9d59eb0151
Previously, these were inconsistent: they used their struct proc argument for bounds checking, but always copied the argument from the current address space (and hence the current process). Drop the struct proc argument and always use the current proc. Suggested by Carmi Merimovich.
142 lines
3.3 KiB
C
142 lines
3.3 KiB
C
#include "types.h"
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#include "defs.h"
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#include "param.h"
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#include "memlayout.h"
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#include "mmu.h"
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#include "proc.h"
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#include "x86.h"
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#include "syscall.h"
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// User code makes a system call with INT T_SYSCALL.
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// System call number in %eax.
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// Arguments on the stack, from the user call to the C
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// library system call function. The saved user %esp points
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// to a saved program counter, and then the first argument.
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// Fetch the int at addr from the current process.
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int
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fetchint(uint addr, int *ip)
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{
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if(addr >= proc->sz || addr+4 > proc->sz)
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return -1;
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*ip = *(int*)(addr);
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return 0;
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}
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// Fetch the nul-terminated string at addr from the current process.
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// Doesn't actually copy the string - just sets *pp to point at it.
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// Returns length of string, not including nul.
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int
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fetchstr(uint addr, char **pp)
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{
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char *s, *ep;
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if(addr >= proc->sz)
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return -1;
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*pp = (char*)addr;
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ep = (char*)proc->sz;
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for(s = *pp; s < ep; s++)
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if(*s == 0)
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return s - *pp;
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return -1;
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}
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// Fetch the nth 32-bit system call argument.
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int
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argint(int n, int *ip)
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{
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return fetchint(proc->tf->esp + 4 + 4*n, ip);
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}
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// Fetch the nth word-sized system call argument as a pointer
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// to a block of memory of size n bytes. Check that the pointer
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// lies within the process address space.
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int
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argptr(int n, char **pp, int size)
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{
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int i;
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if(argint(n, &i) < 0)
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return -1;
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if((uint)i >= proc->sz || (uint)i+size > proc->sz)
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return -1;
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*pp = (char*)i;
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return 0;
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}
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// Fetch the nth word-sized system call argument as a string pointer.
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// Check that the pointer is valid and the string is nul-terminated.
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// (There is no shared writable memory, so the string can't change
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// between this check and being used by the kernel.)
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int
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argstr(int n, char **pp)
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{
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int addr;
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if(argint(n, &addr) < 0)
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return -1;
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return fetchstr(addr, pp);
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}
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extern int sys_chdir(void);
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extern int sys_close(void);
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extern int sys_dup(void);
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extern int sys_exec(void);
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extern int sys_exit(void);
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extern int sys_fork(void);
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extern int sys_fstat(void);
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extern int sys_getpid(void);
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extern int sys_kill(void);
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extern int sys_link(void);
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extern int sys_mkdir(void);
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extern int sys_mknod(void);
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extern int sys_open(void);
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extern int sys_pipe(void);
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extern int sys_read(void);
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extern int sys_sbrk(void);
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extern int sys_sleep(void);
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extern int sys_unlink(void);
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extern int sys_wait(void);
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extern int sys_write(void);
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extern int sys_uptime(void);
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static int (*syscalls[])(void) = {
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[SYS_fork] sys_fork,
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[SYS_exit] sys_exit,
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[SYS_wait] sys_wait,
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[SYS_pipe] sys_pipe,
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[SYS_read] sys_read,
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[SYS_kill] sys_kill,
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[SYS_exec] sys_exec,
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[SYS_fstat] sys_fstat,
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[SYS_chdir] sys_chdir,
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[SYS_dup] sys_dup,
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[SYS_getpid] sys_getpid,
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[SYS_sbrk] sys_sbrk,
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[SYS_sleep] sys_sleep,
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[SYS_uptime] sys_uptime,
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[SYS_open] sys_open,
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[SYS_write] sys_write,
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[SYS_mknod] sys_mknod,
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[SYS_unlink] sys_unlink,
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[SYS_link] sys_link,
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[SYS_mkdir] sys_mkdir,
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[SYS_close] sys_close,
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};
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void
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syscall(void)
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{
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int num;
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num = proc->tf->eax;
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if(num >= 0 && num < SYS_open && syscalls[num]) {
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proc->tf->eax = syscalls[num]();
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} else if (num >= SYS_open && num < NELEM(syscalls) && syscalls[num]) {
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proc->tf->eax = syscalls[num]();
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} else {
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cprintf("%d %s: unknown sys call %d\n",
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proc->pid, proc->name, num);
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proc->tf->eax = -1;
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}
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}
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