0ac1aaccca
- Changed VFS-FS protocol to only store OK or negative error code in m_type field of reply messages. - Changed VFS to treat nonzero positive replies from FS as requests. - Added backwards compatibility to VFS and MFS. No protection of global data structures is provided in VFS, so many VFS calls cannot be made safely by FS servers during many FS calls. Use with caution (or, preferably, not at all).
155 lines
4.3 KiB
C
155 lines
4.3 KiB
C
/* This file handles nested counter-request calls to VFS sent by file system
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* (FS) servers in response to VFS requests.
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*
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* The entry points into this file are
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* nested_fs_call perform a nested call from a file system server
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*/
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#include "fs.h"
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#include "fproc.h"
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#include <string.h>
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#include <assert.h>
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#include <minix/callnr.h>
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#include <minix/endpoint.h>
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/* maximum nested call stack depth */
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#define MAX_DEPTH 1
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/* global variables stack */
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PRIVATE struct {
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struct fproc *g_fp; /* pointer to caller process */
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message g_m_in; /* request message */
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message g_m_out; /* reply message */
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int g_who_e; /* endpoint of caller process */
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int g_who_p; /* slot number of caller process */
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int g_call_nr; /* call number */
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int g_super_user; /* is the caller root? */
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short g_cum_path_processed; /* how many path chars processed? */
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char g_user_fullpath[PATH_MAX+1]; /* path to look up */
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} globals[MAX_DEPTH];
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PRIVATE int depth = 0; /* current globals stack level */
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#if ENABLE_SYSCALL_STATS
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EXTERN unsigned long calls_stats[NCALLS];
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#endif
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FORWARD _PROTOTYPE( int push_globals, (void) );
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FORWARD _PROTOTYPE( void pop_globals, (void) );
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FORWARD _PROTOTYPE( void set_globals, (message *m) );
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/*===========================================================================*
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* push_globals *
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*===========================================================================*/
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PRIVATE int push_globals()
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{
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/* Save the global variables of the current call onto the globals stack.
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*/
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if (depth == MAX_DEPTH)
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return EPERM;
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globals[depth].g_fp = fp;
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globals[depth].g_m_in = m_in;
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globals[depth].g_m_out = m_out;
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globals[depth].g_who_e = who_e;
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globals[depth].g_who_p = who_p;
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globals[depth].g_call_nr = call_nr;
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globals[depth].g_super_user = super_user;
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globals[depth].g_cum_path_processed = cum_path_processed;
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/* XXX is it safe to strcpy this? */
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assert(sizeof(globals[0].g_user_fullpath) == sizeof(user_fullpath));
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memcpy(globals[depth].g_user_fullpath, user_fullpath, sizeof(user_fullpath));
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/* err_code is not used across blocking calls */
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depth++;
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return OK;
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}
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/*===========================================================================*
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* pop_globals *
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*===========================================================================*/
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PRIVATE void pop_globals()
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{
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/* Restore the global variables of a call from the globals stack.
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*/
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if (depth == 0)
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panic("VFS", "Popping from empty globals stack!", NO_NUM);
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depth--;
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fp = globals[depth].g_fp;
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m_in = globals[depth].g_m_in;
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m_out = globals[depth].g_m_out;
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who_e = globals[depth].g_who_e;
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who_p = globals[depth].g_who_p;
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call_nr = globals[depth].g_call_nr;
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super_user = globals[depth].g_super_user;
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cum_path_processed = globals[depth].g_cum_path_processed;
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memcpy(user_fullpath, globals[depth].g_user_fullpath, sizeof(user_fullpath));
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}
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/*===========================================================================*
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* set_globals *
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*===========================================================================*/
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PRIVATE void set_globals(m)
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message *m; /* request message */
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{
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/* Initialize global variables based on a request message.
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*/
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m_in = *m;
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who_e = m_in.m_source;
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who_p = _ENDPOINT_P(who_e);
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call_nr = m_in.m_type;
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fp = &fproc[who_p];
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super_user = (fp->fp_effuid == SU_UID ? TRUE : FALSE);
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/* the rest need not be initialized */
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}
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/*===========================================================================*
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* nested_fs_call *
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*===========================================================================*/
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PUBLIC void nested_fs_call(m)
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message *m; /* request/reply message pointer */
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{
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/* Handle a nested call from a file system server.
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*/
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int r;
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/* Save global variables of the current call */
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if ((r = push_globals()) != OK) {
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printf("VFS: error saving global variables in call %d from FS %d\n",
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m->m_type, m->m_source);
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} else {
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/* Initialize global variables for the nested call */
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set_globals(m);
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/* Perform the nested call */
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if (call_nr < 0 || call_nr >= NCALLS) {
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printf("VFS: invalid nested call %d from FS %d\n", call_nr,
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who_e);
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r = ENOSYS;
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} else {
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#if ENABLE_SYSCALL_STATS
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calls_stats[call_nr]++;
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#endif
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r = (*call_vec[call_nr])();
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}
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/* Store the result, and restore original global variables */
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*m = m_out;
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pop_globals();
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}
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m->m_type = r;
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}
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