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--- etc:users:jcmvbkbc:omap-support-pieces [2009/06/29 22:48] – gdb session script jcmvbkbc
+++ etc:users:jcmvbkbc:omap-support-pieces [2016/08/08 20:53] (current) – ↷ Page moved from users:jcmvbkbc:omap-support-pieces to etc:users:jcmvbkbc:omap-support-pieces kel
@@ Line 1: / Line 1: @@
 ====== N8x0 support in linux-omap ======
+Current kernel: 2.6.35
+[[http://jcmvbkbc.spb.ru/~dumb/ws/osll/n8x0/|Rootfs and kernel config]]
+===== Startup plan =====
+  * [2/3] find optimal debugging techniques and real HW/qemu split;
+  * [3/4] make minimal working/debuggable configuration;
+  * [0] compile domain glossary.
 ===== Debug interfaces =====
 ===== Subsystems' status =====
+  * SPI, MMC, USB, mac80211: ok
 ===== Debugging in qemu =====
-Need CONFIG_DEBUG_INFO=y in kernel configuration for the following to work.
+==== Kernel configuration ====
+  * CONFIG_DEBUG_INFO=y for symbolic debugging to work;
+  * CONFIG_FRAME_POINTER=y (which is only possible when CONFIG_ARM_UNWIND=n) + CONFIG_DEBUG_BUGVERBOSE=y for symbolic backtrace on oopses and BUGs;
-Magic numbers:
+==== Kernel command line parameters ====
+  * initcall_debug=1 -- make kernel print all _init function calls during kernel_init;
+==== Magic numbers ====
   * 0x80000000 -- here the kernel is loaded
-  * 0x80008000 -- here we jump after it's been decompressed
+  * 0x80008000 -- here we jump after decompression (.text.head that has VA of 0xc0008000 has PA 0x80008000 until MMU is active)
-  * 0x80027000 -- 'arm-linux-gnu-objdump -x vmlinux' says that .text starts here (if .text.head is at 0x80008000)
+  * 0xc0026000 -- 'arm-linux-gnu-objdump -x vmlinux' says that .text starts here
-Script for gdb session:
+==== Booting n8x0 kernel in qemu ====
+<code>
+qemu-system-arm -M n810 -kernel "linux-omap-2.6/arch/arm/boot/zImage" -s -sd mmcblk0 -usb
+</code>
+==== Script for gdb session ====
 <code>
 target remote 127.0.0.1:1234
 break *0x80008000
-add-symbol-file ~/ws/osll/omap/20090610/linux-omap-2.6/vmlinux 0x80027000 -s .text.head 0x80008000
 </code>
+To debug kernel as usual:
+  symbol-file linux-omap-2.6/vmlinux
+To debug compression-related stuff from the very beginning (start, arch/arm/boot/compressed/head.S) till start_kernel:
+  add-symbol-file linux-omap-2.6/arch/arm/boot/compressed/vmlinux 0x80000000
+To debug kernel from stext (arch/arm/kernel/head.S) until MMU is active:
+  add-symbol-file linux-omap-2.6/vmlinux 0x80026000 -s .text.head 0x80008000
+To debug kernel from start_kernel (init/main.c):
+  add-symbol-file linux-omap-2.6/vmlinux 0xc0026000
+==== "Blank screen" debugging ====
+Whatever happens, ^C breaks into the running kernel. If the screen is blank, dmesg-like log may be viewed through
+  x/10000s log_buf
+Or even through
+  dump memory kmsg.log log_buf log_buf+10000
 ===== Debugging on real HW =====
+==== Dealing with retu watchdog ====
+Need to periodically touch it, like this:
+<file>
+while true
+do
+ echo 63 > /sys/devices/platform/retu-watchdog/period
+ sleep 1
+done
+</file>