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Philipp Oppermann
2021-10-17 17:37:55 +02:00
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blog/content/edition-1/extra/naked-exceptions/02-better-exception-messages/index.md
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@@ -628,7 +628,7 @@ bitflags! {
- When the `PROTECTION_VIOLATION` flag is set, the page fault was caused e.g. by a write to a read-only page. If it's not set, it was caused by accessing a non-present page.
- The `CAUSED_BY_WRITE` flag specifies if the fault was caused by a write (if set) or a read (if not set).
- The `USER_MODE` flag is set when the fault occurred in non-priviledged mode.
- The `USER_MODE` flag is set when the fault occurred in non-privileged mode.
- The `MALFORMED_TABLE` flag is set when the page table entry has a 1 in a reserved field.
- When the `INSTRUCTION_FETCH` flag is set, the page fault occurred while fetching the next instruction.

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blog/content/edition-1/extra/naked-exceptions/03-returning-from-exceptions/index.md
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@@ -426,7 +426,7 @@ The page fault is gone and we see the _“It did not crash”_ message again!
So the page fault occurred because our exception handler didn't preserve the scratch register `rax`. Our new `handler!` macro fixes this problem by saving all scratch registers (including `rax`) before calling exception handlers. Thus, `rax` still contains the valid memory address when `rust-main` continues execution.
## Multimedia Registers
When we discussed calling conventions above, we assummed that a x86_64 CPU only has the following 16 registers: `rax`, `rbx`, `rcx`, `rdx`, `rsi`, `rdi`, `rsp`, `rbp`, `r8`, `r9`, `r10`, `r11`.`r12`, `r13`, `r14`, and `r15`. These registers are called _general purpose registers_ since each of them can be used for arithmetic and load/store instructions.
When we discussed calling conventions above, we assumed that a x86_64 CPU only has the following 16 registers: `rax`, `rbx`, `rcx`, `rdx`, `rsi`, `rdi`, `rsp`, `rbp`, `r8`, `r9`, `r10`, `r11`.`r12`, `r13`, `r14`, and `r15`. These registers are called _general purpose registers_ since each of them can be used for arithmetic and load/store instructions.
However, modern CPUs also have a set of _special purpose registers_, which can be used to improve performance in several use cases. On x86_64, the most important set of special purpose registers are the _multimedia registers_. These registers are larger than the general purpose registers and can be used to speed up audio/video processing or matrix calculations. For example, we could use them to add two 4-dimensional vectors _in a single CPU instruction_: