How to read, understand, analyze, and debug a Linux kernel panic?
c, debugging, linux, linux-kernel, panic
Solution
It's just an ordinary backtrace. Those functions are called in reverse order; the first function listed was called by the next. Below I added `[was called]` to further clarify:
(unwind_backtrace+0x0/0xf8) [was called] from (warn_slowpath_common+0x50/0x60)
(warn_slowpath_common+0x50/0x60) [was called] from (warn_slowpath_null+0x1c/0x24)
(warn_slowpath_null+0x1c/0x24) [was called] from (local_bh_enable_ip+0xa0/0xac)
(local_bh_enable_ip+0xa0/0xac) [was called] from (bdi_register+0xec/0x150)
The `bdi_register+0xec/0x150` is the symbol + the offset/length. There's more information about this in Understanding a Kernel Oops and how you can debug a kernel oops. Also, there's this excellent tutorial on Debugging the Kernel.
Note: as suggested below by Eugene, you may want to try addr2line first. It will need an image with debugging symbols though. For example:
`addr2line -e vmlinux_with_debug_info 0019594c(+offset)`
Problem
Consider the following Linux kernel dump stack trace; e.g., you can trigger a panic from the kernel source code by calling `panic("debugging a Linux kernel panic");`: ``` [<001360ac>] (unwind_backtrace+0x0/0xf8) from [<00147b7c>] (warn_slowpath_common+0x50/0x60) [<00147b7c>] (warn_slowpath_common+0x50/0x60) from [<00147c40>] (warn_slowpath_null+0x1c/0x24) [<00147c40>] (warn_slowpath_null+0x1c/0x24) from [<0014de44>] (local_bh_enable_ip+0xa0/0xac) [<0014de44>] (local_bh_enable_ip+0xa0/0xac) from [<0019594c>] (bdi_register+0xec/0x150) ``` - In `unwind_backtrace+0x0/0xf8` what does `+0x0/0xf8` stand for? - How can I see the C code of `unwind_backtrace+0x0/0xf8`? - How to interpret the panic's content?