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.
17int
18fetchint(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.
31int
32fetchstr(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.
49int
50argint(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.
58int
59argptr(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.)
76int
77argstr(int n, char **pp)
78{
79 int addr;
80 if(argint(n, &addr) < 0)
81 return -1;
82 return fetchstr(addr, pp);
83}
84
85extern int sys_chdir(void);
86extern int sys_close(void);
87extern int sys_dup(void);
88extern int sys_exec(void);
89extern int sys_exit(void);
90extern int sys_fork(void);
91extern int sys_fstat(void);
92extern int sys_getpid(void);
93extern int sys_kill(void);
94extern int sys_link(void);
95extern int sys_mkdir(void);
96extern int sys_mknod(void);
97extern int sys_open(void);
98extern int sys_pipe(void);
99extern int sys_read(void);
100extern int sys_sbrk(void);
101extern int sys_sleep(void);
102extern int sys_unlink(void);
103extern int sys_wait(void);
104extern int sys_write(void);
105extern int sys_uptime(void);
106
107static 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
131void
132syscall(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