michaelkuc6/blog_os
1
0
Fork 0
mirror of https://github.com/phil-opp/blog_os.git synced 2025-12-16 22:37:49 +00:00
Code Issues Projects Releases Wiki Activity

Fix typo. (#306)

Browse Source
This commit is contained in:
Ahmed Charles
2017-04-01 02:38:33 -07:00
committed by Philipp Oppermann
parent 38c6561252
commit 657f34ae5e
1 changed files with 1 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
blog/content/post/09-handling-exceptions.md
View File

@@ -185,7 +185,7 @@ The `x86-interrupt` calling convention is a powerful abstraction that hides almo
- **Retrieving the arguments**: Most calling conventions expect that the arguments are passed in registers. This is not possible for exception handlers, since we must not overwrite any register values before backing them up on the stack. Instead, the `x86-interrupt` calling convention is aware that the arguments already lie on the stack at a specific offset.
- **Returning using `iretq`**: Since the exception stack frame completely differs from stack frames of normal function calls, we can't return from handlers functions through the normal `ret` instruction. Instead, the `iretq` instruction must be used.
- **Handling the error code**: The error code, which is pushed for some exceptions, makes things much more complex. It changes the stack alignment (see the next point) and needs to be popped off the stack before returning. The `x86-64` handles all that complexity. However, it doesn't know which handler function is used for which exception, so it needs to deduce that information from the number of function arguments. That means that the programmer is still responsible to use the correct function type for each exception. Luckily, the `Idt` type defined by the `x86_64` crate ensures that the correct function types are used.
- **Handling the error code**: The error code, which is pushed for some exceptions, makes things much more complex. It changes the stack alignment (see the next point) and needs to be popped off the stack before returning. The `x86-interrupt` calling convention handles all that complexity. However, it doesn't know which handler function is used for which exception, so it needs to deduce that information from the number of function arguments. That means that the programmer is still responsible to use the correct function type for each exception. Luckily, the `Idt` type defined by the `x86_64` crate ensures that the correct function types are used.
- **Aligning the stack**: There are some instructions (especially SSE instructions) that require a 16-byte stack alignment. The CPU ensures this alignment whenever an exception occurs, but for some exceptions it destroys it again later when it pushes an error code. The `x86-interrupt` calling convention takes care of this by realigning the stack in this case.
If you are interested in more details: We also have a series of posts that explains exception handling using [naked functions] linked [at the end of this post][too-much-magic].