# FreeBSD Introduction - Trace Code

## 1

- Reading: sys/*.h

Please write a one-line summary for the following header files, some outdate header file are not included. The first few lines are examples.

* acct.h - accounting structure
* acl.h - access-control list (ACL) definitions
* aio.h - asynchronous I/O definitions
* alq.h - asynchronous-logging queue definitions
* bio.h - description of an I/O operation in the kernel
* bitstring.h
* blist.h
* buf.h
* bufobj.h
* bus.h
* bus_dma.h
* callout.h
* clist.h
* clock.h
* condvar.h
* conf.h
* cons.h
* consio.h
* cpu.h
* ctype.h
* device_port.h
* devicestat.h
* dir.h
* dirent.h
* disk.h
* disklabel.h
* diskmbr.h
* domain.h
* dvdio.h
* elf32.h
* elf64.h
* elf_common.h
* elf_generic.h
* endian.h
* errno.h
* event.h
* eventhandler.h
* eventvar.h
* exec.h
* extattr.h
* fbio.h
* fcntl.h
* fdcio.h
* file.h
* filedesc.h
* fnv_hash.h
* gmon.h
* gpt.h
* imgact.h
* imgact_elf.h
* inflate.h
* interrupt.h
* _iovec.h
* ipc.h
* jail.h
* kbio.h
* kdb.h
* kernel.h
* kerneldump.h
* kobj.h
* kse.h
* kthread.h
* ktr.h
* ktrace.h
* _label.h
* libkern.h
* limits.h
* linedisc.h
* link_elf.h
* linker.h
* linker_set.h
* _lock.h
* lock.h
* lockf.h
* lockmgr.h
* mac.h
* mac_policy.h
* malloc.h
* mbpool.h
* mbuf.h
* mchain.h
* md5.h
* mdioctl.h
* mman.h
* module.h
* mount.h
* mouse.h
* msg.h
* msgbuf.h
* mutex.h
* _mutex.h
* namei.h
* _null.h
* param.h
* pciio.h
* pcpu.h
* pipe.h
* pmckern.h
* pmclog.h
* poll.h
* power.h
* priority.h
* proc.h
* procfs.h
* protosw.h
* _pthreadtypes.h
* _sigset.h
* ptrace.h
* queue.h
* random.h
* reboot.h
* resource.h
* resourcevar.h
* rman.h
* rtprio.h
* runq.h
* sbuf.h
* sched.h
* select.h
* selinfo.h
* sem.h
* sema.h
* sf_buf.h
* shm.h
* sigio.h
* signal.h
* signalvar.h
* sleepqueue.h
* smp.h
* snoop.h
* socket.h
* socketvar.h
* sockio.h
* stat.h
* statvfs.h
* sx.h
* sysctl.h
* sysent.h
* syslimits.h
* syslog.h
* systm.h
* _task.h
* taskqueue.h
* termios.h
* thr.h
* time.h
* timepps.h
* times.h
* _timespec.h
* timespec.h
* timetc.h
* _timeval.h
* timex.h
* tree.h
* tty.h
* ttychars.h
* ttydefaults.h
* turnstile.h
* _types.h
* types.h
* ucontext.h
* ucred.h
* uio.h
* umtx.h
* un.h
* unistd.h
* unpcb.h
* user.h
* uuid.h
* vmmeter.h
* vnode.h
* wait.h
* watchdog.h

## 2

- Understand how a system boot up.
- I don't know how to trace the code ;(

## 3

- Understand how a syscall occurs, and be handled.
- You may have to read the following files:
- [sys/riscv/riscv/exception.S](https://github.com/freebsd/freebsd-src/blob/main/sys/riscv/riscv/exception.S)
- read function: cpu_exception_handler_user
- know how the program pass the parameter from assembly to c
- [sys/riscv/riscv/trap.c](https://github.com/freebsd/freebsd-src/blob/main/sys/riscv/riscv/trap.c)
- read functions: do_trap_user, ecall_handler
- [sys/riscv/riscv/elf_machdep.c](https://github.com/freebsd/freebsd-src/blob/main/sys/riscv/riscv/elf_machdep.c)
- read struct: static struct sysentvec
- [sys/sys/proc.h](https://github.com/freebsd/freebsd-src/blob/main/sys/sys/proc.h#L733)
- read struct: `proc`
- As for now, you can assume proc->p_sysent=elf64_freebsd_sysvec.
- [sys/kern/subr_syscall.c](https://github.com/freebsd/freebsd-src/blob/main/sys/kern/subr_syscall.c#L53)
- read functions: syscallenter, syscallret
- [sys/kern/subr_trap.c](https://github.com/freebsd/freebsd-src/blob/main/sys/kern/subr_trap.c)
- read functions: userret
- You don't have to understand the code, but you have to read the remarks.
- [System Calls Table](https://alfonsosiciliano.gitlab.io/posts/2021-01-02-freebsd-system-calls-table.html)

## 4

- Understand how a process launchs and executes an arbituary program and finally exit.
- You may have to read the following files:
- sys/kern/kern_*.c
- sys/kern/imgact_*.c
- Closely read the following files/functions:
- sys/kern/kern_fork.c: sys_fork, fork1
- sys/kern/kern_exec.c: sys_execve, kern_execve, do_execve,
- sys/kern/imgact_shell.c: exec_shell_imgact