minix/servers/vfs/utility.c
Ben Gras 565f13088f make vfs & filesystems use failable copying
Change the kernel to add features to vircopy and safecopies so that
transparent copy fixing won't happen to avoid deadlocks, and such copies
fail with EFAULT.

Transparently making copying work from filesystems (as normally done by
the kernel & VM when copying fails because of missing/readonly memory)
is problematic as it can happen that, for file-mapped ranges, that that
same filesystem that is blocked on the copy request is needed to satisfy
the memory range, leading to deadlock. Dito for VFS itself, if done with
a blocking call.

This change makes the copying done from a filesystem fail in such cases
with EFAULT by VFS adding the CPF_TRY flag to the grants. If a FS call
fails with EFAULT, VFS will then request the range to be made available
to VM after the FS is unblocked, allowing it to be used to satisfy the
range if need be in another VFS thread.

Similarly, for datacopies that VFS itself does, it uses the failable
vircopy variant and callers use a wrapper that talk to VM if necessary
to get the copy to work.

	. kernel: add CPF_TRY flag to safecopies
	. kernel: only request writable ranges to VM for the
	  target buffer when copying fails
	. do copying in VFS TRY-first
	. some fixes in VM to build SANITYCHECK mode
	. add regression test for the cases where
	  - a FS system call needs memory mapped in a process that the
	    FS itself must map.
	  - such a range covers more than one file-mapped region.
	. add 'try' mode to vircopy, physcopy
	. add flags field to copy kernel call messages
	. if CP_FLAG_TRY is set, do not transparently try
	  to fix memory ranges
	. for use by VFS when accessing user buffers to avoid
	  deadlock
	. remove some obsolete backwards compatability assignments
        . VFS: let thread scheduling work for VM requests too
          Allows VFS to make calls to VM while suspending and resuming
          the currently running thread. Does currently not work for the
          main thread.
        . VM: add fix memory range call for use by VFS

Change-Id: I295794269cea51a3163519a9cfe5901301d90b32
2014-07-28 17:05:14 +02:00

215 lines
6 KiB
C

/* This file contains a few general purpose utility routines.
*
* The entry points into this file are
* clock_timespec: ask the clock task for the real time
* copy_path: copy a path name from a path request from userland
* fetch_name: go get a path name from user space
* panic: something awful has occurred; MINIX cannot continue
* in_group: determines if group 'grp' is in rfp->fp_sgroups[]
*/
#include "fs.h"
#include <minix/callnr.h>
#include <minix/endpoint.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <time.h>
#include "file.h"
#include "vmnt.h"
/*===========================================================================*
* copy_path *
*===========================================================================*/
int copy_path(char *dest, size_t size)
{
/* Go get the path for a path request. Put the result in in 'dest', which
* should be at least PATH_MAX in size.
*/
vir_bytes name;
size_t len;
assert(size >= PATH_MAX);
name = (vir_bytes) job_m_in.VFS_PATH_NAME;
len = job_m_in.VFS_PATH_LEN;
if (len > size) { /* 'len' includes terminating-nul */
err_code = ENAMETOOLONG;
return(EGENERIC);
}
/* Is the string contained in the message? If not, perform a normal copy. */
if (len > M3_STRING)
return fetch_name(name, len, dest);
/* Just copy the path from the message */
strncpy(dest, job_m_in.VFS_PATH_BUF, len);
if (dest[len - 1] != '\0') {
err_code = ENAMETOOLONG;
return(EGENERIC);
}
return(OK);
}
/*===========================================================================*
* fetch_name *
*===========================================================================*/
int fetch_name(vir_bytes path, size_t len, char *dest)
{
/* Go get path and put it in 'dest'. */
int r;
if (len > PATH_MAX) { /* 'len' includes terminating-nul */
err_code = ENAMETOOLONG;
return(EGENERIC);
}
/* Check name length for validity. */
if (len > SSIZE_MAX) {
err_code = EINVAL;
return(EGENERIC);
}
/* String is not contained in the message. Get it from user space. */
r = sys_datacopy_wrapper(who_e, path, VFS_PROC_NR, (vir_bytes) dest, len);
if (r != OK) {
err_code = EINVAL;
return(r);
}
if (dest[len - 1] != '\0') {
err_code = ENAMETOOLONG;
return(EGENERIC);
}
return(OK);
}
/*===========================================================================*
* isokendpt_f *
*===========================================================================*/
int isokendpt_f(const char *file, int line, endpoint_t endpoint, int *proc,
int fatal)
{
int failed = 0;
endpoint_t ke;
*proc = _ENDPOINT_P(endpoint);
if (endpoint == NONE) {
printf("VFS %s:%d: endpoint is NONE\n", file, line);
failed = 1;
} else if (*proc < 0 || *proc >= NR_PROCS) {
printf("VFS %s:%d: proc (%d) from endpoint (%d) out of range\n",
file, line, *proc, endpoint);
failed = 1;
} else if ((ke = fproc[*proc].fp_endpoint) != endpoint) {
if(ke == NONE) {
assert(fproc[*proc].fp_pid == PID_FREE);
} else {
printf("VFS %s:%d: proc (%d) from endpoint (%d) doesn't match "
"known endpoint (%d)\n", file, line, *proc, endpoint,
fproc[*proc].fp_endpoint);
assert(fproc[*proc].fp_pid != PID_FREE);
}
failed = 1;
}
if(failed && fatal)
panic("isokendpt_f failed");
return(failed ? EDEADEPT : OK);
}
/*===========================================================================*
* clock_timespec *
*===========================================================================*/
struct timespec clock_timespec(void)
{
/* This routine returns the time in seconds since 1.1.1970. MINIX is an
* astrophysically naive system that assumes the earth rotates at a constant
* rate and that such things as leap seconds do not exist.
*/
register int r;
struct timespec tv;
clock_t uptime;
clock_t realtime;
time_t boottime;
r = getuptime(&uptime, &realtime, &boottime);
if (r != OK)
panic("clock_timespec err: %d", r);
tv.tv_sec = boottime + (realtime/system_hz);
/* We do not want to overflow, and system_hz can be as high as 50kHz */
assert(system_hz < LONG_MAX/40000);
tv.tv_nsec = (realtime%system_hz) * 40000 / system_hz * 25000;
return tv;
}
/*===========================================================================*
* in_group *
*===========================================================================*/
int in_group(struct fproc *rfp, gid_t grp)
{
int i;
for (i = 0; i < rfp->fp_ngroups; i++)
if (rfp->fp_sgroups[i] == grp)
return(OK);
return(EINVAL);
}
/*===========================================================================*
* sys_datacopy_wrapper *
*===========================================================================*/
int sys_datacopy_wrapper(endpoint_t src, vir_bytes srcv,
endpoint_t dst, vir_bytes dstv, size_t len)
{
/* Safe function to copy data from or to a user buffer.
* VFS has to be a bit more careful as a regular copy
* might trigger VFS action needed by VM while it's
* blocked on the kernel call. This wrapper tries the
* copy, invokes VM itself asynchronously if necessary,
* then tries the copy again.
*
* This function assumes it's between VFS and a user process,
* and therefore one of the endpoints is SELF (VFS).
*/
int r;
endpoint_t them = NONE;
vir_bytes themv = -1;
int writable = -1;
r = sys_datacopy_try(src, srcv, dst, dstv, len);
if(src == VFS_PROC_NR) src = SELF;
if(dst == VFS_PROC_NR) dst = SELF;
assert(src == SELF || dst == SELF);
if(src == SELF) { them = dst; themv = dstv; writable = 1; }
if(dst == SELF) { them = src; themv = srcv; writable = 0; }
assert(writable >= 0);
assert(them != SELF);
if(r == EFAULT) {
/* The copy has failed with EFAULT, this means the kernel has
* given up but it might not be a legitimate error. Ask VM.
*/
if((r=vm_vfs_procctl_handlemem(them, themv, len, writable)) != OK) {
return r;
}
r = sys_datacopy_try(src, srcv, dst, dstv, len);
}
return r;
}