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Better Exception Messages: Take stack_frame argument as reference

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This commit is contained in:
Philipp Oppermann
2016-10-30 17:52:40 +01:00
parent 15feb9a120
commit e129da8cc2
1 changed files with 10 additions and 11 deletions
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21
blog/post/10-better-exception-messages.md
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@@ -55,12 +55,11 @@ Now we need a way to find the memory address of this stack frame. When we look a
// in src/interrupts/mod.rs
extern "C" fn divide_by_zero_handler() -> ! {
let stack_frame: *const ExceptionStackFrame;
let stack_frame: &ExceptionStackFrame;
unsafe {
asm!("mov $0, rsp" : "=r"(stack_frame) ::: "intel");
println!("\nEXCEPTION: DIVIDE BY ZERO\n{:#?}",
*stack_frame);
};
}
println!("\nEXCEPTION: DIVIDE BY ZERO\n{:#?}", stack_frame);
loop {}
}
```
@@ -169,7 +168,7 @@ extern "C" fn divide_by_zero_wrapper() -> ! {
}
}
extern "C" fn divide_by_zero_handler(stack_frame: *const ExceptionStackFrame)
extern "C" fn divide_by_zero_handler(stack_frame: &ExceptionStackFrame)
-> !
{
println!("\nEXCEPTION: DIVIDE BY ZERO\n{:#?}",
@@ -433,7 +432,7 @@ macro_rules! handler {
sub rsp, 8 // align the stack pointer
call $0"
:: "i"($name as extern "C" fn(
*const ExceptionStackFrame) -> !)
&ExceptionStackFrame) -> !)
: "rdi" : "intel");
::core::intrinsics::unreachable();
}
@@ -442,7 +441,7 @@ macro_rules! handler {
}}
}
```
The macro takes a single Rust identifier (`ident`) as argument and expands to a `{}` block (hence the double braces). The block defines a new wrapper function that calls the function `$name` and passes a pointer to the exception stack frame. Note that we're fixing the argument type to `*const ExceptionStackFrame`. If we used a `_` like before, the passed function could accept an arbitrary argument, which would lead to ugly bugs at runtime.
The macro takes a single Rust identifier (`ident`) as argument and expands to a `{}` block (hence the double braces). The block defines a new wrapper function that calls the function `$name` and passes a pointer to the exception stack frame. Note that we're fixing the argument type to `&ExceptionStackFrame`. If we used a `_` like before, the passed function could accept an arbitrary argument, which would lead to ugly bugs at runtime.
Now we can remove the `divide_by_zero_wrapper` and use our new `handler!` macro instead:
@@ -475,7 +474,7 @@ lazy_static! {
};
}
extern "C" fn invalid_opcode_handler(stack_frame: *const ExceptionStackFrame)
extern "C" fn invalid_opcode_handler(stack_frame: &ExceptionStackFrame)
-> !
{
let stack_frame = unsafe { &*stack_frame };
@@ -527,7 +526,7 @@ macro_rules! handler_with_error_code {
sub rsp, 8 // align the stack pointer
call $0"
:: "i"($name as extern "C" fn(
*const ExceptionStackFrame, u64) -> !)
&ExceptionStackFrame, u64) -> !)
: "rdi","rsi" : "intel");
::core::intrinsics::unreachable();
}
@@ -544,7 +543,7 @@ Let's write a page fault handler which analyzes and prints the error code:
```rust
// in src/interrupts/mod.rs
extern "C" fn page_fault_handler(stack_frame: *const ExceptionStackFrame,
extern "C" fn page_fault_handler(stack_frame: &ExceptionStackFrame,
error_code: u64) -> !
{
println!(
@@ -626,7 +625,7 @@ bitflags! {
Now we can improve our page fault error message by using the new `PageFaultErrorCode`. We also print the accessed memory address:
```rust
extern "C" fn page_fault_handler(stack_frame: *const ExceptionStackFrame,
extern "C" fn page_fault_handler(stack_frame: &ExceptionStackFrame,
error_code: u64) -> !
{
use x86::controlregs;