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Fix macOS exact-address mmap falling back to MAP_FIXED (#214)

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The PS5 image loader requires guest images to land at fixed virtual
addresses (e.g. the 32 GiB main image base). On macOS the exact-address
mmap path only ever passed that address as a hint, never MAP_FIXED, to
avoid clobbering untracked host mappings (dyld, JIT heap, Rosetta).

On Apple Silicon under Rosetta 2 the kernel does not reliably honor
that hint, so the allocation failed deterministically before a single
guest instruction ran (reported in #194). Retry with true MAP_FIXED
as a fallback only when the hint-only attempt doesn't land at the
requested address, so the safer hint path is still tried first.
This commit is contained in:
Nicola Pomarico
2026-07-15 23:28:39 +02:00
committed by GitHub
parent b5930465f2
commit 90651f26a9
1 changed files with 20 additions and 0 deletions
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20
src/SharpEmu.HLE/Host/Posix/PosixHostMemory.cs
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@@ -271,6 +271,26 @@ internal sealed unsafe class PosixHostMemory : IHostMemory
var exactFlags = OperatingSystem.IsMacOS() ? flags : flags | MAP_FIXED_NOREPLACE; var exactFlags = OperatingSystem.IsMacOS() ? flags : flags | MAP_FIXED_NOREPLACE;
result = mmap((nint)address, (nuint)alignedSize, posixProtect, exactFlags, -1, 0); result = mmap((nint)address, (nuint)alignedSize, posixProtect, exactFlags, -1, 0);
if (result != MAP_FAILED && (ulong)result != (ulong)address)
{
munmap(result, (nuint)alignedSize);
result = MAP_FAILED;
}
if (result == MAP_FAILED && OperatingSystem.IsMacOS())
{
// The hint-only attempt above didn't land at the requested
// address. This is routinely the case for the PS5's fixed
// 32 GiB image base under Rosetta 2 on Apple Silicon, where
// the kernel never honors that hint. Retry with true
// MAP_FIXED: this can clobber an untracked host mapping
// (dyld, the runtime's JIT heap, Rosetta) if one already
// sits exactly there, but without it guest images that
// require this base never load at all on macOS.
Trace($"exact mmap hint failed, retrying with MAP_FIXED: addr=0x{(ulong)address:X16}");
result = mmap((nint)address, (nuint)alignedSize, posixProtect, flags | MAP_FIXED, -1, 0);
}
if (result == MAP_FAILED || (ulong)result != (ulong)address) if (result == MAP_FAILED || (ulong)result != (ulong)address)
{ {
Trace($"exact mmap failed: addr=0x{(ulong)address:X16} got=0x{(ulong)result:X16} size=0x{alignedSize:X} errno={Marshal.GetLastPInvokeError()}"); Trace($"exact mmap failed: addr=0x{(ulong)address:X16} got=0x{(ulong)result:X16} size=0x{alignedSize:X} errno={Marshal.GetLastPInvokeError()}");