pcsx2/common/Linux/LnxHostSys.cpp

// SPDX-FileCopyrightText: 2002-2024 PCSX2 Dev Team
// SPDX-License-Identifier: LGPL-3.0+

#include "common/Assertions.h"
#include "common/BitUtils.h"
#include "common/Console.h"
#include "common/CrashHandler.h"
#include "common/Error.h"
#include "common/HostSys.h"

#include <cstdio>
#include <csignal>
#include <cerrno>
#include <fcntl.h>
#include <mutex>
#include <sys/mman.h>
#include <ucontext.h>
#include <unistd.h>

#include "fmt/core.h"

// FreeBSD does not have MAP_FIXED_NOREPLACE, but does have MAP_EXCL.
// MAP_FIXED combined with MAP_EXCL behaves like MAP_FIXED_NOREPLACE.
#if defined(__FreeBSD__) && !defined(MAP_FIXED_NOREPLACE)
#define MAP_FIXED_NOREPLACE (MAP_FIXED | MAP_EXCL)
#endif

static __ri uint LinuxProt(const PageProtectionMode& mode)
{
	u32 lnxmode = 0;

	if (mode.CanWrite())
		lnxmode |= PROT_WRITE;
	if (mode.CanRead())
		lnxmode |= PROT_READ;
	if (mode.CanExecute())
		lnxmode |= PROT_EXEC | PROT_READ;

	return lnxmode;
}

void* HostSys::Mmap(void* base, size_t size, const PageProtectionMode& mode)
{
	pxAssertMsg((size & (__pagesize - 1)) == 0, "Size is page aligned");

	if (mode.IsNone())
		return nullptr;

	const u32 prot = LinuxProt(mode);

	u32 flags = MAP_PRIVATE | MAP_ANONYMOUS;
	if (base)
		flags |= MAP_FIXED_NOREPLACE;

	void* res = mmap(base, size, prot, flags, -1, 0);
	if (res == MAP_FAILED)
		return nullptr;

	return res;
}

void HostSys::Munmap(void* base, size_t size)
{
	if (!base)
		return;

	munmap((void*)base, size);
}

void HostSys::MemProtect(void* baseaddr, size_t size, const PageProtectionMode& mode)
{
	pxAssertMsg((size & (__pagesize - 1)) == 0, "Size is page aligned");

	const u32 lnxmode = LinuxProt(mode);

	const int result = mprotect(baseaddr, size, lnxmode);
	if (result != 0)
		pxFail("mprotect() failed");
}

std::string HostSys::GetFileMappingName(const char* prefix)
{
	const unsigned pid = static_cast<unsigned>(getpid());
#if defined(__FreeBSD__)
	// FreeBSD's shm_open(3) requires name to be absolute
	return fmt::format("/tmp/{}_{}", prefix, pid);
#else
	return fmt::format("{}_{}", prefix, pid);
#endif
}

void* HostSys::CreateSharedMemory(const char* name, size_t size)
{
	const int fd = shm_open(name, O_CREAT | O_EXCL | O_RDWR, 0600);
	if (fd < 0)
	{
		std::fprintf(stderr, "shm_open failed: %d\n", errno);
		return nullptr;
	}

	// we're not going to be opening this mapping in other processes, so remove the file
	shm_unlink(name);

	// ensure it's the correct size
	if (ftruncate(fd, static_cast<off_t>(size)) < 0)
	{
		std::fprintf(stderr, "ftruncate(%zu) failed: %d\n", size, errno);
		return nullptr;
	}

	return reinterpret_cast<void*>(static_cast<intptr_t>(fd));
}

void HostSys::DestroySharedMemory(void* ptr)
{
	close(static_cast<int>(reinterpret_cast<intptr_t>(ptr)));
}

void* HostSys::MapSharedMemory(void* handle, size_t offset, void* baseaddr, size_t size, const PageProtectionMode& mode)
{
	const uint lnxmode = LinuxProt(mode);

	const int flags = (baseaddr != nullptr) ? (MAP_SHARED | MAP_FIXED_NOREPLACE) : MAP_SHARED;
	void* ptr = mmap(baseaddr, size, lnxmode, flags, static_cast<int>(reinterpret_cast<intptr_t>(handle)), static_cast<off_t>(offset));
	if (ptr == MAP_FAILED)
		return nullptr;

	return ptr;
}

void HostSys::UnmapSharedMemory(void* baseaddr, size_t size)
{
	if (munmap(baseaddr, size) != 0)
		pxFailRel("Failed to unmap shared memory");
}

SharedMemoryMappingArea::SharedMemoryMappingArea(u8* base_ptr, size_t size, size_t num_pages)
	: m_base_ptr(base_ptr)
	, m_size(size)
	, m_num_pages(num_pages)
{
}

SharedMemoryMappingArea::~SharedMemoryMappingArea()
{
	pxAssertRel(m_num_mappings == 0, "No mappings left");

	if (munmap(m_base_ptr, m_size) != 0)
		pxFailRel("Failed to release shared memory area");
}


std::unique_ptr<SharedMemoryMappingArea> SharedMemoryMappingArea::Create(size_t size)
{
	pxAssertRel(Common::IsAlignedPow2(size, __pagesize), "Size is page aligned");

	void* alloc = mmap(nullptr, size, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
	if (alloc == MAP_FAILED)
		return nullptr;

	return std::unique_ptr<SharedMemoryMappingArea>(new SharedMemoryMappingArea(static_cast<u8*>(alloc), size, size / __pagesize));
}

u8* SharedMemoryMappingArea::Map(void* file_handle, size_t file_offset, void* map_base, size_t map_size, const PageProtectionMode& mode)
{
	pxAssert(static_cast<u8*>(map_base) >= m_base_ptr && static_cast<u8*>(map_base) < (m_base_ptr + m_size));

	// MAP_FIXED is okay here, since we've reserved the entire region, and *want* to overwrite the mapping.
	const uint lnxmode = LinuxProt(mode);
	void* const ptr = mmap(map_base, map_size, lnxmode, MAP_SHARED | MAP_FIXED,
		static_cast<int>(reinterpret_cast<intptr_t>(file_handle)), static_cast<off_t>(file_offset));
	if (ptr == MAP_FAILED)
		return nullptr;

	m_num_mappings++;
	return static_cast<u8*>(ptr);
}

bool SharedMemoryMappingArea::Unmap(void* map_base, size_t map_size)
{
	pxAssert(static_cast<u8*>(map_base) >= m_base_ptr && static_cast<u8*>(map_base) < (m_base_ptr + m_size));

	if (mmap(map_base, map_size, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0) == MAP_FAILED)
		return false;

	m_num_mappings--;
	return true;
}

namespace PageFaultHandler
{
	static std::recursive_mutex s_exception_handler_mutex;
	static bool s_in_exception_handler = false;
	static bool s_installed = false;
} // namespace PageFaultHandler

#ifdef _M_ARM64

void HostSys::FlushInstructionCache(void* address, u32 size)
{
	__builtin___clear_cache(reinterpret_cast<char*>(address), reinterpret_cast<char*>(address) + size);
}

[[maybe_unused]] static bool IsStoreInstruction(const void* ptr)
{
	u32 bits;
	std::memcpy(&bits, ptr, sizeof(bits));

	// Based on vixl's disassembler Instruction::IsStore().
	// if (Mask(LoadStoreAnyFMask) != LoadStoreAnyFixed)
	if ((bits & 0x0a000000) != 0x08000000)
		return false;

	// if (Mask(LoadStorePairAnyFMask) == LoadStorePairAnyFixed)
	if ((bits & 0x3a000000) == 0x28000000)
	{
		// return Mask(LoadStorePairLBit) == 0
		return (bits & (1 << 22)) == 0;
	}

	switch (bits & 0xC4C00000)
	{
		case 0x00000000: // STRB_w
		case 0x40000000: // STRH_w
		case 0x80000000: // STR_w
		case 0xC0000000: // STR_x
		case 0x04000000: // STR_b
		case 0x44000000: // STR_h
		case 0x84000000: // STR_s
		case 0xC4000000: // STR_d
		case 0x04800000: // STR_q
			return true;

		default:
			return false;
	}
}

#endif // _M_ARM64

namespace PageFaultHandler
{
	static void SignalHandler(int sig, siginfo_t* info, void* ctx);
} // namespace PageFaultHandler

void PageFaultHandler::SignalHandler(int sig, siginfo_t* info, void* ctx)
{
#if defined(__linux__)
	void* const exception_address = reinterpret_cast<void*>(info->si_addr);

#if defined(_M_X86)
	void* const exception_pc = reinterpret_cast<void*>(static_cast<ucontext_t*>(ctx)->uc_mcontext.gregs[REG_RIP]);
	const bool is_write = (static_cast<ucontext_t*>(ctx)->uc_mcontext.gregs[REG_ERR] & 2) != 0;
#elif defined(_M_ARM64)
	void* const exception_pc = reinterpret_cast<void*>(static_cast<ucontext_t*>(ctx)->uc_mcontext.pc);
	const bool is_write = IsStoreInstruction(exception_pc);
#endif

#elif defined(__FreeBSD__)

#if defined(_M_X86)
	void* const exception_address = reinterpret_cast<void*>(static_cast<ucontext_t*>(ctx)->uc_mcontext.mc_addr);
	void* const exception_pc = reinterpret_cast<void*>(static_cast<ucontext_t*>(ctx)->uc_mcontext.mc_rip);
	const bool is_write = (static_cast<ucontext_t*>(ctx)->uc_mcontext.mc_err & 2) != 0;
#elif defined(_M_ARM64)
	void* const exception_address = reinterpret_cast<void*>(static_cast<ucontext_t*>(ctx)->uc_mcontext->__es.__far);
	void* const exception_pc = reinterpret_cast<void*>(static_cast<ucontext_t*>(ctx)->uc_mcontext->__ss.__pc);
	const bool is_write = IsStoreInstruction(exception_pc);
#endif

#endif

	// Executing the handler concurrently from multiple threads wouldn't go down well.
	s_exception_handler_mutex.lock();

	// Prevent recursive exception filtering.
	HandlerResult result = HandlerResult::ExecuteNextHandler;
	if (!s_in_exception_handler)
	{
		s_in_exception_handler = true;
		result = HandlePageFault(exception_pc, exception_address, is_write);
		s_in_exception_handler = false;
	}

	s_exception_handler_mutex.unlock();

	// Resumes execution right where we left off (re-executes instruction that caused the SIGSEGV).
	if (result == HandlerResult::ContinueExecution)
		return;

	// We couldn't handle it. Pass it off to the crash dumper.
	CrashHandler::CrashSignalHandler(sig, info, ctx);
}

bool PageFaultHandler::Install(Error* error)
{
	std::unique_lock lock(s_exception_handler_mutex);
	pxAssertRel(!s_installed, "Page fault handler has already been installed.");

	struct sigaction sa;

	sigemptyset(&sa.sa_mask);
	sa.sa_flags = SA_SIGINFO | SA_NODEFER;
	sa.sa_sigaction = SignalHandler;

	if (sigaction(SIGSEGV, &sa, nullptr) != 0)
	{
		Error::SetErrno(error, "sigaction() for SIGSEGV failed: ", errno);
		return false;
	}

#ifdef _M_ARM64
	// We can get SIGBUS on ARM64.
	if (sigaction(SIGBUS, &sa, nullptr) != 0)
	{
		Error::SetErrno(error, "sigaction() for SIGBUS failed: ", errno);
		return false;
	}
#endif

	s_installed = true;
	return true;
}