minix/servers/vfs/fscall.c
2012-03-25 21:58:14 +02:00

132 lines
3.5 KiB
C

/* This file handles nested counter-request calls to VFS sent by file system
* (FS) servers in response to VFS requests.
*
* The entry points into this file are
* nested_fs_call perform a nested call from a file system server
* nested_dev_call perform a nested call from a device driver server
*
*/
#include "fs.h"
#include "fproc.h"
#include <string.h>
#include <assert.h>
#include <minix/callnr.h>
#include <minix/endpoint.h>
#include <minix/vfsif.h>
/* maximum nested call stack depth */
#define MAX_DEPTH 1
/* global variables stack */
static struct {
struct fproc *g_fp; /* pointer to caller process */
message g_m_in; /* request message */
message g_m_out; /* reply message */
int g_who_e; /* endpoint of caller process */
int g_who_p; /* slot number of caller process */
int g_call_nr; /* call number */
int g_super_user; /* is the caller root? */
char g_user_fullpath[PATH_MAX]; /* path to look up */
} globals[MAX_DEPTH];
static int depth = 0; /* current globals stack level */
static int push_globals(void);
static void pop_globals(void);
static void set_globals(message *m);
/*===========================================================================*
* push_globals *
*===========================================================================*/
static int push_globals()
{
/* Save the global variables of the current call onto the globals stack.
*/
if (depth == MAX_DEPTH)
return(EPERM);
globals[depth].g_fp = fp;
globals[depth].g_m_in = m_in;
globals[depth].g_m_out = m_out;
globals[depth].g_super_user = super_user;
/* err_code is not used across blocking calls */
depth++;
return(OK);
}
/*===========================================================================*
* pop_globals *
*===========================================================================*/
static void pop_globals()
{
/* Restore the global variables of a call from the globals stack.
*/
if (depth == 0)
panic("Popping from empty globals stack!");
depth--;
fp = globals[depth].g_fp;
m_in = globals[depth].g_m_in;
m_out = globals[depth].g_m_out;
}
/*===========================================================================*
* set_globals *
*===========================================================================*/
static void set_globals(m)
message *m; /* request message */
{
/* Initialize global variables based on a request message.
*/
int proc_p;
m_in = *m;
proc_p = _ENDPOINT_P(m_in.m_source);
fp = &fproc[proc_p];
/* the rest need not be initialized */
}
/*===========================================================================*
* nested_fs_call *
*===========================================================================*/
void nested_fs_call(m)
message *m; /* request/reply message pointer */
{
/* Handle a nested call from a file system server.
*/
int r;
/* Save global variables of the current call */
if ((r = push_globals()) != OK) {
printf("VFS: error saving global variables in call %d from FS %d\n",
m->m_type, m->m_source);
} else {
/* Initialize global variables for the nested call */
set_globals(m);
/* Perform the nested call - only getsysinfo() is allowed right now */
if (call_nr == COMMON_GETSYSINFO) {
r = do_getsysinfo();
} else {
printf("VFS: invalid nested call %d from FS %d\n", call_nr,
who_e);
r = ENOSYS;
}
/* Store the result, and restore original global variables */
*m = m_out;
pop_globals();
}
m->m_type = r;
}