arno/linux-insides
1
0
Fork 0
mirror of https://github.com/0xAX/linux-insides.git synced 2024-11-01 04:29:39 +00:00
Code Issues Releases Wiki Activity

fix 1f offset

Browse Source 
on the context,the offset of 1f should be 0x21.
This commit is contained in:
sevico 2016-05-26 21:15:48 +08:00
parent 6b7c961d77
commit 5f56136420
1 changed files with 1 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
Booting/linux-bootstrap-4.md
View File

@ -202,7 +202,7 @@ startup_32 (0x0) +-----------------------+
+-----------------------+ +-----------------------+
``` ```
`startup_32` is linked to run at address `0x0` and this means that `1f` has the address `0x0 + offset to 1f`, approximately `0x22` bytes. The `ebp` register contains the real physical address of the `1f` label. So, if we subtract `1f` from the `ebp` we will get the real physical address of the `startup_32`. The Linux kernel [boot protocol](https://www.kernel.org/doc/Documentation/x86/boot.txt) describes that the base of the protected mode kernel is `0x100000`. We can verify this with [gdb](https://en.wikipedia.org/wiki/GNU_Debugger). Let's start the debugger and put breakpoint to the `1f` address, which is `0x100022`. If this is correct we will see `0x100022` in the `ebp` register: `startup_32` is linked to run at address `0x0` and this means that `1f` has the address `0x0 + offset to 1f`, approximately `0x21` bytes. The `ebp` register contains the real physical address of the `1f` label. So, if we subtract `1f` from the `ebp` we will get the real physical address of the `startup_32`. The Linux kernel [boot protocol](https://www.kernel.org/doc/Documentation/x86/boot.txt) describes that the base of the protected mode kernel is `0x100000`. We can verify this with [gdb](https://en.wikipedia.org/wiki/GNU_Debugger). Let's start the debugger and put breakpoint to the `1f` address, which is `0x100021`. If this is correct we will see `0x100021` in the `ebp` register:
``` ```
$ gdb $ gdb