1 #include "types.h"
2 #include "defs.h"
3 #include "param.h"
4 #include "memlayout.h"
5 #include "mmu.h"
6 #include "proc.h"
7 #include "x86.h"
8 #include "syscall.h"
9
10 // User code makes a system call with INT T_SYSCALL.
11 // System call number in %eax.
12 // Arguments on the stack, from the user call to the C
13 // library system call function. The saved user %esp points
14 // to a saved program counter, and then the first argument.
15
16 // Fetch the int at addr from the current process.
17 int
fetchint(uint addr,int * ip)18 fetchint(uint addr, int *ip)
19 {
20 struct proc *curproc = myproc();
21
22 if(addr >= curproc->sz || addr+4 > curproc->sz)
23 return -1;
24 *ip = *(int*)(addr);
25 return 0;
26 }
27
28 // Fetch the nul-terminated string at addr from the current process.
29 // Doesn't actually copy the string - just sets *pp to point at it.
30 // Returns length of string, not including nul.
31 int
fetchstr(uint addr,char ** pp)32 fetchstr(uint addr, char **pp)
33 {
34 char *s, *ep;
35 struct proc *curproc = myproc();
36
37 if(addr >= curproc->sz)
38 return -1;
39 *pp = (char*)addr;
40 ep = (char*)curproc->sz;
41 for(s = *pp; s < ep; s++){
42 if(*s == 0)
43 return s - *pp;
44 }
45 return -1;
46 }
47
48 // Fetch the nth 32-bit system call argument.
49 int
argint(int n,int * ip)50 argint(int n, int *ip)
51 {
52 return fetchint((myproc()->tf->esp) + 4 + 4*n, ip);
53 }
54
55 // Fetch the nth word-sized system call argument as a pointer
56 // to a block of memory of size bytes. Check that the pointer
57 // lies within the process address space.
58 int
argptr(int n,char ** pp,int size)59 argptr(int n, char **pp, int size)
60 {
61 int i;
62 struct proc *curproc = myproc();
63
64 if(argint(n, &i) < 0)
65 return -1;
66 if(size < 0 || (uint)i >= curproc->sz || (uint)i+size > curproc->sz)
67 return -1;
68 *pp = (char*)i;
69 return 0;
70 }
71
72 // Fetch the nth word-sized system call argument as a string pointer.
73 // Check that the pointer is valid and the string is nul-terminated.
74 // (There is no shared writable memory, so the string can't change
75 // between this check and being used by the kernel.)
76 int
argstr(int n,char ** pp)77 argstr(int n, char **pp)
78 {
79 int addr;
80 if(argint(n, &addr) < 0)
81 return -1;
82 return fetchstr(addr, pp);
83 }
84
85 extern int sys_chdir(void);
86 extern int sys_close(void);
87 extern int sys_dup(void);
88 extern int sys_exec(void);
89 extern int sys_exit(void);
90 extern int sys_fork(void);
91 extern int sys_fstat(void);
92 extern int sys_getpid(void);
93 extern int sys_kill(void);
94 extern int sys_link(void);
95 extern int sys_mkdir(void);
96 extern int sys_mknod(void);
97 extern int sys_open(void);
98 extern int sys_pipe(void);
99 extern int sys_read(void);
100 extern int sys_sbrk(void);
101 extern int sys_sleep(void);
102 extern int sys_unlink(void);
103 extern int sys_wait(void);
104 extern int sys_write(void);
105 extern int sys_uptime(void);
106
107 static int (*syscalls[])(void) = {
108 [SYS_fork] sys_fork,
109 [SYS_exit] sys_exit,
110 [SYS_wait] sys_wait,
111 [SYS_pipe] sys_pipe,
112 [SYS_read] sys_read,
113 [SYS_kill] sys_kill,
114 [SYS_exec] sys_exec,
115 [SYS_fstat] sys_fstat,
116 [SYS_chdir] sys_chdir,
117 [SYS_dup] sys_dup,
118 [SYS_getpid] sys_getpid,
119 [SYS_sbrk] sys_sbrk,
120 [SYS_sleep] sys_sleep,
121 [SYS_uptime] sys_uptime,
122 [SYS_open] sys_open,
123 [SYS_write] sys_write,
124 [SYS_mknod] sys_mknod,
125 [SYS_unlink] sys_unlink,
126 [SYS_link] sys_link,
127 [SYS_mkdir] sys_mkdir,
128 [SYS_close] sys_close,
129 };
130
131 void
syscall(void)132 syscall(void)
133 {
134 int num;
135 struct proc *curproc = myproc();
136
137 num = curproc->tf->eax;
138 if(num > 0 && num < NELEM(syscalls) && syscalls[num]) {
139 curproc->tf->eax = syscalls[num]();
140 } else {
141 cprintf("%d %s: unknown sys call %d\n",
142 curproc->pid, curproc->name, num);
143 curproc->tf->eax = -1;
144 }
145 }
146