root root 512 Jul 6 1999 boot.0300 -rw-r--r-- 1 root root 4540 Jul 22 1999 boot.b -rw-r--r-- 1 root root 612 Jul 22 1999 chain.b -rw------- 1 root root 7168 Jan 29 21:28 map -rw-r--r-- 1 root root 649591 Jan 20 23:54 vmlinux-2.2.13.sound -rw-r--r-- 1 root root 649590 Nov 3 10:45 vmlinuz-2.2.13 -rw-r--r-- 1 root root 659572 Jan 29 21:22 vmlinuz-2.2.14 Did you think this article was informative? As a way to say thanks, why don't you make some suggestions on my html to make this page more attractive. I'm also looking for people to help me design a consistant and pleasant look throughout my linux pages. Please email me. I'm also looking for technical corrections, constructive criticism, etc. --- Slds, Alfonso UNIBOL Av. Santa Cruz #1200 Tel +591 3 33-5717 Fax +591 3 36-5542 Santa Cruz - Bolivia http://www.unibol.net