Initial macOS support (x86_64 with Rosetta 2)

src/setup_darwin.cpp

@@ -0,0 +1,105 @@
+#include "common.h"
+#include "setup.h"
+
+#include "types.h"
+
+#include <cerrno>
+#include <cstdint>
+
+#include <architecture/i386/table.h>
+#include <i386/user_ldt.h>
+
+// https://github.com/apple/darwin-libpthread/blob/03c4628c8940cca6fd6a82957f683af804f62e7f/private/tsd_private.h#L92-L97
+#define _PTHREAD_TSD_SLOT_RESERVED_WIN64 6
+
+#define USER_PRIVILEGE 3
+
+namespace {
+
+inline ldt_entry createLdtEntry(uint32_t base, uint32_t size, bool code) {
+	uint32_t limit;
+	uint8_t granular;
+	if (size > 0xFFFFF) {
+		limit = (size - 1) >> 12;
+		granular = DESC_GRAN_PAGE;
+	} else {
+		limit = size - 1;
+		granular = DESC_GRAN_BYTE;
+	}
+	ldt_entry entry; // NOLINT(cppcoreguidelines-pro-type-member-init)
+	// Must memset to zero to avoid uninitialized padding bytes
+	std::memset(&entry, 0, sizeof(ldt_entry));
+	entry.code.limit00 = static_cast<uint16_t>(limit);
+	entry.code.base00 = static_cast<uint16_t>(base);
+	entry.code.base16 = static_cast<uint8_t>(base >> 16);
+	entry.code.type = code ? DESC_CODE_READ : DESC_DATA_WRITE;
+	entry.code.dpl = USER_PRIVILEGE;
+	entry.code.present = 1;
+	entry.code.limit16 = static_cast<uint8_t>(limit >> 16);
+	entry.code.opsz = DESC_CODE_32B;
+	entry.code.granular = granular;
+	entry.code.base24 = static_cast<uint8_t>(base >> 24);
+	return entry;
+}
+
+constexpr int createSelector(int entryNumber) { return (entryNumber << 3) | 0x4 /* TI=1 */ | USER_PRIVILEGE; }
+
+inline void writeTsdSlot(uint32_t slot, uint64_t val) {
+	// mov qword ptr gs:[slot*8], val
+	*(volatile uint64_t __seg_gs *)(slot * sizeof(void *)) = val;
+}
+
+} // namespace
+
+int tebThreadSetup(int entryNumber, TEB *teb) {
+	bool alloc = entryNumber == -1;
+	if (alloc) {
+		ldt_entry unused{};
+		entryNumber = i386_get_ldt(0, &unused, 1);
+		if (entryNumber < 0) {
+			return entryNumber;
+		}
+		DEBUG_LOG("Allocating LDT entry %d\n", entryNumber);
+		// Create code LDT entry at entry_number + 1
+		ldt_entry codeLdt = createLdtEntry(0, 0xFFFFFFFF, true);
+		int codeLdtEntry = entryNumber++;
+		int ret = i386_set_ldt(codeLdtEntry, &codeLdt, 1);
+		if (ret < 0) {
+			return ret;
+		} else if (ret != codeLdtEntry) {
+			errno = EALREADY;
+			return -EALREADY;
+		}
+		DEBUG_LOG("Code selector %x\n", createSelector(ret));
+		// Create data LDT entry at entry_number + 2
+		ldt_entry dataLdt = createLdtEntry(0, 0xFFFFFFFF, false);
+		int dataLdtEntry = entryNumber++;
+		ret = i386_set_ldt(dataLdtEntry, &dataLdt, 1);
+		if (ret < 0) {
+			return ret;
+		} else if (ret != dataLdtEntry) {
+			errno = EALREADY;
+			return -EALREADY;
+		}
+		DEBUG_LOG("Data selector %x\n", createSelector(dataLdtEntry));
+	}
+	uintptr_t tebBase = reinterpret_cast<uintptr_t>(teb);
+	if (tebBase > 0xFFFFFFFF) {
+		DEBUG_LOG("TEB base address exceeds 32-bit limit\n");
+		errno = EINVAL;
+		return -EINVAL;
+	}
+	// Store the TEB base address in the reserved slot for Windows 64-bit (gs:[0x30])
+	writeTsdSlot(_PTHREAD_TSD_SLOT_RESERVED_WIN64, static_cast<uint32_t>(tebBase));
+	// Rosetta 2 requires size 0x1000 (limit 0xFFF) specifically
+	ldt_entry fsLdt = createLdtEntry(static_cast<uint32_t>(tebBase), 0x1000, false);
+	int ret = i386_set_ldt(entryNumber, &fsLdt, 1);
+	if (ret < 0) {
+		return ret;
+	} else if (ret != entryNumber) {
+		errno = EALREADY;
+		return -EALREADY;
+	}
+	teb->CurrentFsSelector = createSelector(entryNumber);
+	return entryNumber;
+}