Makes the following a block boundary:
- push
- Any non-custom instruction that uses modrm encoding
- Any sse/fpu instruction
This commit affects performance negatively. In order to fix this, the
above instructions need to be implemented using custom code generators
for the memory access.
This commit makes the return type of most basic memory access primitives
Result, where the Err(()) case means a page fault happened, the
instruction should be aborted and execution should continue at the page
fault handler.
The following primites have a Result return type: safe_{read,write}*,
translate_address_*, read_imm*, writable_or_pagefault, get_phys_eip,
modrm_resolve, push*, pop*.
Any instruction needs to handle the page fault cases and abort
execution appropriately. The return_on_pagefault! macro has been
provided to get the same behaviour as the previously used JS exceptions
(local to the function).
Calls from JavaScript abort on a pagefault, except for
writable_or_pagefault, which returns a boolean. JS needs to check
before calling any function that may pagefault.
This commit does not yet pervasively apply return_on_pagefault!, this
will be added in the next commit.
Jitted code does not yet properly handle the new form of page faults,
this will be added in a later commit.
