The JITs used to find a block by overwriting its first instruction with an "emuhack" holding
the offset into the code space, and replacement functions installed their own emuhack the same
way. Anything that read code (savestates, the debugger, memory dumps, cheats, the function
hasher, games reading their own code) had to translate them back.
Blocks now live in a block shadow: one u32 per guest instruction, indexed by the PC masked with
BLOCK_SHADOW_MASK (1GB on 64-bit, folding the kernel and uncached mirrors; 256MB on 32-bit, iOS
and Switch, where address space is short), with the low bits cleared so a misaligned PC can't
read across two entries. Only the ranges under memory views are committed, so a bad PC still
faults in the dispatcher, and the shadow is reserved before the memory map so it can't land in
a gap of the 4GB window. Entries hold full 32-bit offsets, lifting the 16MB limit. The
dispatchers on every backend, and the IR interpreter's loop, look blocks up there.
A hooked instruction without a compiled block gets the JIT's hook value in its entry: the offset
of the dispatcher's compile path (1 for the interpreters, the IR arena keeping that offset
empty), so dispatching there compiles a block, and the frontends substitute the hook. Compiling
replaces the entry with the block's, and destroying the block puts the hook value back. The hook
value is rewritten when the JIT changes or regenerates its dispatcher.
Hooks live in a map keyed by the masked address, and are dropped when the game overwrites the
hooked instruction, or when an icache invalidation finds the function's hash (immediates masked,
as when matching it) changed. Those checks run when queued invalidations are processed, since
cheats and the debugger queue them before writing. Installing and removing hooks invalidates
deferred, as it happens in HLE calls that can run inside a block. The cache instruction goes
through MIPSState, so it drops changed hooks too.
With clean memory, the save/clear/restore around savestates, memory reads and dumps goes away,
as do the source-range invalidations in the memcpy replacements, sceDmac and the cheats.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
The x86-64 path searched for free memory near the code, and if it found some,
committed to it - if that VirtualAlloc failed, ptr was left null and we returned
null, never reaching the else branch that exists precisely to say "can still run,
thanks to RipAccessible".
Finding a free region isn't the same as being able to reserve it. VirtualAlloc
rounds a non-null lpAddress down to the 64K allocation granularity while
SearchForFreeMem only guarantees page alignment, so the rounded-down base can land
back inside a committed region; a concurrent allocation between the VirtualQuery and
the VirtualAlloc does it too. Callers don't check the result - AllocCodeSpace stores
it unchecked and the emitters write from there - so this turned into a wild write
rather than a clean JIT-unavailable fallback.
* Rename LogType to Log
* Explicitly use the Log:: enum when logging. Allows for autocomplete when editing.
* Mac/ARM64 buildfix
* Do the same with the hle result log macros
* Rename the log names to mixed case while at it.
* iOS buildfix
* Qt buildfix attempt, ARM32 buildfix
9f24203ef8 added 0x20000000 as a default fallback address hint which
unconditionally disabled MAP_32BIT. FreeBSD cannot use the hints
because without adjusting RLIMIT_DATA lower addresses are reserved for
brk(2) style heap. So, don't try to use hints with MAP_32BIT.
