1 files changed, 75 insertions, 0 deletions
diff --git a/executor/shmem.h b/executor/shmem.h
new file mode 100644
index 000000000..ab9d17300
--- /dev/null
+++ b/executor/shmem.h
@@ -0,0 +1,75 @@
+// Copyright 2024 syzkaller project authors. All rights reserved.
+// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
+
+#include <fcntl.h>
+#include <stddef.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+// ShmemFile is shared memory region wrapper.
+class ShmemFile
+{
+public:
+	// Maps shared memory region of size 'size' from a new file 'file', preferably at the address 'preferred'.
+	ShmemFile(const char* file, void* preferred, size_t size)
+	{
+		fd_ = open(file, O_RDWR | O_CREAT | O_TRUNC, 0600);
+		if (fd_ == -1)
+			failmsg("shmem open failed", "file=%s", file);
+		if (fallocate(fd_, 0, 0, size))
+			failmsg("shmem fallocate failed", "size=%zu", size);
+		Mmap(fd_, preferred, size, true);
+		if (unlink(file))
+			fail("shmem unlink failed");
+	}
+
+	// Maps shared memory region from the file 'fd' in read/write or write-only mode.
+	ShmemFile(int fd, void* preferred, size_t size, bool write)
+	{
+		Mmap(fd, preferred, size, write);
+	}
+
+	~ShmemFile()
+	{
+		if (munmap(mem_, size_))
+			fail("shmem munmap failed");
+		if (fd_ != -1)
+			close(fd_);
+	}
+
+	// Prevents any future modifications to the region.
+	void Seal()
+	{
+		if (mprotect(mem_, size_, PROT_READ))
+			fail("shmem mprotect failed");
+		if (fd_ != -1)
+			close(fd_);
+		fd_ = -1;
+	}
+
+	int FD() const
+	{
+		return fd_;
+	}
+
+	void* Mem() const
+	{
+		return mem_;
+	}
+
+private:
+	void* mem_ = nullptr;
+	size_t size_ = 0;
+	int fd_ = -1;
+
+	void Mmap(int fd, void* preferred, size_t size, bool write)
+	{
+		size_ = size;
+		mem_ = mmap(preferred, size, PROT_READ | (write ? PROT_WRITE : 0), MAP_SHARED, fd, 0);
+		if (mem_ == MAP_FAILED)
+			failmsg("shmem mmap failed", "size=%zu", size);
+	}
+
+	ShmemFile(const ShmemFile&) = delete;
+	ShmemFile& operator=(const ShmemFile&) = delete;
+};