From 08d202b4817cd0cd7e03677a04791730e02773ee Mon Sep 17 00:00:00 2001
From: hinus <hinus@163.com>
Date: Thu, 12 Aug 2021 08:16:24 +0800
Subject: [PATCH] Title: System call 'waitpid' Issue:
 https://gitee.com/hinus/linux_kernel_011/issues/I450PK Description: System
 call 'waitpid'

---
 include/linux/sys.h |  4 +--
 include/sys/wait.h  | 18 ++++++++++
 kernel/exit.c       | 88 ++++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 107 insertions(+), 3 deletions(-)

diff --git a/include/linux/sys.h b/include/linux/sys.h
index baad2a4..2f292bf 100644
--- a/include/linux/sys.h
+++ b/include/linux/sys.h
@@ -5,7 +5,7 @@ extern int sys_read();
 extern int sys_write();
 extern int sys_open();
 extern int sys_close();
-//extern int sys_waitpid();
+extern int sys_waitpid();
 //extern int sys_creat();
 //extern int sys_link();
 //extern int sys_unlink();
@@ -94,7 +94,7 @@ fn_ptr sys_call_table[] = {
     sys_write,
     sys_open,
     sys_close,
-    0, //sys_waitpid,
+    sys_waitpid,
     0, //sys_creat,
     0, //sys_link,
 
diff --git a/include/sys/wait.h b/include/sys/wait.h
index e34e095..d6c3360 100644
--- a/include/sys/wait.h
+++ b/include/sys/wait.h
@@ -1,6 +1,24 @@
 #ifndef _SYS_WAIT_H
 #define _SYS_WAIT_H
 
+#include <sys/types.h>
 
+#define _LOW(v)		( (v) & 0377)
+#define _HIGH(v)	( ((v) >> 8) & 0377)
+
+/* options for waitpid, WUNTRACED not supported */
+#define WNOHANG		1
+#define WUNTRACED	2
+
+#define WIFEXITED(s)	(!((s)&0xFF))
+#define WIFSTOPPED(s)	(((s)&0xFF)==0x7F)
+#define WEXITSTATUS(s)	(((s)>>8)&0xFF)
+#define WTERMSIG(s)	((s)&0x7F)
+#define WCOREDUMP(s)	((s)&0x80)
+#define WSTOPSIG(s)	(((s)>>8)&0xFF)
+#define WIFSIGNALED(s)	(((unsigned int)(s)-1 & 0xFFFF) < 0xFF)
+
+pid_t wait(int *stat_loc);
+pid_t waitpid(pid_t pid, int *stat_loc, int options);
 
 #endif
diff --git a/kernel/exit.c b/kernel/exit.c
index 0364109..8b36d3e 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -12,6 +12,32 @@
 extern int sys_pause();
 extern int sys_close(int fd);
 
+void release(struct task_struct * p) {
+    int i;
+
+    if (!p)
+        return;
+    if (p == current) {
+        printk("task releasing itself\n\r");
+        return;
+    }
+    for (i=1 ; i<NR_TASKS ; i++) {
+        if (task[i]==p) {
+            task[i]=NULL;
+            if (p->p_osptr)
+                p->p_osptr->p_ysptr = p->p_ysptr;
+            if (p->p_ysptr)
+                p->p_ysptr->p_osptr = p->p_osptr;
+            else
+                p->p_pptr->p_cptr = p->p_osptr;
+            free_page((long)p);
+            schedule();
+            return;
+        }
+    }
+    panic("trying to release non-existent task");
+}
+
 static inline int send_sig(long sig,struct task_struct * p,int priv) {
     if (!p)
         return -EINVAL;
@@ -114,7 +140,7 @@ void do_exit(long code) {
 
     current->p_pptr->signal |= (1<<(SIGCHLD-1));
 
-    if (p = current->p_cptr) {
+    if ((p = current->p_cptr)) {
         while (1) {
             p->p_pptr = task[1];
             if (p->state == TASK_ZOMBIE)
@@ -165,3 +191,63 @@ int sys_exit(int error_code) {
     return 0;
 }
 
+int sys_waitpid(pid_t pid,unsigned long * stat_addr, int options) {
+    int flag;
+    struct task_struct *p;
+    unsigned long oldblocked;
+
+    verify_area(stat_addr,4);
+repeat:
+    flag=0;
+    for (p = current->p_cptr ; p ; p = p->p_osptr) {
+        if (pid>0) {
+            if (p->pid != pid)
+                continue;
+        }
+        else if (!pid) {
+            if (p->pgrp != current->pgrp)
+                continue;
+        }
+        else if (pid != -1) {
+            if (p->pgrp != -pid)
+                continue;
+        }
+
+        switch (p->state) {
+            case TASK_STOPPED:
+                if (!(options & WUNTRACED) ||
+                        !p->exit_code)
+                    continue;
+                put_fs_long((p->exit_code << 8) | 0x7f, stat_addr);
+                p->exit_code = 0;
+                return p->pid;
+            case TASK_ZOMBIE:
+                current->cutime += p->utime;
+                current->cstime += p->stime;
+                flag = p->pid;
+                put_fs_long(p->exit_code, stat_addr);
+                release(p);
+                return flag;
+            default:
+                flag=1;
+                continue;
+        }
+    }
+
+    if (flag) {
+        if (options & WNOHANG)
+            return 0;
+        current->state=TASK_INTERRUPTIBLE;
+        oldblocked = current->blocked;
+        current->blocked &= ~(1<<(SIGCHLD-1));
+        schedule();
+        current->blocked = oldblocked;
+        if (current->signal & ~(current->blocked | (1<<(SIGCHLD-1))))
+            return -ERESTARTSYS;
+        else
+            goto repeat;
+    }
+
+    return -ECHILD;
+}
+
-- 
Gitee