From 97ea4986af02f5b73ca8c676ffdca9499a290f69 Mon Sep 17 00:00:00 2001
From: Bananymous <bananymousosq@gmail.com>
Date: Tue, 22 Aug 2023 14:53:12 +0300
Subject: [PATCH] Kernel/LibC: implement proper getpgid and setpgid

---
 kernel/include/kernel/Process.h |  3 +-
 kernel/kernel/Process.cpp       | 99 ++++++++++++++++++++++++++++++++-
 kernel/kernel/Syscall.cpp       |  8 +--
 libc/include/sys/syscall.h      |  4 +-
 libc/unistd.cpp                 | 15 ++++-
 5 files changed, 117 insertions(+), 12 deletions(-)

diff --git a/kernel/include/kernel/Process.h b/kernel/include/kernel/Process.h
index f1fb007a..cf461472 100644
--- a/kernel/include/kernel/Process.h
+++ b/kernel/include/kernel/Process.h
@@ -80,12 +80,13 @@ namespace Kernel
 		BAN::ErrorOr<long> sys_setegid(gid_t);
 		BAN::ErrorOr<long> sys_setreuid(uid_t, uid_t);
 		BAN::ErrorOr<long> sys_setregid(gid_t, gid_t);
-		BAN::ErrorOr<long> sys_setpgrp();
+		BAN::ErrorOr<long> sys_setpgid(pid_t, pid_t);
 
 		BAN::ErrorOr<long> sys_getuid() const { return m_credentials.ruid(); }
 		BAN::ErrorOr<long> sys_getgid() const { return m_credentials.rgid(); }
 		BAN::ErrorOr<long> sys_geteuid() const { return m_credentials.euid(); }
 		BAN::ErrorOr<long> sys_getegid() const { return m_credentials.egid(); }
+		BAN::ErrorOr<long> sys_getpgid(pid_t);
 
 		BAN::ErrorOr<long> sys_open(BAN::StringView, int, mode_t = 0);
 		BAN::ErrorOr<long> sys_openat(int, BAN::StringView, int, mode_t = 0);
diff --git a/kernel/kernel/Process.cpp b/kernel/kernel/Process.cpp
index c0ab10e8..d894025f 100644
--- a/kernel/kernel/Process.cpp
+++ b/kernel/kernel/Process.cpp
@@ -1152,11 +1152,104 @@ namespace Kernel
 		return 0;
 	}
 
-	BAN::ErrorOr<long> Process::sys_setpgrp()
+	BAN::ErrorOr<long> Process::sys_setpgid(pid_t pid, pid_t pgid)
+	{
+		if (pgid < 0)
+			return BAN::Error::from_errno(EINVAL);
+
+		LockGuard _(m_lock);
+
+		if (pid == 0)
+			pid = m_pid;
+		if (pgid == 0)
+			pgid = m_pid;
+
+		if (pid != pgid)
+		{
+			bool pgid_valid = false;
+			for_each_process_in_session(m_sid,
+				[&](Process& process)
+				{
+					if (process.pgrp() == pgid)
+					{
+						pgid_valid = true;
+						return BAN::Iteration::Break;
+					}
+					return BAN::Iteration::Continue;
+				}
+			);
+			if (!pgid_valid)
+				return BAN::Error::from_errno(EPERM);
+		}
+
+		if (m_pid == pid)
+		{
+			if (is_session_leader())
+				return BAN::Error::from_errno(EPERM);
+			m_pgrp = pgid;
+			return 0;
+		}
+
+		int error = ESRCH;
+		for_each_process(
+			[&](Process& process)
+			{
+				if (process.pid() != pid)
+					return BAN::Iteration::Continue;
+
+				if (process.m_parent != m_pid)
+					error = ESRCH;
+				else if (process.is_session_leader())
+					error = EPERM;
+				else if (process.m_has_called_exec)
+					error = EACCES;
+				else if (process.m_sid != m_sid)
+					error = EPERM;
+				else
+				{
+					error = 0;
+					process.m_pgrp = pgid;
+				}
+
+				return BAN::Iteration::Break;
+			}
+		);
+
+		if (error == 0)
+			return 0;
+		return BAN::Error::from_errno(error);
+	}
+
+	BAN::ErrorOr<long> Process::sys_getpgid(pid_t pid)
 	{
 		LockGuard _(m_lock);
-		m_pgrp = pid();
-		return pgrp();
+
+		if (pid == 0 || pid == m_pid)
+			return m_pgrp;
+
+		pid_t result;
+		int error = ESRCH;
+		for_each_process(
+			[&](Process& process)
+			{
+				if (process.pid() != pid)
+					return BAN::Iteration::Continue;
+
+				if (process.sid() != m_sid)
+					error = EPERM;
+				else
+				{
+					error = 0;
+					result = process.pgrp();
+				}
+
+				return BAN::Iteration::Break;
+			}
+		);
+
+		if (error == 0)
+			return result;
+		return BAN::Error::from_errno(error);
 	}
 
 	BAN::ErrorOr<BAN::String> Process::absolute_path_of(BAN::StringView path) const
diff --git a/kernel/kernel/Syscall.cpp b/kernel/kernel/Syscall.cpp
index eac7cdb1..0847fccb 100644
--- a/kernel/kernel/Syscall.cpp
+++ b/kernel/kernel/Syscall.cpp
@@ -173,11 +173,11 @@ namespace Kernel
 		case SYS_GET_PID:
 			ret = Process::current().pid();
 			break;
-		case SYS_GET_PGRP:
-			ret = Process::current().pgrp();
+		case SYS_GET_PGID:
+			ret = Process::current().sys_getpgid((pid_t)arg1);
 			break;
-		case SYS_SET_PGRP:
-			ret = Process::current().sys_setpgrp();
+		case SYS_SET_PGID:
+			ret = Process::current().sys_setpgid((pid_t)arg1, (pid_t)arg2);
 			break;
 		default:
 			dwarnln("Unknown syscall {}", syscall);
diff --git a/libc/include/sys/syscall.h b/libc/include/sys/syscall.h
index 6e1548b5..25ba52dc 100644
--- a/libc/include/sys/syscall.h
+++ b/libc/include/sys/syscall.h
@@ -48,8 +48,8 @@ __BEGIN_DECLS
 #define SYS_SIGNAL_DONE 41
 #define SYS_TCSETPGRP 42
 #define SYS_GET_PID 43
-#define SYS_GET_PGRP 44
-#define SYS_SET_PGRP 45
+#define SYS_GET_PGID 44
+#define SYS_SET_PGID 45
 
 __END_DECLS
 
diff --git a/libc/unistd.cpp b/libc/unistd.cpp
index 93be4e19..3f7f9199 100644
--- a/libc/unistd.cpp
+++ b/libc/unistd.cpp
@@ -210,7 +210,12 @@ gid_t getegid(void)
 
 pid_t getpgrp(void)
 {
-	return syscall(SYS_GET_PGRP);
+	return getpgid(0);
+}
+
+pid_t getpgid(pid_t pid)
+{
+	return syscall(SYS_GET_PGID, pid);
 }
 
 int seteuid(uid_t uid)
@@ -245,7 +250,13 @@ int setregid(gid_t rgid, gid_t egid)
 
 pid_t setpgrp(void)
 {
-	return syscall(SYS_SET_PGRP);
+	setpgid(0, 0);
+	return getpgrp();
+}
+
+int setpgid(pid_t pid, pid_t pgid)
+{
+	return syscall(SYS_SET_PGID, pid, pgid);
 }
 
 int tcsetpgrp(int fildes, pid_t pgid_id)