From 67c9a04d58b2e2041c865a06d39303b897d3b31c Mon Sep 17 00:00:00 2001
From: Matheus <matheusuky@gmail.com>
Date: Fri, 23 Sep 2022 19:37:25 -0300
Subject: [PATCH] fd: change allocation to add a lowest fd option

---
 src/fs/fd.c               | 24 ++++++++++++++----------
 src/include/kernel/fd.h   |  3 +--
 src/sys/sched/scheduler.c |  6 +++---
 src/sys/syscalls/open.c   |  2 +-
 4 files changed, 19 insertions(+), 16 deletions(-)

diff --git a/src/fs/fd.c b/src/fs/fd.c
index d38f487d..de2f531e 100644
--- a/src/fs/fd.c
+++ b/src/fs/fd.c
@@ -4,8 +4,6 @@
 #include <kernel/alloc.h>
 #include <string.h>
 
-// XXX limit the max fd number
-
 int fd_release(fd_t* fd){	
 	spinlock_release(&fd->lock);
 	return 0;
@@ -28,16 +26,19 @@ int fd_access(fdtable_t* fdtable, fd_t** fd, int ifd){
 
 }
 
-int fd_alloc(fdtable_t* fdtable, fd_t** fd, int* ifd){
+int fd_alloc(fdtable_t* fdtable, fd_t** fd, int* ifd, int lowest){
+	if(lowest >= MAX_FD){
+		return EBADF;
+	}
+
 	spinlock_acquire(&fdtable->lock);
 	
 	// find fd to use
 	
 	bool ok = false;
 
-	for(uintmax_t i = fdtable->firstfreefd; i < fdtable->fdcount; ++i){
+	for(uintmax_t i = lowest; i < fdtable->fdcount; ++i){
 		if(!fdtable->fd[i]){
-			fdtable->firstfreefd = i;
 			*ifd = i;
 			ok = true;
 			break;
@@ -46,12 +47,16 @@ int fd_alloc(fdtable_t* fdtable, fd_t** fd, int* ifd){
 
 	// resize table
 
+	int targetfd = fdtable->fdcount > lowest ? fdtable->fdcount : lowest;
+
 	if(!ok){
+
 		if(fdtable->fdcount == MAX_FD){
 			spinlock_release(&fdtable->lock);
 			return EMFILE;
 		}
-		fd_t** tmp = realloc(fdtable->fd, sizeof(fd_t*)*(fdtable->fdcount + 1));
+
+		fd_t** tmp = realloc(fdtable->fd, sizeof(fd_t*)*(targetfd + 1));
 		
 		if(!tmp){
 			spinlock_release(&fdtable->lock);
@@ -59,8 +64,8 @@ int fd_alloc(fdtable_t* fdtable, fd_t** fd, int* ifd){
 		}	
 
 		fdtable->fd = tmp;
-		*ifd = fdtable->fdcount;
-		++fdtable->fdcount;
+		*ifd = targetfd;
+		fdtable->fdcount = targetfd + 1;
 		
 	}
 	
@@ -197,7 +202,7 @@ int fd_duplicate(fdtable_t* table, int src, int dest, int type, int* ret){
 	}
 
 	if(type == 1){ // allocate for dup
-		err = fd_alloc(table, &destfd, &dest);
+		err = fd_alloc(table, &destfd, &dest, dest); // for fcntl F_DUPFD, dest is the lowest fd
 		if(err){
 			fd_release(srcfd);
 			return err;
@@ -226,7 +231,6 @@ int fd_duplicate(fdtable_t* table, int src, int dest, int type, int* ret){
 		if(destfd){
 			spinlock_acquire(&destfd->lock);
 			if(--destfd->refcount == 0){
-				printf("killing\n");
 				if(destfd->node) vfs_close(destfd->node);
 				free(destfd);
 			}
diff --git a/src/include/kernel/fd.h b/src/include/kernel/fd.h
index 16798b36..2f53cdff 100644
--- a/src/include/kernel/fd.h
+++ b/src/include/kernel/fd.h
@@ -46,11 +46,10 @@ typedef struct {
 typedef struct {
 	int lock;
 	size_t fdcount;
-	uintmax_t firstfreefd;
 	fd_t** fd;
 } fdtable_t; 
 
-int fd_alloc(fdtable_t* fdtable, fd_t** fd, int* ifd);
+int fd_alloc(fdtable_t* fdtable, fd_t** fd, int* ifd, int lowest);
 int fd_free(fdtable_t* fdtable, int ifd);
 int fd_access(fdtable_t* fdtable, fd_t** fd, int ifd);
 int fd_release(fd_t* fd);
diff --git a/src/sys/sched/scheduler.c b/src/sys/sched/scheduler.c
index 6dc82bd6..f3ac73b3 100644
--- a/src/sys/sched/scheduler.c
+++ b/src/sys/sched/scheduler.c
@@ -417,9 +417,9 @@ void sched_runinit(){
 
 	fd_t *stdinfd, *stdoutfd, *stderrfd;
 
-	fd_alloc(&proc->fdtable, &stdinfd, &tmp);
-	fd_alloc(&proc->fdtable, &stdoutfd, &tmp);
-	fd_alloc(&proc->fdtable, &stderrfd, &tmp);
+	fd_alloc(&proc->fdtable, &stdinfd, &tmp, 0);
+	fd_alloc(&proc->fdtable, &stdoutfd, &tmp, 0);
+	fd_alloc(&proc->fdtable, &stderrfd, &tmp, 0);
 	
 	#define CONSOLE_PATH "dev/console"
 
diff --git a/src/sys/syscalls/open.c b/src/sys/syscalls/open.c
index 4235d29f..8a2d5e97 100644
--- a/src/sys/syscalls/open.c
+++ b/src/sys/syscalls/open.c
@@ -32,7 +32,7 @@ syscallret syscall_open(const char* pathname, int flags, mode_t mode){
 	int ifd;
 	fd_t* fd;
 
-	int err = fd_alloc(&proc->fdtable, &fd, &ifd);
+	int err = fd_alloc(&proc->fdtable, &fd, &ifd, 0);
 	
 	if(err){
 		retv.errno = err;